Natural carbon sinks absorb half of the human-produced carbon emissions. In the current context of global warming, they play a crucial role in the future of humanity and the planet’s ecosystems. A carbon sink absorbs more carbon than it produces. If they are damaged, as in the case of rainforests during fires or human-driven deforestation, this destruction releases their stored carbon back into the atmosphere.
According to the World Economic Forum (WEF), a carbon sink is specially beneficial if it can store captured carbon indefinitely. While these sinks are in no way a substitute for reducing our emissions, they can slightly offset some climate risks. Here are some of the world’s biggest carbon sinks.
Trees absorb and store carbon. NASA satellite data shows the world’s forests absorb 15.6 billion tonnes of CO2 a year, while deforestation and wildfires release 8.1 billion tonnes back into the atmosphere. These numbers show the importance of protecting forests across the world.
According to the WEF, the amount of woodland on the Earth’s surface has however gone down significantly since the start of this millennium. Data compiled by Global Forest Watch shows global tree cover shrank by an eighth between 2000 and 2022. This loss resulted in 195 billion tonnes of CO2 being released into the atmosphere.
2. Soil and rocks
Scientists estimate Earth’s soils contain 2,500 billion tonnes of carbon, as reported by the WEF. This is three times as much as the atmosphere and four times as much as plants and animals. Sustainable farming methods like crop rotation could boost that total by 1.85 billion tonnes each year.
Carbon is naturally absorbed by certain types of rocks in a process known as carbon mineralization. Scientists are trying to find ways to speed this process up. An ambitious goal is to remove 10 billion tonnes of atmospheric carbon per year by 2050.
Oceans are the “world’s largest carbon sink”, according to the United Nations. Oceans absorb 25% of all carbon emissions and generate half the world’s oxygen. As temperatures rise, oceans also absorb 90% of the excess heat in the atmosphere, which, according to the WEF, combined with the increased levels of CO2 in the atmosphere, is acidifying seawater, which damages sea life and reduces the role that oceans play in stabilizing the climate.
Some scientists believe that mycorrhizas fungi, which live on plant roots extending their reach and extracting nutrients from the soil which they share with their hosts, can capture and store over a third of yearly global carbon emissions. According to the WEF, fungi need protection from modern farming methods because phosphorus-based fertilizers may disrupt their metabolism. This in turn affects the way they help stabilize climate.
Some scientists are proposing the idea that large mammals play an important role in helping to fight global warming because they speed up the natural process of carbon capture. When they eat flammable vegetation, elephants inhibit wildfires. They also step on plants which helps accelerate the process by which carbon in foliage is forced into the soil.