The Amazon rainforest is a vast tract of largely untamed jungle that is Earth’s most biodiverse region, filled with plants and trees and teeming with animals of all types and sizes — including many unknown to science.

It is also the world's largest rainforest, spanning more than 2 million square miles in northern South America, mainly in Brazil but also in parts of Peru, Colombia and six other nations. It’s called a rainforest because of its rainy conditions.

But though it has existed for 50 million years, the Amazon rainforest is now under threat from human activities, including devastating fires set to clear acreage for ranching and agriculture as well as the mining of oil and gas, copper, iron and gold.

The rainforest contributes about $8.2 billion a year to Brazil's economy from products including rubber and timber.

In recent months, the Amazon region has been hit by thousands of fires that collectively have cleared more than 7,400 square miles of rainforest in Brazil. Scientists say the recent spate of fires reverses a long trend toward fewer fires and less deforestation.

Why has there been so many wildfires in the Amazon recently?

Fires break out every year in the Amazon rainforest, often accidentally during the dry months of September and October. But satellite photographs show that many fires in the Brazilian portion of the rainforest were set deliberately to clear land.

“This is a clear difference from recent years,” says Douglas Morton, an ecologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland,

What are the risks of deforestation?

Scientists who study the Amazon worry that deforestation could bring the rainforest to an ecological “tipping point” at which the entire ecosystem collapses. That could cripple regional economies and cause the loss of many indigenous species.

“It is a scary prospect, the potential for a dieback or a collapse of the Amazon region,” Morton says.

The rainforest brings rainfall across South America, and much of the continent would become hotter and drier if large portions of it were to be destroyed. The shift to a more arid climate would devastate the vast agricultural areas farther south; parts of South America would become effectively unlivable.

The decline of the Amazon rainforest could also affect the global climate, although scientists are unsure exactly how. At the least, rainfall patterns across North America, Europe and Africa would change.

Despite some media reports to the contrary, scientists say the loss of the Amazon rainforest wouldn’t dangerously limit sources of breathable oxygen. The oxygen created by vegetation in the rainforest is largely consumed by the animals living there. Most of the oxygen in Earth’s atmosphere was created over millions of years by microscopic ocean plants called phytoplankton.

What is the Amazon rainforest's ecological significance?

The Amazon rainforest stores a huge amount of carbon in its vegetation and soil. If the burning of vegetation released all that carbon into the atmosphere, efforts to limit climate change by cutting down on carbon dioxide emissions from motor vehicles and industrial processes would become pointless, says Yadvinder Malhi, an ecologist at the University of Oxford in England. “Any chance of doing that would be blown out of the water.”

Given the vast numbers of plants and animals that live there, the Amazon rainforest is of incalculable biological and ecological value. It’s home to about 390 billion trees and more than 16,000 plant species and millions of animal species.

“This is the richest place on our planet, from the billions of years of evolution of life before humans were around," Malhi says. "It’s one of the great libraries of nature on Earth.”

Among the animals that live in the rainforest are some of the world’s rarest and most colorful birds; hundreds of monkey species; giant cats like jaguars and black panthers; and unusual creatures like tapirs and capybaras. It’s also home to crocodiles, lizards, giant snakes like the anaconda, amphibians like the famous poison dart frogs we well as rare pink river dolphins and fish like arapaimas and piranhas.

All of these species and thousands more could be lost if the Amazon rainforest were to collapse.