人类与地球正站在悬崖边上

Jon Foley: You sometimes encounter these cliffs where you push the system a little too far, and things would just tip over and fell. And so these boundaries were meant to be defining kinda where the edge of cliff was.

You're listening to Jon Foley, director of the Institute on the Environment at the University of Minnesota. He’s talking about a 2009 paper he co-authored in the journal Nature. The paper introduced the concept of “planetary boundaries” as a way of measuring human impact on the environment.

Jon Foley: Where we define the boundaries, though we are basically about the boundaries where we will cross and change the whole planet to be something so different than we’ve seen for at least the past 10,000 years. And that’s the time of all human history.

In other words, Foley is trying to define an upper limit to human activity on the planet, after which irreversible global damage might occur. He and his team believe boundaries have already been crossed in three major areas: climate change, biodiversity loss, and impact on the nitrogen cycle – that’s a cycle connected to soil, and pollution from agriculture. Foley said there’s no quick fix.

Jon Foley: If you lose a whole ecosystem or a complex part of a food web, how do you put it back again? How do you fix it?

I'm Lindsay Patterson. EarthSky is a clear voice for science. We’re at  http://www.hxen.net