TRANSFER, MODIFICATION, AND EXTIRPATION OF VEGETABLE AND OF ANIMAL
SPECIES.
MODERN GEOGRAPHY EMBRACES ORGANIC LIFE--TRANSFER OF VEGETABLE LIFE--
FOREIGN PLANTS GROWN IN THE UNITED STATES--AMERICAN PLANTS GROWS IN
EUROPE--MODES OF INTRODUCTION OF FOREIGN PLANTS--VEGETABLES, HOW
AFFECTED BY TRANSFER TO FOREIGN SOILS--EXTIRPATION OF VEGETABLES--
ORIGIN OF DOMESTIC PLANTS--ORGANIC LIFE AS A GEOLOGICAL AND GEOGRAPHICAL
AGENCY--ORIGIN AND TRANSFER OF DOMESTIC ANIMALS--EXTIRPATION OF
ANIMALS--NUMBERS OF BIRDS IN THE UNITED STATES--BIRDS AS SOWERS AND
CONSUMERS OF SEEDS, AND AS DESTROYERS OF INSECTS--DIMINUTION AND
EXTIRPATION OF BIRDS--INTRODUCTION OF BIRDS--UTILITY OF INSECTS AND
WORMS--INTRODUCTION OF INSECTS--DESTRUCTION OF INSECTS--REPTILES--
DESTRUCTION OF FISH--INTRODUCTION AND BREEDING OF FISH--EXTIRPATION
OF AQUATIC ANIMALS--MINUTE ORGANISMS.
_Modern Geography embraces Organic Life._
It was a narrow view of geography which confined that science to
delineation of terrestrial surface and outline, and to description of
the relative position and magnitude of land and water. In its improved
form, it embraces not only the globe itself, but the living things which
vegetate or move upon it, the varied influences they exert upon each
other, the reciprocal action and reaction between them and the earth
they inhabit. Even if the end of geographical studies were only to
obtain a knowledge of the external forms of the mineral and fluid masses
which constitute the globe, it would still be necessary to take into
account the element of life; for every plant, every animal, is a
geographical agency, man a destructive, vegetables, and even wild
beasts, restorative powers. The rushing waters sweep down earth from the
uplands; in the first moment of repose, vegetation seeks to reestablish
itself on the bared surface, and, by the slow deposit of its decaying
products, to raise again the soil which the torrent had lowered. So
important an element of reconstruction is this, that it has been
seriously questioned whether, upon the whole, vegetation does not
contribute as much to elevate, as the waters to depress, the level of
the surface.
Whenever man has transported a plant from its native habitat to a new
soil, he has introduced a new geographical force to act upon it, and
this generally at the expense of some indigenous growth which the
foreign vegetable has supplanted. The new and the old plants are rarely
the equivalents of each other, and the substitution of an exotic for a
native tree, shrub, or grass, increases or diminishes the relative
importance of the vegetable element in the geography of the country to
which it is removed. Further, man sows that he may reap. The products of
agricultural industry are not suffered to rot upon the ground, and thus
raise it by an annual stratum of new mould. They are gathered,
transported to greater or less distances, and after they have served
their uses in human economy, they enter, on the final decomposition of
their elements, into new combinations, and are only in small proportion
returned to the soil on which they grew. The roots of the grasses, and
of many other cultivated plants, however, usually remain and decay in
the earth, and contribute to raise its surface, though certainly not in
the same degree as the forest.
The vegetables, which have taken the place of trees, unquestionably
perform many of the same functions. They radiate heat, they condense the
humidity of the atmosphere, they act upon the chemical constitution of
the air, their roots penetrate the earth to greater depths than is
commonly supposed, and form an inextricable labyrinth of filaments which
bind the soil together and prevent its erosion by water. The
broad-leaved annuals and perennials, too, shade the ground, and prevent
the evaporation of moisture from its surface by wind and sun.[38] At a
certain stage of growth, grass land is probably a more energetic
radiator and condenser than even the forest, but this powerful action is
exerted, in its full intensity, for a few days only, while trees
continue such functions, with unabated vigor, for many months in
succession. Upon the whole, it seems quite certain, that no cultivated
ground is as efficient in tempering climatic extremes, or in
conservation of geographical surface and outline, as is the soil which
nature herself has planted.
_Transfer of Vegetable Life._
It belongs to vegetable and animal geography, which are almost sciences
of themselves, to point out in detail what man has done to change the
distribution of plants and of animated life and to revolutionize the
aspect of organic nature; but some of the more important facts bearing
on this subject may pertinently be introduced here. Most of the fruit
trees grown in Europe and the United States are believed, and--if the
testimony of Pliny and other ancient naturalists is to be depended
upon--many of them are historically known, to have originated in the
temperate climates of Asia. The wine grape has been thought to be truly
indigenous only in the regions bordering on the eastern end of the Black
Sea, where it now, particularly on the banks of the Rion, the ancient
Phasis, propagates itself spontaneously, and grows with unexampled
luxuriance.[39] But, some species of the vine seem native to Europe, and
many varieties of grape have been too long known as common to every part
of the United States to admit of the supposition that they were all
introduced by European colonists.[40]
It is an interesting fact that the commerce--or at least the maritime
carrying trade--and the agricultural and mechanical industry of the
world are, in very large proportion, dependent on vegetable and animal
products little or not at all known to ancient Greek, Roman, and Jewish
civilization. In many instances, the chief supply of these articles
comes from countries to which they are probably indigenous, and where
they are still almost exclusively grown; but in many others, the plants
or animals from which they are derived have been introduced by man into
the regions now remarkable for their most successful cultivation, and
that, too, in comparatively recent times, or, in other words, within two
or three centuries.
_Foreign Plants grown in the United States._
According to Bigelow, the United States had, on the first of June, 1860,
in round numbers, 163,000,000 acres of improved land, the quantity
having been increased by 50,000,000 acres within the ten years next
preceding.[41] Not to mention less important crops, this land produced,
in the year ending on the day last mentioned, in round numbers,
171,000,000 bushels of wheat, 21,000,000 bushels of rye, 172,000,000
bushels of oats, 15,000,000 bushels of pease and beans, 16,000,000
bushels of barley, orchard fruits to the value of $20,000,000, 900,000
bushels of cloverseed, 900,000 bushels of other grass seed, 104,000 tons
of hemp, 4,000,000 pounds of flax, and 600,000 pounds of flaxseed. These
vegetable growths were familiar to ancient European agriculture, but
they were all introduced into North America after the close of the
sixteenth century.
Of the fruits of agricultural industry unknown to the Greeks and Romans,
or too little employed by them to be of any commercial importance, the
United States produced, in the same year, 187,000,000 pounds of rice,
18,000,000 bushels of buckwheat, 2,075,000,000 pounds of ginned
cotton,[42] 302,000,000 pounds of cane sugar, 16,000,000 gallons of
cane molasses, 7,000,000 gallons of sorghum molasses, all yielded by
vegetables introduced into that country within two hundred years,
and--with the exception of buckwheat, the origin of which is uncertain,
and of cotton--all, directly or indirectly, from the East Indies;
besides, from indigenous plants unknown to ancient agriculture,
830,000,000 bushels of Indian corn or maize, 429,000,000 pounds of
tobacco, 110,000,000 bushels of potatoes, 42,000,000 bushels of sweet
potatoes, 39,000,000 pounds of maple sugar, and 2,000,000 gallons of
maple molasses. To all this we are to add 19,000,000 tons of hay,
produced partly by new, partly by long known, partly by exotic, partly
by native herbs and grasses, an incalculable quantity of garden
vegetables, chiefly of European or Asiatic origin, and many minor
agricultural products.
The weight of this harvest of a year would be not less than 60,000,000
tons--which is eleven times the tonnage of all the shipping of the
United States at the close of the year 1861--and, with the exception of
the maple sugar, the maple molasses, and the products of the Western
prairie lands and some small Indian clearings, it was all grown upon
lands wrested from the forest by the European race within little more
than two hundred years. The wants of Europe have introduced into the
colonies of tropical America the sugar cane, the coffee plant, the
orange and the lemon,[43] all of Oriental origin, have immensely
stimulated the cultivation of the former two in the countries of which
they are natives, and, of course, promoted agricultural operations which
must have affected the geography of those regions to an extent
proportionate to the scale on which they have been pursued.
_American Plants grown in Europe._
America has partially repaid her debt to the Eastern continent. Maize
and the potato are very valuable additions to the field agriculture of
Europe and the East, and the tomato is no mean gift to the kitchen
gardens of the Old World, though certainly not an adequate return for
the multitude of esculent roots and leguminous plants which the European
colonists carried with them.[44] I wish I could believe, with some, that
America is not alone responsible for the introduction of the filthy
weed, tobacco, the use of which is the most vulgar and pernicious habit
engrafted by the semi-barbarism of modern civilization upon the less
multifarious sensualism of ancient life;[45] but the alleged occurrence
of pipe-like objects in Sclavonic, and, it has been said, in Hungarian
sepulchres, is hardly sufficient evidence to convict those races of
complicity in this grave offence against the temperance and the
refinement of modern society.
_Modes of Introduction of Foreign Plants._
Besides the vegetables I have mentioned, we know that many plants of
smaller economical value have been the subjects of international
exchange in very recent times. Busbequius, Austrian ambassador at
Constantinople about the middle of the sixteenth century--whose letters
contain one of the best accounts of Turkish life which have appeared
down to the present day--brought home from the Ottoman capital the lilac
and the tulip. The Belgian Clusius about the same time introduced from
the East the horse chestnut, which has since wandered to America. The
weeping willows of Europe and the United States are said to have sprung
from a slip received from Smyrna by the poet Pope, and planted by him in
an English garden; and the Portuguese declare that the progenitor of all
the European and American oranges was an Oriental tree transplanted to
Lisbon, and still living in the last generation.[46] The present
favorite flowers of the parterres of Europe have been imported from
America, Japan and other remote Oriental countries, within a century and
a half, and, in fine, there are few vegetables of any agricultural
importance, few ornamental trees or decorative plants, which are not now
common to the three civilized continents.
The statistics of vegetable emigration exhibit numerical results quite
surprising to those not familiar with the subject. The lonely island of
St. Helena is described as producing, at the time of its discovery in
the year 1501, about sixty vegetable species, including some three or
four known to grow elsewhere also. At the present time its flora numbers
seven hundred and fifty species. Humboldt and Bonpland found, among the
unquestionably indigenous plants of tropical America, monocotyledons
only, all the dicotyledons of those extensive regions having been
probably introduced after the colonization of the New World by Spain.
