Could we ‘regrow’ tropical forests after they are destroyed?

Is the destruction of tropical forests a one-way street - or could we regrow them after they are destroyed?

Researchers at Wageningen University found that some tropical forests CAN recover - but it depends on factors such as rain and types of trees.

But the researchers say that planting trees can stimulate regrowth - although care needs to be taken to pick the ‘right’ species to fit in to dry or wet forests.

The researchers analysed data from more than 127,000 trees in 30 tropical forests in North and South America.

Lourens Poorter, forest ecologist at Wageningen University & Research and lead author said: "It is a challenge to compare these forests, because they consist of completely different species. That's like comparing apples and oranges.

"You can also compare forests based on the functional properties of the species, such as leaf size or wood density. As a result, for the first time we were able to compare young forests with the same ecological measure on a continental scale."

"Functional traits influence species growth and survival, and thus ecosystem processes. By analysing forests in terms of their characteristics, we can gain insight not only into how these forests are constructed, but also what this means for their functioning."

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The authors measured seven characteristics for each species.

Some of these traits are important for drought tolerance, such as small compound leaves, tough wood, and the ability to shed leaves in the dry season.

Other traits are important for productivity, such as the ability to fix atmospheric nitrogen, thin leaves that capture light efficiently, and high leaf nitrogen content.

In dry forests, the authors recommend planting species that can are drought tolerant, and fast-growing species in wet forests.

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The researchers say that it is always necessary to use a mix of species with contrasting trait values. This helps to create more natural, biodiverse and resilient landscapes.

Coauthor Danae Rozendaal said, "We found that wet and dry forests differ markedly in their traits. Species of wet forests have traits that increase their growth rate in a productive, wet environment, whereas, species of dry forests have traits that allow them to tolerate or avoid drought."

Forest regrowth is something that has been promoted by the United Nations Decade for Ecosystem Restoration.

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Brazilian coauthor Catarina Jakovac says, "Forest restoration efforts should ideally rely on natural regeneration, as this is a low-cost, natural solution for ecosystem restoration, with the highest gains for biodiversity, ecosystem functioning and services.

"However, when the landscape is too degraded, tree planting can stimulate forest succession."

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