Like all living plants, trees remove carbon dioxide from the atmosphere through the process of photosynthesis. Restoring and preventing further loss of native forests is therefore essential for combating climate change. It reduces human vulnerability to climate change by providing shade and cooling, reduces air pollution, stores carbon, builds natural systems resilience, prevents erosion and reduces flood risk by slowing water flow and supports biodiversity.
However, it is important to remember, just because a tree can grow somewhere, it does not mean that it should. Planting trees in historically unforested areas (grasslands, shrublands, savannas, some peatlands) can reduce biodiversity and increase the risks of damage from climate change. Planting trees in low rainfall areas can for example cause reductions in stream flow and groundwater. Swapping grassy ecosystems for forests may contribute to warming, as forests absorb more warmth than grasslands.
It is therefore essential to target tree planting to the appropriate locations and use appropriate species. Instead of planting trees everywhere, focus on ecosystem restoration. For example, in restoring tropical grassy ecosystems, we can look at actions that cut down trees, enhance grass regrowth, and restore natural fire regimes. We have then a much better chance of both enhancing carbon capture and reducing some of the harmful effects of climate change.