Senior Lecturer, Grantham Institute – Climate Change and Environment, Imperial College London
Even if they can’t save us from climate change, society still depends on forests.
One morning in 2009, I sat on a creaky bus winding its way up a mountainside in central Costa Rica, light-headed from diesel fumes as I clutched my many suitcases. They contained thousands of test tubes and sample vials, a toothbrush, a waterproof notebook and two changes of clothes.
I was on my way to La Selva Biological Station, where I was to spend several months studying the wet, lowland rainforest’s response to increasingly common droughts. On either side of the narrow highway, trees bled into the mist like watercolours into paper, giving the impression of an infinite primeval forest bathed in clouds.
As I gazed out of the window at the imposing scenery, I wondered how I could ever hope to understand a landscape so complex. I knew that thousands of researchers across the world were grappling with the same questions, trying to understand the fate of tropical forests in a rapidly changing world. Author provided
Our society asks so much of these fragile ecosystems, which control freshwater availability for millions of people and are home to two thirds of the planet’s terrestrial biodiversity. And increasingly, we have placed a new demand on these forests – to save us from human-caused climate change.
Plants absorb CO₂ from the atmosphere, transforming it into leaves, wood and roots. This everyday miracle has spurred hopesthat plants – particularly fast growing tropical trees – can act as a natural brake on climate change, capturing much of the CO₂ emitted by fossil fuel burning. Across the world, governments, companies and conservation charities have pledged to conserve or plant massive numbers of trees.
But the fact is that there aren’t enough trees to offset society’s carbon emissions – and there never will be. I recently conducted a review of the available scientific literature to assess how much carbon forests could feasibly absorb. If we absolutely maximised the amount of vegetation all land on Earth could hold, we’d sequester enough carbon to offset about ten years of greenhouse gas emissions at current rates. After that, there could be no further increase in carbon capture.
Yet the fate of our species is inextricably linked to the survival of forests and the biodiversity they contain. By rushing to plant millions of trees for carbon capture, could we be inadvertently damaging the very forest properties that make them so vital to our wellbeing? To answer this question, we need to consider not only how plants absorb CO₂, but also how they provide the sturdy green foundations for ecosystems on land.[…]