In a scenario close to the current one, global warming of 1.5°C could put 9% to 14% of species in all ecosystems at a very high risk of extinction. The planet has already warmed by 1.1°C.
The assessment is part of the new IPCC (UN Intergovernmental Panel on Climate Change) report, released on Monday (28). Prepared by 270 scientists, the study reviewed 34,000 studies and computed the impacts of climate change on human development and biodiversity.
The climate panel rates the risk of extinction of 9% to 14% of species in all ecosystems as likely with a warming of 1.5°C. In a 2°C scenario of mean global warming, the risk of extinction rises to the range of 10% to 18%, reaching a maximum of 48% in a 5°C scenario.
The groups most at risk are invertebrates and pollinators, followed by amphibians and flowering plants. While scenarios in which global warming is contained to 2°C are much less damaging to biodiversity, the report notes that even the lowest predicted extinction rate –9%– is 1,000 times the natural rate.
Since the last report of its kind released by the IPCC in 2014, the geographic coverage of the surveys has expanded, as have the climate models used in the scenario projections.
“One thing that surprised us is that several hotspots [áreas prioritárias] in Brazil, in the Amazon, in the Atlantic Forest and in the Cerrado, are among the best studied in the world in terms of the projected impacts of climate change”, says Mariana Vale, a researcher at UFRJ (Federal University of Rio de Janeiro) and one of the authors of the IPCC report.
“Since the last edition of the report, in 2014, there has been a very large generation of knowledge. But there is still a lack of studies in the caatinga, pantanal and pampas”, she points out.
In the case of endemic species in priority areas for biodiversity conservation, the risk of extinction could double in the scenario of warming between 1.5°C and 2°C and increase at least tenfold if the warming jumps to 3°C, according to the report.
Irreversible damage to biodiversity, the extinction of species triggers a series of impacts on ecosystems and environmental services that affect human health.
“Species are the fundamental unit of ecosystems and increasing risk to them increases risk to ecosystem integrity, functioning and resilience,” the report states.
“As species become rare, their roles in ecosystem functioning decrease. Species loss reduces an ecosystem’s ability to provide services and decreases its resilience to climate change,” the study explains.
The loss of biodiversity and environmental degradation are already observed in all regions of the planet today. Changes in biomes and the risk of fires also increase with rising temperatures.
“Approximately half of globally assessed species have moved to the poles or, on land, also to higher altitudes. Hundreds of local species losses were driven by increases in the magnitude of heat extremes, as well as mass die-off events on land and in the ocean and loss of kelp forests”, points out the climate panel.
The loss of the local population of species is also already happening due to changes in temperature, especially heat waves and prolonged droughts.
Of 976 species evaluated in different regions of the world, 47% suffered extinction of local populations in years of record temperature.
Most of the extinction of local biodiversity populations took place in tropical regions (55%), while 39% took place in temperate regions. Freshwater environments also had greater disappearance of entire populations (74%). Marine habitats suffered 51% losses and terrestrial ones, 46%. Half of the extinct populations were animals (50%), another 39% of the losses were from plants.
The golden frog was one of the species whose extinction in 1990 is linked to climate change. Endemic to Costa Rica’s highland forests, it disappeared after successive extreme droughts.
Another case cited by the UN report is of a species of skunk from Australia, which almost disappeared after heat waves in 2005 – four years later, only two individuals of the species were found.
Studies have evaluated the genetic alterations of some species, but controlled selection experiments and field observations indicate that evolution would not prevent a species from becoming extinct if its climatic space disappeared globally.
“Climate hazards outside of those to which species are adapted are occurring on every continent. More frequent and intense extreme events, superimposed on long-term climate trends, have pushed sensitive species and ecosystems to tipping points beyond the capacity for ecological adaptation. and evolutionary”, points out the report.
However, if there are refuges with lower temperatures, the species may persist.
“Protecting refuges, for example, where soils remain moist during drought or fire risk is reduced and, in some cases, creating cooler microclimates, are promising adaptation measures,” the study concludes, although noting that there is still little scientific literature on the effectiveness of climate adaptation measures to protect ecosystems.
Transversal measures, argues the climate panel, can represent joint solutions for biodiversity and human development.
“Growing evidence shows that ecosystem-based adaptation techniques in urban and rural areas can lessen climate risks to people (in floods, droughts, fires and overheating) and also have benefits for biodiversity and forest protection,” says the report. report.
