The disappearance of tropical forests is not necessarily final: when conditions are favorable, a new forest very similar to the original one grows back in less than 20 years, according to a new study. Natural restoration is thus more efficient and less expensive than tree plantations.
Every year, 10 million hectares of tropical forest disappear from the planet, that is to say the surface of three Olympic swimming pools per second. But what is less talked about is that this forest is regenerating in many places where cleared land has been abandoned for lack of fertility, or because the loggers have moved elsewhere. 28% of land cleared and repopulated with “secondary forests” in the only area of Latin America, according to a study 2016. While these do not necessarily have exactly the same characteristics as the primary forests they replace, they contribute significantly to the objectives of biodiversity conservation, improvement of water quality and the carbon sequestration.
In 20 years, forests regain 80% of their characteristics
The good news is that this regeneration is much faster and easier than expected, according to a new study coordinated by the University of Wageningen (the Netherlands) and the Center for International Cooperation in Agricultural Research for Development (Cirad , France) and published in the review Science. The researchers modeled the restoration trajectories of more than 2,200 parcels of secondary forests across Africa and South America, and found that 20 years after the abandonment of agricultural practices, forests naturally regrowing have recovered nearly 80%. the fertility of their soils, their structure and functioning, and their diversity compared to old-growth forests.
” Surprisingly fast, given the complexity of ecosystems tropical forest », Geraldine Derroire wonders, ecologist from tropical forests at CIRAD. However, some forest attributes recover faster than others. ” For example, soil fertility typically recovers to 90% in less than a decade. By comparison, it takes two to six decades to regain 90% of the diversity of cash that one could find in ancient forests », Continues the researcher.
Growth conditions favorable to a renaissance
According to the authors, this rapid recovery of forests is explained in particular by the seed banks still present in soils not subject to intensive agriculture, as well as by the relatively productive growing conditions, because they are hot and humid, tropics. But it is not so easy everywhere, they warn. The lack of seeds, the invasion of land by native species or soil deterioration may, for example, prevent the recovery of secondary forests.
Natural restoration, more effective than tree plantations
In view of this rapid recovery, scientists are encouraging natural restoration practices that do not require heavy investment and offer multiple co-benefits. No need therefore to embark on massive reforestation campaigns, often doomed to failure because carried out with too little diversity of species or poorly adapted to local conditions. The regeneration of secondary forests is also good news for warming as young forests store more carbon than old-growth forests. This is no excuse, however, for keep on cutting down tropical forests. Because a good part of them will be lost forever, covered with bitumen or damaged by pesticides.
Restoring damaged tropical forests is easy and profitable
Article by Grégoire Macqueron published on 10/25/2009
Tropical forests degraded by logging can recover in just 15 years their capacity to absorb the carbon and their biodiversity. This has just been proven by researchers from the University of Leeds (Great Britain).
Trees in tropical forests absorb large amounts of CO2 atmospheric and make these forest environments one of the main carbon sink terrestrial. According to David Edwards of the Faculty of Biological Sciences at the University of Leeds, restoring exploited areas can restore these environments to their CO storage capacity.2 and therefore benefit from the funding intended for carbon offset. But even more, he specifies, this strategy can, and must, include the Biodiversity so that this carbon offset supports, rather than undermines, the ecological wealth of tropical forests.
Often, replanting for carbon offset projects is based on a single tree species, eucalyptus or oil palm trees, as these generate commercial spinoffs (drink, agrofuel). Unfortunately, these stands monospecific (of a single species) are deserts extremely poor in biodiversity.
Auspicious birds
However, David Edwards has shown that a reasoned restoration of exploited forests, compatible with a carbon offset project, is accompanied by a return to the biodiversity of theavifauna (all birds) prior to exploitation. This in fifteen years, that is to say more quickly than letting the natural regeneration.
” Our research shows that it is possible to obtain both compensation for emissions of carbon and benefits for biodiversity with the same programsays Edwards. Birds are fairly reliable indicators of the response of other groups, such as plants or insects, to habitat management, suggesting that other groups might benefit as well. “.
To achieve this result, the researchers analyzed and compared the biodiversity of avifauna from three different sectors. One was a forest of 10,000 hectares, exploited twenty years previously and actively rehabilitated during the last fifteen years, the other a forest exploited at the same time and regenerated naturally and the last a protected area, never exploited. The numbers and variety of bird species observed in the rehabilitated forest are at levels very close to those in the preserved area. Conversely, the diversity was lower in the forest which had regenerated naturally.
The absence of a tree still hides the forest
” These observations could be strong motivations to protect even the exploited tropical forests which are threatened by deforestation complete for the production of palm oil or other crops “. Indeed, forests which are the object of selective logging are often vulnerable because they are perceived as degraded. The work of David Edwards, however, tends to show that these forests are not doomed to be only ghosts of themselves.
He concludes that ” there are now signs that carbon credits and biodiversity offsets should be combined, which would unlock additional finance for projects that would provide a biodiversity benefit “. Such an approach would be more sustainable than current ones and would make restoration programs for tropical rainforests more effective. Faced with the deforestation of these environments, which are among the hotspots biodiversity, the emergence of such integrated projects could be a close of solution.
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