USA Wetlands
A discussion about the past, the present, and the future of wetlands
- 1.Impacts of wetlands on climate change
Wetlands are defined as transitional lands between terrestrial and aquatic ecosystems that provide valuable services to society. Among these services, wetlands improve water quality due to their ability to remove nutrients and pollutants. Wetlands also help maintain biodiversity by regulating global climate through carbon sequestration and methane emissions. In coastal systems, wetlands serve as storage units that regulate the global water cycle and provide flood mitigation services such as storm surge, wave attenuation, and hurricane protection. Wetlands are endangered ecosystems that provide important habitats for plants and animals around the world. They serve as water and carbon storage units, regulate the global climate and water cycle, and act as a natural barrier against storm surges(Munoz, D. F., Munoz, P., Alipour, A., Moftakhari, H., Moradkhani, H., & Mortazavi, B., 2021).
Local to regional studies have shown that protecting or restoring coastal wetland ecosystems, such as salt marshes and mangroves, can provide nature-based risk mitigation because of their natural capacity to mitigate storm surge impacts and associated flood risks. In the face of global climate change and increased risk of coastal flooding associated with more severe storms and projected sea-level rise, protection of tidal wetlands can promote natural mitigation of coastal mitigating storm surge flood risk, reduce the impact of wave and shoreline erosion, and accumulate sediment as sea level rises. Therefore, nature-based risk mitigation can reduce the threat to coastal areas and populations affected by flooding (Van Coppenolle, R., & Temmerman, S., 2020).
The importance of wetlands to the global carbon cycle and ecosystem services is well known, but the extent to which they affect the carbon cycle (carbon source or sink) is poorly understood. Wetlands may affect the atmospheric carbon cycle in four ways. First, many wetlands have highly unstable carbon, which could be released if water levels are lowered or management practices result in soil oxidation involving both aerobic and anaerobic processes. Second, carbon dioxide enters the wetland system through photosynthesis by wetland plants, allowing it to change its concentration in the atmosphere by sequestration of the carbon in the soil. Third, wetlands easily capture carbon-rich sediments from watershed sources and may also release dissolved carbon into adjacent ecosystems. This, in turn, could affect the rate at which carbon is absorbed and emitted. Finally, even in the absence of climate change, wetlands release methane into the atmosphere. The carbon storage of the wetland ecosystem is high, and the importance of protecting wetland is paid more and more attention. This function can be a way to help improve greenhouse gas emissions (Zamora, S., Sandoval-Herazo, L., Ballut-Dajud, G., Del angel-Coronel, O. A., Betanzo-Torres, E., & Marin-Muniz, J., 2020).
2.Impacts of climate change on wetlands
All of the wetland conservation easements in this study performed the intended function of the NRCS and supported aquatic vegetation during the 2013 and 2014 field seasons. However, even small changes in precipitation, evaporation and transpiration can change the surface or water table by just a few centimeters, enough to reduce or expand the size of many wetlands, alter some wetlands on land, or transfer from one wetland type to another. Climate change will affect naturally occurring and recovering wetlands and their sustainability; However, the impacts of climate change on wetland systems will vary by location and wetland type (Cassatt, M. S., & Wilcox, D. A., 2020). Wetland systems that rely most on precipitation as their primary water source are the most vulnerable to climate change and are likely to experience the most dramatic changes or disappearance. The search for stable groundwater sources and appropriate water resource management should form the basis for positioning and designing new wetland restoration systems and creating adaptive management strategies for invested restoration projects (Cassatt, M. S., & Wilcox, D. A., 2020).
Overall, sea-level rise will negatively affect the vegetation cover, structure, composition, and function of coastal freshwater wetlands. In the United States, increasing salinization and frequent flooding conditions have negatively impacted coastal forest wetland areas, resulting in reduced forest health and productivity, base area and tree density and species diversity; Seed germination and regeneration; As a plant, mortality increases. In addition, the sea level rise causes an increase in salinity which reduces the stability of the bog soil, leading to increased decomposition of soil organic carbon, resulting in a decrease in elevation and a further decline in plant productivity and root biomass. The salt invasion also affected soil microorganisms involved in denitrification, with a reduced rate of up to 70%. In wetlands undergoing early SLR, nitrification is allowed to occur during the dry period between saltwater inundation, but under permanent inundation, ammonium nitrogen is released and nitrogen stocks of large plants are reduced. However, salt conditions combined with warming can increase denitrification and ammonium availability. In freshwater marshes in Louisiana and South Carolina, litter decomposition increases with initial saltwater intrusion, however, with more sustained saltwater flooding, litter decay rates decrease, leading to greater carbon storage. Seawater intrusion greatly increased the release of biologically available phosphorus (PO43−) from the soil of salt marshes and brackish marshes in northern Florida, but not from freshwater marshes, because PO43− can still be absorbed by plants (Grieger, R., Capon, S. J., Hadwen, W. L., & Mackey, B., 2020). The experimental treatment of water level examined the effect of rainfall changes on biological and abiotic responses to CFW. For example, drought conditions increased nitrogen (NH4+) output from recovering wetland sediments and to a lesser extent from forest wetlands. On the contrary, experimental flood conditions reduced the germination rate and species richness of freshwater wetlands. This suggests that biodiversity may be lost and vegetation may change as a result of more frequent and severe floods (Grieger, R., Capon, S. J., Hadwen, W. L., & Mackey, B., 2020).
