Narrator: Extinctions in our National Parks - too little land, or too many people? This is Science Today. Sandy Harcourt, an anthropologist and conservationist at the University of California, Davis, says it turns out endangered species - including bear, mountain sheep and wolves - are affected not by the size of a park, but rather by the amount of people living outside park boundaries.
Harcourt: The graph of extinctions against the amount of land was a completely flat line and what it really looked like is, what was killing off American large mammals is what people are doing around the parks - the number of people around the park is proportional to the number of species going extinct in these parks.
Narrator: Harcourt's findings dispel a common notion that animals in our national parks are safe and it suggests more has to be done to protect them.
Harcourt: We have to manage what people are doing around the national park as well. And the more people there are around the national park, the heavier, the more intense, our management of what those people do is going to have to be.
Narrator: For Science Today, I'm Larissa Branin.