Reference

Current Biology , Rutishauser et al.: "Rapid tree carbon stock recovery in managed Amazonian forests"

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Climate | Selectively logged Amazon forests recover their carbon stock in 20 years

21/09/2015 - Article

Selectively logged tropical Amazonian forests can recover their carbon stocks within a cutting cycle of 20 to 30 years, according to a new study published in the journal Current Biology on 21 September. The findings show that sustainably logged tropical forests continue to play a key role in global carbon sequestration, with important implications for global climate. This study demonstrates that under current timber harvesting intensities, Amazon forests logged with reduced impact logging techniques recover their initial carbon stock in 7 to 21 years. “This is fast compared to the recovery time of commercial volumes that can take up to a century or even more to go back to pre-logging stocks. ” says Ervan Rutishauser, CIRAD consultant and lead author of the study.

Although half of the remaining tropical forests are designated for timber production, our knowledge on the impact of logging on forest dynamics at regional level is still very limited. This study is the first comprehensive assessment of post-logging recovery of above-ground carbon stored in trees across the whole Amazon Basin. It was made possible thank to the recent establishment of TmFO, the Tropical managed Forests Observatory. “TmFO offers unique opportunities to investigate post-logging dynamics over a wide range of conditions on a regional scale ” says Plinio Sist from CIRAD, the coordinator of the network and Head of the CIRAD's BSEF research unit.

The time taken to recover carbon stocks does not significantly vary across the entire Amazon Basin

The researchers focused on 79 permanent TmFO sample plots representing 376 hectares of forested area at 10 sites across the Amazon Basin. They assessed the time within which the forest can recapture carbon emitted through logging. While their analysis revealed a recovery time of 7 to 21 years under current logging intensities (10 to 30 m3/ha), the researchers also demonstrated that the time taken to recover carbon stocks did not significantly vary across the entire Amazon Basin, despite the well-known Northeast-Southwest environmental gradient.

This is a first step towards setting a threshold between the production of timber and the maintenance of key environmental services such as carbon storage. The authors give the first convincing evidence that provided they are carefully managed, Amazonian tropical forests can recover their above-ground carbon stocks within a cutting cycle of 20-30 years and thus can play a key role in global carbon sequestration.

A key role in global carbon sequestration

This study therefore provides a straightforward way to estimate carbon stock recovery after logging, while confirming the overwhelming importance of logging intensity and incidental damage in driving forest resilience at a regional level. “The finding can now serve as a useful decision-making tool for forest managers and policymakers ”, says Bruno Hérault from CIRAD, second author of the publication.

Unfortunately, poor logging practices are continuing to degrade many forests, while others are still being cleared and converted into more profitable pasture and plantations. “It is urgent to promote careful forest management practices in order to maintain tropical forests' capacity to take up carbon and provide other essential environmental services” says Bruno Hérault. While carbon-oriented forestry might trigger a shift toward sustainable forest management, wood supply will remain the principal objective of forest management. “Thanks to TmFO, we have provided scientific evidence and practical guidance to define sustainable harvest intensities that ensure both long-term timber yields and maintenance of essential environmental services such as carbon stocks and biodiversity ”, concludes Plinio Sist.

Tropical managed Forests Observatory (TmFO)

This network, set up in 2012 by Cirad within the CGIAR Forest Trees and Agroforestry (FTA) research programme, involves 24 forest research organizations and more than 40 forest scientists from 22 research institutions. TmFO currently includes 24 experimental sites distributed across three tropical regions, with a total of 490 permanent plots and 921 ha of forest inventory sites.