Parts of Brazil’s Amazon rainforest are being illegally being sold on Facebook.
The protected areas include national forests and land reserved for indigenous peoples.
Some of the plots listed via Facebook’s classified ads service are as large as 1,000 football pitches.
Facebook said it was “ready to work with local authorities”, but indicated it would not take independent action of its own to halt the trade.
“Our commerce policies require buyers and sellers to comply with laws and regulations,” the Californian tech firm added.
The leader of one of the indigenous communities affected has urged the tech firm to do more.
And campaigners have claimed the country’s government is unwilling to halt the sales.
“The land invaders feel very empowered to the point that they are not ashamed of going on Facebook to make illegal land deals,” said Ivaneide Bandeira, head of environmental NGO Kanindé.
Anyone can find the illegally invaded plots by typing the Portuguese equivalents for search terms like “forest”, “native jungle” and “timber” into Facebook Marketplace’s search tool, and picking one of the Amazonian states as the location.
Some of the listings feature satellite images and GPS co-ordinates.
Many of the sellers openly admit they do not have a land title, the only document which proves ownership of land under Brazilian law.
The illegal activity is being fuelled by Brazil’s cattle ranching industry.
Deforestation in the Brazilian Amazon is at a 10-year high, and Facebook’s Marketplace has become a go-to site for sellers like Fabricio Guimarães, who was filmed by a hidden camera.
“There’s no risk of an inspection by state agents here,” he said as he walked through a patch of rainforest he had burnt to the ground.
With the land illegally cleared and ready for farming, he had tripled his initial asking price to $35,000 (£25,000).
Fabricio is not a farmer. He has steady middle-class job in a city, and views the rainforest as being an investment opportunity.