Human Effects on Ecosystems Need More Study

Ecosystems are constantly exchanging materials through the movement of air in the atmosphere and water in lakes and rivers. The effects of humans, however, are another major source of connections among ecosystems.

In a special issue of the journal Frontiers in Ecology and the Environment, ecologists discuss how human influences interact with natural processes to influence global connectivity.

The authors of "Continental-scale ecology in an increasingly connected world" (June 2008) conclude that networks of large-scale experiments are needed to predict long-term ecological change.

"We know that the world has always been connected via a common atmosphere and the movement of water," says Debra Peters, author and a scientist with the Agricultural Research Service at the U.S. Department of Agriculture.

"The world is also becoming highly interconnected through the movement of people and the transport of goods locally to globally," says Peters. "Ecologists are increasingly realizing that these links can have profound influences on the long-term dynamics of ecological systems." The transport of many types of materials, including gases, minerals, and even organisms, can affect natural systems.

This movement results in "greenlash," which occurs when environmental changes localized to a small geographic area have far-reaching effects in other areas. For example, a drought in the 1930s increased soil erosion across the farmlands of the Midwest, leading to intense dust storms. Large amounts of wind-swept dust traveled across the continent, causing the infamous Dust Bowl and affecting air quality, public health, and patterns of human settlement throughout the country.

Because of increasing globalization, people often inadvertently introduce non-native plants, animals, and diseases into new locations.

Invasive species and pathogens, such as fire ants from South America and West Nile virus from Africa, can create large, expensive problems: the U.S. currently spends more than $120 billion per year on measures to prevent and eradicate invasive species.

Understanding ecosystem connectivity across a range of scales--from local to regional to continental--will help scientists predict where invasive species are likely to go next.

The authors agree that field ecology studies should focus on long-term sampling networks that encompass a range of geographical scales. Integrating data from existing and developing networks, such as the National Science Foundation (NSF)'s Long-Term Ecological Research (LTER) network and NSF's National Ecological Observatory Network (NEON), will lead to a level of ecological comparison unparalleled by any one experiment.

Ecologists hope that understanding the patterns of connectivity within and among ecosystems will lead to more accurate predictions of future ecological change, the authors write.

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