The faculty of spontaneous reproduction and perpetuation necessarily
supposes a greater power of accommodation, within a certain range, than
we find in most domesticated plants, for it would rarely happen that the
seed of a wild plant would fall into ground as nearly similar, in
composition and condition, to that where its parent grew, as the soils
of different fields artificially prepared for growing a particular
vegetable are to each other. Accordingly, though every wild species
affects a habitat of a particular character, it is found that, if
accidentally or designedly sown elsewhere, it will grow under conditions
extremely unlike those of its birthplace.[47] Cooper says: "We cannot
say positively that _any_ plant is _uncultivable_ anywhere until it has
been tried;" and this seems to be even more true of wild than of
domesticated vegetation.
The seven hundred new species which have found their way to St. Helena
within three centuries and a half, were certainly not all, or even in
the largest proportion, designedly planted there by human art, and if we
were well acquainted with vegetable emigration, we should probably be
able to show that man has intentionally transferred fewer plants than he
has accidentally introduced into countries foreign to them. After the
wheat, follow the tares that infest it. The weeds that grow among the
cereal grains, the pests of the kitchen garden, are the same in America
as in Europe.[48] The overturning of a wagon, or any of the thousand
accidents which befall the emigrant in his journey across the Western
plains, may scatter upon the ground the seeds he designed for his
garden, and the herbs which fill so important a place in the rustic
materia medica of the Eastern States, spring up along the prairie paths
but just opened by the caravan of the settler.[49] The hortus siccus of
a botanist may accidentally sow seeds from the foot of the Himalayas on
the plains that skirt the Alps; and it is a fact of very familiar
observation, that exotics, transplanted to foreign climates suited to
their growth, often escape from the flower garden and naturalize
themselves among the spontaneous vegetation of the pastures. When the
cases containing the artistic treasures of Thorvaldsen were opened in
the court of the museum where they are deposited, the straw and grass
employed in packing them were scattered upon the ground, and the next
season there sprang up from the seeds no less than twenty-five species
of plants belonging to the Roman campagna, some of which were preserved
and cultivated as a new tribute to the memory of the great Scandinavian
sculptor, and at least four are said to have spontaneously naturalized
themselves about Copenhagen.[50] In the campaign of 1814, the Russian
troops brought, in the stuffing of their saddles and by other accidental
means, seeds from the banks of the Dnieper to the valley of the Rhine,
and even introduced the plants of the steppes into the environs of
Paris. The Turkish armies, in their incursions into Europe, brought
Eastern vegetables in their train, and left the seeds of Oriental wall
plants to grow upon the ramparts of Buda and Vienna.[51] The Canada
thistle, _Erigeron Canadense_, is said to have sprung up in Europe, two
hundred years ago, from a seed which dropped out of the stuffed skin of
a bird.[52]
_Vegetables, how affected by Transfer to Foreign Soils._
Vegetables, naturalized abroad either by accident or design, sometimes
exhibit a greatly increased luxuriance of growth. The European cardoon,
an esculent thistle, has broken out from the gardens of the Spanish
colonies on the La Plata, acquired a gigantic stature, and propagated
itself, in impenetrable thickets, over hundreds of leagues of the
Pampas; and the _Anacharis alsinastrum_, a water plant not much inclined
to spread in its native American habitat, has found its way into English
rivers, and extended itself to such a degree as to form a serious
obstruction to the flow of the current, and even to navigation.
Not only do many wild plants exhibit a remarkable facility of
accommodation, but their seeds usually possess great tenacity of life,
and their germinating power resists very severe trials. Hence, while the
seeds of very many cultivated vegetables lose their vitality in two or
three years, and can be transported safely to distant countries only
with great precautions, the weeds that infest those vegetables, though
not cared for by man, continue to accompany him in his migrations, and
find a new home on every soil he colonizes. Nature fights in defence of
her free children, but wars upon them when they have deserted her
banners and tamely submitted to the dominion of man.[53]
Not only is the wild plant much hardier than the domesticated vegetable,
but the same law prevails in animated brute and even human life. The
beasts of the chase are more capable of endurance and privation and more
tenacious of life, than the domesticated animals which most nearly
resemble them. The savage fights on, after he has received half a dozen
mortal wounds, the least of which would have instantly paralyzed the
strength of his civilized enemy, and, like the wild boar,[54] he has
been known to press forward along the shaft of the spear which was
transpiercing his vitals, and to deal a deathblow on the soldier who
wielded it.
True, domesticated plants can be gradually acclimatized to bear a degree
of heat or of cold, which, in their wild state, they would not have
supported; the trained English racer outstrips the swiftest horse of the
pampas or prairies, perhaps even the less systematically educated
courser of the Arab; the strength of the European, as tested by the
dynamometer, is greater than that of the New Zealander. But all these
are instances of excessive development of particular capacities and
faculties at the expense of general vital power. Expose untamed and
domesticated forms of life, together, to an entire set of physical
conditions equally alien to the former habits of both, so that every
power of resistance and accommodation shall be called into action, and
the wild plant or animal will live, while the domesticated will perish.
The saline atmosphere of the sea is specially injurious both to seeds
and to very many young plants, and it is only recently that the
transportation of some very important vegetables across the ocean has
been made practicable, through the invention of Ward's airtight glass
cases. It is by this means that large numbers of the trees which produce
the Jesuit's bark have been successfully transplanted from America to
the British possessions in the East, where it is hoped they will become
fully naturalized.
_Extirpation of Vegetables._
Lamentable as are the evils produced by the too general felling of the
woods in the Old World, I believe it does not satisfactorily appear that
any species of native forest tree has yet been extirpated by man on the
Eastern continent. The roots, stumps, trunks, and foliage found in bogs
are recognized as belonging to still extant species. Except in some few
cases where there is historical evidence that foreign material was
employed, the timber of the oldest European buildings, and even of the
lacustrine habitations of Switzerland, is evidently the product of trees
still common in or near the countries where such architectural remains
are found; nor have the Egyptian catacombs themselves revealed to us the
former existence of any woods not now familiar to us as the growth of
still living trees.[55] It is, however, said that the yew tree, _Taxus
baccata_, formerly very common in England, Germany, and--as we are
authorized to infer from Theophrastus--in Greece, has almost wholly
disappeared from the latter country, and seems to be dying out in
Germany. The wood of the yew surpasses that of any other European tree
in closeness and fineness of grain, and it is well known for the
elasticity which of old made it so great a favorite with the English
archer. It is much in request among wood carvers and turners, and the
demand for it explains, in part, its increasing scarcity. It is also
worth remarking that no insect depends upon it for food or shelter, or
aids in its fructification, no bird feeds upon its berries--the latter a
circumstance of some importance, because the tree hence wants one means
of propagation or diffusion common to so many other plants. But it is
alleged that the reproductive power of the yew is exhausted, and that it
can no longer be readily propagated by the natural sowing of its seeds,
or by artificial methods. If further investigation and careful
experiment should establish this fact, it will go far to show that a
climatic change, of a character unfavorable to the growth of the yew,
has really taken place in Germany, though not yet proved by instrumental
observation, and the most probable cause of such change would be found
in the diminution of the area covered by the forests.
The industry of man is said to have been so successful in the local
extirpation of noxious or useless vegetables in China, that, with the
exception of a few water plants in the rice grounds, it is sometimes
impossible to find a single weed in an extensive district; and the late
eminent agriculturist, Mr. Coke, is reported to have offered in vain a
considerable reward for the detection of a weed in a large wheatfield on
his estate in England. In these cases, however, there is no reason to
suppose that diligent husbandry has done more than to eradicate the
pests of agriculture within a comparatively limited area, and the cockle
and the darnel will probably remain to plague the slovenly cultivator as
long as the cereal grains continue to bless him.[56]
_Origin of Domestic Plants._
One of the most important, and, at the same time, most difficult
questions connected with our subject is: how far we are to regard our
cereal grains, our esculent bulbs and roots, and the multiplied tree
fruits of our gardens, as artificially modified and improved forms of
wild, self-propagating vegetation. The narratives of botanical
travellers have often announced the discovery of the original form and
habitat of domesticated plants, and scientific journals have described
the experiments by which the identity of particular wild and cultivated
vegetables has been thought to be established. It is confidently
affirmed that maize and the potato--which we must suppose to have been
first cultivated at a much later period than the breadstuffs and most
other esculent vegetables of Europe and the East--are found wild and
self-propagating in Spanish America, though in forms not recognizable by
the common observer as identical with the familiar corn and tuber of
modern agriculture. It was lately asserted, upon what seemed very strong
evidence, that the _AEgilops ovata_, a plant growing wild in Southern
France, had been actually converted into common wheat; but, upon a
repetition of the experiments, later observers have declared that the
apparent change was only a case of temporary hybridation or fecundation
by the pollen of true wheat, and that the grass alleged to be
transformed into wheat could not be perpetuated as such from its own
seed.
The very great modifications which cultivated plants are constantly
undergoing under our eyes, and the numerous varieties and races which
spring up among them, certainly countenance the doctrine, that every
domesticated vegetable, however dependent upon human care for growth and
propagation in its present form, may have been really derived, by a long
succession of changes, from some wild plant not now much resembling it.
