Benefits or losses from tree clearing in pasture systems of Central Queensland, Australia?

Broadscale tree clearing has been widespread in Queensland as landholders try to increase pasture production. The recent government policies aim to stop broadsca1e clearing by 2006, but the debate over the opportunity cost of the regulatory controls continues. Previous studies of the pasture production gains following clearing have identified key improvements, which can be expected to increase livestock production. These studies have all been focused at relatively short term impacts (less than 10 years), raising questions of whether pasture production gains are sustainable over the longer term.The key focus of the research reported in this paper was to determine if pasture production gains following clearing were maintained over the longer term. For this, the pasture yield and the ecological effects of tree clearing over three different time periods for three different vegetation communities in central Queensland. The results indicate that pasture production increases post-clearing, but then declines over the longer term (more than 30 years). A bioeconomic model applied to develop scenarios for pasture production over the 50 years of time frame of clearing, also suggested a decline in pasture yield with age of clearing based on the yearly average increase estimated from the old (30 years) to 50 years of age clearing. Although, the cleared pastures could be economically beneficially as predicted in bioeconomic model, however, it is difficult to predict how the change in ecosystem functions in old pastures (>30 years of clearing), by implication, affect pasture yield. The opportunity cost of clearing to achieve production gains in terms of loss of ecosystem functions and their implication for future production gains, are discussed.