4.1 Introduction There is a major planet-wide experiment under way. Anthropogenic changes to the atmosphere-biosphere system mean that all ecosystems on Earth are now affected by our activities. While outright deforestation is physically obvious, other subtler processes, such as hunting and surface fires. also affect forests in ways that are less evident to the casual observer(cf. Estes et al. 2011: Lewis, Malhi& Phillips 2004a; Malhi& Phillips 2004), Similarly, anthropogenic atmospheric change is intensifying. By the end of the cen tury, carbon dioxide concentrations may reach levels unprecedented for at least 20 million