The massive conversion of the world's natural landscapes to agriculture and other human uses may soon begin to undermine the capacity of the planet's ecosystems to sustain a burgeoning human population.
Writing July 22, 2005 in the journal Science, a group of leading scientists portrays the escalating transformation of the world's forests, wetlands, savannahs, waterways and other native landscapes as the biggest potential threat to human health and global sustainability.
"Short of a collision with an asteroid, land use by humans is the most significant impact on the world's biosphere," according to Jonathan A. Foley, a UW-Madison climatologist and the lead author of the Science paper. "It may be the single most pressing environmental issue of our day."
The new Science paper was written by a group of leading environmental scientists representing a wide range of scientific disciplines, including biology, climatology, medicine, limnology, geography and earth science. Foley directs the UW-Madison Center for Sustainability and the Global Environment in the Gaylord Nelson Institute for Environmental Studies.
Land use, according to the report, is no longer just a local issue. It is a force of global importance as the world's six billion people compete for food, water, fiber and shelter. The report, says Foley, is a comprehensive review of scientific research on the world's major land-use practices - agriculture, urban and rural development, deforestation and other natural resource extraction - and their impacts on the world's ecosystems.
According to Foley, nearly one-third of the world's land surface is now in use for agriculture and millions of acres of natural ecosystems are converted each year. Many of the agricultural practices, built on Western-style methods, are unsustainable, requiring large applications of chemical fertilizers and further sculpting of the landscape to divert water to marginal lands.
"While land use practices vary greatly across the world, their ultimate outcome is generally the same: the acquisition of natural resources for immediate human needs, often at the expense of degrading environmental conditions," the authors write.
The new Science report synthesizes and reflects on decades of research on human impacts on the environment, including changes in atmospheric composition, land cover, the hydrologic cycle and biological diversity.
The survey of global land use practices, Foley says, portrays a need for closer collaboration between scientists and land use planners, hydrologists, farmers, architects and health care professionals to forestall greater environmental degradation.
"Land use has multiple causes. We recognize the need for food, water and shelter," says Foley. "But it also has multiple outcomes, and scientists need to look at the big picture. There is important science to be done here."
One example, Foley says, is changing patterns of human and animal disease as climate changes and allows pathogens to flourish in regions where they previously did not exist. Diseases such as West Nile, malaria, cholera, Rift Valley fever and hanta virus are examples of infectious diseases that have emerged in new places and whose frequency has increased as land use and ecological patterns shift.
Foley emphasizes that scientists must look beyond the world's wilderness and consider the whole landscape, including cities, suburbs and agricultural areas in their assessments of global environmental health. "We need to look at land use in a global context. The whole system needs to be considered."
The report also highlighted examples of sustainable land use practices that provide both economic and environmental advantages:
* New York City's purchase of development rights in the Catskills to enhance the city's water supply. The practice resulted in an estimated $5 billion to $7 billion savings for water purification services.
* Locating coffee farms within 1 kilometer of intact tropical forests to take advantage of wild pollinators can boost bean quality and crop yield by as much as 20 percent.
* Using reflective roofing, adding green space and planting trees in cities to reduce smog, heat-related mortality, and electricity demands from air conditioning.
* Developing a greater reliance on integrated pest management and other tactics to reduce the need for chemical pesticides and increase food availability. Stocking rice paddies with mosquito-eating fish and creating optimal conditions for pest-eating birds, are two proven strategies.
"Land use has gone beyond being a local environmental issue," Foley says. "The global-scale impacts are greater than the sum of local events. Land use is having a transformative effect on the planet."
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