But it is, in every case, a question of evidence. The only satisfactory
proof that a given wild plant is identical with a given garden or field
vegetable, is the test of experiment, the actual growing of the one from
the seed of the other, or the conversion of the one into the other by
transplantation and change of conditions. It is hardly contended that
any of the cereals or other plants important as human aliment, or as
objects of agricultural industry, exist and propagate themselves
uncultivated in the same form and with the same properties as when sown
and reared by human art.[57] In fact, the cases are rare where the
identity of a wild with a domesticated plant is considered by the best
authorities as conclusively established, and we are warranted in
affirming of but few of the latter, as a historically known or
experimentally proved fact, that they ever did exist, or could exist,
independently of man.[58]
_Organic Life as a Geological and Geographical Agency._
The quantitative value of organic life, as a geological agency, seems to
be inversely as the volume of the individual organism; for nature
supplies by numbers what is wanting in the bulk of the plant or animal
out of whose remains or structures she forms strata covering whole
provinces, and builds up from the depths of the sea large islands, if
not continents. There are, it is true, near the mouths of the great
Siberian rivers which empty themselves into the Polar Sea, drift islands
composed, in an incredibly large proportion, of the bones and tusks of
elephants, mastodons, and other huge pachyderms, and many extensive
caves in various parts of the world are half filled with the skeletons
of quadrupeds, sometimes lying loose in the earth, sometimes cemented
together into an osseous breccia by a calcareous deposit or other
binding material. These remains of large animals, though found in
comparatively late formations, generally belong to extinct species, and
their modern congeners or representatives do not exist in sufficient
numbers to be of sensible importance in geology or in geography by the
mere mass of their skeletons.[59] But the vegetable products found with
them, and, in rare cases, in the stomachs of some of them, are those of
yet extant plants; and besides this evidence, the recent discovery of
works of human art, deposited in juxtaposition with fossil bones, and
evidently at the same time and by the same agency which buried these
latter--not to speak of alleged human bones found in the same
strata--proves that the animals whose former existence they testify were
contemporaneous with man, and possibly even extirpated by him.[60] I do
not propose to enter upon the thorny question, whether the existing
races of man are genealogically connected with these ancient types of
humanity, and I advert to these facts only for the sake of the
suggestion that man, in his earliest known stages of existence, was
probably a destructive power upon the earth, though perhaps not so
emphatically as his present representatives.
The larger wild animals are not now numerous enough in any one region to
form extensive deposits by their remains; but they have, nevertheless, a
certain geographical importance. If the myriads of large browsing and
grazing quadrupeds which wander over the plains of Southern Africa--and
the slaughter of which by thousands is the source of a ferocious
pleasure and a brutal triumph to professedly civilized hunters--if the
herds of the American bison, which are numbered by hundreds of
thousands, do not produce visible changes in the forms of terrestrial
surface, they have at least an immense influence on the growth and
distribution of vegetable life, and, of course, indirectly upon all the
physical conditions of soil and climate between which and vegetation a
mutual interdependence exists.
The influence of wild quadrupeds upon vegetable life has been little
studied, and not many facts bearing upon it have been recorded, but, so
far as it is known, it appears to be conservative rather than
pernicious.[61] Few if any of them depend for their subsistence on
vegetable products obtainable only by the destruction of the plant, and
they seem to confine their consumption almost exclusively to the annual
harvest of leaf or twig, or at least of parts of the vegetable easily
reproduced. If there are exceptions to this rule, they are in cases
where the numbers of the animal are so proportioned to the abundance of
the vegetable, that there is no danger of the extermination of the plant
from the voracity of the quadruped, or of the extinction of the
quadruped from the scarcity of the plant. In diet and natural wants the
bison resembles the ox, the ibex and the chamois assimilate themselves
to the goat and the sheep; but while the wild animal does not appear to
be a destructive agency in the garden of nature, his domestic congeners
are eminently so. This is partly from the change of habits resulting
from domestication and association with man, partly from the fact that
the number of reclaimed animals is not determined by the natural
relation of demand and spontaneous supply which regulates the
multiplication of wild creatures, but by the convenience of man, who is,
in comparatively few things, amenable to the control of the merely
physical arrangements of nature. When the domesticated animal escapes
from human jurisdiction, as in the case of the ox, the horse, the goat,
and perhaps the ass--which, so far as I know, are the only
well-authenticated instances of the complete emancipation of household
quadrupeds--he becomes again an unresisting subject of nature, and all
his economy is governed by the same laws as that of his fellows which
have never been enslaved by man; but, so long as he obeys a human lord,
he is an auxiliary in the warfare his master is ever waging against all
existences except those which he can tame to a willing servitude.
_Number of Quadrupeds in the United States._
Civilization is so intimately associated with, if not dependent upon,
certain inferior forms of animal life, that cultivated man has never
failed to accompany himself, in all his migrations, with some of these
humble attendants. The ox, the horse, the sheep, and even the
comparatively useless dog and cat, as well as several species of
poultry, are voluntarily transported by every emigrant colony, and they
soon multiply to numbers very far exceeding those of the wild genera
most nearly corresponding to them.[62] According to the census of the
United States for 1860,[63] the total number of horses in all the
States of the American Union, was, in round numbers, 7,300,000; of asses
and mules, 1,300,000; of the ox tribe, 29,000,000;[64] of sheep,
25,000,000; and of swine, 39,000,000. The only North American quadruped
sufficiently gregarious in habits, and sufficiently multiplied in
numbers, to form really large herds, is the bison, or, as he is commonly
called in America, the buffalo; and this animal is confined to the
prairie region of the Mississippi basin and Northern Mexico. The
engineers sent out to survey railroad routes to the Pacific estimated
the number of a single herd of bisons seen within the last ten years on
the great plains near the Upper Missouri, at not less than 200,000, and
yet the range occupied by this animal is now very much smaller in area
than it was when the whites first established themselves on the
prairies.[65] But it must be remarked that the American buffalo is a
migratory animal, and that, at the season of his annual journeys, the
whole stock of a vast extent of pasture ground is collected into a
single army, which is seen at or very near any one point only for a few
days during the entire season. Hence there is risk of great error in
estimating the numbers of the bison in a given district from the
magnitude of the herds seen at or about the same time at a single place
of observation; and, upon the whole, it is neither proved nor probable
that the bison was ever, at any one time, as numerous in North America
as the domestic bovine species is at present. The elk, the moose, the
musk ox, the caribou, and the smaller quadrupeds popularly embraced
under the general name of deer,[66] though sufficient for the wants of a
sparse savage population, were never numerically very abundant, and the
carnivora which fed upon them were still less so. It is almost needless
to add that the Rocky Mountain sheep and goat must always have been very
rare.
Summing up the whole, then, it is evident that the wild quadrupeds of
North America, even when most numerous, were few compared with their
domestic successors, that they required a much less supply of vegetable
food, and consequently were far less important as geographical elements
than the many millions of hoofed and horned cattle now fed by civilized
man on the same continent.
_Origin and Transfer of Domestic Quadrupeds._
Of the origin of our domestic animals, we know historically nothing,
because their domestication belongs to the ages which preceded written
history; but though they cannot all be specifically identified with now
extant wild animals, it is presumable that they have been reclaimed from
an originally wild state. Ancient annalists have preserved to us fewer
data respecting the introduction of domestic animals into new countries
than respecting the transplantation of domestic vegetables. Ritter, in
his learned essay on the camel, has shown that this animal was not
employed by the Egyptians until a comparatively late period in their
history; that he was unknown to the Carthaginians until after the
downfall of their commonwealth; and that his first appearance in Western
Africa is more recent still. The Bactrian camel was certainly brought
from Asia Minor to the Northern shores of the Black Sea, by the Goths,
in the third or fourth century.[67] The Arabian single-humped camel, or
dromedary, has been carried to the Canary Islands, partially introduced
into Australia, Greece, Spain, and even Tuscany, experimented upon to
little purpose in Venezuela, and finally imported by the American
Government into Texas and New Mexico, where it finds the climate and the
vegetable products best suited to its wants, and promises to become a
very useful agent in the promotion of the special civilization for which
those regions are adapted. America had no domestic quadruped but a
species of dog, the lama tribe, and, to a certain extent, the bison or
buffalo.[68] Of course, it owes the horse, the ass, the ox, the sheep,
the goat, and the swine, as does also Australia, to European
colonization. Modern Europe has, thus far, not accomplished much in the
way of importation of new animals, though some interesting essays have
been made. The reindeer was successfully introduced into Iceland about a
century ago, while similar attempts failed, about the same time, in
Scotland. The Cashmere or Thibet goat was brought to France a generation
since, and succeeds well. The same or an allied species and the Asiatic
buffalo were carried to South Carolina about the year 1850, and the
former, at least, is thought likely to prove of permanent value in the
United States. The yak, or Tartary ox, seems to thrive in France, and
success has attended the recent efforts to introduce the South American
alpaca into Europe.
_Extirpation of Quadrupeds._
Although man never fails greatly to diminish, and is perhaps destined
ultimately to exterminate, such of the larger wild quadrupeds as he
cannot profitably domesticate, yet their numbers often fluctuate, and
even after they seem almost extinct, they sometimes suddenly increase,
without any intentional steps to promote such a result on his part.
During the wars which followed the French Revolution, the wolf
multiplied in many parts of Europe, partly because the hunters were
withdrawn from the woods to chase a nobler game, and partly because the
bodies of slain men and horses supplied this voracious quadruped with
more abundant food. The same animal became again more numerous in Poland
after the general disarming of the rural population by the Russian
Government. On the other hand, when the hunters pursue the wolf, the
graminivorous wild quadrupeds increase, and thus in turn promote the
multiplication of their great four-footed destroyer by augmenting the
supply of his nourishment. So long as the fur of the beaver was
extensively employed as a material for fine hats, it bore a very high
price, and the chase of this quadruped was so keen that naturalists
feared its speedy extinction. When a Parisian manufacturer invented the
silk hat, which soon came into almost universal use, the demand for
beavers' fur fell off, and this animal--whose habits, as we have seen,
are an important agency in the formation of bogs and other modifications
of forest nature--immediately began to increase, reappeared in haunts
which he had long abandoned, and can no longer be regarded as rare
enough to be in immediate danger of extirpation. Thus the convenience or
the caprice of Parisian fashion has unconsciously exercised an influence
which may sensibly affect the physical geography of a distant continent.
Since the invention of gunpowder, some quadrupeds have completely
disappeared from many European and Asiatic countries where they were
formerly numerous. The last wolf was killed in Great Britain two hundred
years ago, and the bear was extirpated from that island still earlier.
The British wild ox exists only in a few English and Scottish parks,
while in Irish bogs, of no great apparent antiquity, are found antlers
which testify to the former existence of a stag much larger than any
extant European species. The lion is believed to have inhabited Asia
Minor and Syria, and probably Greece and Sicily also, long after the
commencement of the historical period, and he is even said to have been
not yet extinct in the first-named two of these countries at the time of
the first Crusades.[69] Two large graminivorous or browsing quadrupeds,
the ur and the schelk, once common in Germany, are utterly extinct, the
eland and the auerochs nearly so. The Nibelungen-Lied, which, in the
oldest form preserved to us, dates from about the year 1,200, though its
original composition no doubt belongs to an earlier period, thus sings:
Then slowe the dowghtie Sigfrid a wisent and an elk,
He smote four stoute uroxen and a grim and sturdie schelk.[70]
Modern naturalists identify the elk with the eland, the wisent with the
auerochs. The period when the ur and the schelk became extinct is not
known. The auerochs survived in Prussia until the middle of the last
century, but unless it is identical with a similar quadruped said to be
found on the Caucasus, it now exists only in the Russian imperial forest
of Bialowitz, where about a thousand are still preserved, and in some
great menageries, as for example that at Schoenbrunn, near Vienna, which,
in 1852, had four specimens. The eland, which is closely allied to the
American wapiti, if not specifically the same animal, is still kept in
the royal preserves of Prussia, to the number of four or five hundred
individuals. The chamois is becoming rare, and the ibex or steinbock,
once common in all the high Alps, is now believed to be confined to the
Cogne mountains in Piedmont, between the valleys of the Dora Baltea and
the Orco.
