Agriculture Reference
In-Depth Information
desertification and the associated loss of economic stability and ecological integrity
will continue to threaten the sustainability of natural resources and people in the
Great Basin (Pellant et al. 2004).
4.5 SUMMARY
Grasslands constitute the largest global land use and are an important part of agri-
cultural and ecological systems on every continent, across a wide range of potential
productivity. Ruminant livestock grazing on these lands constitutes an important
form of agricultural production. It is estimated that 1 billion people depend almost
exclusively on livestock, and livestock serves as at least a partial source of income
and food security for 70% of the world's 880 million rural poor who live on less than
US$ 1 per day. Grazing lands provide a wide range of ecosystem services, including
provision of food, livelihoods, biodiversity, habitat, carbon storage, water filtration,
and others. Grazing lands are particularly important in the world's dry land areas,
which are especially sensitive to land degradation.
The Millennium Ecosystem Assessment (2005) found that 10%-20% of dry lands
were degraded. Additionally, the world's grazing lands are subject to pressures of
increasing population, encroachment of cropping onto former grasslands, uncertain
land tenure, lack of infrastructure (transportation, markets), lack of capital, and are
faced with increasing pressures of variable and changing climate. More than 70% of
the rangelands worldwide are estimated to be affected by soil degradation.
Grazing lands are highly diverse, and there are many opportunities to enhance
soil quality; however, results in the literature about impacts of grazing on soil qual-
ity have been mixed. In dry regions, rangelands are particularly vulnerable to deg-
radation and it is essential that the vegetative and plant litter cover be maintained
to protect the soil from raindrop impact and temperature extremes. In many cases,
excessive grazing has resulted in severe soil degradation. In other situations, where
grazing timing, duration, and intensity are managed, the effects of grazing have had
neutral or positive effects on soil quality characteristics. As demand for cropland
increases, there are many opportunities for mixed crop-livestock systems that may
provide environmental as well as economic benefits. Science must continue to evalu-
ate grazing systems to develop better predictive understanding of the degradation
and regeneration processes of grassland agroecosystems to more effectively develop
improved management practices and systems.
In the future, the pressures on fragile grassland ecosystems will only increase
with increased human population, increased demand for cropland and bioenergy,
increased demand for livestock products, and increasing climate variability and
change. Policies to address these challenges must address the intertwined issues of
poverty, malnutrition and health challenges, and land degradation in pastoral regions.
ACKNOWLEDGMENT
The authors appreciate the review of the draft versions of the manuscript, and the
helpful feedback from Dr. Jan de Leeuw, World Agroforestry Centre (ICRAF),
Nairobi, Kenya.