3.Focus on JUY BAY WETLANDS
Let us go through the features of THE JUY BAY WETLANDS, MARYLAND.
On the map, we can easily find out there is enough rainfall in the JUY BAY areas. But the Major threats to wetland water quality include untreated urban wastewater, industrial wastewater, agricultural runoff, erosion, and changes in sediment flow. With fecal coliform populations increasing in Latin America, Africa, and Asia, severe contamination of rivers with pathogens is a major problem. By 2050, a third of the world's population is expected to be exposed to eutrophication, where excessive concentrations of nutrients cause rapid algae growth and decay that can kill fish and other species (Max Finlayson, C., & Gardner, R. C., 2021).
The following two maps show the hydrologic feature of the soil in the wetland.
The following two maps show the detailed hydrological characteristics with additional frost-free periods added.
The following two maps show the soil types and typical species in the specific areas. One is Palustrine, the other is Estuarine Subtidal.
Some threats to JUY BAY WETLANDS:
Current estimates suggest the global population will reach 10 billion by 2050. Over the past 12 years (2009-2020), we have experienced the 10 hottest years on record, each bringing record floods, droughts, snowfall, snowmelt, and severe storms to some parts of the world. Climate extremes will combine with the resource demands of our growing population, no doubt affecting the biomes of our remaining wetland habitats in unexpected ways. At the same time, we see widespread spatial and taxonomic homogenization of organisms, providing ample opportunity for the introduction of potential invaders into increasingly strained wetland ecosystems (Lazaro-Lobo, A., & Ervin, G. N., 2021).
References
Cao, B., Bai, C., Xue, Y., Yang, J., Gao, P., Liang, H., Zhang, L., Che, L., Wang, J., Xu, J., Duan, C., Mao, M., & Li, G. (2020). Wetlands rise and fall: Six endangered wetland species showed different patterns of habitat shift under future climate change. Science of the Total Environment, 731https://doi.org/10.1016/j.scitotenv.2020.138518
Cassatt, M. S., & Wilcox, D. A. (2020). Potential effects of climate change on NRCS wetland restoration easements: An ecohydrological assessment. Ecohydrology, 13(2)https://doi.org/10.1002/eco.2183
Chun, X., Qin, F., Zhou, H., Dan, D., Xia, Y., & Ulambadrakh, K. (2020). Effects of climate variability and land use/land cover change on the Daihai wetland of Central Inner Mongolia over the past decades. Journal of Mountain Science, 17(12), 3070-3084. https://doi.org/10.1007/s11629-020-6108-1
Dayathilake, D. D. T. L., Lokupitiya, E., & Wijeratne, V. P. I. S. (2021). Estimation of soil carbon stocks of urban freshwater wetlands in the Colombo Ramsar wetland city and their potential role in climate change mitigation. Wetlands, 41(2) https://doi.org/10.1007/s13157-021-01424-7
Doll, P., Trautmann, T., Gollner, M., & Schmied, H. M. (2020). A global-scale analysis of water storage dynamics of inland wetlands: Quantifying the impacts of human water use and man-made reservoirs as well as the unavoidable and avoidable impacts of climate change. Ecohydrology, 13(1)https://doi.org/10.1002/eco.2175
Gedney, N., Huntingford, C., Comyn-Platt, E., & Wiltshire, A. (2019). Significant feedbacks of wetland methane release on climate change and the causes of their uncertainty. Environmental Research Letters, 14(8)https://doi.org/10.1088/1748-9326/ab2726
Grieger, R., Capon, S. J., Hadwen, W. L., & Mackey, B. (2020). Between a bog and a hard place: A global review of climate change effects on coastal freshwater wetlands. Climatic Change, 163(1), 161-179. https://doi.org/10.1007/s10584-020-02815-1
Lazaro-Lobo, A., & Ervin, G. N. (2021). Wetland invasion: A multi-faceted challenge during a time of rapid global change. Wetlands, 41(5)https://doi.org/10.1007/s13157-021-01462-1
Max Finlayson, C., & Gardner, R. C. (2021). Ten key issues from the global wetland outlook for decision makers. Marine and Freshwater Research, 72(3), 301-310. https://doi.org/10.1071/MF20079
Munoz, D. F., Munoz, P., Alipour, A., Moftakhari, H., Moradkhani, H., & Mortazavi, B. (2021). Fusing multisource data to estimate the effects of urbanization, sea level rise, and hurricane impacts on long-term wetland change dynamics. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 14, 1768-1782. https://doi.org/10.1109/JSTARS.2020.3048724
Van Coppenolle, R., & Temmerman, S. (2020). Identifying global hotspots where coastal wetland conservation can contribute to nature-based mitigation of coastal flood risks. Global and Planetary Change, 187https://doi.org/10.1016/j.gloplacha.2020.103125
Zamora, S., Sandoval-Herazo, L., Ballut-Dajud, G., Del angel-Coronel, O. A., Betanzo-Torres, E., & Marin-Muniz, J. (2020). Carbon fluxes and stocks by Mexican tropical forested wetland soils: A critical review of its role for climate change mitigation. International Journal of Environmental Research and Public Health, 17(20), 1-13. https://doi.org/10.3390/ijerph17207372
Images:
https://share.america.gov/us-protects-wetlands/
