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

The changing face of pastoral systems in grass-dominated ecosystems of eastern Africa 21
peoples living in the region, whose livelihoods depend on livestock. These
traditional and often sustainable ways are now being threatened by agricultural
development , the need to produce more food from marginal lands, population
growth and global climate change. Fluctuations in rainfall and drought are
recurring problems in the rangelands of the region and 70 million people in
the Horn of Africa, many of whom are pastoralists, suffer from long-term
chronic food insecurity (FAO, 2000). Poverty levels are high, with more than
half of the people in the region surviving on less than US$ 1 per day (Thornton
et al., 2002). The population of the region has doubled since 1974, and it is
predicted to increase another 40 percent by 2015 (FAO, 2000). Against this
background, the traditional ways of pastoralists continue to change, and many
are settling (or are settled) and diversifying their income-generating activities
into crop production, wage labour and other activities, while other family
members continue to herd the family stock and move to follow the availability
of forage.
This chapter examines the changes in pastoral rangeland systems in eastern
Africa over recent years and estimates future changes in the rangelands of the
region due to global climate change, human population growth and market
opportunities.
Mapping rangelands, livestock and pastoral peoples
The productive potential of the eastern Africa n region varies enormously from
place to place, as shown by the differences in the growing season across the
region (Figure 2.2; Fischer, Velthuizen and Nachtergaele, 2000). On this map,
areas coloured brown and yellow have less than 60 growing days 1 and thus
rarely support crops (= arid , according to White, 1998); areas adequate for shortseason
crops with 60–120 growing days are shown in light green (= semi -arid );
areas with 121–180 days, shaded in medium green, can support longer-season
crops (= dry subhumid); and areas with >180 growing days are in dark green,
and have few production constraints (= wet subhumid). Over the region, about
37 percent of the land surface (or 2.3×10 6 km 2 ) is only agriculturally suitable for
grazing by wildlife and livestock (= arid and semi-arid areas), while the other
63 percent (3.9×10 6 km 2 ) is additionally suitable for crop cultivation , forestry
and other types of land use. Of these arid and semi-arid areas principally suitable
for grazing, about 1.6×10 6 km 2 (or about 70 percent of the grazing land ) is arid
and completely unsuitable for crop production (zero growing days) and thus is
probably only available for grazing during the rare high rainfall years or during a
1 Growing days are defined as “the period (in days) during the year when precipitation (P)
exceeds half the potential evapotranspiration (PET) plus a period required to evapotranspire
up to 100 mm of water from excess precipitation assumed stored in the soil profile” (FAO,
1978). The mean daily temperature during the growing period has to exceed 5°C (Fischer,
Velthuizen and Nachtergaele, 2000).