By Chen Ly.
There is a young secondary forest in Anhembi, Brazil.
Rens Brouwer.
Tropical forests can re-establish themselves quickly on land that was previously deforested. The finding suggests that the recovered forests could play a key role in restoring the environment.
Tropical forests are being destroyed at an alarming rate to make way for pastures and crops. The abandonment of these lands can lead to the regrowth of the forest that was once there.
Lourens Poorter and his colleagues analysed 77 secondary forest sites across the tropical regions of central and south America and west Africa to better understand this process.
Most of the land at the sites was subject to low to medium intensity farming. The team was able to reconstruct what forest recovery looks like over time because the sites were all at various stages of regrowth.
Poorter says that the forests are like apples and pears, with tall, jungle-like rainforests and small, dry tropical forests.
The area of Amazon affected by wildfires is predicted to grow.
To compare recovery across sites, the team contrasted each secondary forest with nearby old-growth forests that haven't had major disturbance. The researchers reasoned that the more similar the secondary forests were to the old-growth forests, the more they had recovered.
The team found that after 20 years, the average secondary forest that had grown from farmland that was used with low to medium intensity had recovered 78 percent of old-growth forest attributes. Poorter says it goes way faster than they thought.
There was significant variation in the recovery time for different forest attributes. Most of the recovery happens within 10 years. It took between 25 to 60 years for plant species diversity to recover, and they projected it would take over a century for the forest to mostly recover.
Poorter says there is hope that the forests can bounce back naturally despite the amount of destruction. Secondary forests make up over 28 per cent of tropical forests in central and south America, and are important for locking up carbon which is crucial to tackle climate change. They attract mammals, birds and insects back to the area, which is important for restoration. They are important for the livelihoods of people who live close by.
The results are promising and show that natural regeneration and assisted natural regeneration are excellent restoration strategies. One limitation is that the sites in this study do not represent regeneration on the average piece of deforested land, and many deforested sites will recover much more slowly than the ones studied here.
The journal is called Science.
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