Does Planting Trees Actually Cool the Planet?

In the fight against climate change, planting trees is often touted as a simple and effective solution. Trees absorb CO2, so planting more should reduce greenhouse gases. However, tree-planting efforts don't always succeed. When is it bad to plant trees, and what strategies can ensure successful re-greening?

The Pitfalls of Afforestation

Many tree-planting initiatives focus on afforestation, planting trees in areas that have long been without forests, rather than reforestation, which restores degraded forests. Governments and organizations often pursue afforestation to meet ambitious tree-planting goals, but this approach can have unintended consequences.

The Bonn Challenge

The Bonn Challenge, launched in 2011, aims to restore 350 million hectares of degraded land by 2030, partly through afforestation. While well-intentioned, such large-scale projects can lead to problems if not carefully planned.

Corporate Greenwashing

Many companies use tree planting to offset emissions and improve their public image. However, a 2021 Oxfam analysis revealed that the land needed to meet the tree-planting goals of just four major oil and gas producers would be twice the size of the UK. This raises questions about the feasibility and sincerity of these efforts.

The Complexities of Carbon Storage

For trees to act as long-term carbon sinks, they must mature and remain standing. However, many afforestation projects involve commercial forestry, which often leads to the planting of non-native trees that are eventually harvested.

The Problem with Plantations

Chile's afforestation efforts, for example, heavily subsidized the commercial forestry industry, leading to the expansion of plantations with non-native species. These plantations are often less effective at carbon storage than natural forests. Studies show that natural forests can store up to 40 times more carbon than plantations.

Flammable Trees

Common plantation trees like pine and eucalyptus are highly flammable. Wildfires can quickly release the stored carbon back into the atmosphere, negating any gains.

The Importance of Ecosystems

Not all land is suitable for forests. Planting trees in savannas, for instance, can harm wildlife that thrive in open spaces. Savannas naturally store carbon below ground, protecting it from fire and herbivores.

Unintended Consequences

In drylands or snowy regions, trees can absorb more of the sun's rays, contributing to warming rather than cooling. It's crucial to consider the local ecosystem when planning tree-planting projects.

Strategies for Successful Re-Greening

To maximize the benefits of tree planting, programs must carefully consider which species to plant, where to plant them, and how to protect the land long-term. Chile is now prioritizing native trees over timber plantations.

Protecting Existing Forests

Some experts argue that protecting existing forests and allowing nature to regenerate is the most effective approach. On deforested land, seeds remain in the soil, and new sprouts emerge from old stumps. Birds and wind carry seeds from nearby forests, aiding natural regeneration.

Assisted Natural Regeneration

Assisted natural regeneration involves helping nature along by:

• Removing grasses that compete with saplings
• Preventing grazing
• Planting trees in small patches

When Tree Planting Goes Wrong

Planting the wrong trees in the wrong places can be detrimental. It's also problematic when tree planting is used as a catch-all solution without addressing the root causes of climate change, such as carbon emissions and deforestation.

Greenwashing

Tree planting can become an act of greenwashing when companies and governments invest in initiatives that have little chance of achieving their promised carbon offsets. True progress requires cutting carbon emissions and protecting existing forests.

The Path Forward

The best investments for a greener future involve reducing carbon emissions and safeguarding existing forests. Thoughtful, well-planned tree-planting initiatives can play a role, but they must be part of a broader strategy to combat climate change.