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

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Grasslands of the world
production potential and greater economic importance – being given the
greatest attention. The research focus has been on supporting government
intervention in three major areas.
The first area receiving government research support is the estimation of
sustainable production (carrying capacity ), which was deemed important, as
government attempted to enforce restrictions on the numbers of livestock on
freehold properties. Grazing trials (mainly on-station), attempted to determine
sustainable production levels, using a number of ecological and animal
performance indices. Ecological indices that were measured to assess livestock
impact on the rangeland included plant species composition, plant vigour and
biomass production. In general, on-station trials did not permit the application
of extreme treatments that would be appropriate to test the ecosystem .
Researchers were reluctant to be perceived to be degrading a state-owned
resource and trials were frequently terminated within the time-frames of
system run-down. Conclusions for each veldt type vary enormously, but we
would like to elaborate on those delivered for the semi -arid grasslands of the
Eastern Cape.
It is well recognized that rainfall is the primary determinant of forage
production and a number of production model s have been developed for
predicting the aboveground primary production in natural rangeland in
southern Africa. Coe, Cumming and Phillipson (1976) demonstrate a linear
relationship between annual rainfall and primary production for conservation
areas in southern Africa. These predictions are regarded as conservative
by commercial graziers, many of whom suggest that production for livestock
can be optimized by rotational grazing (Danckwerts and Teague, 1989). In an
effort to assess the sustainable production of grasslands in the Eastern Cape
Province, a grazing trial was established on a freehold ranch (the so-called
Kroomie Trial ) to test the impact of animal type (cattle or sheep ), number
(light, moderate or heavy stocking rate ) and duration (rotation versus continuous
) on rangeland condition and animal production. Preliminary results
suggest that continuous grazing under moderate stocking rate (that recommended
by the National Department of Agriculture ) yields the best livestock
mass gain. However, in the Kroomie trial, no significant changes in species
composition are obvious and the duration of the trial (10 years) is insufficient
to make conclusive assertions regarding system run-down. Even in situations
like this, where the questions have been clearly defined and the treatments
meticulously applied, no clear answers to “sustainable” production levels are
available. Using SPUR2 (Wight and Skiles, 1987; Hanson et al 1994), Palmer,
Ainslie and Hoffman (1999) simulated a 50-year beef operation under continuous
grazing for a site receiving 500 mm/yr (similar in elevation and rainfall to
the conditions at Kroomie). The “recommended stocking rate”, determined
by the National Department of Agriculture and Land Affairs, was 6 ha/LSU.
When running another simulation at 4 ha/LSU, with ambient CO2 at 330 ppm,