As the planet heats up, we need to reduce emissions of greenhouse gases.
But there might be other opportunities to gain ground against climate change. Take, for example, so-called ‘nature-based climate solutions.’ These are human interventions that utilize natural processes to draw down carbon from the atmosphere.
According to William Anderegg, director of the Wilkes Center for Climate Science and Policy at the University of Utah, planting forests is an especially promising option.
"The central opportunity here is that we can leverage nature," Anderegg says, "and in particular, forests globally have pretty large potential to help with climate change mitigation.”
Anderegg says that while forests can remove billions of tons of emissions from the atmosphere, there are many problems with the programs that seek to plant forests as a climate solution.
In a new paper published in the journal Nature, Anderegg and his colleagues outline several key issues with nature-based climate solutions. First is the idea of a net-cooling effect. While forests remove carbon from the atmosphere, they can warm the earth in other ways
"The real risk here is that if you went out and planted a bunch of really dark conifer trees," Anderegg says, "like black top on a hot summer day, that would absorb more sunlight and can actually more than cancel out the cooling from storing carbon dioxide."
Anderegg and his colleagues add that carbon credit solutions must also take into account the length of time that carbon from the atmosphere will be stored. Trees can draw down carbon from the atmosphere, Anderegg says, but that carbon can be quickly released back into the atmosphere should the tree burn or die and decompose. Global warming is a pressing problem, but not one that will disappear in a couple of decades. Carbon that is removed from the atmosphere needs to stay 'sunk' in terrestrial sources, hopefully for centuries.
Another important issue that nature-based climate solutions need to confront is known as leakage.
Libby Blanchard, a climate policy specialist at the University of Utah and co-author of this study, explains that, “The challenge with leakage is that, anytime you say, protect a forest, you then are changing the supply and demand dynamics for, say, timber, and you're going to have timber suppliers look elsewhere.”
In this example, if timber suppliers pivot to sourcing timber from other places, this might cause more emissions than are sequestered by the protected forest.
Blanchard says that given these issues, nature-based climate solutions alone won’t be enough.
“Using forests to help with climate mitigation could be great," she says, "but it's only going to be useful if we're also rapidly reducing our fossil fuel emissions.”