Decarbonizing the world’s fossil fuel–dominated economy must happen, but many other parts of the solution to the climate crisis are based in nature. As part of this portfolio of approaches, new research shows that we should be taking much better care of our last great intact forests because doing so has remarkable climate benefits.

The numbers reveal a staggering increase in the estimated CO2 released by losses of intact tropical forest between 2000 and 2013—626 percent higher than previously thought.

Yet these intact forests are neglected in the targeting of funds, policies and public concern—eclipsed by more visible deforestation frontiers and reforestation opportunities. If we are going to stay on top of the runaway growth in CO2 levels in the atmosphere, this needs to change.

The key insight of the study homes in on the way intact forests are packing ever more carbon into the living matter, deadwood and soils on each acre of land. Summed across all intact forests, and to a lesser extent some other intact ecosystems like grasslands, this so-called “sink” removes fully a quarter of all humanity’s carbon emissions each year, free of charge—surely one of the most important yet least well-known parts of the climate story. 

If we stop this sink from doing its job, most of that quarter will remain in the atmosphere (with a little of it dissolving in the sea), increasing the rate at which CO2 levels rise each year by a third at a time when we need to be pulling every lever at our disposal to lower carbon dioxide. It would be like yanking out the plug whilst trying to fill the bath.

The study also revealed the insidiousness of forest fragmentation. You don’t have to clear a forest to reduce its ability to act as a sink; you just have to damage it. By looking at the millions of acres across the tropics that were damaged during 2000–2013, the study tallied up the extent to which pressures like fires, logging, and drought along new forest edges reduced the carbon stored and absorbed long-term by previously intact forests. 

The figures were six times worse than conventional estimates that only look at outright forest clearance, with the forgone sink, seldom considered by previous studies of this kind, dominating the picture. In essence, a single episode of serious damage can lead to decades of “lost earnings” in the carbon accounts.

Climate impacts aside, many other environmental services are also put at risk by this damage, including biodiversity, watershed protection, rainfall patterns and the survival of some of the world’s most imperiled cultures. 

More than 7 percent of intact forests were damaged in the study period. These threats are set to worsen. Losses had accelerated by 2016 and will continue to grow in the future, with 25 million kilometers of new road expected to be built by 2050, much in intact areas, and increasing global demand for timber, minerals and food.

The tropics are not the only places to suffer, as few intact forests survive in the temperate belt. Even in the northern boreal zone they are in rapid retreat. By the end of the century, at best a half of today’s intact forest area might still be intact, and probably far less.

What is to be done? Ultimately the damaging processes need to be reined in. We must plan new infrastructure so as to avoid the most critical areas, the fragmentation by farms and fires must be curtailed, and the overhunting of ecologically critical animal species must be brought under control.

The outline of the solution is well understood and has two parts. One is better protection of the key areas, both by governments investing in national parks and protected areas and by indigenous peoples and other local communities through recognition and enforcement of traditional land rights. The other is cleaning up and reorienting the unsustainable supply chains that feed international trade in food, fiber, minerals and energy.

These solutions are simple to describe but have proved very hard to deliver in the face of strong economic drivers and a host of vested interests and other political challenges. To back enhanced action, decisive policy change is needed, making the integrity of ecological systems a priority in international and national policies on climate, biodiversity and the Sustainable Development Goals themselves.

The global community then needs to clean up the financial sector, shifting so-called “gray” investments into “green” ones through better screening, and to reassess the rules of climate funds and other development support, which often divert incentives away from intact forests because of a mistaken belief that they are not at risk or that the impacts are small. Today’s new scientific insights clearly disprove that belief. 

The world’s intact forests, though embattled, are still vast, and at 2.5 billion acres (one billion hectares) represent one the greatest treasures nature has given us. If we are to have any hope of stabilizing our ailing climate, action at every level from international treaty to local community is needed to keep that treasure safe from harm.