Much of the opposition to genetically engineered organisms has emerged from within the environmental movement, but what happens when a new biotechnology has an explicit goal of environmental conservation? An international consortium is investigating the potential deployment of an engineered mouse on islands where invasive mice threaten biodiversity. Theoretically, the mouse would "drive" the population to be all male, crashing the mouse population and leading to eradication without the use of environmentally-risky toxicants. But even testing such a technology, known as a "gene drive," has ecological risks. How do we decide how to proceed in a way that minimizes risk?
