In Physics, every action has a counter-action, and much the same is true in Ecology. Transplanting, cross-breeding, artificial pollination all seem like simple solutions to providing man with what he wants, or thinks he wants, but their side effects cannot be foreseen and inevitably turn out to be bad. The potato is a classic example: introduced as a solution to the problem of food shortages, it soon became the staple and, when attacked by disease, caused widespread famine; reestablished in the U.S., the potato thrived until the advent of the potato beetle—a battle still too close to call. Biological weapons have been used to combat disease in fir trees—and have caused worse damage. And the arrival of man and his cattle destroyed the balance of nature on the Australian plains and the loss of millions and millions of acres of pasture. As they seek an antidote to this bane, what new problems will Australians create? (28 minutes)