Ecosystems are constantly exchanging materials through the movement of air in the atmosphere, the flow of water in rivers and the migration of animals across the landscape. People, however, have also established themselves as another major driver of connectivity among ecosystems.
In the June 2008 Special Issue of Frontiers in Ecology and the Environment, titled "Continental-scale ecology in an increasingly connected world," ecologists discuss how human influences interact with natural processes to influence connectivity at the continental scale. The authors 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, an author in the issue and a scientist with the United States Department of Agriculture's Agricultural Research Service (USDA-ARS). "The world is also becoming highly interconnected through the movement of people and the transport of goods locally to globally. Among ecologists, there is an increasing realization that these connections 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 1930's caused small-scale farmers to abandon their farms across the U.S. Midwest. The absence of crops intensified local soil erosion, leading to powerful 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 the SARS virus from China, can create large, expensive problems: the U.S. currently spends over $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's Long Term Ecological Research network (LTER) and NSF's National Ecological Observatory Network (NEON), will lead to a level of power for ecological comparison unparalleled by any one experiment.
"To draw conclusions about the consequences of increasing connectivity, we need to provide information about processes that span a vast scale of space and time," says David Schimel, an author in the issue and the chief executive officer of the NEON project. "Our observations will characterize ecological processes from the genomic to the continental and document changes from seconds to decades."
Additionally, the authors suggest that long-term studies should include data from social and behavioral science to allow incorporation of human movement patterns into their scientific models. Ecologists hope that understanding the patterns of connectivity within and among ecosystems will lead to more accurate predictions of future ecological change.
The Special Issue of Frontiers was supported by funding from the National Science Foundation, USDA-ARS, and the Consortium for Regional Ecological Observatories. The issue is free and will be available to the public June 1 at http://www.frontiersinecology.org/.
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