In photos: Fires raging in the Amazon rainforest

Every year, farmers in the Amazon rainforest wait until this, the dry season, to clear out areas so their cattle can graze.

But this year's fires are way up over last year, and that has raised concern about what it means for the health of the planet.

The Amazon, the world's largest rainforest, is often referred to as "the planet's lungs" because estimates show that nearly 20% of the oxygen produced by the Earth's land comes from it. The Amazon also puts an enormous amount of water into the atmosphere at a time when cities are drying up.

Environmental campaigners have placed much of the blame on Jair Bolsonaro, Brazil's populist pro-business president who is backed by the country's so-called beef caucus. Bolsonaro has dismissed accusations that he is responsible for the increase in fires, and he declared last week that he would send 43,000 troops to combat the inferno.

The Amazon spans eight countries and covers 40% of South America, but most of it is in Brazil.