_Number of Birds in the United States._
The tame fowls play a much less conspicuous part in rural life than the
quadrupeds, and, in their relations to the economy of nature, they are
of very much less moment than four-footed animals, or than the
undomesticated birds. The domestic turkey[71] is probably more numerous
in the territory of the United States than the wild bird of the same
species ever was, and the grouse cannot, at the period of their greatest
abundance, have counted as many as we now number of the common hen. The
dove, however, must fall greatly short of the wild pigeon in multitude,
and it is hardly probable that the flocks of domestic geese and ducks
are as numerous as once were those of their wild congeners. The pigeon,
indeed, seems to have multiplied immensely, for some years after the
first clearings in the woods, because the settlers warred unsparingly
upon the hawk, while the crops of grain and other vegetable growths
increased the supply of food within the reach of the young birds, at the
age when their power of flight is not yet great enough to enable them
to seek it over a wide area.[72] The pigeon is not described by the
earliest white inhabitants of the American States as filling the air
with such clouds of winged life as astonish naturalists in the
descriptions of Audubon, and, at the present day, the net and the gun
have so reduced its abundance, that its appearance in large numbers is
recorded only at long intervals, and it is never seen in the great
flocks remembered by many still living observers as formerly very
common.
_Birds as Sowers and Consumers of Seeds, and as Destroyers of Insects._
Wild birds form of themselves a very conspicuous and interesting feature
in the _staffage_, as painters call it, of the natural landscape, and
they are important elements in the view we are taking of geography,
whether we consider their immediate or their incidental influence. Birds
affect vegetation directly by sowing seeds and by consuming them; they
affect it indirectly by destroying insects injurious, or, in some cases,
beneficial to vegetable life. Hence, when we kill a seed-sowing bird, we
check the dissemination of a plant; when we kill a bird which digests
the seed it swallows, we promote the increase of a vegetable. Nature
protects the seeds of wild, much more effectually than those of
domesticated plants. The cereal grains are completely digested when
consumed by birds, but the germ of the smaller stone fruits and of very
many other wild vegetables is uninjured, perhaps even stimulated to more
vigorous growth, by the natural chemistry of the bird's stomach. The
power of flight and the restless habits of the bird enable it to
transport heavy seeds to far greater distances than they could be
carried by the wind. A swift-winged bird may drop cherry stones a
thousand miles from the tree they grow on; a hawk, in tearing a pigeon,
may scatter from its crop the still fresh rice it had swallowed at a
distance of ten degrees of latitude,[73] and thus the occurrence of
isolated plants in situations where their presence cannot otherwise well
be explained, is easily accounted for. There is a large class of seeds
apparently specially fitted by nature for dissemination by animals. I
refer to those which attach themselves, by means of hooks, or by viscous
juices, to the coats of quadrupeds and the feathers of birds, and are
thus transported wherever their living vehicles may chance to wander.
Some birds, too, deliberately bury seeds, not indeed with a foresight
aiming directly at the propagation of the plant, but from apparently
purposeless secretiveness, or as a mode of preserving food for future
use.
An unfortunate popular error greatly magnifies the injury done to the
crops of grain and leguminous vegetables by wild birds. Very many of
those generally supposed to consume large quantities of the seeds of
cultivated plants really feed almost exclusively upon insects, and
frequent the wheatfields, not for the sake of the grain, but for the
eggs, larvae, and fly of the multiplied tribes of insect life which are
so destructive to the harvests. This fact has been so well established
by the examination of the stomachs of great numbers of birds in Europe
and New England, at different seasons of the year, that it is no longer
open to doubt, and it appears highly probable that even the species
which consume more or less grain generally make amends, by destroying
insects whose ravages would have been still more injurious.[74] On this
subject, we have much other evidence besides that derived from
dissection. Direct observation has shown, in many instances, that the
destruction of wild birds has been followed by a great multiplication of
noxious insects, and, on the other hand, that these latter have been
much reduced in numbers by the protection and increase of the birds that
devour them. Many interesting facts of this nature have been collected
by professed naturalists, but I shall content myself with a few taken
from familiar and generally accessible sources. The following extract is
from Michelet, _L'Oiseau_ pp. 169, 170:
"The _stingy_ farmer--an epithet justly and feelingly bestowed by
Virgil. Avaricious, blind, indeed, who proscribes the birds--those
destroyers of insects, those defenders of his harvests. Not a grain for
the creature which, during the rains of winter, hunts the future insect,
finds out the nests of the larvae, examines, turns over every leaf, and
destroys, every day, thousands of incipient caterpillars. But sacks of
corn for the mature insect, whole fields for the grasshoppers, which the
bird would have made war upon. With eyes fixed upon his furrow, upon the
present moment only, without seeing and without foreseeing, blind to the
great harmony which is never broken with impunity, he has everywhere
demanded or approved laws for the extermination of that necessary ally
of his toil--the insectivorous bird. And the insect has well avenged the
bird. It has become necessary to revoke in haste the proscription. In
the Isle of Bourbon, for instance, a price was set on the head of the
martin; it disappeared, and the grasshoppers took possession of the
island, devouring, withering, scorching with a biting drought all that
they did not consume. In North America it has been the same with the
starling, the protector of Indian corn.[75] Even the sparrow, which
really does attack grain, but which protects it still more, the
pilferer, the outlaw, loaded with abuse and smitten with curses--it has
been found in Hungary that they were likely to perish without him, that
he alone could sustain the mighty war against the beetles and the
thousand winged enemies that swarm in the lowlands; they have revoked
the decree of banishment, recalled in haste this valiant militia, which,
though deficient in discipline, is nevertheless the salvation of the
country.[76]
"Not long since, in the neighborhood of Rouen and in the valley of
Monville, the blackbird was for some time proscribed. The beetles
profited well by this proscription; their larvae, infinitely multiplied,
carried on their subterranean labors with such success, that a meadow
was shown me, the surface of which was completely dried up, every
herbaceous root was consumed, and the whole grassy mantle, easily
loosened, might have been rolled up and carried away like a carpet."
_Diminution and Extirpation of Birds._
The general hostility of the European populace to the smaller birds is,
in part, the remote effect of the reaction created by the game laws.
When the restrictions imposed upon the chase by those laws were suddenly
removed in France, the whole people at once commenced a destructive
campaign against every species of wild animal. Arthur Young, writing in
Provence, on the 30th of August, 1789, soon after the National Assembly
had declared the chase free, thus complains of the annoyance he
experienced from the use made by the peasantry of their newly won
liberty. "One would think that every rusty firelock in all Provence was
at work in the indiscriminate destruction of all the birds. The wadding
buzzed by my ears, or fell into my carriage, five or six times in the
course of the day." * * "The declaration of the Assembly that every man
is free to hunt on his own land * * has filled all France with an
intolerable cloud of sportsmen. * * The declaration speaks of
compensations and indemnities [to the _seigneurs_], but the ungovernable
populace takes advantage of the abolition of the game laws and laughs at
the obligation imposed by the decree."
The French Revolution removed similar restrictions, with similar
results, in other countries. The habits then formed have become
hereditary on the Continent, and though game laws still exist in
England, there is little doubt that the blind prejudices of the ignorant
and half-educated classes in that country against birds are, in some
degree, at least, due to a legislation, which, by restricting the chase
of all game worth killing, drives the unprivileged sportsman to
indemnify himself by slaughtering all wild life which is not reserved
for the amusement of his betters. Hence the lord of the manor buys his
partridges and his hares by sacrificing the bread of his tenants, and so
long as the farmers of Crawley are forbidden to follow higher game, they
will suicidally revenge themselves by destroying the sparrows which
protect their wheatfields.
On the Continent, and especially in Italy, the comparative scarcity and
dearness of animal food combine with the feeling I have just mentioned
to stimulate still further the destructive passions of the fowler. In
the Tuscan province of Grosseto, containing less than 2,000 square
miles, nearly 300,000 thrushes and other small birds are annually
brought to market.[77]
Birds are less hardy in constitution, they possess less facility of
accommodation,[78] and they are more severely affected by climatic
excess than quadrupeds. Besides, they generally want the means of
shelter against the inclemency of the weather and against pursuit by
their enemies, which holes and dens afford to burrowing animals and to
some larger beasts of prey. The egg is exposed to many dangers before
hatching, and the young bird is especially tender, defenceless, and
helpless. Every cold rain, every violent wind, every hailstorm during
the breeding season, destroys hundreds of nestlings, and the parent
often perishes with her progeny while brooding over it in the vain
effort to protect it.[79] The great proportional numbers of birds, their
migratory habits, and the ease with which they may escape most dangers
that beset them, would seem to secure them from extirpation, and even
from very great numerical reduction. But experience shows that when not
protected by law, by popular favor or superstition, or by other special
circumstances, they yield very readily to the hostile influences of
civilization, and, though the first operations of the settler are
favorable to the increase of many species, the great extension of rural
and of mechanical industry is, in a variety of ways, destructive even to
tribes not directly warred upon by man.[80]
Nature sets bounds to the disproportionate increase of birds, while at
the same time, by the multitude of their resources, she secures them
from extinction through her own spontaneous agencies. Man both preys
upon them and wantonly destroys them. The delicious flavor of game
birds, and the skill implied in the various arts of the sportsman who
devotes himself to fowling, make them favorite objects of the chase,
while the beauty of their plumage, as a military and feminine
decoration, threatens to involve the sacrifice of the last survivor of
many once numerous species. Thus far, but few birds described by ancient
or modern naturalists are known to have become absolutely extinct,
though there are some cases in which they are ascertained to have
utterly disappeared from the face of the earth in very recent times. The
most familiar instances are those of the dodo, a large bird peculiar to
the Mauritius or Isle of France, exterminated about the year 1690, and
now known only by two or three fragments of skeletons, and the solitary,
which inhabited the islands of Bourbon and Rodriguez, but has not been
seen for more than a century. A parrot and some other birds of the
Norfolk Island group are said to have lately become extinct. The
wingless auk, _Alca impennis_, a bird remarkable for its excessive
fatness, was very abundant two or three hundred years ago in the Faroe
Islands, and on the whole Scandinavian seaboard. The early voyagers
found either the same or a closely allied species, in immense numbers,
on all the coasts and islands of Newfoundland. The value of its flesh
and its oil made it one of the most important resources of the
inhabitants of those sterile regions, and it was naturally an object of
keen pursuit. It is supposed to be now completely extinct, and few
museums can show even its skeleton.
