Challenges to ecosystem management and some implications for science and policy

The ecosystems and biota we see today represent the evolution of life over a period of almost four billion years. Over the past several hundred million years the diversity of life has changed markedly as a result of evolutionary and other forces. Environmental fluctuations have led to changes in ecosystems and biota. Over the past 15 million years or so many regions of the planet have become more arid and this has led to changes in their constituent biota.