Carbon sequestration is the natural or engineered process of capturing carbon dioxide (CO₂) from the atmosphere and storing it for long periods of time to reduce the concentration of greenhouse gases that contribute to climate change. In the context of stormwater management, green infrastructure, and watershed restoration, carbon sequestration primarily refers to the ability of trees, wetlands, healthy soils, grasslands, and other vegetation to absorb atmospheric carbon dioxide through photosynthesis and store that carbon in plant tissues and soils.
Carbon sequestration is considered one of the many ecosystem services provided by green infrastructure. While stormwater practices are primarily designed to reduce runoff, improve water quality, and minimize flooding, many also contribute to climate change mitigation by storing carbon that would otherwise remain in the atmosphere.
Plants absorb carbon dioxide from the atmosphere during photosynthesis. Using sunlight, water, and nutrients, they convert CO₂ into carbohydrates that become part of their leaves, stems, trunks, branches, roots, and other tissues. As plants grow, they continue accumulating carbon, often storing it for decades or even centuries.
When leaves, roots, and other plant materials decompose, a portion of that carbon becomes incorporated into the soil as organic matter. Healthy soils can store significant amounts of carbon, especially when they experience minimal disturbance and contain abundant microbial activity.
Certain ecosystems, particularly forests and wetlands, are among the world's most effective natural carbon sinks because they continually capture and store carbon over long periods.
Many stormwater best management practices (BMPs) provide opportunities for carbon sequestration in addition to their primary drainage functions. Examples include:
The amount of carbon stored depends on factors such as plant species, age, climate, soil conditions, maintenance practices, and the lifespan of the vegetation.
Carbon sequestration generally occurs in two primary forms.
Biomass sequestration stores carbon within living vegetation, including trees, shrubs, grasses, and wetland plants. Trees typically store the largest quantities because of their size and longevity.
Soil carbon sequestration occurs when organic matter becomes incorporated into the soil. Healthy soils rich in microorganisms, fungi, and organic material can store substantial amounts of carbon below ground for many years.
Both forms contribute to reducing atmospheric carbon dioxide levels.
Carbon sequestration provides numerous environmental benefits beyond reducing greenhouse gases. Landscapes that store carbon often also:
Because these benefits often occur simultaneously, green infrastructure projects can deliver multiple ecosystem services from a single investment.
The effectiveness of carbon sequestration depends on several factors, including:
Protecting mature trees and preserving healthy soils generally results in greater long-term carbon storage than repeatedly removing and replacing vegetation.
As communities increasingly address climate resilience, carbon sequestration has become an important consideration during the planning and design of green infrastructure projects. Municipalities may select native trees with long life spans, restore wetlands, preserve riparian forests, or improve soil health to maximize carbon storage while also meeting stormwater management objectives.
Although carbon sequestration is rarely the primary purpose of stormwater infrastructure, it is an increasingly valuable co-benefit that supports broader sustainability and climate adaptation goals.
In summary, carbon sequestration is the process of removing carbon dioxide from the atmosphere and storing it in vegetation, soils, wetlands, and other natural systems. In stormwater management, green infrastructure practices such as urban forests, rain gardens, bioswales, constructed wetlands, and riparian buffers not only reduce runoff and improve water quality but also capture and store carbon, helping mitigate climate change while providing numerous ecological and community benefits.