Much of the Amazon’s biodiversity is under fire — literally.
In the last two decades, deforestation and forest fires have encroached on the ranges of thousands of plant and animal species in the Amazon rainforest, including up to 85 percent of threatened species in the region, researchers report September 1 in Nature.
The extent of the damage is closely tied to the enforcement, or lack thereof, of regulations in Brazil aimed at protecting the forest from widespread logging as well as the fires often used to clear open space in the forest and other encroachments. The findings illustrate the key role that forest use regulations have in the fate of the Amazon rainforest, the researchers argue.
Threats to the survival of this biodiversity could have long-term effects. Biodiversity boosts a forest’s resilience to drought, says Arie Staal, an ecologist at Utrecht University in the Netherlands who was not involved with this research. A deep bench of tree species allows the plants to replace those that may not survive drought conditions, he says. “If fire-impacted area continues to rise, not only does the Amazon lose forest cover, but also some of its capacity to cope with the changing climate.”
And as fires advance deeper into the rainforest, more species will experience fire for the first time, Staal says. “These species, including many threatened ones, have not evolved under circumstances with regular fires, so the consequences for those species can be severe.” Such consequences may include increased risk of population declines or extinction, similar to the fears following the major outbreak of fires in Australia in 2019 and 2020 (SN: 3/9/21).
In recent decades, ongoing deforestation and periodic drought in the Amazon basin have been associated with intensifying fires there (SN: 11/20/15). In 2019, a particularly severe series of fires scorched the region (SN: 8/23/19).
“But we do not know how fires are impacting the biodiversity across the Amazon basin,” says Xiao Feng, a biogeographer at Florida State University in Tallahassee. The Amazon “is a huge area, and it is generally impossible for people to go there and count the number of species before the fire and after the fire,” he says. “That’s an incredible amount of work.”
So Feng and a team of collaborators from Brazil, China, the Netherlands and the United States instead investigated how Amazonian plant and animal species’ geographic ranges have been exposed to recent fires. The team compiled range maps of 11,514 plant and 3,079 vertebrate species, creating what may be the most comprehensive dataset of range maps for the Amazon. The team compared these maps with satellite images of Amazon forest cover from 2001 to 2019. Those images let the team track how logging and fires have led to the degradation of rainforest habitat.
Fire impacted up to about 190,000 square kilometers — an area roughly the size of Washington state, the team found. Up to about 95 percent of the species featured in the study had ranges that overlapped with fires during this period, though for many species, burned areas made up less than 15 percent of their overall range.
Affected species include up to 85 percent of the 610 considered threatened — so vulnerable to extinction or already endangered or critically endangered — by the International Union for Conservation of Nature. This category includes as many as 264 kinds of plants, 107 amphibians and 55 mammals. In 2019 alone, over 12,000 species experienced fire somewhere in their geographic range.
Starting in 2009, when a series of regulations aimed at reducing deforestation started being enforced, the extent of fires generally decreased, except in drought years, the team found. Then in 2019, fires ticked back up again, coinciding with a relaxation of regulations. Much of the fire-driven forest loss was congregated along the more intensely logged southern reaches of the rainforest.
The shift suggests that effective forest preservation policies can slow this trend of destruction, and may be crucial for preventing the region from reaching a tipping point. That point would occur when the cycle of deforestation, drying and fire triggers widespread transformation of the Amazon basin into a savanna-like habitat.
While this study couldn’t track the fate of specific plants or animals, Feng now plans to look at fire’s impact on certain groups of species that may have very different vulnerabilities to an increasingly flammable Amazon. “We know some trees may be more resistant to burns, but some may not. So it may also be really important to distinguish differences,” he says.
sciencenews.org, 1 September 2021