There seems to be strong reason to believe that our boasted modern
civilization is guiltless of one or two sins of extermination which have
been committed in recent ages. New Zealand formerly possessed three
species of dinornis, one of which, called _moa_ by the islanders, was
much larger than the ostrich. The condition in which the bones of these
birds have been found and the traditions of the natives concur to prove
that, though the aborigines had probably extirpated them before the
discovery of New Zealand by the whites, they still existed at a
comparatively late period. The same remarks apply to a winged giant the
eggs of which have been brought from Madagascar. This bird must have
much exceeded the dimensions of the moa, at least so far as we can judge
from the egg, which is eight times as large as the average size of the
ostrich egg, or about one hundred and fifty times that of the hen.
But though we have no evidence that man has exterminated many species of
birds, we know that his persecutions have caused their disappearance
from many localities where they once were common, and greatly diminished
their numbers in others. The cappercailzie, _Tetrao urogallus_, the
finest of the grouse family, formerly abundant in Scotland, had become
extinct in Great Britain, but has been reintroduced from Sweden.[81] The
ostrich is mentioned by all the old travellers, as common on the
Isthmus of Suez down to the middle of the seventeenth century. It
appears to have frequented Syria and even Asia Minor at earlier periods,
but is now found only in the seclusion of remoter deserts.
The modern increased facilities of transportation have brought distant
markets within reach of the professional hunter, and thereby given a new
impulse to his destructive propensities. Not only do all Great Britain
and Ireland contribute to the supply of game for the British capital,
but the canvas-back duck of the Potomac, and even the prairie hen from
the basin of the Mississippi, may be found at the stalls of the London
poulterer. Kohl[82] informs us that on the coasts of the North Sea,
twenty thousand wild ducks are usually taken in the course of the season
in a single decoy, and sent to the large maritime towns for sale. The
statistics of the great European cities show a prodigious consumption of
game birds, but the official returns fall far below the truth, because
they do not include the rural districts, and because neither the poacher
nor his customers report the number of his victims. Reproduction, in
cultivated countries, cannot keep pace with this excessive destruction,
and there is no doubt that all the wild birds which are chased for their
flesh or their plumage are diminishing with a rapidity which justifies
the fear that the last of them will soon follow the dodo and the
wingless auk.
Fortunately the larger birds which are pursued for their flesh or for
their feathers, and those the eggs of which are used as food, are, so
far as we know the functions appointed to them by nature, not otherwise
specially useful to man, and, therefore, their wholesale destruction is
an economical evil only in the same sense in which all waste of
productive capital is an evil. If it were possible to confine the
consumption of game fowl to a number equal to the annual increase, the
world would be a gainer, but not to the same extent as it would be by
checking the wanton sacrifice of millions of the smaller birds, which
are of no real value as food, but which, as we have seen, render a most
important service by battling, in our behalf, as well as in their own,
against the countless legions of humming and of creeping things, with
which the prolific powers of insect life would otherwise cover the
earth.
_Introduction of Birds._
Man has undesignedly introduced into new districts perhaps fewer species
of birds than of quadrupeds; but the distribution of birds is very much
influenced by the character of his industry, and the transplantation of
every object of agricultural production is, at a longer or shorter
interval, followed by that of the birds which feed upon its seeds, or
more frequently upon the insects it harbors. The vulture, the crow, and
other winged scavengers, follow the march of armies as regularly as the
wolf. Birds accompany ships on long voyages, for the sake of the offal
which is thrown overboard, and, in such cases, it might often happen
that they would breed and become naturalized in countries where they had
been unknown before.[83] There is a familiar story of an English bird
which built its nest in an unused block in the rigging of a ship, and
made one or two short voyages with the vessel while hatching its eggs.
Had the young become fledged while lying in a foreign harbor, they would
of course have claimed the rights of citizenship in the country where
they first took to the wing.[84]
Some enthusiastic entomologist will, perhaps, by and by discover that
insects and worms are as essential as the larger organisms to the proper
working of the great terraqueous machine, and we shall have as eloquent
pleas in defence of the mosquito, and perhaps even of the tzetze fly, as
Toussenel and Michelet have framed in behalf of the bird.[85] The
silkworm and the bee need no apologist; a gallnut produced by the
puncture of an insect on a Syrian oak is a necessary ingredient in the
ink I am writing with, and from my windows I recognize the grain of the
kermes and the cochineal in the gay habiliments of the holiday groups
beneath them. But agriculture, too, is indebted to the insect and the
worm. The ancients, according to Pliny, were accustomed to hang
branches of the wild fig upon the domestic tree, in order that the
insects which frequented the former might hasten the ripening of the
cultivated fig by their punctures--or, as others suppose, might fructify
it by transporting to it the pollen of the wild fruit--and this process,
called caprification, is not yet entirely obsolete. The earthworms long
ago made good their title to the respect and gratitude of the farmer as
well as of the angler. The utility of the earthworms has been pointed
out in many scientific as well as in many agricultural treatises. The
following extract, cut from a newspaper, will answer my present purpose:
"Mr. Josiah Parkes, the consulting engineer of the Royal Agricultural
Society of England, says that worms are great assistants to the drainer,
and valuable aids to the farmer in keeping up the fertility of the soil.
He says they love moist, but not wet soils; they will bore down to, but
not into water; they multiply rapidly on land after drainage, and prefer
a deeply dried soil. On examining with Mr. Thomas Hammond, of Penhurst,
Kent, part of a field which he had deeply drained, after long-previous
shallow drainage, he found that the worms had greatly increased in
number, and that their bores descended quite to the level of the pipes.
Many worm bores were large enough to receive the little finger. Mr.
Henry Handley had informed him of a piece of land near the sea in
Lincolnshire, over which the sea had broken and killed all the
worms--the field remained sterile until the worms again inhabited it. He
also showed him a piece of pasture land near to his house, in which
worms were in such numbers that he thought their casts interfered too
much with its produce, which induced him to have it rolled at night in
order to destroy the worms. The result was, that the fertility of the
field greatly declined, nor was it restored until they had recruited
their numbers, which was aided by collecting and transporting multitudes
of worms from the fields.
"The great depth into which worms will bore, and from which they push up
fine fertile soil, and cast it on the surface, has been admirably traced
by Mr. C. Darwin, of Down, Kent, who has shown that in a few years they
have actually elevated the surface of fields by a large layer of rich
mould, several inches thick--thus affording nourishment to the roots of
grasses, and increasing the productiveness of the soil."
It should be added that the writer quoted, and others who have discussed
the subject, have overlooked one very important element in the
fertilization produced by earthworms. I refer to the enrichment of the
soil by their excreta during life, and by the decomposition of their
remains when they die. The manure thus furnished is as valuable as the
like amount of similar animal products derived from higher organisms,
and when we consider the prodigious numbers of these worms found on a
single square yard of some soils, we may easily see that they furnish no
insignificant contribution to the nutritive material required for the
growth of plants.[86]
The perforations of the earthworm mechanically affect the texture of the
soil and its permeability by water, and they therefore have a certain
influence on the form and character of surface. But the geographical
importance of insects proper, as well as of worms, depends principally
on their connection with vegetable life as agents of its fecundation,
and of its destruction.[87] I am acquainted with no single fact so
strikingly illustrative of this importance, as the following statement
which I take from a notice of Darwin's volume, On Various Contrivances
by which British and Foreign Orchids are Fertilized by Insects, in the
_Saturday Review_, of October 18, 1862: "The net result is, that some
six thousand species of orchids are absolutely dependent upon the agency
of insects for their fertilization. That is to say, were those plants
unvisited by insects, they would all rapidly disappear." What is true of
the orchids is more or less true of many other vegetable families. We do
not know the limits of this agency, and many of the insects habitually
regarded as unqualified pests, may directly or indirectly perform
functions as important to the most valuable plants as the services
rendered by certain tribes to the orchids. I say directly or indirectly,
because, besides the other arrangements of nature for checking the undue
multiplication of particular species, she has established a police among
insects themselves, by which some of them keep down or promote the
increase of others; for there are insects, as well as birds and beasts,
of prey. The existence of an insect which fertilizes a useful vegetable
may depend on that of another, which constitutes his food in some stage
of his life, and this other again may be as injurious to some plant as
his destroyer is beneficial to another. The equation of animal and
vegetable life is too complicated a problem for human intelligence to
solve, and we can never know how wide a circle of disturbance we produce
in the harmonies of nature when we throw the smallest pebble into the
ocean of organic life.
This much, however, we seem authorized to conclude: as often as we
destroy the balance by deranging the original proportions between
different orders of spontaneous life, the law of self-preservation
requires us to restore the equilibrium, by either directly returning the
weight abstracted from one scale, or removing a corresponding quantity
from the other. In other words, destruction must be either repaired by
reproduction, or compensated by new destruction in an opposite quarter.
