Patrick Greenfield writes:

Forests and nature are centre stage at Cop26. On the second day of the Glasgow summit, world leaders are announcing a commitment to halting and reversing deforestation. As the second largest source of greenhouse gases after energy, the land sector accounts for 25% of global emissions, with deforestation and forest degradation contributing to half of this.

But why do forests matter to the climate, and how can we halt deforestation?

What is a forest?
There are an estimated three trillion trees on Earth. Some form part of enormous forest ecosystems like the Congo rainforest, while others stand in sparsely populated landscapes such as on the edges of the Sahara desert. Of the 60,000 known tree species, nearly a third are threatened with extinction, according to a recent assessment.

Scientists cannot decide on a single definition of a forest due to disagreements over tree density, height and canopy cover. But the Food and Agriculture Organization’s version is commonly used: “Land with a tree canopy cover of more than 10% and area of more than 0.5 hectares.” Forest covered almost a third of the world’s landmass in 2020, with more than half found in just five countries: Russia, Brazil, Canada, the US and China. The taiga – also known as northern boreal forest – is the world’s largest, stretching around the northern hemisphere through Siberia, Canada and Scandinavia.

Temperate, tropical and boreal are the three main types of forest that include a great diversity of ecosystems: cloud forest, rainforest, mangrove swamps, and tropical dry forest, among many others.

Why do forests matter for the climate?
Forests are among the most biodiverse places on the planet and form an enormous carbon store, regulating the world’s weather and climate. They hold about 861 gigatons of carbon – equivalent to nearly a century’s worth of annual fossil fuel emissions at the current rate – and absorbed twice as much carbon as they emitted in the last two decades. More carbon is stored in soil (44%) than living biomass (42%), with the rest found in dead wood (8%) and forest litter (5%). Forests like the Congo basin rainforest – the world’s second largest – affect rainfall thousands of miles away around the Nile. Billions of humans rely on forests for food, building materials and shelter. [Continue reading…]