[revised 6/30/25]

Humans have been chopping down and burning trees for a long time, and deforestation is ongoing. Sometimes forest grow back on their own (“natural regeneration”). In the US, most of New England is forested again, after the farms that once replaced trees were abandoned.¹ Humans also plant trees. “Reforestation” is planting trees to restore forests while “afforestation” refers to planting where there were no trees before or not recently. Could we plant trees, a trillion of them, to save ourselves from climate change? What does large-scale tree planting look like?

Franklin D. Roosevelt conceived of the Great Plains Shelterbelt in response to the Dust Bowl. From 1935 to 1942, 220 million trees were planted in 30,233 shelterbelts from Canada to Texas. Besides protecting crops and reducing erosion, FDR’s Great Green Wall also provided wood and a home for birds and game, trapped snow which helped to increase soil moisture, and protected structures from harsh winds – houses and schools could have more windows!² Many shelterbelts are gone now, as farmers plant fencerow-to-fencerow and make room for mechanical irrigators.³

China’s Three-North Shelterbelt Forest Program is the world’s largest tree planting program, begun in 1978 to counter land degradation (“desertification”) by bringing tree cover to an area over northwestern, northern, and northeastern provinces. More than 30 million hectares (74 million acres) of trees have been planted.⁴ But China’s Great Green Wall had a rough start, with die-offs of trees not used to arid conditions. Single species plantations erased biodiversity and were vulnerable to pests and diseases.⁵ Tree planting can have negative effects, such as taking land away from farmers, introducing invasive species, and destroying grasslands or other ecosystems.⁶

The Great Green Wall for the Sahara and the Sahel is an African-led initiative to grow an 8,000 km band of vegetation across the width of Africa.⁷ It began with tree planting but has become more flexible, with a mosaic of projects restoring about 18 million hectares (44 million acres) of degraded land restored so far. Examples include planting crops among trees, growing trees from stumps, digging retention basins to store rainwater, and selecting useful native species such as the baobab and tamarind, frankincense and gum acacia, and African grape, for food, income, and medicine.^{8 9} Projects succeed when managed by local stakeholders whose livelihoods rest on sustaining crops and trees for the long term.

Trees remove carbon from the atmosphere as they grow and can store carbon for long periods of time. Carbon is released when trees die.¹⁰ How much carbon is sequestered by trees depends on tree species, ages, and durations, where they are planted, on how much land, and other variables.¹¹ Addressing global warming always comes back to cutting greenhouse gas emissions produced by burning fossil fuels and by deforestation. After that, preserving existing forest is far better than planting trees. It’s cost-effective, supports water balance and biodiversity, and provides immediate carbon storage. Also important is recovering deforested areas, preferably by letting them regrow naturally^{12 13} or with limited assistance. What about the monoculture plantations favored for timber production? Fast growing trees absorb carbon, but are soon harvested, often for paper, cardboard and wood chip products that degrade rapidly and release carbon back into the atmosphere. Such plantations can still be useful if they prevent deforestation elsewhere.

Planting trees must be done carefully. Which trees should be planted, and where?¹⁴ If the “right tree, right place” dictum isn’t followed, trees won’t thrive or survive, as seen in China’s Great Green Wall in early phases. Africa’s Great Green Wall recognizes the key role of local peoples and builds on their input, stewardship, and resilience. When planting trees, it’s better to look to the wellbeing of communities and ecosystems, rather than to focus solely on carbon or the number of trees planted. The shelterbelts on the Great Plains had value in the past, but are dwindling as farms change. Two great forest initiatives continue in China and Africa, making adjustments as lessons are learned. The final accountings may yet show that ambitious projects are better than none.¹⁵

FOOTNOTES

1. A Trillion Trees. Restoring our forests by trusting in nature. F Pearce, 2021. On-the-ground stories from around the world on restoring forests, why and how ↩︎
2. FDR’s ‘Great Wall of Trees’ continues to provide lessons. L Reed, May 2017 (https://news.unl.edu/article/fdr-s-great-wall-of-trees-continues-to-provide-lessons) ↩︎
3. Uprooting FDR’s ‘Great Wall of Trees’. C Vaughan, Nov 2017 (https://thefern.org/2017/11/uprooting-fdrs-great-wall-trees/) Many shelterbelts are gone now, as farmers plant fencerow-to-fencerow, make room for mechanical irrigators, and adopt other advances. ↩︎
4. Can China’s afforestation knowledge green the world? F Hao, Aug 2019 (https://dialogue.earth/en/forests/11480-can-china-s-afforestation-knowledge-green-the-world/) ↩︎
5. Why China’s ‘Great Green Wall’ might not be the ecological victory it seems – a biologist explains. S Travers, Mar 2025 (https://www.forbes.com/sites/scotttravers/2025/03/25/why-chinas-great-green-wall-might-not-be-the-ecological-victory-it-seems-a-biologist-explains/) ↩︎
6. Tree planting is not a simple solution. KD Holl & PHS Brancalion. May 2020 (https://www.weforest.org/wp-content/uploads/Tree-planting-is-not-a-simple-solution_Karen-D.-Holl-Pedro-H.-S.-Brancalion_0.pdf) ↩︎
7. “The Great Green Wall is an African-led movement to grow an 8,000km green swath across the entire width of Africa” (https://thegreatgreenwall.org/about-great-green-wall) ↩︎
8. Progress is slow on Africa’s Great Green Wall, but some bright spots bloom. S Raman, Aug 2023 (https://news.mongabay.com/2023/08/progress-is-slow-on-africas-great-green-wall-but-some-bright-spots-bloom/) ↩︎
9. Five ways the Great Green Wall is helping to reforest the Sahel region. S Newell, undated (https://www.bbcearth.com/news/five-ways-the-great-green-wall-is-helping-to-reforest-the-sahel-region). Another example is circular gardens, developed by a Senegalese agriculture engineer, in which drought-resistant trees and shrubs planted around the outside protect smaller food-producing species in inner circles. ↩︎
10. How many new trees would we need to offset our carbon emissions? A Moseman et al, Jan 2024 (https://climate.mit.edu/ask-mit/how-many-new-trees-would-we-need-offset-our-carbon-emissions) ↩︎
11. The potentials and limitations of tree plantings as a climate solution. N Forrester, Jun 2020 (https://science.feedback.org/the-potentials-and-limitations-of-tree-plantings-as-a-climate-solution/) ↩︎
12. Restore natural forests to meet climate goals (referencing an article by SL Lewis, et al), Apr 2019 (https://www.sciencedaily.com/releases/2019/04/190402081533.htm). Land put aside for natural forests holds 6 times more carbon than agroforestry and 40 times more carbon than plantations. ↩︎
13. How do you save a rainforest? Leave it alone. M Simon, Nov 2024 (https://grist.org/climate/save-rainforest-carbon-science-biodiversity/) ↩︎
14. Ten golden rules for reforestation to optimize carbon sequestration, biodiversity recovery and livelihood benefits. A Di Sacco & KA Hardwick et al, Jan 2021 (https://doi.org/10.1111/gcb.15498  https://onlinelibrary.wiley.com/doi/10.1111/gcb.15498) ↩︎
15. China’s ‘great green wall’ boosts carbon sink, study finds. Z Nannan, Oct 2023 (https://phys.org/news/2023-10-china-great-green-wall-boosts.html) ↩︎