Disturbed fraction of vegetation across South America simulated by the HadGEM2-ES Earth System Model, at 1860, 2005, and four future scenarios at 2100: RCP2.6 (high mitigation), RCP4.5, RCP6.0, and RCP8.5 (high emissions). Graphic: Marengo, et al., 2018 / Frontiers in Earth Science

By Rodrigo de Oliveira Andrade
24 January 2019

SÃO PAULO (SciDev.Net) – Brazil’s new government, led by President Jair Bolsonaro, has quickly taken steps to loosen environmental law enforcement. Now a review paper shows that the deforestation that could result may have terrible consequences for the Amazon rainforest, including dramatic biodiversity loss, intensified dry seasons, droughts, all ultimately leading to a “state of collapse”.

Scientists worldwide say Bolsonaro’s stance on science and the environment is worrying. He promotes development at all costs and has threatened to follow US President Donald Trump and pull Brazil out of the 2015 Paris agreement.

During the election campaign, he made no secret of his desire to open indigenous lands to mining, farming and dam building, even though about 13 per cent of Brazilian territory is recognised as indigenous lands and protected by law.

Now a review by the climatologist José Marengo, from the National Centre for Monitoring and Early Warning of Natural Disasters, and his colleagues draws together a broad set of data on the Amazon climate to analyse, among other things, the probable effects of large-scale deforestation.

Marengo says that studies recently begun to suggest that Amazon deforestation could reach a tipping point beyond which the ecosystem could collapse. “The combined effects of drought and deforestation, along with fire, might amplify impacts and potentially cause the collapse of the rainforest ecosystem,” he says.

About 19 per cent of the Brazilian rainforest that existed in 1970 has already been cut down. One study from 2018 suggested the tipping point could be as low as 25 per cent deforestation. “If this tipping point is crossed, part of forest might be converted into a savannah,” says Marengo. “It would potentially have large-scale impacts on climate, biodiversity, and the people living there.”

Extreme climatic events, such as droughts, floods, changes in the rainy and dry seasons, and forest fires could also increase, he says. [more]

Brazil’s government may push the Amazon to destruction

ABSTRACT: This paper shows recent progress in our understanding of climate variability and trends in the Amazon region, and how these interact with land use change. The review includes an overview of up-to-date information on climate and hydrological variability, and on warming trends in Amazonia, which reached 0.6–0.7°C over the last 40 years, with 2016 as the warmest year since at least 1950 (0.9°C + 0.3°C). We focus on local and remote drivers of climate variability and change. We review the impacts of these drivers on the length of dry season, the role of the forest in climate and carbon cycles, the resilience of the forest, the risk of fires and biomass burning, and the potential “die back” of the Amazon forests if surpassing a “tipping point”. The role of the Amazon in moisture recycling and transport is also investigated, and a review of model development for climate change projections in the region is included. In sum, future sustainability of the Amazonian forests and its many services requires management strategies that consider the likelihood of multi-year droughts superimposed on a continued warming trend. Science has assembled enough knowledge to underline the global and regional importance of an intact Amazon region that can support policymaking and to keep this sensitive ecosystem functioning. This major challenge requires substantial resources and strategic cross-national planning, and a unique blend of expertise and capacities established in Amazon countries and from international collaboration. This also highlights the role of deforestation control in support of policy for mitigation options as established in the Paris Agreement of 2015.

Changes in Climate and Land Use Over the Amazon Region: Current and Future Variability and Trends



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