Climate change is one of our planet’s greatest threats, affecting ecosystems, communities, and economies worldwide. Rising temperatures, extreme weather events, and rising sea levels endanger human and natural systems. Amid this crisis, wetlands emerge as powerful allies in the fight against climate change. These ecosystems store carbon, protect coastlines, filter water, and support biodiversity. However, California’s wetlands have experienced a significant decline, with 90% lost since 1850. This dramatic loss threatens biodiversity, weakens coastal resilience, and diminishes the region’s ability to combat climate change through natural carbon storage. Protecting and expanding these habitats is essential to preserving their ecological functions and ensuring they continue to benefit both the environment and local communities. The Kendall-Frost Marsh Reserve (KFMR) in Mission Bay, San Diego, is one of the last remaining wetlands in the region, making it an important site for conservation and research. A recent study conducted by environmental ecology student Finn Schwartz, under the guidance of Dr. Matthew Costa at UC San Diego’s Scripps Institution of Oceanography, investigates carbon storage at KFMR. Specifically, it aims to determine whether habitat type (salt marsh versus mudflat) or elevation influences carbon stock. Using 16 sediment cores, researchers found no strong correlation between carbon storage and these factors. Statistical analysis, including ANOVA (F = 1.22, P > 0.05) and Pearson’s correlation (R = 0.27, P > 0.05), confirmed that neither habitat type nor elevation significantly influenced carbon stock. These findings suggest that carbon stock can be estimated based on wetland acreage alone, simplifying restoration planning and reinforcing the importance of preserving and expanding wetlands as natural carbon sinks.
What Are Wetlands, and Why Are They Important?
Wetlands are dynamic ecosystems that serve as natural water filters, storm buffers, and carbon sinks. By trapping pollutants, they reduce water treatment costs for cities like San Diego by up to $264,000 annually. Additionally, they provide habitats for fish and wildlife, support commercial fisheries, and offer recreational opportunities such as birdwatching, kayaking, paddleboarding, and nature walks, strengthening local investment and community engagement.
Wetlands also hold cultural significance for indigenous communities such as the Kumeyaay in California, who have relied on them for centuries. With climate change accelerating sea level rise, potentially up to two meters by 2100, wetlands play a crucial role in protecting coastal areas from erosion and flooding. Wetlands are nature’s all-in-one toolbox: keeping the water clean, protecting the shore, and absorbing carbon.
Wetlands capture carbon by accumulating organic material in their soils. Despite covering only 5.5% of the U.S. land area, they store approximately 2.9 billion metric tons of carbon, making them critical tools for mitigating climate change. Since the 1850s, 90% of California’s wetlands have disappeared, with San Diego County losing 31% of its wetlands. The wetlands in Mission Bay, which once spanned 4,000 acres, have been reduced to just 40 acres due to urban development. The Kendall-Frost Marsh Reserve (KFMR) is the last remaining wetland in Mission Bay, but it faces challenges such as reduced sediment input, which could impact its ability to sequester carbon. As noted by researchers from UC San Diego, this dramatic loss threatens biodiversity, weakens coastal resilience, and diminishes the region’s ability to combat climate change through natural carbon storage (Noto 2017). In response, restoration efforts are underway, including San Diego’s Climate Action Plan, which aims to restore up to 700 acres of wetlands by 2035. Protecting and expanding these habitats is essential to preserving their ecological functions and ensuring they continue to benefit both the environment and local communities.
Research Question and Hypothesis
This study aims to determine whether elevation or habitat type influences carbon storage at KFMR. It is hypothesized that higher elevations and salt marsh habitats would store more carbon due to increased vegetation. By testing this hypothesis, the researchers hope to provide valuable data for guiding wetland restoration efforts.
Materials and Methods
KFMR is a 40-acre tidal wetland in Mission Bay, San Diego, managed by UC San Diego’s Natural Reserve System. It consists of salt marshes, mudflats, and tidal channels, receiving about nine inches of annual rainfall. Elevations range from 1.33 to 5.55 feet above sea level.
