UN report says tree planting can result in more greenhouse gas emissions

It is common knowledge that trees act as carbon sinks. Through the process of photosynthesis, trees take in carbon dioxide and release oxygen that we breathe. It is part of the intricate system of life on Earth.

For this reason, many people think that planting more trees across the United States and the world is good for reducing the amount of carbon dioxide in the atmosphere. The Paris Agreement, and policies like carbon pricing and voluntary carbon markets reflect this viewpoint. However, forest growth can sometimes lead to less carbon sequestration rather than more.

A report published by the United Nations University in May explains that tree planting campaigns don’t take into account the reality that trees are part of delicate ecosystems that oftentimes include wildfire. As a result, planting too many trees in the wrong ecosystems can lead to disastrous outcomes.

Many forests today, especially in the western United States, are too dense and overgrown. For example, one study from the US Forest Service found that between 1911-2011, tree density in western forests on average increased by six to seven fold.

This is one of the primary reasons why wildfires are so much more destructive today than they have been historically. Fires burn bigger and hotter when they have more fuel to burn through.

Moreover, the UN University report alludes to the fact that the more trees there are, the more thirsty roots there are in the ground sucking up water. This can contribute to drought conditions that can also lead to more destructive wildfires.

Additionally, wildfires emit enormous amounts of carbon dioxide emissions. Oftentimes, policy choices that encourage tree planting to lower carbon emissions don’t recognize that whatever emissions are going to be saved through photosynthesis are going to be significantly outweighed by the exacerbated emissions from the next wildfire.

Encouraging the planting of more and more trees when it is not prudent can worsen wildfires. The exacerbated wildfire risk of planting trees in the wrong places is yet another problem climate policies fail to account for.