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10% Of Frogs And Toads Face Extinction From Climate Change In Brazil

Publicado em 20 setembro 2018

Por Sam Bezerra

As climate change threatens to reorder the world as we know it, species across the world will lose their habitats and be subject to new climate conditions. Many of these species will be forced to adapt or face extinction. How significant the impact will be is not yet known, but it could be severe.

In a new study, researchers from Brazil’s São Paulo State University have found that climate change could cause the extinction of 10 percent of the existing frog and toad species in the Atlantic Rainforest within the next 50 years.

The study is published in the journal Ecology and Evolution.

A changing habitat

The researchers examined the predicted climate conditions in the Atlantic Rainforest and the Cerrado (the Brazilian savanna) between 2050 and 2070 and found that a host of species will be unfit to survive under the new climate conditions.

The Atlantic Rainforest, home to tens of thousands of species of plants and animals, is one of the most biodiverse ecosystems on the planet, second only to the Amazon. Likewise, the Cerrado is the world’s most biodiverse savanna, home to 5 percent of the planet’s animals and plants.

Many of these species are specially adapted to the climate and habitat conditions that they evolved under.

The major shifts in temperature and precipitation patterns that are predicted to occur as a result of climate change could therefore pose a serious threat to the survival of species that are less adaptable to different climates.

“We see a variety of environments in which amphibians can occur, but any variation in climate can be enough to affect an amphibian lifestyle,” said herpetologist Tiago da Silveira Vasconcelos, a researcher at São Paulo State’s School of Sciences and the first author of the study.

As climate change threatens to reorder the world as we know it, species across the world will lose their habitats and be subject to new climate conditions. Many of these species will be forced to adapt or face extinction. How significant the impact will be is not yet known, but it could be severe.

In a new study, researchers from Brazil’s São Paulo State University have found that climate change could cause the extinction of 10 percent of the existing frog and toad species in the Atlantic Rainforest within the next 50 years.

The study is published in the journal Ecology and Evolution.

A changing habitat

The researchers examined the predicted climate conditions in the Atlantic Rainforest and the Cerrado (the Brazilian savanna) between 2050 and 2070 and found that a host of species will be unfit to survive under the new climate conditions.

The Atlantic Rainforest, home to tens of thousands of species of plants and animals, is one of the most biodiverse ecosystems on the planet, second only to the Amazon. Likewise, the Cerrado is the world’s most biodiverse savanna, home to 5 percent of the planet’s animals and plants.

Many of these species are specially adapted to the climate and habitat conditions that they evolved under.

The major shifts in temperature and precipitation patterns that are predicted to occur as a result of climate change could therefore pose a serious threat to the survival of species that are less adaptable to different climates.

“We see a variety of environments in which amphibians can occur, but any variation in climate can be enough to affect an amphibian lifestyle,” said herpetologist Tiago da Silveira Vasconcelos, a researcher at São Paulo State’s School of Sciences and the first author of the study.

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“So any variation in temperature and precipitation regimes, year by year, has the potential to disrupt some life cycle characteristic of toads and frogs, and those organisms more dependent on a specific microhabitat (such as forest-dependent species) are those ones more vulnerable to the effects of climate change.”

Today, there are 550 known species of anurans (tailless amphibians such as frogs and toads) inhabiting the Atlantic Rainforest, along with 209 known species inhabiting the Cerrado.

The study examined the 350 species in the Atlantic Rainforest and 155 species in the Cerrado that have more than five occurrence records.

Of these, the researchers found that climate change will likely lead to the complete extinction of 37 species in the Atlantic Rainforest and five species in the Cerrado due to the loss of favorable climate conditions in the observed time period.

The study

In the study, the researchers used four algorithms — generalized linear models, boosted regression trees, random forests and support vector machines — to create models that predict the occurrence of species based on climate conditions, known as environmental niche models, in the Atlantic Rainforest and the Cerrado.

The algorithms generated maps of the two biomes that show areas where species would be able to survive because of similar climate conditions. Then, using climate projections from the WorldClim global climate database, the researchers adjusted the maps to predict species distribution in the future.

“In projecting future climate change conditions for 2050 and 2070, we used two carbon gas emission scenarios — one more optimistic with less global warming and the other more pessimistic and warmer,” Vasconcelos said in a statement. “We also used three different atmosphere-ocean global circulation models.”

The scenarios and models used in the study were gathered from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), an international body for the assessment of climate change established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988.

In total, the researchers generated 24 distribution maps for each of the 505 species analyzed in the study, creating a total of 12,000 maps. These maps were then used to build a consensus map and a species presence-absence matrix, which could be used to forecast the occurence of each species.

“Our study is based on a correlational approach in which we characterize the climatic preference of species according to the specific occurrence points of each species,” said Vasconcelos. “We then project this climatic species preference (formally climatic niche) into different bioclimatic scenarios (2050, 2070). So, we are able to look for future climatically suitable areas.

“For 10 percent of the studied species in the Atlantic Forest, we found no climatically suitable area by 2050 or 2070, which means that these species have no climatically similar area in the future compared to those that they have today.”

The shifts in climate will have varied effects across the Atlantic Rainforest and the Cerrado, making some conditions more favorable to certain species while making others entirely uninhabitable.

“The results of our research show expansion of the areas with favorable climate conditions for anuran amphibians,” Vasconcelos said in a statement. “Rising temperatures will lead to the expansion of Cerrado areas in a northern and northwestern direction, occupying what is now Amazon forest. The savannization of Amazon forest areas will open up new areas for occupation by amphibians from the Cerrado.”

But Vasconcelos also noted that climate change will likely lead to the homogenization of anuran species across the Cerrado, as the species more adapted to climate variation will expand while others will decrease in population.

Potential effects

The loss of these anuran species could have ripple effects throughout the ecosystem, and could even affect human populations living in these areas.

“If amphibians go extinct, or have severe population declines, this may lead to the proliferation of some insects that frogs and toads feed on,” said Vasconcelos. “Of course, insects may also respond to climate change, but we know that frogs and toads feed on a wide variety of insects, including those vectors of important human diseases, such as dengue fever and Zika virus, so an increasing incidence of these diseases may occur.”

“Additionally, if amphibians prey less on insects, the agricultural sector may also be affected due to the infestation of herbivores insects on plantations,” he added.

What can we do?

Unfortunately, there is no way to completely prevent these changes from occuring. Vasconcelos noted that climate change is already underway. Even if the human population stopped pumping greenhouse gases into the environment tomorrow, we would still feel the effects of over a century of persistent fossil fuel emissions.

But adopting sustainable practices, both small and large scale, could help mitigate the effects and potentially help a number of species survive.

By reusing, recycling and reducing, individuals can help decrease the emission of greenhouse gases.

Meanwhile, noted Vasconcelos, organizations and governments must collaborate to find ways to decrease broad-scale greenhouse gas emissions by supporting the development and use of renewable energy.

“Additionally,” he said, “due to the wide consensus among scientists on the potential redistribution of species in future climate change scenarios, it is also important that decision-makers and politicians consider scientists’ opinions for more effective conservation actions that deal with biodiversity redistribution under climate change.”