Study finds huge potential to grow trees, capture carbon emissions

James Marshall
July 5, 2019

"Restoration of trees may be "among the most effective strategies", but it is very far indeed from "the best climate change solution available", and a long way behind reducing fossil fuel emissions to net zero", said Myles Allen, a geosystem science professor at Oxford.

In a first of its kind study, a team at ETH Zurich has calculated the potential area and impact of a new forest large enough to slash roughly two-thirds off the atmospheric carbon pool.

The study published on Thursday in the journal Science showed that the world's forest land can be increased by a third without affecting existing cities or agriculture. They zoomed in on thousands of areas around the world to characterize the tree cover and then extrapolate that data to a broader area.

Several researchers expressed reservations, taking issue with the idea that planting trees was the best climate solution available to the world right now. About 2.8 billion hectares already exist, which means more than 1.6 billion hectares are available for forest restoration.

'We all knew that restoring forests could play a part in tackling climate change, but we didn't really know how big the impact would be, ' Crowther said.

"If we act now, this could cut carbon dioxide in the atmosphere by up to 25 percent, to levels last seen nearly a century ago", said Crowther.

'But we must act quickly, as new forests will take decades to mature and achieve their full potential as a source of natural carbon storage'.

"Every other climate change solution requires that we all change our behavior, or we need some top-down decision from a politician who may or may not believe in climate change, or it's a scientific discovery we don't yet have", he told the Thomson Reuters Foundation.

The study's calculations make sense, said Stanford University environmental scientist Chris Field, who wasn't part of the study.

But, not all forested areas would be well-suited for this type of restoration, the team notes.

Worldwide, there are about 5.5 billion hectares of forest.

But despite its prevalence in the climate conversation, scientists have yet to work out where exactly all these trees could grow and how much carbon they'd trap without eliminating space that humans now rely on. It confirms that this scenario projection is "undoubtedly achievable under the current climate".

The Intergovernmental Panel on Climate Change (IPCC) said that if the world wanted to limit the rise to 1.5C by 2050, an extra 1bn hectares (2.4bn acres) of trees would be needed.

The Crowther Lab finds that forests could be regrown on 1.7-1.8 billion hectares of land in areas with low human activity that are not now used as urban or agricultural land, adding 0.9 billion hectares of tree canopy. Importantly, these are not areas that would naturally be grasslands or wetlands, but degraded ecosystems that would naturally support some level of tree cover. "But the question of whether it is actually feasible to restore this much forest is much more hard", he said.

The Paris Agreement, which was first signed in 2015, is an global agreement to control and limit climate change.

Six nations with the most room for new trees are Russian Federation, the US, Canada, Australia, Brazil and China.

However not everyone was as effusive about the new study.

The most effective way to fight global warming is to plant lots of trees, a study says. It finds that there is likely to be an increase in the area of Northern "Boreal" forests in regions such as Siberia, where tree cover averages 30-40%. However, this would be outweighed by losses in dense tropical forests, which typically have 90-100% tree cover. "A hugely important blueprint for governments and private sector".

"The estimate that 900 million hectares restoration can store an addition 205 billion tonnes of carbon is too high and not supported by either previous studies or climate models", said Prof Simon Lewis from University College London.

A tool on the Crowther Lab website enables users to look at any point on the globe, and identify the areas for restoration and learn which native tree species exist there. It also offers lists of for-est restoration organisations. This was made possible because of a unique global dataset of forest observations and the free mapping software of Google Earth Engine.

As Earth warms, and especially as the tropics dry, tree cover is being lost, he noted.

Other reports by Click Lancashire

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