Answer:
Biosphere 2 is a unique facility that allows scientists to research ecosystems and environmental effects in a controlled environment. The controlled environment of the biosphere allows researches to obviate uncontrolled variables that might have an unintended effect on their research. This allows for specific hypothesis about the environment to be tested with a higher degree of certainty. They can study how the ecosystem is affected when there are artifically induced limiting factors. The ability of the scientists to control factors in the ecosystem lets them model almost any environment on earth.