In the largest study of its kind, researchers found that new-growth rainforests can absorb 11 times as much atmospheric carbon versus old-growth forest.
Secondary forests as they are sometimes called grow very quickly compared to primary or old-growth forests. In doing so, this rapid growth pulls in a more sunlight for photosynthesis which then requires the carbon dioxide from the atmosphere. With this rapid growth the new forests reached 90 percent of old-growth forest levels in just 66 years.
“Regenerating secondary forests could play a critical role in carbon sequestration and climate change mitigation,” said Daisy Dent from the Smithsonian Tropical Research Institute (STRI) in Panama and the University of Stirling in the UK. “However, previous studies have tended to focus on single sites. This study brings together data from many sites that span the Neotropics. We illustrate that secondary forests are highly productive and resilient.”
This study was conducted over 1,478 plots, across 45 sites in 8 different countries. It encompassed over 168,000 trees. It even spanned the entire latitude of the tropics from 20 degrees north to 22 degrees south.
As the study reported in Nature, a regenerated forest is capable of 11 times the carbon uptake of Amazonian old-growth forest after 20 years. And twice that of selectively logged Amazonian forest sites.
“According to this analysis, tropical secondary forests have enormous potential for removing carbon from the atmosphere,” one of the team, Susan Letcher from Purchase College State University of New York, wrote at The Conversation. “The rate of biomass recovery varies widely across the region, with the fastest regrowth in areas with high rainfall. The median time for a forest to reach 90 percent of old-growth biomass levels was 66 years, but recovery can be much faster in some areas.”
Tropical regrowth seems to be a win for carbon absorption and ecology in general. It does not seem to matter if it is from natural or man-made deforestation.
“Secondary forests can harbour a high diversity of ethnobotanically important species that can be used for medicines,” writes Letcher. “They can serve as extractive reserves, where limited harvesting of timber, game animals and other forest products will prevent the exploitation of resources in vulnerable protected areas. They protect watersheds and prevent erosion.”
Promising, But Not A Solution
The scientist warn that just because new forest are more efficient at carbon absorption, doesn’t mean we should clear old-growth forest to spring up new growth forests. The rapid accumulation of trapped carbon when new-forest are young eventually becomes the biomass of the old-growth forest.
“Shifting focus to the conservation of regenerating forests should not take away from the urgent imperative to conserve the remaining uncut tropical forest,”writes Letcher. “The clearing of old-growth tropical forests is a major source of human-induced greenhouse gas emissions, second only to fossil fuel combustion. Clearly, keeping the carbon that’s currently stored in intact tropical forests from being released to the atmosphere should be a priority.”