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

The changing face of pastoral systems in grass-dominated ecosystems of eastern Africa 57
HOW HAVE PASTORAL ECOSYSTEMS CHANGED IN RESPONSE TO
LIVESTOCK AND HUMAN-USE CHANGES?
Overgrazing
A discussion of the impacts of grazing is provided in the preceding section and
will not be considered further here, but grazing is without doubt one of the
major forces effecting change in pastoral systems .
Competition between livestock and wildlife
Livestock can and do compete with several species of wildlife for forage in
eastern Africa , but this may vary according to rainfall . Wildlife appear to avoid
heavily grazed areas completely in arid northern Kenya (De Leeuw et al.,
2001), but mix more closely with livestock in semi -arid rangelands in southern
Kenya (Waweru and Reid, unpub. data).
Wildlife probably avoid areas close to settlements because livestock remove
most of the forage. Around Samburu pastoral settlements in northern Kenya,
Grevy’s zebra graze away from the settlements during the day, but move close
to them during the night (Williams, 1998). Samburu build their settlements
along riverine areas, within walking distance of streambeds where Samburu dig
wells . After livestock are put into their corrals for the night, zebra come down
to the streambeds to drink and leave by the next morning. They may also come
close to the settlements at night for better predator protection as well .
In the group ranches around the Maasai Mara game reserve , wildlife avoid
areas very close to settlements, but cluster at intermediate distances from settlements
(Reid et al., 2001). Wildlife may cluster around settlements to have
access to moderately grazed grasslands, where their access to energy and nutrients
is very high. They may also graze close by for protection from predators .
Current settlements tend to be built on areas that have been settled for a long
time and contain numerous old settlement scars where nutrient enrichment in
the soils below old livestock corrals can last for a century or more (Muchiru,
Western and Reid, submitted).
Changes in rangeland burning regimes
Livestock grazing and less frequent rangeland burning can strongly affect the
state of the vegetation in rangeland systems . Wildlife and livestock systems, when
side-by-side, often are of two different vegetative states: wildlife systems remain
grasslands if elephants and fire are present (e.g. Dublin, 1995), while neighbouring
livestock systems are much more woody (Western, 1989). Traditional rangeland
burning is an essential practice to maintain the grassland state critical to grazers,
but may reduce the amount of carbon sequestered in these ecosystems .
Rangeland fragmentation and loss of wildlife habitat
Fragmentation can also occur when fence lines are built to prevent the spread
of disease or to prevent wildlife from foraging in enclosed pastures. This