The parlor aquarium has taught even those to whom it is but an amusing
toy, that the balance of animal and vegetable life must be preserved,
and that the excess of either is fatal to the other, in the artificial
tank as well as in natural waters. A few years ago, the water of the
Cochituate aqueduct at Boston became so offensive in smell and taste as
to be quite unfit for use. Scientific investigation found the cause in
the too scrupulous care with which aquatic vegetation had been excluded
from the reservoir, and the consequent death and decay of the animalculae
which could not be shut out, nor live in the water without the vegetable
element.[88]
_Introduction of Insects._
The general tendency of man's encroachments upon spontaneous nature has
been to increase insect life at the expense of vegetation and of the
smaller quadrupeds and birds. Doubtless there are insects in all woods,
but in temperate climates they are comparatively few and harmless, and
the most numerous tribes which breed in the forest, or rather in its
waters, and indeed in all solitudes, are those which little injure
vegetation, such as mosquitoes, gnats, and the like. With the cultivated
plants of man come the myriad tribes which feed or breed upon them, and
agriculture not only introduces new species, but so multiplies the
number of individuals as to defy calculation. Newly introduced
vegetables frequently escape for years the insect plagues which had
infested them in their native habitat; but the importation of other
varieties of the plant, the exchange of seed, or some mere accident, is
sure in the long run to carry the egg, the larva, or the chrysalis to
the most distant shores where the plant assigned to it by nature as its
possession has preceded it. For many years after the colonization of the
United States, few or none of the insects which attack wheat in its
different stages of growth, were known in America. During the
Revolutionary war, the Hessian fly, _Cecidomyia destructor_, made its
appearance, and it was so called because it was first observed in the
year when the Hessian troops were brought over, and was popularly
supposed to have been accidentally imported by those unwelcome
strangers. Other destroyers of cereal grains have since found their way
across the Atlantic, and a noxious European aphis has first attacked the
American wheatfields within the last four or five years. Unhappily, in
these cases of migration, the natural corrective of excessive
multiplication, the parasitic or voracious enemy of the noxious insect,
does not always accompany the wanderings of its prey, and the bane long
precedes the antidote. Hence, in the United States, the ravages of
imported insects injurious to cultivated crops, not being checked by the
counteracting influences which nature had provided to limit their
devastations in the Old World, are much more destructive than in Europe.
It is not known that the wheat midge is preyed upon in America by any
other insect, and in seasons favorable to it, it multiplies to a degree
which would prove almost fatal to the entire harvest, were it not that,
in the great territorial extent of the United States, there is room for
such differences of soil and climate as, in a given year, to present in
one State all the conditions favorable to the increase of a particular
insect, while in another, the natural influences are hostile to it. The
only apparent remedy for this evil is, to balance the disproportionate
development of noxious foreign species by bringing from their native
country the tribes which prey upon them. This, it seems, has been
attempted. The United States' Census Report for 1860, p. 82, states that
the New York Agricultural Society "has introduced into this country from
abroad certain parasites which Providence has created to counteract the
destructive powers of some of these depredators."
This is, however, not the only purpose for which man has designedly
introduced foreign forms of insect life. The eggs of the silkworm are
known to have been brought from the farther East to Europe in the sixth
century, and new silk spinners which feed on the castor oil bean and the
ailanthus, have recently been reared in France and in South America with
promising success. The cochineal, long regularly bred in aboriginal
America, has been transplanted to Spain, and both the kermes insect and
the cantharides have been transferred to other climates than their own.
The honey bee must be ranked next to the silkworm in economical
importance.[89] This useful creature was carried to the United States
by European colonists, in the latter part of the seventeenth century; it
did not cross the Mississippi till the close of the eighteenth, and it
is only within the last five or six years that it has been transported
to California, where it was previously unknown. The Italian stingless
bee has very lately been introduced into the United States.
The insects and worms intentionally transplanted by man bear but a small
proportion to those accidentally introduced by him. Plants and animals
often carry their parasites with them, and the traffic of commercial
countries, which exchange their products with every zone and every stage
of social existence, cannot fail to transfer in both directions the
minute organisms that are, in one way or another, associated with almost
every object important to the material interests of man.[90]
The tenacity of life possessed by many insects, their prodigious
fecundity, the length of time they often remain in the different phases
of their existence,[91] the security of the retreats into which their
small dimensions enable them to retire, are all circumstances very
favorable not only to the perpetuity of their species, but to their
transportation to distant climates and their multiplication in their new
homes. The teredo, so destructive to shipping, has been carried by the
vessels whose wooden walls it mines to almost every part of the globe.
The termite, or white ant, is said to have been brought to Rochefort by
the commerce of that port a hundred years ago.[92] This creature is more
injurious to wooden structures and implements than any other known
insect. It eats out almost the entire substance of the wood, leaving
only thin partitions between the galleries it excavates in it; but as it
never gnaws through the surface to the air, a stick of timber may be
almost wholly consumed without showing any external sign of the damage
it has sustained. The termite is found also in other parts of France,
and particularly at Rochelle, where, thus far, its ravages are confined
to a single quarter of the city. A borer, of similar habits, is not
uncommon in Italy, and you may see in that country, handsome chairs and
other furniture which have been reduced by this insect to a framework of
powder of post, covered, and apparently held together, by nothing but
the varnish.
The carnivorous, and often the herbivorous insects render an important
service to man by consuming dead and decaying animal and vegetable
matter, the decomposition of which would otherwise fill the air with
effluvia noxious to health. Some of them, the grave-digger beetle, for
instance, bury the small animals in which they lay their eggs, and
thereby prevent the escape of the gases disengaged by putrefaction. The
prodigious rapidity of development in insect life, the great numbers of
the individuals in many species, and the voracity of most of them while
in the larva state, justify the appellation of nature's scavengers which
has been bestowed upon them, and there is very little doubt that, in
warm countries, they consume a much larger quantity of putrescent
organic material than the quadrupeds and the birds which feed upon such
aliment.
_Destruction of Insects._
It is well known to naturalists, but less familiarly to common
observers, that the aquatic larvae of some insects constitute, at certain
seasons, a large part of the food of fresh-water fish, while other
larvae, in their turn, prey upon the spawn and even the young of their
persecutors.[93] The larvae of the mosquito and the gnat are the favorite
food of the trout in the wooded regions where those insects abound.[94]
Earlier in the year the trout feeds on the larvae of the May fly, which
is itself very destructive to the spawn of the salmon, and hence, by a
sort of house-that-Jack-built, the destruction of the mosquito, that
feeds the trout that preys on the May fly that destroys the eggs that
hatch the salmon that pampers the epicure, may occasion a scarcity of
this latter fish in waters where he would otherwise be abundant. Thus
all nature is linked together by invisible bonds, and every organic
creature, however low, however feeble, however dependent, is necessary
to the well-being of some other among the myriad forms of life with
which the Creator has peopled the earth.
I have said that man has promoted the increase of the insect and the
worm, by destroying the bird and the fish which feed upon them. Many
insects, in the four different stages of their growth, inhabit in
succession the earth, the water, and the air. In each of these elements
they have their special enemies, and, deep and dark as are the minute
recesses in which they hide themselves, they are pursued to the
remotest, obscurest corners by the executioners that nature has
appointed to punish their delinquencies, and furnished with cunning
contrivances for ferreting out the offenders and dragging them into the
light of day. One tribe of birds, the woodpeckers, seems to depend for
subsistence almost wholly on those insects which breed in dead or dying
trees, and it is, perhaps, needless to say that the injury these birds
do the forest is imaginary. They do not cut holes in the trunk of the
tree to prepare a lodgment for a future colony of boring larvae, but to
extract the worm which has already begun his mining labors. Hence these
birds are not found where the forester removes trees as fast as they
become fit habitations for such insects. In clearing new lands in the
United States, dead trees, especially of the spike-leaved kinds, too
much decayed to serve for timber, and which, in that state, are worth
little for fuel, are often allowed to stand until they fall of
themselves. Such _stubs_, as they are popularly called, are filled with
borers, and often deeply cut by the woodpeckers, whose strong bills
enable them to penetrate to the very heart of the tree and drag out the
lurking larvae. After a few years, the stubs fall, or, as wood becomes
valuable, are cut and carried off for firewood, and, at the same time,
the farmer selects for felling, in the forest he has reserved as a
permanent source of supply of fuel and timber, the decaying trees which,
like the dead stems in the fields, serve as a home for both the worm and
his pursuer. We thus gradually extirpate this tribe of insects, and,
with them, the species of birds which subsist principally upon them.
Thus the fine, large, red-headed woodpecker, _Picus erythrocephalus_,
formerly very common in New England, has almost entirely disappeared
from those States, since the dead trees are gone, and the apples, his
favorite vegetable food, are less abundant.
There are even large quadrupeds which feed almost exclusively upon
insects. The ant bear is strong enough to pull down the clay houses
built by the species of termites that constitute his ordinary diet, and
the curious ai-ai, a climbing quadruped of Madagascar--of which I
believe only a single specimen, secured by Mr. Sandwith, has yet reached
Europe--is provided with a very slender, hook-nailed finger, long enough
to reach far into a hole in the trunk of a tree, and extract the worm
which bored it.
_Reptiles._
But perhaps the most formidable foes of the insect, and even of the
small rodents, are the reptiles. The chameleon approaches the insect
perched upon the twig of a tree, with an almost imperceptible slowness
of motion, until, at the distance of a foot, he shoots out his long,
slimy tongue, and rarely fails to secure the victim. Even the slow toad
catches the swift and wary housefly in the same manner; and in the warm
countries of Europe, the numerous lizards contribute very essentially to
the reduction of the insect population, which they both surprise in the
winged state upon walls and trees, and consume as egg, worm, and
chrysalis, in their earlier metamorphoses. The serpents feed much upon
insects, as well as upon mice, moles, and small reptiles, including also
other snakes. The disgust and fear with which the serpent is so
universally regarded expose him to constant persecution by man, and
perhaps no other animal is so relentlessly sacrificed by him. In
temperate climates, snakes are consumed by scarcely any beast or bird of
prey except the stork, and they have few dangerous enemies but man,
though in the tropics other animals prey upon them.[95] It is doubtful
whether any species of serpent has been exterminated within the human
period, and even the dense population of China has not been able
completely to rid itself of the viper. They have, however, almost
entirely disappeared from particular localities. The rattlesnake is now
wholly unknown in many large districts where it was extremely common
half a century ago, and Palestine has long been, if not absolutely free
from venomous serpents, at least very nearly so.[96]
_Destruction of Fish._
The inhabitants of the waters seem comparatively secure from human
pursuit or interference by the inaccessibility of their retreats, and by
our ignorance of their habits--a natural result of the difficulty of
observing the ways of creatures living in a medium in which we cannot
exist. Human agency has, nevertheless, both directly and incidentally,
produced great changes in the population of the sea, the lakes, and the
rivers, and if the effects of such revolutions in aquatic life are
apparently of small importance in general geography, they are still not
wholly inappreciable. The great diminution in the abundance of the
larger fish employed for food or pursued for products useful in the arts
is familiar, and when we consider how the vegetable and animal life on
which they feed must be affected by the reduction of their numbers, it
is easy to see that their destruction may involve considerable
modifications in many of the material arrangements of nature. The whale
does not appear to have been an object of pursuit by the ancients, for
any purpose, nor do we know when the whale fishery first commenced.[97]
It was, however, very actively prosecuted in the Middle Ages, and the
Biscayans seem to have been particularly successful in this as indeed in
other branches of nautical industry.[98] Five hundred years ago, whales
abounded in every sea. They long since became so rare in the
Mediterranean as not to afford encouragement for the fishery as a
regular occupation; and the great demand for oil and whalebone for
mechanical and manufacturing purposes, in the present century, has
stimulated the pursuit of the "hugest of living creatures" to such
activity, that he has now almost wholly disappeared from many favorite
fishing grounds, and in others is greatly diminished in numbers.
