Tropical forests show speedy recovery

Tropical forests can recover by 78% within as little as 20 years, much more rapidly than anticipated, says new research published in the journal Science...

We know all too well that tropical forests are heavily impacted by humans through deforestation. These areas of land can are cut down for cultivating crops or rearing animals. If humans later abandon these areas, due to soil nutrient depletion as an example, the forest is able to recover in its natural way. These recovered forests are termed secondary forests.

Lead author, Lourens Poorter from Wageningen University, along with a team of 90 researchers investigated the time scale of secondary forest recovery, measuring 12 forest attributes covering soil fertility, species range and composition. Through comparison with measurements taken at nearby old-growth forests - meaning those that have suffered minimal disturbances - the recovery rate of each attribute could be determined.

The large team measured attributes across 77 secondary forest sites of varying ages (number of forest recovery years) providing a series of 'snapshots' from which time-scales could be determined.

Soil fertility (nitrogen and carbon content) was found to return to 90% of its original value in under a decade, which is incredibly fast.

Species diversity of secondary forests, though, takes longer to recover - up to 60 years - with species composition taking over 120 years to return.

Interestingly, a few factors were linked with a speedier recovery. Remnant trees - such as those that were too big to be cut down during deforestation - can act as hotspots for reforestation. Similarly, secondary forests within 200 metres of another forest showed faster recovery.

This study is a message of hope, showcasing that forests can return to their original state in a fairly short amount of time. However, Poorter is quick to warn that this research does not provide ‘a licence to kill’. We should still work to protect our existing old-growth forests - which currently make up less than 50% of tropical rainforests globally.