Researchers collected sediment cores from 16 locations across various habitat types to assess carbon storage, including salt marshes, mudflats, tidal channels, and open water. A diverse spread of site selections ensured representation of different habitat types and elevation ranges. Cores were extracted using GPS devices and Russian Peat Corers, specialized tools designed for retrieving intact soil samples from wet, organic-rich environments. The Russian Peat Corer consists of a semi-cylindrical chamber attached to a rotating handle, allowing researchers to drive the corer into the soil and extract samples while minimizing disturbance. According to scientists who published a journal review regarding measuring wetland carbon pools and fluxes, this method is particularly effective in wetland environments, where preserving sediment structure is crucial for accurate carbon stock analysis.
In the lab, samples were dried, homogenized, and analyzed for organic carbon content. Statistical analyses, including Pearson’s correlation and ANOVA, were performed using Minitab® and Excel® to assess the relationship between carbon storage, elevation, and habitat type. Given the variability in carbon storage, additional sediment cores may be needed in future studies to refine these findings.
Results
An analysis of 16 sediment cores collected between 2019 and 2022 estimated the total carbon stock at KFMR to be approximately 2,440 metric tons. Statistical tests confirmed that neither habitat type nor elevation significantly affected carbon storage. Pearson’s correlation results showed a weak positive relationship between carbon storage and elevation (R = 0.27, P > 0.05), and ANOVA revealed no significant difference between salt marshes and mudflats in carbon stock (F = 1.22, P > 0.05).
Interestingly, neither habitat type nor elevation significantly predicts carbon storage at Kendall-Frost. Elevation had a weak correlation (R = 0.27, P > 0.05), and habitat comparisons fizzled, with no significant difference between mudflats and salt marshes. Translation? Carbon storage here is like an open buffet: it does not play favorites.
One limitation of this study is the sample size, as only a limited number of sediment cores were analyzed. Further data collection may refine these findings. Future research should explore how long carbon remains stored in wetland soils and what environmental factors influence its retention. Radiocarbon dating and soil chemistry analysis could provide deeper insight into long-term sequestration processes.
Wetland restoration is a promising strategy for increasing carbon sequestration and enhancing climate resilience. San Diego’s Climate Action Plan includes a goal to restore 700 acres of wetlands by 2035, with one proposed project focusing on restoring 227 acres in Mission Bay. If implemented, this restoration could store an estimated 16,900 metric tons of carbon over time, reinforcing the critical role of wetlands in climate mitigation.
This study provides valuable insights for restoration planning by demonstrating that neither habitat type nor elevation significantly influences carbon storage at KFMR. Instead, the data suggest that total wetland acreage is the key factor in determining carbon stock. This means that restoration efforts should prioritize expanding wetland areas rather than focusing on specific habitat types. By simplifying carbon stock estimation to a function of wetland size, this study helps streamline decision-making for conservationists and policymakers, making it easier to predict the carbon benefits of proposed restoration projects. Additionally, understanding that all wetland habitats contribute similarly to carbon storage supports the argument for broad-scale restoration rather than targeting specific habitat features. These findings reinforce the urgency of protecting and expanding wetlands as a nature-based solution for climate change mitigation.
Conclusion
Wetlands have drastically declined since the 1900s, so the need to restore and protect them is crucial. Coastal wetlands, such as the KFMR, can store large amounts of carbon and help fight against climate change while simultaneously preserving natural spaces near cities. The studies show that canon storage at the KFMR does not depend on elevation or habitat type, so the best estimate is averaged across different areas. This underscores a big takeaway: even small wetlands can have a major climate impact, reinforcing why saving and expanding them should be a priority. Nonetheless, further research is needed to understand sediment accumulation rates and long-term carbon storage dynamics. Finn is hoping to explore why different ecosystems store the same amount of carbon by looking at how much carbon is stored and released, along with what determines carbon sources from carbon sinks, or what actions need to be taken to prevent these ecosystems from releasing their stored carbon. These findings can help predict how much carbon could be stored with future wetland restoration plans for Mission Bay. At the end of the day, this research highlights why wetlands should be at the forefront of climate action. They are not just swamps or soggy patches of land, they are powerful climate warriors, capable of storing carbon, protecting coastlines, and supporting biodiversity. If we want to tackle climate change head-on, investing in wetland restoration is not just an option; it is a necessity.