Environmental Crisis Midterm

The Effect

The dry season is lengthening and rainfall has dropped by a quarter in some regions. Meanwhile, precipitation, when it comes, sometimes arrives in more intense bursts, leading to massive floods in 2009, 2012, and 2014. The region's climate system is oscillating more wildly. In the study she led, published in the journal Global Change Biology with more than a hundred other scientists as co-authors, Esquivel-Muelbert found that during the past 30 years, more drought-tolerant plant species have appeared in the Amazon, while species that predominantly emerge in wet areas are declining. Fast-growing trees and taller trees that are better at accessing the sun are outcompeting shorter, damp-loving species.

Another study shows the rate of tree deaths is increasing. It's not clear whether all this is the beginning of the shift Lovejoy and Nobre predicted—or something else. "But it's still important because the species are beginning to change, and that can change how the forest behaves," Esquivel-Muelbert says. How will that change the interactions among tens of thousands of species within the jungle? No one yet knows. "It's sending ripples through the system, and we have no idea where they are going to lead," Lovejoy says. "It could become a much simpler ecosystem, and what that means in terms of its overall stability is a real question." If Lovejoy is right, and heat and deforestation lead to less rain and a transition to a different type of landscape, consequences will be felt far and wide.

Around The Examples

Brazil

Indonesia

Venezuela

Madagascar

Expansion

For starters, it's impossible to quantify the true value of lost diversity. In one recent review, a team found evidence that 381 new types of plants or animals had been discovered in the Amazon during a single two-year period from 2014 to 2015—the equivalent of one new species every other day. "It's kind of a cliché that the cure for cancer might be in the Amazon, but it's also kind of true," Esquivel-Muelbert says.

Moisture from the Amazon also nourishes the winter rains that supply Uruguay, northern Argentina and Paraguay with water. The recent drought that led to water shortages in São Paulo, Brazil’s largest city, were probably exacerbated by rainforest shifts. In some places, rainfall in the Amazon also helps supply water to the very soy farmers and beef ranchers who are clearing the forest. Brazilian agriculture, it seems, actually needs the Amazon.

"We need to have forest in order to have the rain necessary to plant crops," Esquivel-Muelbert says. Massive deforestation of the Amazon could change weather outside South America as well. Because water vapour heats the air as it condenses high in the sky to form liquid raindrops, a significant reduction in rain caused by deforestation would actually cool the atmosphere above the region. That cooling perturbation would leave the southern hemisphere in atmospheric waves—generating untold ripple effects around the planet. According to one modeling study, for example, if the Amazon were ever completely deforested, the snowpack in the Sierra Nevada mountains—a crucial water reservoir for California—would be diminished by half. That’s without even considering the effect on CO2 and climate.

Burning Time

"The Amazon stores a tremendous amount of carbon," Nobre says.

Instead of sucking CO2 from the sky, a deforested Amazon could instead begin releasing stored greenhouse gases. If 60 percent of the forest were to degrade to a savanna, Nobre says, that could unleash the equivalent of five or six years’ worth of global fossil-fuel emissions. Michael Mann, a climate scientist and director of the Earth System Science Centre at Pennsylvania State University, called it "another aggravating climate feedback" loop, where drying rainforest leads to less absorption of CO2, which in turn promotes more climate change, drying more forest. "We depend quite a bit on the continued functioning of key carbon sinks," he says. "That’s just one of the many things that makes climate change a global problem."

In fact, deforestation, fire, and climate change already work synergistically in the Amazon. In recent years, climate change has sparked droughts that let wildfires burn bigger and longer. Between 2003 and 2013, forest clearing dropped by 76 percent, but the increase in wildfire, especially during the drought of 2015, erased half the increased absorption of CO2. That's why Lovejoy and Nobre conclude that—contrary to Bolsonaro's campaign promise—what the Amazon needs is not deforestation, but a massive campaign of tree planting.

"It really makes sense to do some active reforestation to build that margin of safety," Lovejoy says. "It doesn't have to be the forest primeval, but you need something with trees and relatively complex communities."At the very least, says Esquivel-Muelbert, Brazil should avoid clearing more. Asked what message she would send to Brazil's new president, she said: "Please, don't make things worse."