Undisturbed tropical forests are absorbing nearly a fifth of carbon dioxide released annually by the burning of fossil fuels, according to an analysis of 40 years of data from rainforests in the Central African country of Gabon.
Writing in the journal Nature, Simon Lewis and colleagues report that natural forests are an immense carbon sink, helping slow the rise in atmospheric CO2 levels.
“We are receiving a free subsidy from nature,” said Simon Lewis, a Royal Society research fellow at the University of Leeds. “Tropical forest trees are absorbing about 18% of the CO2 added to the atmosphere each year from burning fossil fuels, substantially buffering the rate of climate change.”
But the good news may not last for long. Other research suggests that as tropical forests fall to loggers, dry out due to rising temperatures, and burn, their capacity to absorb carbon is reduced.
The research, which combined the new data from African rainforests with previously published data from the Americas and Asia, lends support to the idea that old-growth forests are critical to addressing climate change. Recent climate negotiations have included debates on compensating tropical countries for reducing emissions from deforestation and forest degradation (“REDD” or “avoided deforestation”).
“To get an idea of the value of the sink, the removal of nearly 5 billion tonnes of carbon dioxide from the atmosphere by intact tropical forests, based on realistic prices for a tonne of carbon, should be valued at around £13 billion per year,” said study co-author Lee White, Gabon’s Chief Climate Change Scientist. “This is a compelling argument for conserving tropical forests.”
“Predominantly rich polluting countries should be transferring substantial resources to countries with tropical forests to reduce deforestation rates and promote alternative development pathways,” added Lewis.
The new findings show that tropical forests account for roughly half of the 8.5 billion tons of carbon that is sequestered in terrestrial sources each year, the balance is absorbed by soils and other types of vegetation. Another 8.5 billion tons dissolved in oceans, leaving 15 billion of the 32 billion tons emitted by humans each year in the atmosphere. Deforestation accounts for roughly 6 billion tons of greenhouse gas emissions – greater than the emissions from all the world’s planes, ships, trucks, and cars.
Note – the contention by Muller-Landau that the Lewis and colleagues’ findings are not realistic due to ‘regeneration’ demonstrates her ignorance of recent work demonstrating the sequestration aspect of mature forests. But more importantly, this cherry-picked gripe, even if it were plausible, is almost of no consequence. With much of the world’s tropical forests already badly degraded or destroyed, there will inevitably be large areas of regenerating forests for centuries to come (i.e., time periods relevant to climate change projections). We haven’t even managed to reduce the RATE of tropical deforestation, so the opportunities for regeneration will persist, making the Lewis result all the more important. Muller-Landau is known for her unrealistic and anti-conservationist views, so her comments are hardly surprising. My advice – take her opinions with a very large shaker of salt (or better yet, ignore entirely).