Yale Bulletin and Calendar

November 22, 2002|Volume 31, Number 12|Two-Week Issue

Use of artificial ecosystems in research
can yield false results, study shows

A new study by a faculty member at the ,School of Forestry & Environmental Studies (F&ES) calls into question the reliability of a research method widely used by environmental scientists in their experiments.

In a paper published in the journal Ecology, F&ES associate professor David Skelly examines how well mesocosms, or artificial ecosystems, develop a realistic picture of the natural world.

His conclusion: "Mesocosms might not be all they are cracked up to be."

A mesocosm, which means "middle-sized world," offers scientists a compromise between conducting experiments in the laboratory, where conditions can be controlled but are unnatural, or in the natural world, where conditions can make it difficult to conduct studies or interpret results.

Since the concept was first introduced 20 years ago, thousands of experiments have been conducted in mesocosms, and the research methodology is used to study critical environmental issues, such as drinking water standards, the effects of global climate change and the fate of endangered species.

To determine how accurately mesocosms mimic the natural world, Skelly conducted the same experiment on tadpoles both in mesocosms -- plastic 250-gallon tanks -- and within enclosures placed in natural ponds at Yale-Myers Forest. He found that two different amphibian species that compete intensely in mesocosms show no signs of competition in natural pond enclosures.

"I used results from both the mesocosms and the pond enclosures to make predictions about wild amphibian populations (wood frogs)," says Skelly. "The mesocosms were simply not able to provide accurate predictions. Results from the enclosures, on the other hand, can be used to make excellent predictions about wild populations."

This does not mean that environmental scientists should abandon the use of mesocosms for their experiments, he notes. "The public will not be anxious to have scientists dumping cadmium into wetlands to evalute its effects on the environment," Skelly says. "We need other settings for this work, and mesocosms in some form are our best hope right now."

However, he believes further research needs to be done to refine how mesocosms are used. "I hope that this work will encourage scientists to cast a critical eye over their experimental designs and ask themselves whether their results will be as realistic as they wish them to be."

Skelly adds: "I believe that a focus on this issue is going to lead to better experiments in laboratories, in mesocosms and in natural environments. ... We have a lot of hard work to do to figure out what it will take to achieve results that reflect what's going on in the natural world."

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