Agriculture Reference
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from severe land degradation. Dregne concludes that desertification “will blunt crop
production increases in the subhumid and semiarid regions of the United States and
Mexico, as well as in the Central American mountains.” In South America, “land
degradation is most severe on the cultivated lands of the Andes Mountains” and “water
and wind erosion have damaged some Argentine farmland.” Dregne also emphasizes
the fragility of soils in the Amazon Basin, where deforestation and encouragement of
development have been intensifying in more recent years.
Among the many environmental problems now facing less developed countries
(LDCs), soil erosion has the most serious economic consequences. If allowed to
continue at current rates, soil loss will reduce many countries' capacity for agricul-
tural production (Wolman 1993). Also, erosion is causing sizable external costs in
the third world; soil washed from agricultural and other land is being deposited in
reservoirs, irrigation canals, and navigable waterways at high rates.
Rapp (1977) and Robinson (1981) suggest that this experience is by no means
restricted to Latin America, and Linsley and Franzini (1979) argue that it is not
limited to developing countries. National aggregate off-site cost estimates for soil
erosion established the magnitude of the problem in the United States over 25 years
ago. Clark et al. (1985) estimated total annual off-farm costs for all agricultural ero-
sion sources to range between $3 and $13 billion with a point estimate of $6.1 billion,
of which $2.2 billion was attributed to cropland erosion (in 1980 dollars). Damage to
recreational uses accounted for the largest share of costs—comprising nearly 33%
of total costs—and boating was the largest recreation subgroup. Other high impact
receptors or users and their percent of total costs included municipal and industrial
(14.8%), water storage facilities (11.3%), dredging (8.5%), and preservation values
(8.2%). Cropland erosion was the largest source at 38% of total erosion. A reanalysis
of these results suggested a $7.1 billion point estimate (Ribaudo 1986a).
Later analysis of the Conservation Reserve Program (CRP) by Ribaudo et al.
(1989) found that water quality benefits from the first 23 million acres enrolled in
the CRP totaled $2.05 billion or an average of $219.83 per hectare. This suggests
that Ribaudo's 1986 point estimate should be adjusted downward by about $2 billion.
However, both the Clark and Ribaudo analyses omit several categories of down-
stream impacts (e.g., dredge spoil disposal, delays to commercial shipping, biologi-
cal impacts, etc.), which may make their estimates very conservative. More recent
concerns in the United States have shifted to loss of CRP acres due to tight federal
budgets and a reduced cap on CRP enrollment, perceived to be needed to get these
acres back into crop production with high corn and soybean prices driven in part by
corn ethanol tariffs and subsidies (Kiger 2009; Wright 2011).
Clearly, any threat to the longevity of existing and future water resource develop-
ments could have serious repercussions and warrants careful evaluation and plan-
ning. The primary and most immediate threat to hydroelectric and other water
storage projects is sedimentation. A major cause is excessive erosion from watershed
overuse or misuse. In many LDCs, the general pattern of heavy land use leading
to high erosion rates results from a combination of traditional shifting agriculture
and population growth. In reservoir watersheds, this pattern may be preexisting,
or the reservoir project may, as with the Anchicaya reservoir in Columbia reported
by Allen (1972), provide the access route for transient farmers into a previously
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