Jon Foley: You sometimes encounter these cliffs where you push the system a little too far, and things would just tip over and fall. So these boundaries were meant to be defining where the cliff was.
Jon Foley is director of the Institute on the Environment at the University of Minnesota. He’s talking about a 2009 paper he co-authored with an interdisciplinary team of scientists 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 are where we will cross and become something so different than we’ve seen for 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?
Not all scientists agree with Foley’s concept, or with how and where the boundaries should be defined. Foley said the purpose is to think about how humans will adjust to large-scale environmental changes. Earth’s systems function in unpredictable ways, says Foley, and it’s hard to know exactly where the “cliffs,” or tipping points are.
Jon Foley: We worry about this with biodiversity. If we lose one more species, another species, how many can you lose before all those webs of relationships fall apart, and the system collapses?
He said that people are used to thinking of environmental damages, such as oil spills, which can be cleaned up or fixed. The effects of crossing planetary boundaries are in a different league, Foley said.
Jon Foley: What happens generally is you cross a boundary where things get a lot worse a lot faster, and they are mostly irreversible damages. 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?
Still, he said, there is time before we see the impacts.
Jon Foley: Sometimes people expect the environmental apocalypse, and it’s not going to happen like that. It’s going to be slow, steady deterioration, punctuated by some very big changes once in a while.
To put this in context, Foley said that for the past 10,000 years – the period known as the Holocene – humans have existed with a relatively stable climate, supply of food and water, along with many of the species we know today.
Jon Foley: So that’s everything we know as a civilization – every scrap of human history occurred during this one little period of the Earth’s record.
He said crossing these boundaries will change the world as we know it.
Planetary Boundaries was published as a Nature feature on September 23, 2009.
Learning to love science. As a producer for EarthSky, Lindsay Patterson interviews some of the world's most fascinating scientists. Through EarthSky, her work content is syndicated on some of the world's top media websites, including USAToday.com and Reuters.com. Patterson is also charged with helping to stay in steady communication with the thousands of scientists who contribute to EarthSky's work of making the voice of science heard in a noisy world. She graduated from Colorado College with a degree in creative writing, and a keen interest in all forms of journalism and media.