At the local level, individuals and governments can help to reclaim and
protect their lands. In areas of sand dunes, covering the dunes with
large boulders or petroleum will interrupt the wind regime near the face
of the dunes and prevent the sand from moving. Sand fences are used
throughout the Middle East and the United States, in the same way snow
fences are used in the north. Placement of straw grids, each up to a
square meter in area, will also decrease the surface wind velocity.
Shrubs and trees planted within the grids are protected by the straw
until they take root. In areas where some water is available for
irrigation, shrubs planted on the lower one-third of a dune’s windward
side will stabilize the dune. This vegetation decreases the wind
velocity near the base of the dune and prevents much of the sand from
moving. Higher velocity winds at the top of the dune level it off and
trees can be planted atop these flattened surfaces.
[Illustration: Straw grids (one of which is shown above) and vegetation
irrigated by water from the Yellow River stabilize dunes in this part of
China’s Tengger Desert (shown below) and protect a nearby railroad from
windblown sand.]
[Illustration: Tengger Desert]
Oases and farmlands in windy regions can be protected by planting tree
fences or grass belts. Sand that manages to pass through the grass belts
can be caught in strips of trees planted as wind breaks 50 to 100 meters
apart adjacent to the belts. Small plots of trees may also be scattered
inside oases to stabilize the area. On a much larger scale, a “Green
Wall,” which will eventually stretch more than 5,700 kilometers in
length, much longer than the famous Great Wall, is being planted in
northeastern China to protect “sandy lands”—deserts believed to have
been created by human activity.
More efficient use of existing water resources and control of
salinization are other effective tools for improving arid lands. New
ways are being sought to use surface-water resources such as rain water
harvesting or irrigating with seasonal runoff from adjacent highlands.
New ways are also being sought to find and tap groundwater resources and
to develop more effective ways of irrigating arid and semiarid lands.
Research on the reclamation of deserts also is focusing on discovering
proper crop rotation to protect the fragile soil, on understanding how
sand-fixing plants can be adapted to local environments, and on how
grazing lands and water resources can be developed effectively without
being overused.
[Illustration: From wasteland to vineyard. Ground water and underground
channels help this vineyard flourish on land reclaimed from desert
pavement in China’s Turpan Depression.]
If we are to stop and reverse the degradation of arid and semiarid
lands, we must understand how and why the rates of climate change,
population growth, and food production adversely affect these
environments. The most effective intervention can come only from the
wise use of the best earth-science information available.