we learn of their existence, understand the role that they play in ecosystem functioning, and therefore comprehend what that loss might mean. The services that these species and ecosystems provide to human societies are, therefore, increasingly uncertain.
Global economic development and the implementation of new technologies have greatly improved many aspects of human well-being, but they have also extended the reach of human activity further into the natural world than ever before and have greatly increased its influence. Human mobility now connects ecological systems that have evolved in relative isolation over millions of years while technology facilitates the unsustainable exploitation of resources that accumulated over vast timescales. Human-induced environmental change is occurring across a very broad front and at unprecedented rates, with profound ramifications for atmospheric and oceanic chemistry, as well as species distributions and the process of evolution itself. These human interventions have global consequences, of which changing climates are only one manifestation. They also affect the landscapes and fisheries that underpin the global food supply, even as those resources will be required to support a human population at least 50 percent greater than exists today and three times as large as existed just 50 years ago.6 Measures proposed to feed and supply energy to the rising human population, while simultaneously mitigating climate-changing emissions (e.g., biofuels and intensive farming in the developing world), imply the large-scale modification of much of the world’s remaining habitat that supports wildlife. Ongoing alterations to global landscapes are amplified by increased ease of air and sea transport, which together with the widening and deepening of international travel and trade have succeeded in globalizing not only business and production but also diseases and natural pests on a scale never seen before.
The increasing capacity for humans to modify ecological systems and evolutionary and geological processes at a global scale poses challenges for understanding and managing ecosystems for human well-being, now and into the future. One hundred and fifty years after Darwin offered a framework for comprehending the origin of diversity in the natural world, and despite progress in understanding the processes by which ecosystems function and are sustained (see Figure 1-1), humankind is undertaking a
6 Lutz, W., W. Sanderson, and S. Scherbov. 2007 Update of Probabilistic World Population Projections. IIASA World Population Program Online Data Base of Results 2008, http://www.iiasa.ac.at/Research/POP/proj07/index.html?sb=5. Accessed July 2009.