By David Baldwin
The United Nations Framework Convention on Climate Change calls for the stabilization of atmospheric greenhouse gas (GHG) to a level prevents further human interference with the climate. To meet this goal, it requires carbon sequestration: the capture and storage carbon back to either the environment or engineered system. That is where wetlands come in.
It is essential to appreciate the carbon sequestration capabilities of wetlands, even in urban settings. These ecosystems, whether in natural or constructed forms, possess a remarkable ability to lock away atmospheric carbon. Through photosynthesis, the wetland plants absorb carbon dioxide from the atmosphere and convert it through a series of molecular processes into cellulose and other carbon compounds in plants, effectively removing excess carbon from the atmosphere. Moreover, wetlands, by their waterlogged nature, inhibit the decomposition, of organic matter, allowing the carbon of the organic matter to accumulate in the form of peat-rich soils. This carbon storage is, in essence, an effective mitigation strategy against climate change. It's akin to a vault or carbon, securely tucked away from the atmosphere for centuries.
The protection of wetlands holds significant implications for Earth's natural carbon cycles, as a substantial proportion of the planet's carbon resides within wetland soils. For example, peatlands in tropical regions house an impressive carbon pool exceeding 600 petagrams (PgC), or billion metric tons, making them some of the world's largest carbon reserves. This is comparable to the carbon stored in global forest biomass. In the continental U.S., wetlands a reservoir amounting to 13.5 billion PgC according to the Global Change Research Program
Carbon comes in many forms, and it is not just the abundant carbon dioxide that wetlands can sequester. Methane is a hydrogen and carbon compound about 25 times more effective at trapping heat than carbon dioxide over a 100-year period. Wetlands, however, have a fascinating dual role concerning methane. While they can be sources of methane due to anaerobic (low oxygen) conditions in waterlogged soils, they are also sinks: a natural mechanism for nutrient storage. Microorganisms within wetlands, in a remarkable act of ecological balance, consume much of the methane they produce, preventing its release into the atmosphere. This helps in keeping a check on methane levels and mitigating its impact on global warming.
I now want to turn to what we can do with all this information. Wetlands are a recurring topic of discussion at COP events. During COP 28, a significant focal point in the discourse on water quality and access is the enhancement of urban water resilience. I eagerly anticipate engaging in productive conversations regarding the contribution of wetlands to this critical issue.
Urban wetlands are clear player in reaching the United Nation’s Sustainable Development Goal 13: Climate Action. I believe they are also a powerhouse in environmental justice and can aid in our journey toward reducing inequality and sustainable communities: Goals 10 and 11. These ecosystems, natural or engineered, offer a beacon of hope, especially for marginalized communities facing disproportionate environmental challenges. Minoritized groups often find themselves residing in areas more vulnerable to flooding and lacking the necessary resources for recovery. Wetlands play a pivotal role in maintaining water quality, both within their boundaries and downstream. Their unique hydrological and biological characteristics (the soil, plants, and flow of water) allow them to absorb excess nutrients and filter out various contaminants. This purification capacity ensures that water, as it flows through wetlands, emerges cleaner and less burdened by harmful substances. In this manner, wetlands play a fundamental role in mitigating the detrimental impacts of chemical pollution, thus preserving the health of aquatic ecosystems, and safeguarding the surrounding communities.
In a similar process, a process called sedimentation relies on the slow-moving nature of water, allowing nutrient-rich particulate matter sediments to settle. As water flows through the wetland, these sediments are captured and retained, preventing their downstream transport. Additionally, aquatic plants within wetlands serve as biological sponges, absorbing nutrients from the water. Through a process known as nutrient assimilation, these plants incorporate nitrogen and phosphorus into their tissues, effectively removing excess nutrients from the ecosystem. A healthy wetland has nutrient rich sediment, and nutrient poor water, and a healthy environment promotes a healthy community.
Protecting wetlands is not just a matter of ecological importance; it's a matter of justice and equity in our pursuit of sustainability.