Global warming: half of the replanted trees do not survive

At a time when major forest restoration actions are being carried out across the planet, both to preserve biodiversity but also to fight against climate change, a study points to the survival rate of replanted trees: half young shoots planted do not survive more than five years.

Preserving wildlife and the resources offered by the forest is a necessity, as is storing the carbon in the soil emitted by human activities. In this context of global warmingglobal warmingthe backupbackup of forests is more topical than ever. About 15% of the world’s tropical forests are located in Southeast Asia and they are among the best storage areas of carboncarbonthanks to their incredible biological diversity: in addition to sheltering an extremely diversified vegetation, they are the habitat ofspeciesspecies threatened as tigerstigers, primates and elephants. However, in recent decades, this region has been affected by massive deforestation: 32 million hectares disappeared between 1990 and 2010. Faced with this ecological disaster, major reforestation actions have been carried out. But does this reforestation really work? This is precisely the aim of a study conducted by an international team bringing together scientists from 29 universities and research centers. The idea is to assess the long-term results of these actions on forest regeneration and the results are quite mixed.

The more the forests are degraded, the less likely the seedlings are to survive

The study, published in Philosophical Transactions of the Royal Society B: Biological Sciences, analyzed the growth and life of 176 nature restoration sites in Asia, in areas where natural forests have suffered from degradation. The team found that on average, 18% of young trees planted die in the first year, and this figure rises to 44% after five years. However, this survival rate varies enormously from one site to another, but also according to the species. At some sites, 80% of the trees are still alive after five years, while at others, 80% are dead after the same period.

Why such a high mortality? The problem would come from the density of plantation, the choice of species, global climatic conditions, phenomena weather reportweather report sometimes extreme which ravaged the sites during certain seasonsseasons, but also the state of degradation of the forest before the arrival of young shoots. The team found that in areas where deforestation has completely wiped out the tree population, young trees have a harder time surviving. Seedlings planted in areas where there are still mature trees are 20% more likely to survive, likely due to the weather protection that larger trees provide to smaller ones.

Reforestation remains faster than letting nature regenerate

However, attempts at reforestation are far from useless: active restoration of vegetation gives faster results than letting nature take its course on its own, natural regeneration being much slower. One of the authors, Professor David Burslemexplain that ” this study also serves as a warning. It is necessary to protect our current forests as much as possible, because we realize two things: that the results of the restoration of the vegetation are very uncertain and not guaranteed, but also because we need the seeds of the forests still in life to be able to plant new ones! » As another researcher who participated in the study pointed out, Robin Chazdonplanting trees like we are doing now is not enough, we have to make sure they can grow and help forests survive in the long term”.

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