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Pasture Degradation and Recovery
in Australia's Rangelands: Learning from History
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The Future
The aim of this report was to understand the causes of major
episodes of degradation and recovery in Australia's pastoral rangelands, so
that the community might better prepare for the future. A dominant feature of
the eight episodes studied was the severe and extended nature of the drought
periods. However, from our review, we concluded that other non-climatic factors
contributed to the observed degradation. In some cases, the drought period revealed
the damage already done in terms of the loss of desirable perennial vegetation
(grasses and shrubs) and surface soil protection. This damage was the result
of the over-expectation, by some graziers and governments, of the stocking rate
that the resource could carry both in and out of drought. To some extent this
over-expectation was falsely reinforced by relatively short periods (approximately
five years) of above-average rainfall. In some cases, rapid declines in commodity
prices contributed to the economic pressure to stock with too many animals.
The property histories highlighted that sustainable and profitable use of the
rangelands is possible. However, the histories also documented the difficulties
encountered during the first experience of severe and extended drought. These
histories raised the question - does every new owner or manager have to learn
from the painful experience of over-expectation of carrying capacity? The challenge
for rangeland science is to provide and communicate the knowledge gained from
hard-won grazier experience, and the understanding emerging from climate and
ecological research. The episodes described here indicate that such knowledge
is as important as skills in pasture management, animal husbandry and financial
management.
Over the last decade, projects in cooperation with the grazing industry have
addressed (and are continuing to address) the issue of sustainable grazing management
and the extrapolation of successful grazier experience (e.g. Johnston et
al. 2000). However, there remain major information and knowledge gaps that
will have to be addressed if we are to prevent the next degradation episode.
Systems for monitoring rangeland condition especially vegetation and soil cover
are being put in place so as to provide `near real-time' resource assessment
and alerts of increased risk of degradation. However, our review indicates that
prevention of degradation will require a more timely reduction in numbers of
livestock and other herbivores based on better risk assessment of the likelihood
of extended drought periods. Our review of the current understanding of climate
drivers of rangeland rainfall (and temperature) provided a tantalising glimmer
of what might be possible at longer time scales (e.g. Power et al. 1999,
White et al. 2003) than the current three-monthly outlooks.
The rapid growth in knowledge in climate science, fuelled in
part by a desperate race to understand current climate trends and anticipate
the impacts of future climate change, has not yet been regarded as mature enough
to be included in operational climate forecasting systems for rangeland regions.
Hence research to improve mechanistic understanding, skill and lead time is
a high priority. Nevertheless, the initial understanding of El Niño-Southern
Oscillation and other factors ( e.g. Indian Ocean sea surface temperatures)
has underpinned current operational forecasting systems and community understanding
since the late 1980s. The continuing use and availability of knowledge of historical
climate variability and climate forecasts at least challenges graziers, their
advisers, and governments to better manage for future climate variability to
avoid repeating the mistakes of the past.
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