Page 254 - Environment: The Science Behind the Stories

All told, the landscape-level (pp.
131–133) McKinney Flats project may be
New
Arizona the largest replicated terrestrial ecological
Mexico
experiment in North America. It has helped
Malpai Borderlands
spur a number of other research initiatives,
and the Malpai Borderlands Group now
hosts a scientific conference each year
featuring research from the region.
The scientists have also helped
ranchers develop a cycle of “grass-
banking,” in which cattle are allowed
to graze on shared plots of land while
other areas recover. Ranchers must
also work with the weather. Scientists
have found that controlled burns or
grassbanking should track with cycles
Figure 1 To restore native grasslands, the Malpai borderlands group reinstated fire as of rain and drought to bring back grass.
a landscape process, conducting controlled burns. Monitoring indicates that restoring fire Because of such research, con-
has improved ecological conditions in the region. trolled burns are now a regular part of
the Malpai landscape. Ranchers have
burned more than 100,000 ha (250,000
monitor each treatment for the distribu- acres) since 1994, and natural fires
tion and abundance of birds, insects, are often allowed to run their course
animals, and vegetation (Figure 2). with little or no intervention. Damaged
By comparing areas where fire is
suppressed to those where fire can areas have been reseeded with native
grasses.
burn, researchers have documented Scientists increasingly believe
how the suppression of fire leads to that sustainable ranching, if managed
more brush and trees and less grass. properly, can help restore grasslands
Conversely, when fire burns an area, damaged by overgrazing. “We cannot
woody plants such as mesquite trees assume rangelands will recover on
are damaged and their seed production their own,’’ Curtin wrote in a recent
is disrupted, and grass subsequently study on the Malpai Borderlands.
returns to replace the trees. Such “Conservation of grazed lands
changes follow both natural fires and Figure 2 researchers measure requires restoring and sustaining
carefully monitored, deliberately set vegetation on research plots in the natural processes.”
controlled burns. Malpai borderlands.

crops that require a great deal of water in areas prone to be used as food or pasture. A third option is to bring in large
salinization. A second way is to irrigate with water low in quantities of less-saline water with which to flush the soil. CHAPTER 9 • So I l AN d A gr I culT ure
salt content. A third way is to irrigate efficiently, supply- However, using too much water may cause waterlogging.
ing no more water than a crop requires. This minimizes the
amount of water that evaporates and hence the amount of salt
that accumulates in the topsoil. Fertilizers boost crop yields but can
If salinization has occurred, one potential way to miti- be overapplied
gate it is to stop irrigating and wait for rain to flush salts
from the soil. However, this solution is unrealistic because Plants require nitrogen, phosphorus, and potassium to grow, as
in dryland areas where salinization is most often a problem, well as smaller amounts of over a dozen other nutrients. Plants
precipitation is rarely adequate to flush soils. A better option remove these nutrients from soil as they grow, and leach-
may be to plant salt-tolerant plants, such as barley, that can ing likewise removes nutrients. If agricultural soils come to 253

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