Green carbon refers to the carbon stored naturally within land-based, or terrestrial, ecosystems. This stored carbon is an integral part of the Earth’s natural carbon cycle. It encompasses the carbon captured and held by plants and soils across various landscapes, playing a role in regulating atmospheric carbon dioxide levels.
The Role of Terrestrial Ecosystems
Terrestrial ecosystems capture and store carbon primarily through photosynthesis. Plants absorb carbon dioxide from the atmosphere, using sunlight to convert it into organic compounds like carbohydrates. This carbon becomes incorporated into their biomass, forming the structure of trunks, branches, leaves, and roots. As plants grow, they continuously draw down atmospheric carbon, effectively acting as natural carbon sinks.
Beyond living biomass, significant carbon is stored in the soil as organic matter. When plants shed leaves or die, their organic material decomposes, enriching the soil with carbon. This soil organic carbon (SOC) can remain stored for decades. Forests, grasslands, and peatlands represent major green carbon reservoirs, with forests storing substantial carbon in woody biomass and grasslands holding up to 90% of their carbon underground. Globally, terrestrial ecosystems contain at least twice the amount of carbon found in the atmosphere.
Differentiating Carbon Colors
Blue carbon refers to carbon captured and stored in coastal and marine ecosystems. These include habitats such as mangrove forests, seagrass meadows, and salt marshes, where carbon accumulates in the sediments beneath the water. Unlike terrestrial systems, blue carbon ecosystems are characterized by their proximity to the ocean and unique underwater storage mechanisms.
Black carbon, in contrast, is not a stored form of carbon but rather a particulate matter. It is a component of soot, produced by the incomplete combustion of fossil fuels, biofuels, and biomass. This airborne pollutant results from sources like diesel engines, cookstoves, wood burning, and wildfires. Black carbon contributes to warming by absorbing sunlight in the atmosphere and reducing the reflectivity of ice and snow upon deposition.
Threats to Green Carbon Sinks
Human activities pose significant threats to green carbon reservoirs, causing the release of stored carbon back into the atmosphere. Deforestation, often driven by agriculture, timber harvesting, and urban development, leads to direct carbon emissions. When forests are cleared or burned, the carbon previously stored in trees and soil is released as carbon dioxide. Such land-use changes have contributed to atmospheric greenhouse gas increases.
Land degradation further diminishes the capacity of terrestrial ecosystems to store carbon. Practices that deplete soil health, such as intensive tillage and insufficient organic matter replenishment, lead to the loss of soil carbon. Poor agricultural methods can reduce soil organic carbon stocks, which in turn impairs land productivity. Agricultural activities contribute significantly to carbon release.
Conservation and Management Strategies
Protecting and enhancing green carbon sinks involves a range of deliberate strategies. Reforestation, the replanting of trees in areas that were previously forested but have been cleared or degraded, directly restores carbon-capturing biomass. Afforestation involves establishing new forests on lands that have not been forested before, such as barren or agricultural lands, significantly increasing overall forest cover. Both practices contribute to carbon sequestration by enhancing the amount of carbon stored in living plants and in the soil.
Sustainable forest management ensures the long-term health and productivity of existing forests. This approach includes practices like selective logging, which allows for careful harvesting while maintaining forest structure, and thinning, which promotes healthier tree growth. Regenerative agriculture practices are also important for soil carbon. Techniques such as no-till farming, which minimizes soil disturbance, and cover cropping, planting non-cash crops to protect and enrich the soil, help build and maintain soil carbon. These strategies enhance the land’s natural ability to absorb and store carbon, addressing past land-use challenges.