Why the Tree-Planting Climate Debate Needs a Reality Check — And How We Can Get It Right

New research suggests that the climate benefits of planting trees may not be as significant as previously thought. While reforestation, or replanting trees in damaged areas, can help reduce greenhouse gas emissions, its overall impact is limited. If we don’t adjust current practices, reforestation alone won’t significantly contribute to achieving net zero emissions.

Trees absorb carbon dioxide (CO₂) from the air and store it. This makes reforestation an important climate tool. However, our study found that the potential for reforestation is much lower than some estimates. Without a change in our approach, the benefits won’t be enough to meet climatic targets.

Close to 135 countries have pledged to reach net zero emissions, which means they’ll remove CO₂ from the atmosphere. Reforestation is seen as a key part of this goal. For instance, China has successfully stored about 7 billion metric tons of CO₂ through extensive reforestation efforts over the past 40 years.

In contrast, Australia’s initiatives, like the 20 Million Trees Program, are projected to capture a mere 0.2 million tons of CO₂ each year, representing only 0.04% of the nation’s total emissions. Other factors, such as expanding agriculture and urban areas, further complicate where trees can be planted.

Interestingly, not all areas are suitable for reforestation. Our study focused on land previously covered by forests, excluding urban and agricultural zones, as well as areas sensitive to biodiversity loss. We found that around 389 million hectares are available for potential reforestation—about half of earlier estimations. Most of this suitable land is in the Americas and Europe, with Brazil, Russia, and the U.S. holding the most promise.

However, the global commitment to reforestation isn’t enough. For the years 2021-2030, nations promised to reforest about 230 million hectares, which is 59% of the available area mentioned in our findings. Yet, these commitments largely come from lower-income countries facing land limitations. For example, many African nations have made pledges, but their land represents only a small fraction of available reforestation space.

Our research also highlights how much carbon can be stored. By employing a new machine-learning model, we analyzed data from over 3,000 locations worldwide. If trees were planted in all suitable areas, up to 4.9 billion metric tons of CO₂ could be captured annually by 2050. However, considering current commitments, this number could drop to 1.5 billion tons, still only a fraction of global emissions.

This emphasizes that while reforestation is important, it cannot replace efforts to reduce fossil fuel emissions. Globally, reforestation currently captures around 1.9 billion metric tons of CO₂, making up only about 5% of emissions from fossil fuels, which total around 36 billion tons each year.

Our study shows a gap between ambition and reality. Many countries that have pledged to reforest lack the suitable land to do so effectively. Wealthy nations, which possess ample potential for reforestation, aren’t stepping up as they should.

To move forward, high-income countries need to commit more land to reforestation. Additionally, they should finance projects in lower-income nations. Market initiatives that put a financial value on environmental preservation are gaining traction, rewarding landholders who engage in tree-planting. Local communities and indigenous peoples should also play key roles to ensure these projects align with regional needs and cultures.

Ultimately, reforestation must complement efforts to halt deforestation and reduce reliance on fossil fuels, not serve as a substitute for these actions.

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