As humans continue to rapidly expand the scope of their domination of nature – bulldozing and burning down forests and other natural areas, wiping out species, and breaking down ecosystem functions – a growing number of influential scientists and conservationists think that protecting half of the planet in some form is going to be key to keeping it habitable.

The idea first received public attention in 2016 when E.O. Wilson, the legendary 90-year-old conservation biologist, published the idea in his book Half Earth: Our Planet’s Fight for Life. “We now have enough measurements of extinction rates and the likely rate in the future to know that it is approaching a thousand times the baseline of what existed before humanity came along,” he told The New York Times in a 2016 interview.

Once thought of as aspirational, many are now taking these ideas seriously, not only as a firewall to protect biodiversity, but also to mitigate continued climate warming.

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One of the major reasons for adoption of these extreme preservation goals is a 2019 report by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), which found that more than 1 million species are at risk of extinction. Conducted by hundreds of researchers around the world, the study is considered the most comprehensive analysis of the state of the world’s biodiversity ever.

That report concluded that it’s not only species that are at risk, however. The myriad life-support functions that these species and ecosystems provide also are threatened — everything from clean water and air to flood control and climate regulation, food and a host of other services.