Land use is top global environmental concern.

The large-scale conversion of natural landscapes to agriculture and other human uses is a leading threat to human health and global sustainability, researchers reported in the July 22 issue of Science. The authors conclude that accelerated transformation of critical landscapes, including forests, wetlands, savannahs, and waterways, could soon undermine the capacity of Earth's ecosystems to sustain a burgeoning human population.

The cross-disciplinary study synthesizes decades of research on human impacts on the environment, covering land-use practices from agriculture to natural resource extraction, and evaluating changes in land cover, atmospheric composition, the hydrologic cycle, and biological diversity. Land use is no longer just a local issue, the report notes, but of global importance as 6 billion people compete for food, water, fiber, and shelter. "Modern land-use practices, while increasing the short-term supplies of material goods, may undermine many ecosystem services in the long run," note the authors.

According to the study, nearly one-third of Earth's land surface is now used for agriculture, with millions more acres being converted each year. And as more countries adopt industrial agricultural methods, including heavy use of chemical fertilizers and large-scale diversion of water to marginal lands, the risks of ecosystem destruction are only growing.

The report points to the role of landscape alteration in climate change as well, asserting that land use activities account for roughly 35 percent of human-caused carbon dioxide emissions since 1850. Changing land-use patterns are also influencing the evolution of disease, enabling infections such as West Nile virus, malaria, cholera, Rift Valley fever, and hanta virus to emerge in new places and increase in frequency.

To address these impacts and slow further degradation, the reports calls for closer collaboration between scientists and experts in other disciplines, including land use planners, hydrologists, architects, farmers, and health care professionals. It also stresses the importance of considering entire landscapes, including both urban and rural areas, as whole systems when assessing global environmental health.

The authors highlight several sustainable land use practices that can have positive environmental, social, and economic benefits. These include strategies to boost agricultural production per unit of land or water, increase soil organic matter in croplands, augment green space in urban areas, and maintain local biodiversity and ecosystem services. Locating coffee farms near intact tropical forests to take advantage of wild pollinators, for instance, can boost bean quality and crop yield by as much as 20 percent.

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