Monday, November 06, 2023

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Forest chump? Scientists take a closer look at tree planting projects

2023/11/06
There are many forestation projects underway and while these are a good idea, some make more sense than others, say researchers. 
Thomas Warnack/dpa

If your work and lifestyle leave a heavy carbon footprint, you can have trees planted to compensate. Companies do the same, because trees store carbon dioxide (CO2), which helps the climate, right?

Mostly yes, though it can be more complicated. Even if planted trees benefit the climate, the degree to which they do so is often impossible to quantify, say scientists.

In the worst case, planting trees can even have the opposite effect, though in principle, the idea is not a bad one, says Christopher Reyer of Germany's Potsdam Institute for Climate Impact Research (PIK).

"We need more forests," is the bottom line, after all.

Researchers in Britain recently analysed the sustainability reports of 100 of the world's largest companies. Of these, 66 said they implement ecological measures and 44 plant trees, Science magazine reports.

The study shows that more than 90% did not report any ecological results. Moreover, none of the reports quantified the social or economic impact on local stakeholders.

"At the moment there is very little transparency, which makes it hard for anyone to assess if projects are delivering benefits for ecosystems or people," says lead study author Tim Lamont from Lancaster University.

"When a business says it has planted thousands of trees to restore habitat and soak up carbon – how do we know if this has been delivered, if the trees will survive, and if it has resulted in a functioning ecosystem that benefits biodiversity and people?"

In many cases, the evidence provided by large corporations to support their claims was insufficient, Lamont adds. Large international corporations could play a key role in restoring ecosystems, but accountability is key, the study concludes.

Trees remove CO2 from the air and store carbon. How much carbon they capture depends on the species, site conditions and the trees' lifespan. The heavier and denser the wood, the more carbon is stored.

For photosynthesis - the process by which plants turn sunlight into sugars and then emit oxygen - trees also take CO2 from the atmosphere, using the carbon to form roots, trunks and leaves. Much is stored in the tree, while the oxygen is released into the air.

A tree's carbon storage capacity also depends on its age. Young forests store less than old ones. Geographical location also plays a role, writes the Hamburg-based Forest Enterprise Foundation, which promotes nature conservation and forest research.

Tropical forests grow faster than forests in Europe and therefore store more CO2 over the same period of time. Generally, the foundation says one hectare of forest stores about six tonnes of CO2 per year across all age classes.

Planting to faciliate carbon storage does work, says PIK's Reyer, who researches effects of climate change for forests and possible countermeasures. "But in practice it's just often not done so well."

When companies plant trees, that doesn't mean those trees will survive, he notes. Planting only one type of tree usually makes no sense as monocultures have little resistance to storms or drought and fall victim to pests more quickly.

Some forestation projects can also destroy local ecosystems, for example moors or steppes. Elsewhere, planting can involve the clearing of illegal settlements, prompting people to build new dwellings elsewhere, damaging intact ecosystems.

A newly planted forest could also dry out the soil or have other side effects, he says.

"Ultimately, you have to keep an eye on the overall climate balance," says Reyer.

This data is not new and there are many great projects that take these factors into account, he says. But consumers, trying to ease their conscience with an "indulgence trade-off" through planting, cannot distinguish between the projects out there.

Reyer is critical of the numerous certification systems on the market as there is no legal framework for tree planting campaigns, just a lot of uncontrolled growth.

Instead, he favours reforestation over new planting, because that at least ensures the site is suitable for a forest.

Even if tree projects alone won't save the climate, forests can contribute a lot to climate protection, according to a 2022 report by the European Forest Institute.

The EU aims to be climate-neutral by 2050 – an economy with net-zero greenhouse gas emissions.

But a more holistic approach is needed that avoids deforestation, increases afforestation and reforestation and employs different uses of wood and recycling, the institute says.

Combine all that with action in other sectors, say the authors, and reaching climate neutrality by 2050 might be possible.

The world needs forests but not all forestation projects are equal.



Avoiding monocultures is important when it comes to reforestation. 

Trees grow at different rates and absorb differing amounts of carbon, scientists say. 

Daniel Vogl/dpa

© Deutsche Presse-Agentur GmbH

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