摘要
This paper develops a dynamic model of grazing land degradation. The model illustrates the relationship between live-stock levels and grazing land degradation over time. It identifies the mechanisms by which the factors internal to the livestock local production system and those drawn from the larger economic context of livestock marketing influence livestock-grazing land relationship. The paper shows that overstocking leads to degradation which leads to declining relative prices of livestock as quality declines and mortality increases. As relative price of livestock falls, consumption increases. The increased consumption and mortality ultimately leads to lower livestock population, which leads to de-creased degradation. The model results show that medium term dynamics of grazing land degradation are quite differ-ent from long term dynamics. It is shown that although grazing land sustainability situation is adverse in the medium term, yet it is favourable in the long term. The livestock system is dynamic and can adjust when longer term system dy-namics are allowed to play out. Part of the adjustment mechanism is built in the livestock system and the other part comes from the economic system. The built-in adjustment mechanism works through the two-way relationship between the stock and degradation. The external adjustment mechanism, originating from the economic system, works through economic growth, relative prices and foreign trade. In the medium term, opportunistic management strategy and poli-cies that facilitate access to grazing land and water are crucial for mitigating degradation. The results suggest that the views of the mainstream range management paradigm and the new thinking of range ecology can be reconciled.
This paper develops a dynamic model of grazing land degradation. The model illustrates the relationship between live-stock levels and grazing land degradation over time. It identifies the mechanisms by which the factors internal to the livestock local production system and those drawn from the larger economic context of livestock marketing influence livestock-grazing land relationship. The paper shows that overstocking leads to degradation which leads to declining relative prices of livestock as quality declines and mortality increases. As relative price of livestock falls, consumption increases. The increased consumption and mortality ultimately leads to lower livestock population, which leads to de-creased degradation. The model results show that medium term dynamics of grazing land degradation are quite differ-ent from long term dynamics. It is shown that although grazing land sustainability situation is adverse in the medium term, yet it is favourable in the long term. The livestock system is dynamic and can adjust when longer term system dy-namics are allowed to play out. Part of the adjustment mechanism is built in the livestock system and the other part comes from the economic system. The built-in adjustment mechanism works through the two-way relationship between the stock and degradation. The external adjustment mechanism, originating from the economic system, works through economic growth, relative prices and foreign trade. In the medium term, opportunistic management strategy and poli-cies that facilitate access to grazing land and water are crucial for mitigating degradation. The results suggest that the views of the mainstream range management paradigm and the new thinking of range ecology can be reconciled.