What special functions, besides his uses to man, are assigned to the
whale in the economy of nature, we do not know; but some considerations,
suggested by the character of the food upon which certain species
subsist, deserve to be specially noticed. None of the great mammals
grouped under the general name of whale are rapacious. They all live
upon small organisms, and the most numerous species feed almost wholly
upon the soft gelatinous mollusks in which the sea abounds in all
latitudes. We cannot calculate even approximately the number of the
whales, or the quantity of organic nutriment consumed by an individual,
and of course we can form no estimate of the total amount of animal
matter withdrawn by them, in a given period, from the waters of the sea.
It is certain, however, that it must have been enormous when they were
more abundant, and that it is still very considerable. A very few years
since, the United States had more than six hundred whaling ships
constantly employed in the Pacific, and the product of the American
whale fishery for the year ending June 1st, 1860, was seven millions and
a half of dollars.[99] The mere bulk of the whales destroyed in a single
year by the American and the European vessels engaged in this fishery
would form an island of no inconsiderable dimensions, and each one of
those taken must have consumed, in the course of his growth, many times
his own weight of mollusks. The destruction of the whales must have been
followed by a proportional increase of the organisms they feed upon, and
if we had the means of comparing the statistics of these humble forms of
life, for even so short a period as that between the years 1760 and
1860, we should find a difference sufficient, possibly, to suggest an
explanation of some phenomena at present unaccounted for.
For instance, as I have observed in another work,[100] the
phosphorescence of the sea was unknown to ancient writers, or at least
scarcely noticed by them, and even Homer--who, blind as tradition makes
him when he composed his epics, had seen, and marked, in earlier life,
all that the glorious nature of the Mediterranean and its coasts
discloses to unscientific observation--nowhere alludes to this most
beautiful and striking of maritime wonders. In the passage just referred
to, I have endeavored to explain the silence of ancient writers with
respect to this as well as other remarkable phenomena on psychological
grounds; but is it not possible that, in modern times, the animalculae
which produce it may have immensely multiplied, from the destruction of
their natural enemies by man, and hence that the gleam shot forth by
their decomposition, or by their living processes, is both more frequent
and more brilliant than in the days of classic antiquity?
Although the whale does not prey upon smaller creatures resembling
himself in form and habits, yet true fishes are extremely voracious, and
almost every tribe devours unsparingly the feebler species, and even
the spawn and young of its own. The enormous destruction of the pike,
the trout family, and other ravenous fish, as well as of the fishing
birds, the seal, and the otter, by man, would naturally have occasioned
a great increase in the weaker and more defenceless fish on which they
feed, had he not been as hostile to them also as to their persecutors.
We have little evidence that any fish employed as human food has
naturally multiplied in modern times, while all the more valuable tribes
have been immensely reduced in numbers.[101] This reduction must have
affected the more voracious species not used as food by man, and
accordingly the shark, and other fish of similar habits, though not
objects of systematic pursuit, are now comparatively rare in many waters
where they formerly abounded. The result is, that man has greatly
reduced the numbers of all larger marine animals, and consequently
indirectly favored the multiplication of the smaller aquatic organisms
which entered into their nutriment. This change in the relations of the
organic and inorganic matter of the sea must have exercised an influence
on the latter. What that influence has been, we cannot say, still less
can we predict what it will be hereafter; but its action is not for that
reason the less certain.
_Introduction and Breeding of Fish._
The introduction and successful breeding of fish of foreign species
appears to have been long practised in China and was not unknown to the
Greeks and Romans. This art has been revived in modern times, but thus
far without any important results, economical or physical, though there
seems to be good reason to believe it may be employed with advantage on
an extended scale. As in the case of plants, man has sometimes
undesignedly introduced new species of aquatic animals into countries
distant from their birthplace. The accidental escape of the Chinese
goldfish from ponds where they were bred as a garden ornament, has
peopled some European, and it is said American streams with this
species. Canals of navigation and irrigation interchange the fish of
lakes and rivers widely separated by natural barriers, as well as the
plants which drop their seeds into the waters. The Erie Canal, as
measured by its own channel, has a length of about three hundred and
sixty miles, and it has ascending and descending locks in both
directions. By this route, the fresh-water fish of the Hudson and the
Upper Lakes, and some of the indigenous vegetables of these respective
basins, have intermixed, and the fauna and flora of the two regions have
now more species common to both than before the canal was opened. Some
accidental attraction not unfrequently induces fish to follow a vessel
for days in succession, and they may thus be enticed into zones very
distant from their native habitat. Several years ago, I was told at
Constantinople, upon good authority, that a couple of fish, of a species
wholly unknown to the natives, had just been taken in the Bosphorus.
They were alleged to have followed an English ship from the Thames, and
to have been frequently observed by the crew during the passage, but I
was unable to learn their specific character.
Many of the fish which pass the greater part of the year in salt water
spawn in fresh, and some fresh-water species, the common brook trout of
New England for instance, which, under ordinary circumstances, never
visit the sea, will, if transferred to brooks emptying directly into the
ocean, go down into the salt water after spawning time, and return again
the next season. Sea fish, the smelt among others, are said to have been
naturalized in fresh water, and some naturalists have argued from the
character of the fish of Lake Baikal, and especially from the existence
of the seal in that locality, that all its inhabitants were originally
marine species, and have changed their habits with the gradual
conversion of the saline waters of the lake--once, as is assumed, a
maritime bay--into fresh.[102] The presence of the seal is hardly
conclusive on this point, for it is sometimes seen in Lake Champlain at
the distance of some hundreds of miles from even brackish water. One of
these animals was killed on the ice in that lake in February, 1810,
another in February, 1846,[103] and remains of the seal have been found
at other times in the same waters.
The remains of the higher orders of aquatic animals are generally so
perishable that, even where most abundant, they do not appear to be now
forming permanent deposits of any considerable magnitude; but it is
quite otherwise with shell fish, and, as we shall see hereafter, with
many of the minute limeworkers of the sea. There are, on the southern
coast of the United States, beds of shells so extensive that they were
formerly supposed to have been naturally accumulated, and were appealed
to as proofs of an elevation of the coast by geological causes; but they
are now ascertained to have been derived from oysters, consumed in the
course of long ages by the inhabitants of Indian towns. The planting of
a bed of oysters in a new locality might, very probably, lead, in time,
to the formation of a bank, which, in connection with other deposits,
might perceptibly affect the line of a coast, or, by changing the course
of marine currents, or the outlet of a river, produce geographical
changes of no small importance. The transplantation of oysters to
artificial ponds has long been common, and it appears to have recently
succeeded well on a large scale in the open sea on the French coast. A
great extension of this fishery is hoped for, and it is now proposed to
introduce upon the same coast the American soft clam, which is so
abundant in the tide-washed beach sands of Long Island Sound as to form
an important article in the diet of the neighboring population.
The intentional naturalization of foreign fish, as I have said, has not
thus far yielded important fruits; but though this particular branch of
what is called, not very happily, _pisciculture_, has not yet
established its claims to the attention of the physical geographer or
the political economist, the artificial breeding of domestic fish has
already produced very valuable results, and is apparently destined to
occupy an extremely conspicuous place in the history of man's efforts to
compensate his prodigal waste of the gifts of nature. The restoration of
the primitive abundance of salt and fresh water fish, is one of the
greatest material benefits that, with our present physical resources,
governments can hope to confer upon their subjects. The rivers, lakes,
and seacoasts once restocked, and protected by law from exhaustion by
taking fish at improper seasons, by destructive methods, and in
extravagant quantities, would continue indefinitely to furnish a very
large supply of most healthful food, which, unlike all domestic and
agricultural products, would spontaneously renew itself and cost nothing
but the taking. There are many sterile or wornout soils in Europe so
situated that they might, at no very formidable cost, be converted into
permanent lakes, which would serve not only as reservoirs to retain the
water of winter rains and snow, and give it out in the dry season for
irrigation, but as breeding ponds for fish, and would thus, without
further cost, yield a larger supply of human food than can at present be
obtained from them even at a great expenditure of capital and labor in
agricultural operations. The additions which might be made to the
nutriment of the civilized world by a judicious administration of the
resources of the waters, would allow some restriction of the amount of
soil at present employed for agricultural purposes, and a corresponding
extension of the area of the forest, and would thus facilitate a return
to primitive geographical arrangements which it is important partially
to restore.
_Extirpation of Aquatic Animals._
It does not seem probable that man, with all his rapacity and all his
enginery, will succeed in totally extirpating any salt-water fish, but
he has already exterminated at least one marine warm-blooded
animal--Steller's sea cow--and the walrus, the sea lion, and other large
amphibia, as well as the principal fishing quadrupeds, are in imminent
danger of extinction. Steller's sea cow, _Rhytina Stelleri_, was first
seen by Europeans in the year 1741, on Bering's Island. It was a huge
amphibious mammal, weighing not less than eight thousand pounds, and
appears to have been confined exclusively to the islands and coasts in
the neighborhood of Bering's Strait. Its flesh was very palatable, and
the localities it frequented were easily accessible from the Russian
establishments in Kamtschatka. As soon as its existence and character,
and the abundance of fur animals in the same waters, were made known to
the occupants of those posts by the return of the survivors of Bering's
expedition, so active a chase was commenced against the amphibia of that
region, that, in the course of twenty-seven years, the sea cow,
described by Steller as extremely numerous in 1741, is believed to have
been completely extirpated, not a single individual having been seen
since the year 1768. The various tribes of seals in the Northern and
Southern Pacific, the walrus and the sea otter, are already so reduced
in numbers that they seem destined soon to follow the sea cow, unless
protected by legislation stringent enough, and a police energetic
enough, to repress the ardent cupidity of their pursuers.
