According to a study recently published in Nature, global forests, if restored and protected, could help remove some 226 billion tons of carbon from the atmosphere.That is equivalent to about 20 years of emissions from burning fossil fuels at current rates.Some experts say the new study provides a more reliable estimate of forest carbon capture potential than the previous controversial study, but critics are skeptical that the new figure will be achieved.
Wayne Walker, chief scientific officer at the Woodville Center for Climate Research, who was not involved in the study, said new research demonstrates that forests play a substantial role in responding to the climate crisis.While there is still considerable uncertainty about the exact amount of additional carbon that forests can absorb, the evidence is sufficient to justify actions to grow, restore and protect forests.
For the forests that once existed, humans have cut down a large part, or even half.Deforestation accounts for 15 per cent of total human greenhouse gas emissions each year.So scientists have been interested in how much carbon trees can absorb from the atmosphere if forests are allowed to regenerate.
In 2019, a team led by Thomas Crowther, an ecologist at the Federal Institute of Technology in Zurich, Switzerland, estimated in Science that 205 billion tons of carbon could be absorbed if forests were restored on 900 million hectares of land.Other scientists think the figure is too high because it assumes that 227 tons of carbon will be captured and stored per hectare of forest.
Simon Lewis, a global change scientist at University College London and the University of Leeds, said 227 tonnes were "an absurd number".Some also fear that the study will encourage efforts to mitigate climate change, such as planting large planted forests, which are less beneficial to biodiversity and carbon capture than natural and diversified forests.
Crowther's team used satellite data to estimate the amount of carbon currently stored in the forest and model how much carbon the forest could store if reforestation took place.In the new study, Crowther's team also used satellite data, but also made separate estimates of forest carbon based on ground data, which were extrapolated globally using machine learning models.Two estimates of global forest carbon differ by about 12 per cent.
Crowther and colleagues also calculated how much carbon they would store if existing forests grew into primeval forests.The team's estimates include not only carbon stored in trees, but also carbon stored in dead wood, leaves on the ground, roots and soil.They found that if existing forests were protected from deforestation, they could eventually absorb 138 billion tons of carbon
"This is a very exciting opportunity to achieve large-scale carbon capture by protecting our existing ecosystems.”Crowther说。They also found that restoring existing tree cover would consume an additional 88 billion tonnes of carbon, a considerable figure, although well below the team's 2019 estimate of 205 billion tonnes.
In order for forests to absorb and store large amounts of carbon, they must be protected from the heat and drought caused by climate change, which can trigger devastating wildfires.The reality is that we need to reduce fossil fuel emissions, end deforestation, and restore ecosystems in order to stabilize the climate.”Lewis。