Talks

Trees alone can’t solve climate change

 By Mike Scott

It has long been recognised that planting trees can play a central role in helping to limit the impacts of climate change due to their ability to remove and store COfrom the atmosphere…

A new study from ETH Zurich, published in the journal Science, says there are approximately 900m hectares of land around the world—about the size of the USA—that could be reforested, capturing an estimated two-thirds of man-made carbon emitted since the Industrial Revolution. The study excluded cities and agricultural areas. Professor Thomas Crowther, co-author of the study and founder of the Crowther Lab at ETH Zurich, explains: “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. Our study shows clearly that forest restoration is the best climate change solution available today. 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.” The countries best suited for reforestation are unsurprisingly those with large land masses—Russia, the US, Canada, China, Brazil and Australia. However, it is most important that tropical areas are reforested because trees grow faster and consume more CO2 in those regions, and because tree cover in those regions is 90-100%, rather than the 30-40% in northern forests.

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World's reforestation initiatives are raising (onetreeplanted.org)

In addition to capturing CO2, forests offer a host of other environmental benefits, including reducing the risk of droughts, floods and soil degradation, and improving water and air quality. Writing for the World Economic Forum, Crowther explains that all other proposed solutions to cut emissions “from electricity generation, to transport, food, education and land use have one thing in common: primarily, they only prevent future emissions. To stop climate change, we must draw down the carbon already emitted into the atmosphere. Ecologically speaking, trees are the most effective means to capture and store carbon.” Yet while the study is heartening, many experts say that planting trees alone will not be enough to tackle climate change. In an accompanying commentary to the Science article, Robin Chazdon, a member of the University of Connecticut Department of Ecology and Evolutionary Biology, says that “the numbers are definitely the maximum possible, but they’re not going to be very attainable.” An earlier study suggested that “the sheer scale of biomass plantations that would be required to meaningfully mitigate our carbon dioxide emissions is mind-boggling, and likely to involve unbearable human or environmental costs.”

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Biomass plantation in the Markham Valley, Papua New Guinea (pngbiomass.com)

Ecosystems that are already stressed would be further threatened by turning huge swathes of natural landscapes into biomass plantations, while planting trees on agricultural land would make it even more difficult to feed a global population that is growing fast. In addition, if fertilizers are used to help trees grow, this releases more greenhouse gases. Plantations could also increase pressure on scarce water resources. It is clear then that, while planting trees may be “the biggest and cheapest tool” for tackling climate change, it cannot be the only one. The first and simplest measure is to stop the deforestation that is taking place in the Amazon, Africa and across Asia. The CDP reports that some 5m hectares of forest are cleared every year. As Bloomberg columnist Faye Flam writes: “The build-up of greenhouse gases is simply to be solved by one course of action alone, whether it’s increasing the use of solar energy or giving up beef or capturing carbon from the atmosphere. A recent estimate that planting lots of trees could soak up most of our excess carbon is, unfortunately, a little too good to be true.”

A long way to zero emissions

Professor Myles Allen, who teaches geosystem science at the University of Oxford, adds: “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. Yes, heroic reforestation can help, but it is time to stop suggesting there is a ‘nature-based solution’ to ongoing fossil fuel use. There isn’t. Sorry.” Other measures, such as decarbonizing the energy, transport and heating/cooling systems, along with eating less meat, are just as important. It is imperative that tree-planting programs—significant as they are—are not used as the only carbon reduction measure but in conjunction with other beneficial efforts.

READ MORE: Reforestation around the world by Thomas Schueneman

about the author
Mike Scott
Journalist. Environment, Sustainability, Climate Change, Investing, Energy, Supply Chain, Transport, Circular Economy, Stranded Assets, ESG, Smart Cities, Wealth Management, Family Offices, Asset Management, EU.