The Amazon faces a new wave of exploitation, as Brazil, Peru, and other Amazonian countries look to the vast expanse of forests and rivers to supply expanding energy and natural resource needs. Hundreds of infrastructure projects—dams, roads, railroads, pipelines, and more—are planned. But the deforestation that usually accompanies such projects threatens biodiversity as well as the Amazon’s role as the world’s largest terrestrial carbon sink, says biologist Thomas Lovejoy of George Mason University, Fairfax, in Virginia.
Lovejoy is one of five new U.S. science envoys appointed by the U.S. Department of State and the White House to promote scientific collaboration between the United States and other countries. He plans to use his new role to encourage efforts to understand the Amazon’s climate dynamics and help prevent deforestation from tipping the region from carbon sink to net carbon emitter. He recently spoke with Science in Lima. This interview has been edited for clarity and brevity.
Q: What do you consider the greatest threat to the Amazon?
A: The intersection between uncoordinated infrastructure and the hydrological cycle. The Amazon makes half of its own rainfall [through evapotranspiration], and the water recycles five or six times as it crosses the basin. [Deforestation disrupts] the hydrological cycle [and] is going to have effects on the weather system. With the droughts of 2005, 2010, and the current one—I think we're seeing flickers of the potential tipping point.
Q: Do we know where the tipping point from carbon sink to source will be?
A: One estimate is at about 40% deforestation. That doesn't include other impacts on the hydrological cycle from climate change itself and the widespread use of fire. Fire not only burns the forest, it also dries it out and makes it more vulnerable. I think it's reasonable to think the tipping point is around 20% deforestation.
Q: Dams are controversial; can hydropower be environmentally sound?
A: It depends on designing [dams] so they don't block the rivers, [and] they allow for a lot of natural sediment flow and permit fish migrations. Impeding the sediment flow will degrade agricultural productivity. If you block the migratory fish pathways, it will be the end of the major fish resources. [Some species] use the entire length of the Amazon in the course of their life span. Perfection would be having no dams, but that's not going to happen, so let's make them an example of sustainable infrastructure.
Q: What kind of planning is needed so that Amazonian cities can develop without so much deforestation?
A: I've been to modest-size communities on the Rio Negro that are entirely solar powered. Communities near small rivers could use little generators in the river. … One question is how you feed people in those cities. Aquaculture potential is enormous. [One starting point might be] a fisheries agreement among the Amazon nations, from the headwaters to the estuary, for some of those big catfish. That's something everybody understands, everybody values, and it depends on the hydrological cycle.
Q: What do you see as research priorities?
A: How to design sustainable infrastructure [such as transmission line towers that rise far above the canopy, with no cleared right-of-way below]. Also, a better understanding of biodiversity distribution patterns. At least in the eastern two-thirds of the Amazon, we're finding that … there's a lot of unrevealed biodiversity that needs to be looked at.