Primary Source: Liu, Z., Fagherazzi, S. & Cui, B. Success of coastal wetlands restoration is driven by sediment availability. Commun Earth Environ 2, 44 (2021). https://doi.org/10.1038/s43247-021-00117-7https://www.nature.com/articles/s43247-021-00117-7
Wetland ecosystems have historically been undervalued by society. They can’t easily be built on and are difficult to navigate by most means of transportation. However, this underappreciated environment has been seeing a comeback in recent years, as they have been found to purify wastewater, protect coastlines during floods, and sequester carbon. In response to the current climate crisis these abilities have made wetland ecosystems an incredibly crucial environment worldwide. As such, many programs around the world have been attempting to bring historic wetland ecosystems to their former glory to combat the effects of climate change, most notably rising sea levels threatening to flood coastal communities. While these programs vary in specific application due to regional differences, these attempts are known largely as nature-based solutions. In comparison to less biological approaches, such as the construction of sea-walls, nature-based solutions are more cost effective and more consistent, as they require relatively little supervision and upkeep, and usually require less investment of money and resources. Sea-walls and similar non-nature based solutions typically act as a stopping point for severe waves and rising tides, which fail if put under too much stress too quickly. Comparatively, nature-based solutions reduce the effects of these environmental conditions over a wider area. While these effects of nature-based solutions in comparison to non-nature-based solutions has been made clear by many studies, a recent review-analysis of 268 published papers on restored wetlands has helped clarify the factors that influence the success of wetland restoration in combating sea level rise. By analyzing the success of nature-based solutions thus far, we can hopefully improve our restoration methods to fight the concerning consequences of climate change more effectively.
Sedimentary, Dear Watson
After standardizing measurements from the many different wetland studies and completing any missing information with openly available data recorded by NOAA, statistical tests were done to see which measurements produced a significant difference in mitigating sea level rise, measured in this recent analysis by the size of the effect introduced nature-based solutions had on sediment accretion and deposition. This analysis was also separated by classification of wetland between salt marshes and mangrove ecosystems to acknowledge that mechanistic differences between them may impact their individual responses to environmental changes. Mangrove wetlands’ prominent feature are mangroves, flexible trees with complex roots that excel at catching sediment. Salt marshes, on the other hand, are composed of vast expanses of varying grasses which have evolved different strategies for tolerating the high-salt environment of the shore, holding the soil together with the interwoven root-systems of entire populations. Interestingly, measurements such as height of significant waves during the testing period, elevation of the test site, and tidal range had much less effect on sediment accretion and deposition than expected. While researchers determined that nature-based solutions generally provided a significant increase to combating the loss of sediment to rising sea levels, they discovered that one measurement altered the degree of this increase more-so than other factors. A wetland ecosystem’s ability to retain sediment is boosted more greatly by nature-based solutions when the wetland’s source of sediment (such as a river further inland) is rich in suspended matter. In short, if a wetland has a consistent source of new sediment, nature-based solutions will benefit the wetland’s ability to combat the rising sea level, regardless of factors contributing to the removal of sediment, such as wave severity.
With these findings on steady introduction of new sediment, frequently brought to wetlands through river outlets, we can take further actions to restore wetland ecosystems more effectively. For example, many rivers that supply wetlands have been dammed up. While not an inherent issue, dams may inadvertently stop sediment before it has a chance to reach an outlet to the ocean. New restoration efforts could focus on alterations to waterway infrastructure to allow for the transport of sediment across. Alternatively, efforts could be made to provide wetland ecosystems for which there is no longer a suitable natural source of sediment with a synthetic supply of new sediment. Overall, these findings show that even functional restoration techniques can be re-evaluated and improved. As climate change becomes an exponentially worrying concern, so too can we exponentially grow in remediating our societal relationship with the natural world.