University of Tasmania, Australia

Over the last 50 years rainforests have expanded while populations of a fire sensitive conifer (Callitris) have collapsed throughout the Australian monsoon tropics. This contradictory pattern may be an ecological symptom of global environmental change.

To resolve this we will study sites from north Queensland to Tasmania, determining:

• (a) variation in the rate and magnitude of rainforest expansion and
• (b) changes in Callitris populations analysing tree growth.

These findings will

• (i) quantify the dynamics of landscape change
• (ii) evaluate the importance of fire and climate in controlling tree growth
• (iii) resolve uncertainty about past impact of Aboriginal burning and
• (iv) improve understanding CO2 enrichment on the global carbon cycle.

Human-caused climate change is a fact but the ecological responses are uncertain. These could include accelerated tree growth, expansion of rainforest, and thickening of woodlands, although cessation of Aboriginal firing may be equally important. We will provide a historical context to understand how and why Australian forests have changed. Our results will inform management and policy debates about:

• (i) rainforest conservation
• (ii) the role of fire in forest management
• (iii) the likely impact of increased CO2 (‘fertiliser effect’) of forest productivity
• (iv) national carbon accounting and
• (v) the consequences of climate change on forest ecosystems, particularly the respective wetting and drying trends in the north and south of Australia.