Tropical deforestation releases deadly infections

A huge range of animals – and their pathogens – lives in the forests of Brazil. Image: by Nate Johnston on Unsplash

Brazil’s burning forests are bad news for the global climate. Now scientists say the trees harbour deadly infections too.

SÃO PAULO, 29 April, 2020 − As forest destruction continues unabated in Brazil, scientists are alarmed that, as well as spurring climate change, it may unleash new and deadly infections on humankind.

There is growing awareness that large-scale tropical deforestation, as in the Amazon, not only brings disastrous consequences for the climate, but releases new diseases like Covid-19 by enabling infections to pass from wild animals to human beings.

As one well-known Amazon scientist, biologist Philip Fearnside, puts it: “Amazon deforestation facilitates transmission both of new diseases and of old ones like malaria.

“The connection between deforestation and infectious diseases is just one more impact of deforestation, added to impacts of losing both Amazonia’s biodiversity and the forest’s vital climate functions in avoiding global warming and in recycling water.”

He is one of the co-authors of a paper by a team led by Joel Henrique Ellwanger on the impacts of Amazon deforestation on infectious diseases and public health, which has just been published in the Annals of the Brazilian Academy.

Dr Fearnside adds: “Many ‘new’ human diseases originate from pathogens transferred from wild animals, as occurred with the Covid-19 coronavirus. Amazonia contains a vast number of animal species and their associated pathogens with the potential to be transferred to humans.”

No surprise

The warnings are not new. Ana Lúcia Tourinho, with a Ph.D in ecology at the Federal University of Mato Grosso (UFMT), interviewed by Deutsche Welle, said: “For at least two decades scientists have repeated the warning: as populations advance on the forests, the risk grows of micro-organisms – up till then in equilibrium – migrating to humans and causing victims.

“That is why news of the propagation of the new coronavirus detected in China, which has spread throughout the world, was not a surprise.

“When a vírus which is not part of our evolutionary history leaves its natural host and enters our body it brings chaos”, she said.

Isolated and in equilibrium with their habitats, like dense forests, this sort of vírus would not be a threat to humans. The problem comes when this natural reservoir is destroyed and occupied (by other species).

Scientific studies published years before the present pandemic already showed the connection between the loss of forest, proliferation of bats in the degraded areas, and the coronavirus.

One example is the study by Dr Aneta Afelt, a researcher at the University of Warsaw, who concluded that the high rates of forest destruction in the last 40 years in Asia were an indication that the next serious infectious disease could come from there.

“For at least two decades scientists have repeated the warning: as populations advance on the forests, the risk grows of micro-organisms migrating to humans”

To reach this conclusion, she followed the trail of previous pandemics triggered by other coronaviruses like Sars in 2002 and 2003, and Mers in 2012.

“Because it’s one of the regions where population growth is most intense, where sanitary conditions remain bad and where the rate of deforestation is high, south-east Asia has all the conditions for becoming the place where infectious diseases emerge or re-emerge”, she wrote in 2018.

If destruction of the Amazon continues at the present accelerated pace, Dr Tourinho says, and it is turned into an area of savannah, “we cannot imagine what might come out of there in terms of diseases.”

The relationship between deforestation and the increase of diseases in the Amazon has been studied by Brazil’s Institute of Applied Economic Research (IPEA).

A 2015 survey in 773 Amazon towns showed that for each 1% of forest destroyed, malaria cases increased by 23%. The incidence of leishmaniasis, a disease spread by the bite of sand flies, which causes skin sores, disfigurement and can kill, also increased.

Since Jair Bolsonaro, an extreme right-wing climate denier, became president of Brazil in January 2019, the rate of deforestation, followed by forest fires, has exploded.

Officially-sanctioned illegality

This year the Institute of People and the Environment of the Amazon (Imazon)’s deforestation alert system (SAD) reports that an area of 254 sq km in the Amazon region was deforested in March, a increase of 279% over the same month last year.

This is even more alarming because traditionally deforestation begins in June, at the end of the rainy season. This year it has begun three months earlier.

The illegal clearing of the forest, much of it in indigenous reserves or conservation areas, by land grabbers, for cattle, soy, and logging projects, and by miners panning for gold, has been openly encouraged by Bolsonaro and his so-called Environment Minister, Ricardo Salles.

The Amazon Council set up by the president to coordinate action in the region does not include a single scientist, environmentalist or Amazon researcher, or even any experts from the government agencies for the environment and indigenous affairs, Ibama and Funai.

Instead, all its members are officers of the armed forces or the police. The likelihood that it will do anything serious to stop deforestation is zero.

Yet the destruction of the Amazon is a disaster not only for the world’s climate but also for its health, and Brazil is set to become one of the worst-affected countries. Climate News Network