By 2050, the planet's population will increase to 9 billion, with most people migrating to massive cities. Better vaccines will lessen the epidemic of HIV and offset flu pandemics. The global economy will quadruple. Demand for food, fresh water and raw materials for construction and heat will stretch natural resources to their limits, according to an analysis released Thursday.
If major changes are not made in the way humans consume natural resources, there will be widespread famine, severe shortages of clean water and huge impacts from natural disasters such as hurricanes. Cities will be beset by vast amounts of wastewater and sewage. Sea levels will rise, fisheries will collapse, emerging disease epidemics will sweep across the globe and coral reefs will die off, said authors of the new report, "The Millennium Ecosystem Assessment." Commissioned by the United Nations, the work is a four-year effort by 1,300 scientists from 95 countries.
This grim scenario, however, can be avoided through policy decisions that emphasize environmental technology, poverty reduction and investments in education and health, the report's authors said.
"Despite what looks like steady decline, this is a story of hope," said Stephen Carpenter, a lead author of the report and expert on ecosystem management at the University of Wisconsin-Madison. "The good news is that we can make a very positive difference by 2050."
During the last 50 years, living conditions have improved for a majority of the planet's population: People live longer, are better nourished and wealthier and are able to participate more in government, said Walter Reid, a professor at Stanford University's Institute for the Environment and director of the assessment. That progress, though, has come at a heavy cost to natural resources. The continued degradation of resources such as forests and fresh water will severely affect quality of life, particularly for the poor, he said.
"There's an unbreakable link between human well-being and the health of the planet," Reid said at a news briefing in Washington to release the report.
One way to improve the future of both the planet and its residents, Reid said, is through "green" technology, such as the construction of energy-efficient homes and offices.
"The number of buildings that will be built in the 21st century is on the order of the number of buildings built in the entirety of human history," Carpenter said.
Agricultural practices will also have to improve because farming is the most extensive modification of the Earth's surface caused by humans and is the largest user of fresh water, he said.
The report also calls for natural resources such as water to be priced to reflect their true value and not as though they were infinite.
Countries also need to start curtailing the use of fossil fuels to limit the effects of climate change, which could raise temperatures by 3.5 degrees by 2050 and increase sea levels by several inches, the report says. Although climate change could bring more rain and fresh water to some areas, it also could cause flooding and increase vulnerability to hurricanes in others.
All of the technologies and policy changes needed to improve the planet's future outlook are available today, Carpenter said, but they are not in widespread use and face political hurdles. "Substantial changes would have to be made," he said.
One suggestion calls for ending the subsidies that many rich nations give to farmers. These policies keep food prices artificially low and discourage crop production in poorer countries that could use the economic boost that can accompany agricultural production. Ending subsidies would also encourage the reversion of much farmland now under cultivation to more natural states -- forests or meadows -- that could improve the environment, said Prabhu Pingali, a director of the U.N.'s Food and Agriculture Organization and one of the report's authors. Pingali, an economist, said the world's poorest people had the most to lose if improvements were not made. Economic policy changes could improve the environment, which in turn could boost economies, he added. "Ecology and economics can work together," he said.
The authors said that reaction to the report was favorable, with some countries, including China and the Netherlands, already implementing some suggestions or planning national assessments. Many developing countries said they were not embracing the report as readily because they lacked the resources to implement many of the changes. The U.S. Environmental Protection Agency and U.S. Department of Agriculture's Forest Service are studying the report and may implement some suggestions, Reid said.
"The Millennium Ecosystem Assessment" is the first analysis that includes natural resources and land use in projections of how population and the economy will change over the long term, its authors said.