A “carbon tree” refers to the ability of trees to absorb carbon dioxide (CO2) from the atmosphere and store it, helping to regulate Earth’s climate. This natural process is a fundamental part of the global carbon cycle, where carbon moves between the atmosphere, oceans, land, and living organisms. Trees play a significant role in managing atmospheric carbon and maintaining environmental balance, making them components of the planet’s natural infrastructure.
How Trees Capture Carbon
Trees capture carbon through a biological process called photosynthesis, which is driven by sunlight. This process primarily occurs in the leaves, where a green pigment called chlorophyll absorbs light energy. Water is drawn up from the roots to the leaves, and carbon dioxide enters the leaves through tiny pores called stomata.
Inside the chloroplasts within the leaf cells, chlorophyll facilitates a chemical reaction between the absorbed CO2 and water using the light energy. This reaction converts inorganic compounds into glucose, a type of sugar that serves as the tree’s food, and releases oxygen back into the atmosphere as a byproduct. The carbon atoms from the CO2 are incorporated into the glucose molecules, becoming the building blocks for the tree’s growth and energy.
Carbon Storage Within Trees and Soil
Once captured, the carbon is stored in various parts of the tree, including the trunk, branches, leaves, and roots, as biomass. As a tree grows, it continuously accumulates more biomass, increasing the amount of carbon it stores. This stored carbon is largely in the form of carbohydrates, which provide energy for the tree’s immediate needs and long-term development.
Trees also contribute to carbon storage in the soil. Roots transfer carbon to the soil through exudates, substances released by the roots into the surrounding soil. When leaves, branches, and roots die and decompose, their organic matter becomes incorporated into the soil, enriching it with carbon. This process makes forest soils a carbon sink, with some studies indicating that soil can store at least three times more carbon than the biomass above ground.
The Scale of Carbon Sequestration
Individual trees contribute to carbon sequestration, but vast forests collectively act as carbon sinks, absorbing amounts of CO2 from the atmosphere. Globally, forests absorb approximately 16 billion metric tonnes of carbon dioxide annually, holding an estimated 861 gigatonnes of carbon in their branches, leaves, roots, and soils. Preserving and maintaining healthy forests is an effective strategy in combating climate change.
A single mature tree can absorb up to 48 pounds (around 21.7 kilograms) of CO2 per year. Over its lifetime, this can add up to a significant amount of stored carbon. While new trees play a role, older, mature, and old-growth forests are effective, continuing to sequester carbon throughout their long lifespans. Forests worldwide are considered the largest component of the 29% of atmospheric carbon absorbed by land, highlighting their role in climate regulation.