It is fairly widely accepted that deforestation is one of the leading causes of climate change. We hear it over and over, but what exactly about deforestation accelerates global warming? Well, there are a few reasons. The most direct and well-known reason is that trees absorb carbon from the atmosphere and so the less trees, the less carbon absorbed from the atmosphere. Moreover, not only are there less trees to sequester carbon, when trees are cut down and burned they release their stored carbon into the atmosphere. This means that when whole forests are cleared a carbon ‘bomb’ is essentially set off.
A second, less direct impact of deforestation is the effect it has on the soil. When the trees are cut down they no longer have roots to help hold the soil together and retain water in the ecosystem. Once the trees are gone soil becomes vulnerable to the wind, rains and floods that cause erosion. The topsoil that is eroded first contains essential nutrients for plants to grow. This soil erosion can cause multiple issues. The first being sediment and nutrients that runoff into local bodies of water. These heavy layers of sediment can clog waterways, leading to flooding, and cause declines in fish and other species. Clogged streams and rivers can also affect the amount of carbon sequestered from the atmosphere, as a study has shown that rivers essentially flush carbon from the land to the oceans, reducing the amount that is released into the environment as carbon dioxide. This becomes a vicious cycle when you consider that climate change can increase frequency and intensity of storms which will cause more soil erosion to flow into streams and rivers.
The top metre of the world’s soil contains three times as much carbon as the entire atmosphere, making it a major carbon sink alongside forests and oceans. Deforestation allows this carbon-dense soil to be eroded, reducing the efficiency of one of our natural carbon sinks. The soil left behind will struggle to hold water due to the lack of nutrients and tree roots. This will then dry out, killing the biodiverse organisms that live within it and making the ground inhospitable to grow any kind of crops, plants or vegetation on.
Once cleared, this soil is often then used for agriculture which is responsible for 11% of global greenhouse gas emissions. Agriculture causes emissions in multiple ways: enteric fermentation, responsible for about 40% of agricultural emissions is a natural digestive process that occurs in animals such as cattle, sheep and goals; manure left on pasture accounts for 15%; rice cultivation and synthetic fertilisers account for about 10% each.
Finally, all of these factors combined – removal of trees, soil erosion, climate change, overgrazing of livestock – can lead to desertification. As Sir David Attenborough highlighted in his documentary Life On Our Planet, if we don’t make sufficient change fast enough in the 2030s the Amazon rainforest would be cut down until it degrades into a dry savanna, producing huge species loss and altering the global water cycle.
Aside from the soil erosion, deforestation destroys habitats for many animals, causing huge reduction in biodiversity.
Deforestation is a very real environmental problem. In 2019 forest land the size of a football pitch was destroyed every six seconds and the numbers prevail today. The good news is that reforestation offers us hope. Also mentioned in Attenborough’s documentary, ‘re-wilding’ the earth could be our best hope for reversing the damage we have done to our planet. Many initiatives are going ahead, both government and company run, that you can support. For example, the African-led Great Green Wall, with the ambition to grow an 8,000km wall of trees the entire width of Africa. When completed it will be the largest living structure on the planet, three times the size of the Great Barrier Reef. Companies are also doing their part with many using reforestation projects to offset their footprint. Brewdog in particular has purchased 2,050 acres of land in Scotland with the plan to plant trees and create the first Brewdog forest.