In celebration of Earth Month, Living on Earth dips into our archives and revisits some of our favorite stories. In 2001, Alan Coukell reported on the problem of possums in New Zealand. The non-native species ate tens of thousands of tons of forest each day and can spread tuberculosis to other animals. Host Steve Curwood talks with Philip Cowan from New Zealand's Land Care Research to find out how the battle to control possums has progressed in the eight years since our story was produced.