Environment 360: In the gentle hills outside York, England, a controversial experiment is quietly unfolding. It began in the summer of 2000 when Steven Willis, a biologist at the University of Durham, and his colleagues drove to a wildlife preserve called Wingate Quarry. In the back of their car was a cage full of butterflies called Marbled Whites. Willis and his colleagues removed the cage from the car, opened it, and let 500 butterflies flutter away across the scrubby meadows. Marbled Whites are …