- Thousands of fires are ravaging the Amazon rainforest - the most intense blazes for almost a decade.
- The smoke has been travelling as far as the Atlantic coast. It has even caused skies to darken in São Paulo - more than 3,200km away.
- The Amazon basin - home to about three million species of plants and animals, and one million indigenous people - is crucial to regulating global warming, with its forests absorbing millions of tonnes of carbon emissions every year.
Thousands of fires are ravaging the Amazon rainforest in Brazil - the most intense blazes for almost a decade.
The northern states of Roraima, Acre, Rondônia and Amazonas as well as Mato Grosso do Sul have been particularly badly affected.
However, images purported to be of the fires - including some shared under the hashtag #PrayforAmazonas - have been shown to be decades old or not even in Brazil.
So what's actually happening and how bad are the fires?
There have been a lot of fires this year with Brazil having seen the record number of them in 2019 according to the Brazilian space agency.
The National Institute for Space Research (Inpe) says its satellite data shows an 85 percent increase on the same period in 2018.
The official figures show more than 75,000 forest fires were recorded in Brazil in the first eight months of the year - the highest number since 2013. That compares with 40,000 in the same period in 2018.
CAUSE OF THE FIRES
Wildfires often occur in the dry season in Brazil but they are also deliberately started in efforts to illegally deforest land for cattle ranching.
"The dry season creates the favourable conditions for the use and spread of fire, but starting a fire is the work of humans, either deliberately or by accident," Inpe researcher Alberto Setzer told Reuters news agency.
Ricardo Mello, head of the World Wide Fund for Nature (WWF) Amazon Programme, said the fires were "a consequence of the increase in deforestation seen in recent figures".
Activists say the anti-environment rhetoric of Brazilian President Jair Bolsonaro has encouraged such tree-clearing activities.
In response, Mr Bolsonaro, a long-time climate sceptic, accused non-governmental organisations of starting the fires themselves to damage his government's image.
He later said the government lacked the resources to fight the flames.
MOST AFFECTED AREAS
The north of Brazil has been the worst-affected region.
Roraima, Acre, Rondônia and Amazonas all saw a large percentage increase in fires when compared with the average across the last four years (2015-2018).