For the climate: keep old trees or plant new ones?

by Dr. Philipp Staudacher, 27.04.2022
"Plant a tree and save the climate"; Various initiatives make it their mission to plant as many trees as possible to prevent climate collapse. Restoring forests is indeed a great idea, but do you know what you can do with trees for the climate that is even better?

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Young trees absorb little CO2

You learned it at school: Trees grow by absorbing light and taking in CO2 and water. In turn they exhale oxygen. Recently, CO2 uptake has attracted great public interest because trees (and other plants) are a natural solution for absorbing CO2 from the air. However, trees grow very slowly. Foresters do not usually experience the cutting down of a young tree they manage. Trees absorb the most CO2 when they are fully grown, which is usually not for several decades. This means that if we desperately need to remove CO2 from the atmosphere, planting new trees, also known as reforestation, might be too slow.

What is the fastest, cheapest and most effective way to reduce CO2 emissions?

In addition to ecosystem restoration, there are two other ways that trees can have a positive impact on CO2 sequestration: One is to improve management, and the other is to protect what already exists. A recent publication compared these three options in terms of scale, speed, cost-effectiveness, and additional benefits. All three paths are legitimate and have their advantages. However, because most organizations are constrained to a budget, the researchers rank the variants:

Protecting ecosystems is the cheapest fast option

Protection of existing natural ecosystems ranks number one. This offers a high reduction potential that can be realized quickly and at a comparatively low cost per ton of CO2. In addition, protecting existing ecosystems has many positive side effects, such as limiting deforestation and halting biodiversity loss. Protection mainly prevents the release of additional emissions from changes in land use.

Improving management means investing in what you already have

Improved managementrainforest from above comes second because it is less expensive than reforestation. In addition to forest management, examples of improved management can be found in regenerative agriculture, such as trees in cropland, improved rice cultivation, or nutrient management. As these examples show, they go hand in hand with existing commodity production and are therefore less likely to shift problems to neighboring regions. This could happen, for example, if the land is placed under protection and farmers or foresters move to the next unprotected area. Improved management means focusing on preventing the release of further emissions while removing CO2 from the atmosphere.

Forest restoration has the greatest potential but fails without the other measures

Out of all three options, reforestation has the greatest potential to remove CO2 from the atmosphere. However, it alone cannot compensate for what may be lost if we do not protect the existing ecosystems. In addition, reforestation projects are only cost-effective if they are carried out on a large scale and over decades. They allow the trees to mature and absorb a maximum of carbon from the atmosphere.

What does that mean for me?

If you have now decided on contributing to forest-based solutions to the climate crisis, here is what to consider before spending your money:

  • How long has the organization been active? Chances are good that an entity that started conservation or restoration projects before the 2015 Paris Agreement is taking its work seriously.
  • How big are the projects they are involved in? It’s not just planting new trees that benefits from scale. Ecosystem protection also works best on a larger scale.
  • What are your personal opportunity cost? Can you invest the money to educate yourself and help others reduce their emissions? Can you organize your everyday working life in such a way that you emit fewer emissions, e.g. because you travel less frequently?

To defeat the climate crisis, we need everything to work together and immediately

The above hierarchy – ecosystem protection first, improved management second, and restoration third – is to be considered as a rule of thumb at the global level. However, depending on the political context in each area, one or the other may be preferred.

In any case, we must act now. Protecting ecosystems means no more destruction and stopping carbon release immediately. If we plant trees today, they will be mature by 2050, when we must achieve at least a net-zero balance. The best time to do both is today.




Cook-Patton et al., 2021 – Protect, manage and then restore lands for climate mitigation

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