AUDIE CORNISH, HOST:
Ecologist Dan Nepstad has studied the Amazon for more than 30 years. He explained to me why it's hard to know the true extent of these fires.
DAN NEPSTAD: In an intact Amazon forest - a virgin forest - if it's a really dry year and the fire gets going, it's shin-high. You can step over it, and that means it doesn't register a lot of heat, and the satellites don't pick up that as an act of fire. The best way to know if a forest is burning is to see smoke coming out the top. So it's really hard to know how much of the virgin forests of the Amazon are catching fire. If they're open fires or fires burning damaged forests, they're much easier to spot, and that's most of what we're seeing this year.
CORNISH: Talk more about what we are seeing this year. How is it different from fires in the past?
NEPSTAD: Well, it's a big fire year. It's the biggest one in the last decade. A lot of the fires burning now are persistent, and that means that those are felled forests - the giant rainforest trees that have been cut down with chainsaws, allowed to dry, and now they're being burned in preparation for crops or pasture or whatever. A lot of smoke because there's so much tree biomass, a lot of energy, meaning that smoke goes really high into the atmosphere - and it can spread across entire regions.
CORNISH: You've written that the biggest threat to the Amazon is the large-scale displacement of scrub vegetation. What is that, and what does that mean in terms of the Amazon being exposed to more and more fires?
NEPSTAD: So what was deep, dense shade that kept the litter layer - the fuel layer - moist and difficult to burn is drying out, and there's a lot more of it. The next fire is much more intense. It kills more trees, and pretty soon, grasses and shrubs start to move into what was a pristine forest, and that's what I call this scrub vegetation. So that - eventually, you really can't recognize that that's a forest that was - never saw a chainsaw, but it's completely altered. That, for me, is the most worrisome long-term scenario for the Amazon.
CORNISH: What, then, is the solution? What steps can the Brazilian government take to protect the Amazon?
NEPSTAD: You know, I think there's a huge opportunity to solve this, and not just with dumping water or putting out fires. But to really come up with a systemic strategy that is long-term, we really need to shift from fire-prone systems, like extensive cattle, to more intensive forms that are tree-based so that the landholder will be more reluctant to use fire to manage their land and they'll invest more in fire prevention.
CORNISH: Before I let you go, I've heard over and over the last few days this idea that the Amazon is the lungs of the world. Is that a good way to think of it?
NEPSTAD: That's a little misleading. There's a lot of big, old trees, and they respire a lot. Just like people have to breathe in oxygen, those tree trunks also have to breathe in oxygen, and all of that dead wood, as it rots, is taking up oxygen- much better to focus on the Amazon as a cooling system for the planet. You know, really, every time a little droplet of water leaves a leaf and goes into vapor, it's absorbing energy and it's cooling things down. And the Amazon is so big that if we lose it, it's going to change the way air and energy move around the planet, and that means our climate will change. For me, that's something that really ties us to the health of the Amazon wherever we are on the planet.
CORNISH: That's Dan Nepstad. He's president and founder of the Earth Innovation Institute.
Thank you for explaining this to us.
NEPSTAD: My pleasure - great talking to you. Transcript provided by NPR, Copyright NPR.