By Abbas Nazil
Coastal wetlands, including mangroves, saltmarshes, and seagrass meadows, play a critical role in climate regulation, coastal protection, and supporting biodiversity, according to a recent article in Reviews of Geophysics.
These low-lying ecosystems, shaped by tidal processes, provide essential services such as shoreline protection from storms and erosion, water filtration, and habitat for fisheries, while also storing significant amounts of carbon in their soils.
Despite covering a relatively small portion of the Earth’s surface, coastal wetlands punch well above their weight in ecosystem contributions, making them vital for both nature and human communities.
The carbon stored in these ecosystems, often called “blue carbon,” is captured through photosynthesis by vegetation and transferred to sediments via roots.
Wetland plants can sequester carbon up to forty times faster than terrestrial forests, and waterlogged, oxygen-poor sediments allow carbon to remain stored for centuries to millennia.
Groundwater processes also play a crucial but less visible role in transporting dissolved carbon into and out of wetlands, which is essential for accurately assessing long-term carbon storage and wetland responses to environmental changes.
Over the past century, human activities such as agriculture, urban development, port construction, and flood protection infrastructure have drained, filled, or otherwise degraded coastal wetlands.
These modifications disrupt natural water flow, reduce plant productivity, and expose carbon-rich soils to oxygen, releasing stored carbon as greenhouse gases.
Groundwater extraction and altered flow paths further diminish wetland function, causing many previously carbon-sequestering wetlands to become net emitters of greenhouse gases.
Restoring coastal wetlands can reverse these impacts by re-establishing natural tidal flow, hydrology, and vegetation cover, which enhances sediment accumulation and resumes carbon burial.
Successful restoration also reconnects groundwater and surface water systems, stabilizing conditions that favor long-term carbon preservation in sediments.
Restoration strategies typically involve removing or modifying levees and barriers, reconnecting wetlands to tidal regimes, re-establishing vegetation, and managing sediment supply.
Site-specific designs that consider hydrology, geomorphology, and sea-level rise are critical for ensuring that restored wetlands function as effective carbon sinks.
Despite growing interest in restoration, major knowledge gaps remain, particularly in understanding groundwater’s influence on carbon storage and greenhouse gas emissions across different wetland types and climates.
Long-term measurements are also needed to determine whether restored wetlands maintain carbon sequestration under rising sea levels and increasing climate variability.
Integrating hydrology, biogeochemistry, and ecology into predictive models remains a challenge but is essential for improving carbon accounting, guiding restoration investments, and strengthening wetlands’ role in climate mitigation strategies.
By restoring coastal wetlands, communities can achieve climate benefits while also improving biodiversity, coastal protection, and water quality, making these ecosystems a powerful nature-based solution in the fight against climate change.
