The UNEP Year Book 2009 presents work in progress on scientific understanding of global environmental change, as well as foresight about possible issues on the horizon. The aim is to raise awareness of the interlinkages among environmental issues that can accelerate the rates of change and threaten human wellbeing. All ecosystems are undergoing change, but some transitions are more dramatic than others.
Certainly one of the most visible and significant ecosystem changes is the widespread degradation and conversion of tropical and sub-tropical ecosystems (Figure 1). Increasing demands for food and other agricultural products has led to the intensification of agricultural production and the drastic expansion of land under cultivation (Yadvinder and others 2008). Today, farmland covers nearly a quarter of the planet’s surface. Entire forest systems have effectively disappeared in at least 25 countries and have declined by 90
per cent in another 29 countries (Dietz and Henry 2008). This destruction continues at staggering rates.