Wednesday, August 29, 2007

At Australia’s Bunny Fence, Variable Cloudiness Prompts Climate Study

"Rabbit-Proof Fence Has Unintended Consequences"

August 14, 2007 -- By Sonal Noticewala, The New York Times

"A fence built to prevent rabbits from entering the Australian outback has unintentionally allowed scientists to study the effects of land use on regional climates.

The rabbit-proof fence — or bunny fence — in Western Australia was completed in 1907 and stretches about 2,000 miles. It acts as a boundary separating native vegetation from farmland. Within the fence area, scientists have observed a strange phenomenon: above the native vegetation, the sky is rich in rain-producing clouds. But the sky on the farmland side is clear.

Researchers led by Tom Lyons of Murdoch University in Australia and Udaysankar S. Nair of the University of Alabama in Huntsville have come up with three possible explanations for this difference in cloudiness.

One theory is that the dark native vegetation absorbs and releases more heat into the atmosphere than the light-colored crops. These native plants release heat that combines with water vapor from the lower atmosphere, resulting in cloud formation.

Another hypothesis is that the warmer air on the native scrubland rises, creating a vacuum in the lower atmosphere that is then filled by cooler air from cropland across the fence. As a result, clouds form on the scrubland side.

A third idea is that a high concentration of aerosols — particles suspended in the atmosphere — on the agricultural side results in small water droplets and a decrease in the probability of rainfall. On the native landscape, the concentration of aerosols is lower, translating into larger droplets and more rainfall.

Within the last few decades, about 32 million acres of native vegetation have been converted to croplands west of the bunny fence. On the agricultural side of the fence, rainfall has been reduced by 20 percent since the 1970s.

Dr. Nair speculates that increases in the world’s population will prompt the clearing of more land to increase food production. But he wonders whether, in the long run, “we will reach a point of land clearing that will diminish food production,” because rainfall has decreased.

Dr. Lyons said he hoped the research would help scientists “understand the relationships between the land surface and atmosphere and to provide ideas for sustainable agricultural practices.”

The bunny fence, as it turns out, failed to prevent rabbits from entering the farmland, but it has successfully blocked kangaroos and emus."

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If we consider the loss of oak groves and wetlands in the Sacto/San Jo valley ecosystem, maybe the air in the summer months are much drier without these trees and the moisture produced from their transpiration (evaporation thrrough leaves)??

Valley oak groves can also be seen as a food resource, and an essential foundation for woodland ecosystems. Even one oak tree remaining on a field can become an island refuge for a variety of species. How about helping our farmers connect those oak islands??

"Acorns may be California's single greatest natural resource. An oak tree can bear more than 400 pounds of acorns a year. There are an estimated 1 billion oak trees in California. That's hundreds of millions of pounds of nutrient that serves as the staple for more kinds of creatures than any other food source in the state. But the bulk of nutrients oaks churn out is only the beginning of their contribution. Oak trees form the organizational backbone of numerous habitats from coastal valley bottoms to highland meadows, providing food, shelter, and stability for whole communities of organisms. According to a 1997 University of California study, California's oak woodlands harbor more biodiversity than any other major habitat type in the state: At least 4,000 kinds of insects inhabit them, along with 2,000 kinds of plants, thousands of fungi and lichens, 170 different birds, 60 amphibians and reptiles, and 100 different mammals."

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