The seals, the otter tribe, and many other amphibia which feed almost
exclusively upon fish, are extremely voracious, and of course their
destruction or numerical reduction must have favored the multiplication
of the species of fish principally preyed upon by them. I have been
assured by the keeper of several tamed seals that, if supplied at
frequent intervals, each seal would devour not less than fourteen pounds
of fish, or about a quarter of his own weight, in a day.[104] A very
intelligent and observing hunter, who has passed a great part of his
life in the forest, after carefully watching the habits of the
fresh-water otter of the Northern American States, estimates their
consumption of fish at about four pounds per day.
Man has promoted the multiplication of fish by making war on their brute
enemies, but he has by no means thereby compensated his own greater
destructiveness.[105] The bird and beast of prey, whether on land or in
the water, hunt only as long as they feel the stimulus of hunger, their
ravages are limited by the demands of present appetite, and they do not
wastefully destroy what they cannot consume. Man, on the contrary,
angles to-day that he may dine to-morrow; he takes and dries millions of
fish on the banks of Newfoundland, that the fervent Catholic of the
shores of the Mediterranean may have wherewithal to satisfy the cravings
of the stomach during next year's Lent, without imperilling his soul by
violating the discipline of the papal church; and all the arrangements
of his fisheries are so organized as to involve the destruction of many
more fish than are secured for human use, and the loss of a large
proportion of the annual harvest of the sea in the process of curing, or
in transportation to the places of its consumption.[106]
Fish are more affected than quadrupeds by slight and even imperceptible
differences in their breeding places and feeding grounds. Every river,
every brook, every lake stamps a special character upon its salmon, its
shad, and its trout, which is at once recognized by those who deal in or
consume them. No skill can give the fish fattened by food selected and
prepared by man the flavor of those which are nourished at the table of
nature, and the trout of the artificial ponds in Germany and Switzerland
are so inferior to the brook fish of the same species and climate, that
it is hard to believe them identical. The superior sapidity of the
American trout to the European species, which is familiar to every one
acquainted with both continents, is probably due less to specific
difference than to the fact that, even in the parts of the New World
which have been longest cultivated, wild nature is not yet tamed down to
the character it has assumed in the Old, and which it will acquire in
America also when her civilization shall be as ancient as is now that of
Europe.
Man has hitherto hardly anywhere produced such climatic or other changes
as would suffice of themselves totally to banish the wild inhabitants of
the dry land, and the disappearance of the native birds and quadrupeds
from particular localities is to be ascribed quite as much to his direct
persecutions as to the want of forest shelter, of appropriate food, or
of other conditions indispensable to their existence. But almost all the
processes of agriculture, and of mechanical and chemical industry, are
fatally destructive to aquatic animals within reach of their influence.
When, in consequence of clearing the woods, the changes already
described as thereby produced in the beds and currents of rivers, are in
progress, the spawning grounds of fish are exposed from year to year to
a succession of mechanical disturbances; the temperature of the water is
higher in summer, colder in winter, than when it was shaded and
protected by wood; the smaller organisms, which formed the sustenance of
the young fry, disappear or are reduced in numbers, and new enemies are
added to the old foes that preyed upon them; the increased turbidness of
the water in the annual inundations chokes the fish; and, finally, the
quickened velocity of its current sweeps them down into the larger
rivers or into the sea, before they are yet strong enough to support so
great a change of circumstances.[107] Industrial operations are not
less destructive to fish which live or spawn in fresh water. Milldams
impede their migrations, if they do not absolutely prevent them, the
sawdust from lumber mills clogs their gills, and the thousand
deleterious mineral substances, discharged into rivers from
metallurgical, chemical, and manufacturing establishments, poison them
by shoals.
_Minute Organisms._
Besides the larger creatures of the land and of the sea, the quadrupeds,
the reptiles, the birds, the amphibia, the crustacea, the fish, the
insects, and the worms, there are other countless forms of vital being.
Earth, water, the ducts and fluids of vegetable and of animal life, the
very air we breathe, are peopled by minute organisms which perform most
important functions in both the living and the inanimate kingdoms of
nature. Of the offices assigned to these creatures, the most familiar to
common observation is the extraction of lime, and more rarely, of silex,
from the waters inhabited by them, and the deposit of these minerals in
a solid form, either as the material of their habitations or as the
exuviae of their bodies. The microscope and other means of scientific
observation assure us that the chalk beds of England and of France, the
coral reefs of marine waters in warm climates, vast calcareous and
silicious deposits in the sea and in many fresh-water ponds, the common
polishing earths and slates, and many species of apparently dense and
solid rock, are the work of the humble organisms of which I speak,
often, indeed, of animalculae so small as to become visible only by the
aid of lenses magnifying a hundred times the linear measures. It is
popularly supposed that animalculae, or what are commonly embraced under
the vague name of infusoria, inhabit the water alone, but the
atmospheric dust transported by every wind and deposited by every calm
is full of microscopic life or of its relics. The soil on which the city
of Berlin stands, contains at the depth of ten or fifteen feet below the
surface, living elaborators of silex;[108] and a microscopic examination
of a handful of earth connected with the material evidences of guilt has
enabled the naturalist to point out the very spot where a crime was
committed. It has been computed that one sixth part of the solid matter
let fall by great rivers at their outlets consists of still recognizable
infusory shells and shields, and, as the friction of rolling water must
reduce much of these fragile structures to a state of comminution which
even the microscope cannot resolve into distinct particles and identify
as relics of animal or of vegetable life, we must conclude that a
considerably larger proportion of river deposits is really the product
of animalcules.[109]
It is evident that the chemical, and in many cases the mechanical
character of a great number of the objects important in the material
economy of human life, must be affected by the presence of so large an
organic element in their substance, and it is equally obvious that all
agricultural and all industrial operations tend to disturb the natural
arrangements of this element, to increase or to diminish the special
adaptation of every medium in which it lives to the particular orders
of being inhabited by it. The conversion of woodland into pasturage, of
pasture into plough land, of swamp or of shallow sea into dry ground,
the rotations of cultivated crops, must prove fatal to millions of
living things upon every rood of surface thus deranged by man, and must,
at the same time, more or less fully compensate this destruction of life
by promoting the growth and multiplication of other tribes equally
minute in dimensions.
I do not know that man has yet endeavored to avail himself, by
artificial contrivances, of the agency of these wonderful architects and
manufacturers. We are hardly well enough acquainted with their natural
economy to devise means to turn their industry to profitable account,
and they are in very many cases too slow in producing visible results
for an age so impatient as ours. The over-civilization of the nineteenth
century cannot wait for wealth to be amassed by infinitesimal gains, and
we are in haste to _speculate_ upon the powers of nature, as we do upon
objects of bargain and sale in our trafficking one with another. But
there are still some cases where the little we know of a life, whose
workings are invisible to the naked eye, suggests the possibility of
advantageously directing the efforts of troops of artisans that we
cannot see. Upon coasts occupied by the corallines, the reef-building
animalcule does not work near the mouth of rivers. Hence the change of
the outlet of a stream, often a very easy matter, may promote the
construction of a barrier to coast navigation at one point, and check
the formation of a reef at another, by diverting a current of fresh
water from the former and pouring it into the sea at the latter. Cases
may probably be found in tropical seas, where rivers have prevented the
working of the coral animalcules in straits separating islands from each
other or from the mainland. The diversion of such streams might remove
this obstacle, and reefs consequently be formed which should convert an
archipelago into a single large island, and finally join that to the
neighboring continent.
Quatrefages proposed to destroy the teredo in harbors by impregnating
the water with a mineral solution fatal to them. Perhaps the labors of
the coralline animals might be arrested over a considerable extent of
sea coast by similar means. The reef builders are leisurely architects,
but the precious coral is formed so rapidly that the beds may be
refished advantageously as often as once in ten years.[110] It does not
seem impossible that this coral might be transplanted to the American
coast, where the Gulf stream would furnish a suitable temperature beyond
the climatic limits that otherwise confine its growth; and thus a new
source of profit might perhaps be added to the scanty returns of the
hardy fisherman.
In certain geological formations, the diatomaceae deposit, at the bottom
of fresh-water ponds, beds of silicious shields, valuable as a material
for a species of very light firebrick, in the manufacture of water glass
and of hydraulic cement, and ultimately, doubtless, in many yet
undiscovered industrial processes. An attentive study of the conditions
favorable to the propagation of the diatomaceae might perhaps help us to
profit directly by the productivity of this organism, and, at the same
time, disclose secrets of nature capable of being turned to valuable
account in dealing with silicious rocks, and the metal which is the base
of them. Our acquaintance with the obscure and infinitesimal life of
which I have now been treating is very recent, and still very imperfect.
We know that it is of vast importance in the economy of nature, but we
are so ambitious to grasp the great, so little accustomed to occupy
ourselves with the minute, that we are not yet prepared to enter
seriously upon the question how far we can control and direct the
operations, not of unembodied physical forces, but of beings, in popular
apprehension, almost as immaterial as they.
Nature has no unit of magnitude by which she measures her works. Man
takes his standards of dimension from himself. The hair's breadth was
his minimum until the microscope told him that there are animated
creatures to which one of the hairs of his head is a larger cylinder
than is the trunk of the giant California redwood to him. He borrows his
inch from the breadth of his thumb, his palm and span from the width of
his hand and the spread of his fingers, his foot from the length of the
organ so named; his cubit is the distance from the tip of his middle
finger to his elbow, and his fathom is the space he can measure with his
outstretched arms. To a being who instinctively finds the standard of
all magnitudes in his own material frame, all objects exceeding his own
dimensions are absolutely great, all falling short of them absolutely
small. Hence we habitually regard the whale and the elephant as
essentially large and therefore important creatures, the animalcule as
an essentially small and therefore unimportant organism. But no
geological formation owes its origin to the labors or the remains of the
huge mammal, while the animalcule composes, or has furnished, the
substance of strata thousands of feet in thickness, and extending, in
unbroken beds, over many degrees of terrestrial surface. If man is
destined to inhabit the earth much longer, and to advance in natural
knowledge with the rapidity which has marked his progress in physical
science for the last two or three centuries, he will learn to put a
wiser estimate on the works of creation, and will derive not only great
instruction from studying the ways of nature in her obscurest, humblest
walks, but great material advantage from stimulating her productive
energies in provinces of her empire hitherto regarded as forever
inaccessible, utterly barren.[111]