Tropical forests and global atmospheric change: a synthesis.

We present a personal perspective on the highlights of the Theme Issue 'Tropical forests and global atmospheric change'. We highlight the key findings on the contemporary rate of climatic change in the tropics, the evidence-gained from field studies-of large-scale and rapid change in the dynamics and biomass of old-growth forests, and evidence of how climate change and fragmentation can interact to increase the vulnerability of plants and animals to fires. A range of opinions exists concerning the possible cause of these observed changes, but examination of the spatial 'fingerprint' of observed change may help to identify the driving mechanism(s). Studies of changes in tropical forest regions since the last glacial maximum show the sensitivity of species composition and ecology to atmospheric changes. Model studies of change in forest vegetation highlight the potential importance of temperature or drought thresholds that could lead to substantial forest decline in the near future. During the coming century, the Earth's remaining tropical forests face the combined pressures of direct human impacts and a climatic and atmospheric situation not experienced for at least 20 million years. Understanding and monitoring of their response to this atmospheric change are essential if we are to maximize their conservation options.