Fires in the Brazilian rainforest have reached record numbers with data from the National Institute for Space Research showing a rise of over 80% from last year.
More than half of these are in the Amazon region.
As the world's largest rainforest, the Amazon is a vital store of carbon, which slows down the pace of global warming.
Boris Johnson says he's "deeply concerned" by the wildfires and has called for international action.
The prime minister has vowed to push for a renewed focus on tackling climate change at the G7 summit this weekend.
The Brazilian president has accused world leaders of interfering after Emmanuel Macron described the blazes, which are emitting smoke that can be seen in space, as an "international crisis".
Environmentalists have blamed Brazil's leader for perpetuating the problem by encouraging farmers and loggers to clear land there.
Conservation director at A Rocha UK, Andy Lester told Premier of his concerns about the fires. He said: "There are currently nine and a half thousand fires burning across the rain forest that have been started illegally, by people wanting to cattle ranch or mine on land that is not owned by them. That is a major problem because it depleting the rain forest at a rapid rate.
"If we're seeing huge fires across an area, the size of the UK or more in Brazil, then we know that in some areas of the world like Brazil, far more trees are disappearing than are being planted."
President Bolsonaro has been accused of blaming non-governmental organisations for starting the fires as revenge for cuts to their funding.
Mr Lester says the Brazilian government is not taking the issue seriously: "Bolsonaro's response has been typical, as many populist political leaders we see them around the world at the moment, which is putting the finger of blame, in this case on the very organisations who are trying to protect indigenous people, and the rain forest from destruction.
Jair Bolsanaro has a strong evangelical Christian following in Brazil and Mr Lester is concerned that the Christian community there are supporting him.
"Unfortunately, he has a big following and many people will believe exactly what he's saying."
"We would certainly be calling all Christians worldwide, but especially those in Brazil, to stop supporting him, boycott Bolsonaro.
"We do not want to be supporting as a Christian community someone who is encouraging the illegal clearance of rain forest, and encouraging the dispersal and removal of indigenous people who have ownership rights to that land.
"It's immoral, irresponsible, and is wrong."
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