- What could become of the some 300 species of mammals living in Amazonia if deforestation and global warming lead to the savannization of the rainforest?
- Researchers analyzed images from 400 photo traps placed in four natural enclaves of the Cerrado biome in southern Amazonia to find some answers; analysis of the photos showed that, when given the choice between preserved Amazon Rainforest and preserved Cerrado, most species chose the rainforest.
- Another study analyzed rainforests around the world, finding that savannization may happen sooner than expected; in Amazonia, this occurrence will mean reduced population and range for mammals like jaguars, tapirs and deer.
If increasing global warming and deforestation were to transform Amazonia into an irreversibly degraded dry savanna, what could happen to the approximately 300 species of mammals that live there? These include jaguars, tapirs and deer.
This is the question that biologists Daniel Rocha and Rahel Sollmann tried to answer in a recently published article in Animal Conservation journal.
Their study involved the analysis of images taken by 400 photo traps installed in four natural enclaves of the Cerrado biome located in Amazonia, which were formed thousands of years ago: in the state of Amazonas, Campos Amazônicos National Park and Mapinguari National Park; and in the state of Rondônia, the Guaporé Biological Reserve and Corumbiara State Park.Their goal was to understand how medium- and large-sized land mammals behave in these isolated patches of savanna in the middle of the rainforest. In doing so, they were able to project what may happen if, some years from now, the climate and vegetation of the planet’s largest tropical forest were to change.
Researchers have been warning of that the savannization of Amazonia is a risk. This is the tipping point when the forest, after suffering from a combination of deforestation and climate change, turns into a vast, treeless plain.
“Studies suggest that, because of global warming, the vegetation in Amazonia will change due to diminished rainfall in the region. As you lose forest, precipitation levels drop,” affirmed Rocha, professor at Southern Nazarene University in Oklahoma, U.S.
With increasing effects of climate change, it is expected that areas of sparse vegetation will progressively spread across Amazonia, especially along the southern and eastern borders of the biome — the region known as the Deforestation Arc where the agricultural frontier is advancing toward the rainforest.
The term “savannization” is commonly used for parts of the forest that become drier and more open, with an appearance similar to the structure of the Cerrado, which is considered a savanna.
But Rocha pointed out that the term “savannization” is not the right one: “This suggests that the rainforest would be substituted by natural savannas. In fact, we are talking about degraded forests that possess nowhere near the richness and diversity of an original savanna.”
“Unfortunately, there are more losers than winners”
During their study, Rocha and Sollmann collected thousands of images with their photo traps over a four-year period from 2016-20.
Using statistical models, the scientists then quantified how 31 land mammal species had used selected areas of Amazon Rainforest and isolated patches of Cerrado, and which they preferred. Many animals are known to move back and forth between the two biomes.
The list of species studied included forest specialists like the Amazonian brown brocket (Mazama nemorivaga) and the short-eared dog (Atelocynus microtis); so-called generalists that inhabit both the forest and the savanna like the spotted jaguar (Panthera onca), the tapir (Tapirus terrestris), the white-lipped peccary (Tayassu pecari) the cougar (Puma concolor) and the collared anteater (Tamandua tetradactyla); as well as those preferring open terrain.
“After gathering the field images, we got to know [the habits of] each species and quantified the intensity of the use they made of each habitat. In other words, how often they were present in each location. What we saw is that most animals use the forested areas more,” said Rocha.
According to their analysis, even the species that become used to using both the forest and savanna environments show preference for those with denser, more closed vegetation. It is believed that these offer greater availability of resources, meaning shelter, hiding places from predators and places to find food.
Only some animals that are specialists in open terrain preferred the Cerrado. These included the maned wolf (Chrysocyon brachyurus), the marsh deer, (Blastocerus dichotomus) and the pampas deer (Ozotoceros bezoarticus).
“All data indicates that these species would be the least affected by the savannization process,” said Rocha. “But unfortunately, there are more losers than winners. Most Amazon species, given the choice between preserved forest and preserved Cerrado, choose the forest.”
The study did not speak to the extinction of these species, but to shrinking populations and range.
Savannization: sooner than we think
According to another study published at the beginning of March in the journal Nature, the risk of savannization in parts of Amazonia may be closer than we think. Researchers at the University of Leeds in the U.K. made a correlation between the loss of tree covering and reduced rainfall in tropical forests in South America, the Democratic Republic of the Congo and Southeast Asia.
Satellite imagery and precipitation data from 2003-17 on deforested terrain with no vegetation and other areas that had not been deforested clearly showed how cutting down forest influences the hydric cycle and rainfall.
The larger the deforested area, the greater the drop in rainfall. In the case of the Congo, if the current rate of destruction continues, rainfall there could drop by 8-12% by the end of this century.
“The loss of forest projected in Amazonia would result in a drop in precipitation of around 2 millimeters [0.1 inches] per month for each percentage point of lost forest covering, which equals an approximately 1% decline in rainfall,” affirmed researcher Callum Smith, the study’s main author.
In the Brazilian Amazon, it is noteworthy that in the month of February 2023, a historic negative record was set: 322 square kilometers (124 square miles) of rainforest were razed that month — the highest index for the month of February since INPE, Brazil’s National Institute for Space Research, began collecting data in 2015.
For Rocha, it is also important to remember that climatic changes are among the main vectors for possible savannization of Amazonia — and these are not local phenomena, but global. They will affect all areas, including protected ones.
“All the conservation units that were part of our study will be subject to this process. So our ability to protect these animal species will drop in both protected and unprotected areas. This is worrisome,” he affirmed.
Banner image: The marsh deer in savanna terrain inside the Corumbiara State Park. Photo courtesy of Daniel Rocha.
Rocha, D. G., & Sollmann, R. (2023). Habitat use patterns suggest that climate‐driven vegetation changes will negatively impact mammal communities in the Amazon. Animal Conservation. doi:10.1111/acv.12853
Smith, C., A. Baker, J. C., & Spracklen, D. V. (2023). Tropical deforestation causes large reductions in observed precipitation. Retrieved from https://www.nature.com/articles/s41586-022-05690-1