Rainforests Regrowth Boosts CO2 Capture

Margherita Olivo
February 15th 2016

Secondary tropical forests are able to regenerate after cutting, and this process can often be quite fast. This news comes from Panama, home to the Smithsonian Tropical Research Institute, where a group of scientists recently released results of a study aimed to investigate the forestry regeneration capacity of earlier surfaces almost completely deforested for agricultural purposes.

Less than half world heritage of tropical forests can be considered as primary. In fact, the rest are regrown forests (called secondary), as a result of human activity. And although we know that growing forests can accumulate carbon quickly, none so far had proven how fast this regeneration happens. The group of scientists has shown that half of the surveyed forests in the study have reconstituted 90% of the biomass level of a primary forest in 66 years or less.

An extremely significant discovery since "the regeneration of secondary forests could play a key role in carbon capture and sequestration operations, and then in the mitigation of climate change. However, other studies so far have focused on individual sites. This research instead combines data from several stations at the turn of the neotropical region" as Daisy Dent, professor at the University of Stirling involved in the project, stated.

In fact, this is quite an unprecedented project: 45 sites in eight countries, for a total of 1478 survey points between Mexico and Brazil, along a positive gradient of precipitation and soil fertility. The international team of scientists compiled data from almost 1.500 plots at 45 sites across the Neotropics, covering southern and central America. This allowed them to produce a map highlighting the carbon sequestration potential of areas across the Neotropics. In order to have more access to sunlight, nutrients and water, new trees grow quickly. This means the plants sequester a much greater amount of carbon from the atmosphere and uses it as part of the photosynthesis process. The team found that in optimum conditions, new-growth vegetation could sequester up to 11 times as much carbon as old-growth forests.

Co-author Lourens Poorter from Wageningen University, The Netherlands, explains that while it is important to halt deforestation, it is also important to recognize the role of secondary forests in a climate mitigation context. "There is a potential for forests to regrow" he said. "You can either do that actively by planting but it can also be done passively (via natural regrowth). What we have tried to do in this study is to get a comprehensive picture of how fast this recovery is in terms of biomass. If you have abandoned areas that have been used for agriculture, how fast do the forests regrow naturally and how much biomass has been taken up - we call that the recovery or resilience of biomass".

The right conclusions to be drawn concern the managerial instructions to be implemented. This study has shown us a map of the biomass and carbon sequestration recovery in the Neotropical region. So, if in the forests of Central America and Amazon, characterized by a high potential for recovery, it is right to plan the restoration and reforestation, in the forests of Mexico and northeastern Brazil, with a pronounced dry season, it is more convenient to focus on the retention of residual limbs.

Details of the study have been published in the journal Nature.

Source: BBC. Image: Shutterstock

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