It is generally recognized that a potent influence is exerted by
man, and the lower animals, in shaping the flora of an arid region,
not only as regards the kind and number of plants, but also as
concerns certain of the leading characteristics of the plants
themselves. The action is largely such as brings about a survival
of the “useless” forms, so that we do not know, from the plants
we meet in the desert to-day, how many or what kinds of plants it
might support. It also may be true that no desert shows the modifying
effects of the causes suggested more than the northern Sahara.
The gazelle (_Gazella dorcas_) is the leading wild animal preying
upon the desert plants in the northern Sahara. It is frequently
seen by the traveler to-day and was present in large numbers no
longer ago than 50 years (Tristram). It is said by the Arabs to
feed on the fresh shoots and leaves of many species of shrubs and
trees, especially the betoum (_Pistacia atlantica_), as well as on
the annual vegetation for the relatively short period when it is
to be had. Other species of gazelle, according to Tristram, range
farther to the south. Other herbivorous animals of the region are
hares, antelope, moufflon, and bubale. The moufflon, at the time of
Tristram’s visit, was “far from uncommon throughout the whole of
the mountain districts, whether wooded or bare,” but the bubale,
“the wildest of the wild game of North Africa,” appears not to
go north of the Oued Rirh, while its home is farther south. It is
impossible to know the number of wild animals subsisting on native
desert vegetation, but the list given, which might be extended,
suggests that it is by no means small. Although the population
of wild herbivorous animals is at present considerable, it was
probably much greater a few years ago, the decrease being due,
as Tristram says, not so much to the greatly increased population
as to the more efficient weapons used by the Arabs in hunting.[11]
Laghouat has been inhabited by the Arabs continuously for about
1,000 years, during which time the oasis and its environs have
been the source of supply of all of the fuel used and for much,
if not the most, of the food consumed both by the Arab and his
flocks. Naturally, the food for the inhabitants of the oasis is
won from the oasis itself, but that for the beasts is derived from
the desert. While it is impossible to learn the number of sheep,
camels, and goats which from century to century have ranged over
the desert pastures, there is no reason for supposing it was not
large, as at present is the case. For example, in the department
of Algiers, in 1907-08, the number of sheep is reported to have
been 2,109,071; of goats 1,156,500, and of camels 23,912.[12] Of
these a large percentage is to be found in and to the south of the
Saharan Atlas Mountains. In portions of the colony farther south,
or in regions even more desertic than at Laghouat, the number of
camels, sheep, and goats is surprisingly large. The statistics
for 1907-08 give the population of the three classes of animals in
the southern territories, that is, the territories of Ain-Sefra,
Ghardaia, Touggourt, and the oases of the Sahara, as follows: sheep,
1,932,392; goats, 588,121; camels, 126,088.
The flocks of sheep and goats range at various distances from the
source of their water-supply. It is quite usual for the goatherds
to gather their flocks in early morning, returning to the oasis
in the evening to distribute the goats to their various owners;
but probably in most cases the flocks of sheep, with some goats,
return to water once in two or three days, thus being able to stray
from 20 to 40 kilometers into the desert. Being less dependent on
water, the camels range a much greater distance. It thus appears
that the area grazed over by the flocks of the Arabs is fairly
circular in form, with a radius of 40 or more kilometers from the
wells, and that the range of the camels may be much greater than
this. It should also be noted that the caravan routes are broad
tracts where all vegetation fit for fuel or food has been utilized
Between the two sources of destruction referred to, the stationary
and continuous and the frequent but not continuous, little territory
passes untouched as a source of food-supply.
A visit to the wood markets of the town indicates to what ends the
natives resort to obtain fuel. (See figs. 2 and 3.) Among many kinds
of wood, some are from the oasis itself, such as the willow, plane,
and palm; some from the mountains, like juniper, pine, and oak;
and some from the oued, like the jujube and _Tamarix_. Much of the
fuel is at present brought three days’ journey by camel. Usually
the subaerial portions only of the plants are used, but in the
case of the jujube both root and branches are gathered. The fuel
requirements have apparently brought about the extinction of some
species from certain of their earlier habitats; for example, the
betoum (_Pistacia atlantica_) probably formerly either grew in the
oasis of Laghouat or near by, since it was formerly in common use
as a fuel. Tristram mentions the betoum, and no other species,
as a source of fuel, but inquiry failed to show that at present
this species is in general use for this purpose; but the betoum
is a familiar sight in the region of the dayas south of Laghouat,
where it is the only arboreal species of the region.
From what has been said regarding the large numbers of domestic
animals that gain their entire living on the desert, it follows
that of plants growing within the range of the flocks only such
as are poisonous, distasteful, armed, or otherwise protected,
escape partial or complete consumption. Only such species as are
too small for fuel or can not be eaten by animals attain to the
usual development year by year. In the vicinity of Laghouat the
most prominent of the immune plants is the quedad (_Acanthyllis
tragacanthoides_), which is well protected by its stout spines;
and even this species is not wholly undisturbed. The jujube, also,
although not common here, is provided with short spines. It is
stated by Massart[13] that the camels used by him, not having eaten
for five days, consumed the branches of the jujube in spite of the
spines, and that _Anvillea radiata_, a composite with acrid juice,
was passed by. Perhaps the plants most frequently eaten are of
the genus _Haloxylon_, generally distributed from the High Plateau
southward into the region of the M’Zab. That this genus is not
exterminated is interesting, since it is rarely permitted to come
into flower and fruit, and it appears not to reproduce to any extent,
if at all, in a vegetative way.
=FROM LAGHOUAT TO GHARDAIA.=