Grasslands of the World.pdf - Disasters and Conflicts - UNEP

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Grasslands of the world
with wildlife and sometimes a change in soils when use is prolonged and heavy.
The impacts depend to some degree on the level and variability of rainfall
(Ellis and Swift, 1988). In areas of southern Ethiopia with more and reliable
rainfall supporting perennial vegetation (an equilibrium grazing system ), the
impacts of grazing in one season can reduce vegetative cover and production
in the next (Coppock, 1994). In systems on the edge of perennial grass production,
heavy grazing, especially in combination with drought , can reduce
vegetative cover and production, even during subsequent wet years when more
lightly grazed areas recover fully (de Queiroz, 1993). In systems with low and
erratic rainfall (non-equilibrium systems), heavy grazing may (Milchunas and
Laurenroth, 1993) or may not (Hiernaux, 1996) strongly influence production
in subsequent seasons. Heavy grazing in annual grasslands changes the species
composition of grassland vegetation, with more species in areas protected from
grazing and fewer in heavily grazed areas (Hiernaux, 1998).
The nature of interrelationships and thresholds between biophysical,
socio-economic, institutional and policy factors at different spatial scales and
temporal dimensions influencing land degradation and desertification are
still poorly understood. A recent initiative on land degradation assessment
in drylands (LADA project), executed by FAO, responds to the need for an
accurate assessment of land degradation in drylands at a flexible scale and to
strengthen support to plan actions and investments to reverse land degradation,
improve socio-economic livelihoods, conserve dryland ecosystems and their
unique biological diversity (see: http:/www.fao.org/ag/agl/agll/lada/home.
stm). Besides developing a set of tools and methods to assess and quantify
the nature, extent , severity and impacts of land degradation on ecosystems,
catchments, river basins and carbon storage in drylands at a range of spatial
and temporal scales, the project also aims to build national, regional and global
assessment capacities to enable the design and planning of interventions to
mitigate land degradation and establish sustainable land use and management
practices (Nachtergaele, 2002).
Another useful livestock evaluation tool to enhance early warning systems
to detect changes in livestock condition is being developed under the USAID
Global Livestock Collaborative Research Support Program (CRSP) by Texas
A&M University (Corbett et al., 1998). The Livestock Early Warning System
(LEWS) integrates advanced crop and grazing models , based on empirical
relationships between weather, vegetation , regrowth potential, soil and climate
dynamics , with near infra-red spectroscopy (NIRS) for faecal analysis to detect
changes in diet of free ranging livestock. These changes are linked to changes
in vegetation patterns and can be used to predict drought and feed shortages
for livestock some 6 to 8 weeks before pastoralists begin to see changes in the
condition of the rangelands and their livestock. This allows them to better prepare
for the coming feed shortages and nutritional crises in a timely manner by
transhumance , as well as avoiding overgrazing of the rangeland resources .