Authors: Jonah Busch, Jens Engelmann, Susan C. Cook-Patton, Bronson W. Griscom, Timm Kroeger, Hugh Possingham, & Priya Shyamsundar
Full citation: Busch, J., Engelmann, J., Cook-Patton, S. C., Griscom, B. W., Kroeger, T., Possingham, H., & Shyamsundar, P. (2019). Potential for low-cost carbon dioxide removal through tropical reforestation. Nature Climate Change, 9(6), 463.
Abstract: Reforestation offers one of the best ways to remove carbon dioxide from the atmosphere, turning it into solid carbon through photosynthesis and storing it in tree trunks, branches, roots, and soil. Reforestation can be a cost-effective climate solution, too, according to a recent study in Nature Climate Change of the cost of reforestation across 90 tropical countries that I conducted with colleagues at The Nature Conservancy and the University of Wisconsin.
According to our analysis, a hypothetical tropics-wide carbon price of $20 per ton of carbon dioxide—around the current price in European and Californian carbon markets—would incentivize land users to increase reforestation by enough to remove an additional 5.7 billion tons of carbon dioxide (5.6%) from 2020-2050, equivalent to thirty years of current greenhouse gas emissions from Kuwait (Figure 1).
A higher price of $50-100 per ton of carbon dioxide—consistent with what’s needed to achieve the Paris Climate Agreement—would increase removals by between 15.1 and 33.3 billion tons of carbon dioxide (14.8-32.5%) between 2020-2050—equivalent to thirty years of current emissions from the United Kingdom or Japan.
We came to our conclusions by simulating the effects of payments for increased carbon removals on future land-cover changes, accounting for geographical differences across sites, and assuming that land users would be as responsive to changes in carbon prices as they were to historical variation in agricultural prices.
The cost of reforestation compares favorably to other “negative emissions technologies” (NETs). We compared our cost estimates for tropical reforestation to Sabine Fuss and colleagues’ cost estimates for NETs that may become operational by 2050. On a cost-per-ton basis, tropical reforestation is more cost-effective in 2050 than bio-energy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS). It’s as cost-effective in 2050 as biochar, and less cost-effective than enhanced weathering or soil carbon sequestration.
On average, avoiding deforestation is 7-10 times more cost-effective than reforestation, but reforestation is more cost-effective than avoiding deforestation in some places. Reforestation offers more abatement than avoided deforestation at $20 per ton in 21 out of 90 tropical countries studied.
Tropical reforestation and avoided deforestation combined offer up to one-third of a comprehensive, cost-effective, near-term solution to climate change. The combined potential of increasing removals from reforestation and reducing emissions from deforestation at $20-50-100 per ton is 161-123-192 billion tons from 2020-2050. Averaged out on a per-decade basis, those levels of mitigation represent, respectively, 10-21-33% of the 197 billion tons of mitigation needed from 2020-2030 to hold global warming below 2 °C. This supports the finding of a landmark 2017 study by Bronson Griscom and colleagues, which found that twenty natural climate solutions worldwide offer more than one-third of the cost-effective near-term solution to climate change.
Based on these findings, tropical countries should accelerate reforestation, and developed countries should step up international finance for reforestation, especially through provisions of the Paris Climate Agreement related to reducing emissions from deforestation and forest degradation, “plus” re-growing forests (REDD+).
Figure 1. Marginal abatement cost curves for increased removals from tropical reforestation and reduced emissions from avoided deforestation.