Planting trees won’t solve climate change

2020-05-27

in Politics, Science, The environment

Back in 2009, I described various ways to try to deliberately engineer the Earth system to reduce the severity of climate change and noted:

The first way to do this is to encourage the growth of biomass. This is relatively easy, but has limited potential. Biomass is like a giant carbon cushion: it can be thick or thin, but it cannot keep growing forever. Increasing the amount of biomass on Earth could draw down the amount of CO2 in the atmosphere a bit, but only if we also manage to cut our greenhouse gas emissions to practically zero.

Now that Prime Minister Trudeau has pledged to plant 2 billion trees as a climate solution (using expected pipeline revenue, to try to justify Canada’s continuing fossil fuel expansion) it’s worth having a post specifically on the limited ability of tree-planting to combat the problem.

A recent Slate article notes:

The notion that any significant percent of the carbon humanity spews can be sucked up by planted trees is a pipe dream. But it got rocket boosters in July, when Zurich’s Crowther Lab published a paper, in Science, proclaiming that planting a trillion trees could store “25 percent of the current atmospheric carbon pool.” That assertion is ridiculous, because planting a trillion trees, one-third of all trees currently on earth, is impossible. Even a start would require the destruction of grasslands (prairies, rangelands, and savannas) that reflect rather than absorb solar heat and that, with current climate conditions, are better carbon sinks than natural forests, let alone plantations. Also, unlike trees, grasslands store most of their carbon underground, so it’s not released when they burn.

The Crowther paper horrified climate scientists and ecologists, 46 of whom wrote a rebuttal, explaining that planting trees in the wrong places would exacerbate global warming, create fire hazards, and devastate wildlife. They rebuked the authors for “suggesting grasslands and savannas as potential sites for restoration using trees” and for overestimating by a factor of 5 “potential for new trees to capture carbon.”

Counter-intuitively, growing trees in order to burn them could actually be more of a climate solution, provided we develop the carbon capture and storage technology and infrastructure needed to bury the resulting CO2.

{ 5 comments… read them below or add one }

Oleh May 31, 2020 at 5:25 am

I hope that as these different methods of combatting climate change are developed. That the long term effects are considered.

I was reading in passing in the Economist how nuclear power was placed alongside renewables as sources of energy that are fossil energy free.

Anon June 5, 2020 at 3:36 am

Doesn’t this just mean that the process needs to be about rebuilding diverse ecosystems which can be resilient in the face of things like pests and fires and store carbon long-term? It won’t correct for continuing to use fossil fuels forever, but it could help mitigate how harmful the pollution we have already caused will be.

. June 8, 2020 at 7:43 pm
alena prazak June 8, 2020 at 7:55 pm

Justin Trudeau likes to say, promise and do nice things. He wants to be remembered as a good and caring guy. Although his decisions, especially economic ones, may not be smart for the future, his heart seems to be in the right place. Like BC’s Dr. Bonnie Henry, he handled the Covid-19 crisis calmly and perhaps contributed to its gentler course in our country.

. June 22, 2020 at 4:04 pm

Climate change: Planting new forests ‘can do more harm than good’

Rather than benefiting the environment, large-scale tree planting may do the opposite, two new studies have found.

One paper says that financial incentives to plant trees can backfire and reduce biodiversity with little impact on carbon emissions.

A separate project found that the amount of carbon that new forests can absorb may be overestimated.

The key message from both papers is that planting trees is not a simple climate solution

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