Consider MIT's Joint Program on the Science and Policy of Global Change. In 2009 the program quietly updated its Integrated Global System Model, which tracks and predicts climate change from 1861 to 2100. Its revised projection indicates that if we stick with business as usual, in terms of carbon dioxide emissions, average surface temperatures on earth by 2100 will hit levels far beyond anything humans have ever experienced.
Or consider the Millennium Ecosystem Assessment, first produced by the United Nations in 2005. This comprehensive, peer-reviewed scientific analysis by 1,300 experts "assessed the consequences of ecosystem change for human well-being." The report concluded that the ability of the earth's ecosystem to absorb our impacts is rapidly diminishing: "At the heart of this assessment is a stark warning. Human activity is putting such strain on the natural functions of Earth that the ability of the planet's ecosystems to sustain future generations can no longer be taken for granted." The MEA spelled out the many "services," or benefits, that human beings derive from nature—from forests that maintain watersheds, prevent silting, and provide timber for building and filtration for the air we breathe, to oceans that provide habitats for fish that we depend upon for food, to coral reefs that keep those oceans and their inhabitants healthy. The National Oceanic and Atmospheric Administration estimates that there may be millions of undiscovered species of organisms living in and around reefs. According to the report, "Many drugs are now being developed from coral reef animals and plants as possible cures for cancer, arthritis, human bacterial infections, viruses, and other diseases." Yet because most nations do not put a price on these services, they too are "underpriced" and therefore easily overexploited—with the profits privatized and the losses socialized. This has been particularly true in the last fifty years. The MEA report noted that 60 percent of the world's ecosystems have now been degraded; more land was converted to agriculture since 1945 than in the eighteenth and nineteenth centuries combined; between 10 and 30 percent of the mammal, bird, and amphibian species on earth are currently threatened with extinction. More than a billion people today already suffer from water scarcity; deforestation in the tropics alone destroys an area the size of Greece every year—more than twenty-five million acres; more than half the world's fisheries are overfished or fished at their limit.
No wonder the World Wildlife Fund's Living Planet 2008 Report concluded that we are already operating 25 percent above the planet's biological capacity to support life. And that is before we add another billion people by the early 2020s. "The world is currently struggling with the consequences of over-valuing its financial assets, but a more fundamental crisis looms ahead—an ecological credit crunch caused by undervaluing the environmental assets that are the basis of all life and prosperity," said WWF International Director-General James Leape, in the foreword to the report. "Most of us are propping up our current lifestyles, and our economic growth, by drawing—and increasingly overdrawing— on the ecological capital of other parts of the world."