How Climate Change Is Threatening the Biodiversity of the Brazilian Savanna
The Cerrado, a tropical savanna in Brazil that covers an area larger than Mexico, has already lost half of its native vegetation.
Climate change threatens to push endemic species in the Cerrado, Brazil’s vast tropical savanna, into extinction while allowing the spread of species already commonplace elsewhere, a new study says.
This will make the Cerrado, which covers more than 20 percent of Brazil’s territory—an area greater than the size of Mexico—and which has already lost over 50 percent of its native vegetation, less resilient to future changes.
“The study adds to mounting evidence that future climate change is poised to change the very fabric of biological life on Earth,” said Julian Olden, a professor of ecology at the University of Washington, who was not affiliated with the study.
The study, published in March in the journal Perspectives in Ecology and Conservation by ecologist José Hidasi-Neto and colleagues at the Federal University of Goiás–Brazil, found a general decrease in species richness, and a homogenization pattern in certain areas, like the southern Cerrado, despite the high rate of influx of species from other biomes into the savanna.
“Generally speaking this represents a future where the Cerrado will have [fewer] species of mammals and where generalist species coming from other biomes, like the Amazon and Atlantic Forests, will expand their ranges into the Cerrado,” said Marcus Cianciaruso, a contributing author to the study. “As a consequence we will have dramatic changes in Cerrado mammal species composition, where specialist species will be lost and generalist species will dominate all the landscapes of the Cerrado.”
Different Kinds of Biodiversity Under Threat
Around 30 percent of Brazil’s biodiversity is found in the Cerrado, including 837 species of birds, 120 reptiles, 150 amphibians, 1,200 fish, 90,000 insects, and 199 mammals, some of which are endemic to the biome. Naturally occurring species in local terrestrial ecosystems worldwide are estimated to have lost at least 20 percent of their original abundance on average, according to a recent high-profile report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. In hotspots of endemic species, like the Cerrado, that percentage goes up.
The flat landscape of the Cerrado, which contains 5 percent of the world’s total biodiversity, makes it both ecologically more vulnerable, and also favored for mechanized agriculture. Agriculture has already transformed around 50 percent of the native vegetation, which ranges from forest to grasslands, to farmland.
The researchers looked at ecological conditions and requirements for 309 mammals that are adapted to or could adapt to the Cerrado under different climate change scenarios, commonly used by the international community to represent different possible future atmospheric concentrations of greenhouse gases.
According to the study, nine mammalian species may become regionally extinct by 2070. These include not just species that are already endangered, according to IUCN Red List categories, but also those not currently under threat.
Hidasi-Neto said the finding came as a surprise. “That is something that is important to note; even currently non-threatened species in the Cerrado might be threatened by climate change,” he said.
Biodiversity in general is important as it influences how well and how fast a community can adapt to environmental disturbances, but it can be measured in various ways. Many biodiversity studies look at species richness in an area, known in ecological terms as alpha-diversity. In this study, the richness of the Cerrado’s mammalian communities is expected to decrease.
The study also looked at the composition of species across different regions, known as beta-diversity—considered an ecologically important indicator of how a region as a whole might adapt to climate change.
Worldwide, human destruction of ecosystems directly through agriculture and urbanization, and indirectly through anthropogenic climate change has led to the loss of native species from ecosystems. At the same time, increased global trade and other factors have introduced many non-native, common species. These two processes have contributed to the widespread erosion of differences between ecological communities, known in ecological terms as biotic homogenization. According to the IPBES report, this is one of eight ways that nature and ecosystem services are deteriorating as a result of human activity.
Biotic homogenization, what the IPBES report refers to as the “anthropogenic blender,” has prompted some ecologist to herald the coming era in Earth’s history as the “Homogocene.”
“The projected biotic homogenization of mammalian faunas in the Cerrado biodiversity hotspot is very concerning,” Olden said. “These changes are predicted to occur across multiple dimensions of biodiversity, with potential long-term implications for ecosystem function.”
Low beta-diversity results in this biotic homogenization, where many of the species in different regions become more similar. This study found that biotic homogenization would peak in the southern Cerrado, the area currently experiencing the most rapid amount of agricultural development.
“The paper has fundamental implications for the focal group of organisms in the region,” Akira Mori, an ecologist at Yokohama National University, who was not affiliated with the research, told Mongabay. He said that, overall, the paper confirmed some of the key issues related to climate change.
The results align with previous studies that show that one of the most pervasive effects of climate change is a reduction in beta-diversity—especially important in regions that are subject to large environmental fluctuations and disturbances.
“Think about the amazingly diverse gastronomic scene in New York being replaced only by fast-food restaurants,” Cianciaruso said of biotic homogenization. “Everywhere you go you could only find hamburgers and nothing else.”
Implications for the Conservation of the Cerrado
The results of the study tie into a larger body of work that looks at how protected areas will become less effective in the future due to the range shifts of many species in response to climate change. For the authors of the paper, one of the biggest implications of this study is its contribution to ongoing discussions about how to best conserve the Cerrado.
“The impacts of climate change will be broad, so we don’t just need some protected areas in some spaces,” Hidasi-Neto said. “We need a network of protected areas to serve different species, so it will be easier for them to migrate.”
Currently, less than 3 percent of the Cerrado constitutes formal protected areas, such as national parks, state parks, and biological reserves. An additional 4.1 percent comprises indigenous lands. The total falls far short of the 17 percent minimum of ecologically important areas targeted for conservation by 2020 under the Convention on Biological Diversity, which Brazil has ratified.
Major biodiversity loss has been called both one of the most likely and also most serious global risks with “irreversible consequences for the environment, resulting in severely depleted resources for humankind as well as industries,” according to the 2019 Global Risks Report from the World Economic Forum. The IPBES report warns that up to 1 million species already face extinction, many within decades, unless action is taken to reduce the intensity of drivers of biodiversity loss.
This story originally appeared at the website of global conservation news service Mongabay.com. Get updates on their stories delivered to your inbox, or follow @Mongabay on Facebook, Instagram, or Twitter.