President Trump and congressional Republicans are rallying around the idea of planting a trillion trees to boost their environmental credentials ahead of the 2020 election.
House Republican leader Kevin McCarthy of California touts planting trees, the Earth’s “lungs,” as the “most efficient way on the planet to capture carbon” emissions. He’s co-authored legislation coming out soon that would be a vital plank of a broader GOP climate agenda. Trump has endorsed the concept, without citing climate change as the reason, announcing the United States would join an initiative for the world to plant a trillion trees.
While Republicans describe tree-planting as ready-made and easy to understand, it cannot alone make a big dent in cutting carbon, and it carries a host of practical, political, and scientific questions.
“Hypothetically, if we had a unified world government, we could do this relatively easily,” said Seaver Wang, a climate and energy analyst at the Breakthrough Institute. “But even if we did it, a trillion trees don’t dent emissions that much.”
The concept spawned from remarks by an ecologist last year at a meeting held by the American Association for the Advancement of Science, who said that planting 1.2 trillion trees could “cancel out” the last decade of the world’s carbon emissions.
“There is no limit to how much carbon we can store in wood,” said Republican Rep. Bruce Westerman, a co-sponsor of the tree-planting bill with McCarthy, in a recent interview with the Washington Examiner.
The Republican bill would incentivize companies, nonprofit organizations, and individuals to plant trees domestically and abroad by creating “a framework for companies to donate seedlings and other resources,” according to the discussion draft.
Thomas Crowther, the ETH Zurich ecologist who conceived of the 1.2 trillion trees idea and is now the chief scientific adviser to the United Nations’s Trillion Tree Campaign, says there are 400 gigatons of carbon stored in the world’s 3 trillion trees.
There are only 300 billion trees currently in the U.S.
Increasing the world’s trees by another trillion could store the carbon equivalent of wiping out a decades’ worth of accumulated emissions.
But Wang argues that’s not as effective as policies that reduce fossil fuel use, given the emissions reduced from planting trees is a “one-time shot” compared to using zero-emission sources of energy in perpetuity. Most Republicans do not support policies such as carbon taxes or regulations that would lead to less fossil fuel use.
“We know trees alone are not enough by a long shot,” Wang said.
Wang and other experts, however, acknowledge that planting trees and other so-called “natural solutions” are the most cost-effective and accessible carbon capture techniques compared to using machines to capture carbon from power or industrial plants or swipe it directly from the air.
“We can’t think of this as a substitute for decarbonizing the economy,” said Steven Hamburg, chief scientist of the Environmental Defense Fund. “But if we don’t do this, the job gets much harder.”
Wang said there is enough land in the world for a trillion more trees, but the space required for such a project would at least be half the size of the land area of China.
Accessing the land to plant trees would require cooperation across countries, governments, and local populations.
Some of the lands are privately owned and used for other purposes such as agriculture or grazing.
Another potential problem is that global warming is creating more difficult growing conditions for forests.
In the near term, Wang says, planting more trees may have a warming effect in certain parts of the world. Planting in high-latitude regions in the Northern Hemisphere could lead to forest cover darker than Earth’s surface, causing it to absorb more heat, mainly when there’s snow on the ground (think of wearing a black shirt in the sun compared to a lighter color). It’s better to plant trees in tropical areas, but worsening extreme weather events such as droughts, floods, and wildfires put forests at risk of destruction, which would release the stored carbon.
“With a changing climate, we don’t know how forests will hold up,” Wang said.
Also, most current tree-planting programs pick only a few species to plant, which could make the forest more vulnerable to disease and destruction.
Another challenge is the possibility of public resistance to trading land used for food production for planting trees, given the need to feed the world’s growing population.
“What we do with the world’s extra land is an important question of what humanity will need,” Wang said.
Experts say planting trees is not as effective as protecting them from being cut down in the first place because it takes decades for new forests to mature.
“We can plant all the trees we want, but it takes a lot of time for that carbon-storing reservoir to build up,” said Wayne Walker, associate scientist at the Woods Hole Research Center.
Much of the northeast of the U.S. was deforested for agriculture in the 19th century. However, about 80% of that land has been naturally regenerated back to forest, according to Hamburg, because agriculture was not economically viable, and people left the land to pursue different trades.
“To get a forest back, you don’t usually need to plant trees,” Hamburg said. “You want natural regeneration if possible. It is usually faster, it gets higher biodiversity, and it’s cheaper.”
However, recent deforestation trends appear more permanent. Brazil’s right-wing president, Jair Bolsonaro, has implemented policies in the Amazon aimed at deforestation in favor of business development. The Amazon, the world’s largest rainforest, lost an area about 12 times the size of New York City from August 2018 through July 2019, according to government data reviewed by the New York Times.
“You want to absolutely eliminate deforestation as your highest priority,” Hamburg said. “That will have the biggest rate of impact for addressing climate change. Reforesting is a much slower process of getting the same benefits.”
