4 Coastal Wetlands and River Delta by Mushran Siddiqui
Introduction
Coastal wetlands and river delta biomes are essential ecosystems that play significant roles in carbon sequestration, biodiversity conservation, and climate regulation. They also shield coastal populations from floods and intense storms as salt marshes and mangroves provide nature-based risk mitigation (Van Coppenolle & Temmerman, 2020). Coastal wetlands act as crucial carbon sinks, sequestering carbon and aiding climate change mitigation. A meta-analysis comparing CO2 fluxes between inland and coastal wetlands highlights these ecosystems’ essential role in global carbon cycling (Tang et al., 2022; Lu et al., 2016). Coastal wetlands, including marshes and mangroves, are known as blue carbon ecosystems due to their exceptional carbon sequestration capabilities (Gao et al., 2022). They are also essential for maintaining ecosystem services and supporting biodiversity (Fastelli et al., 2017). River deltas, such as the Lena River Delta in Siberia, are characterized by diverse biomes ranging from river channels to marshes and peat swamps, supporting unique flora and fauna (Kutzbach et al., 2007). These deltas are essential for carbon exchange with the atmosphere and serve as critical habitats for various species, including migratory fishes (Bailly et al., 2021).
However, these unique biomes are under severe threat from environmental changes such as warming temperatures, rising sea levels, and human activities like agriculture and urbanization (Lazarus, 2017; Nill et al., 2019). The Yellow River Delta in China, for instance, has witnessed significant wetland loss due to land use change, aquaculture pond expansion, and flow-sediment regulation, as depicted in Fig.1 (Zhu et al., 2018). These changes have resulted in the conversion of natural wetlands into farmland and aquaculture ponds, impacting the biodiversity and ecological functions of the region (Yu et al., 2016; Chunying et al., 2018). Similarly, the Po River Delta in Italy has experienced significant land subsidence and wetland loss, primarily due to natural processes and human activities (Gaglio et al., 2016).
Therefore, this study explores the valuation of coastal wetlands and river deltas for 2023 and compares it to the study conducted by Costanza et al. (2014) and De Groot et al. (2020).
Methodology
The methodology for evaluating the economic value of ecosystem services provided by coastal wetlands and river deltas is as follows:
Data Source: The study heavily relied on the Ecosystem Services Valuation Database (ESVD) developed by Brander et al. (2023). This database is a comprehensive repository of ecosystem service value records, which support decision-making on nature conservation, restoration, and sustainable land management.
Data Extraction and Filtering: Data were initially extracted from the ESVD for 1,168 observations of coastal wetlands and river deltas. Through filtering, observations interacting with other biomes were identified and refined to focus only on those primarily associated with coastal wetlands and river deltas. This resulted in 785 primary observations used for detailed analysis.
Valuation of Ecosystem Services: The economic valuation involved categorizing the ecosystem services provided by these biomes into provision, regulation, maintenance and support, and cultural services. Each category was evaluated based on its economic benefits, using data from the ESVD and other referenced studies of Costanza et al. (2014) and De Groot (2020).
Analysis of Global Surface Area: The global surface area data from sources such as Davidson et al. (2019) were used to calculate the total area covered by coastal wetlands, including categories such as mangroves and salt marshes. This step was critical for understanding these ecosystems’ overall impact and contribution on a global scale.
Lastly, the study analyzed the price per hectare per year for coastal wetlands and river deltas, drawing comparisons between various studies to highlight the change in values and trends over time. Analyzing ecosystem service values is crucial for understanding the economic implications of environmental changes and conservation efforts.
Results and Discussion
This study assumes that coastal wetlands or river deltas have the same price per ha per year as they are mostly interconnected with numerous shared characteristics. These ecosystems share water retention and sediment trapping functions, which influence coastal areas’ biogeochemical processes. (Christensen et al. 2020). Therefore, coastal wetlands and river deltas may possess similar values because of their ecological. The grouping of these ecosystems is due to data constraints, but their diverse attributes suggest a need for separate valuations. This underscores the importance of future research to assess each biome accurately.
Table 1: Mean standardized values per ecosystem services of Coastal Wetlands and River Delta (Int$/hectare per year; 2020 price levels).
The analysis of 785 observations from Table 1 highlights the economic values of coastal wetlands and river deltas, showing significant variability in ecosystem service valuations, with an average of $86,743 and a median of $11,897 per hectare per year. Regulation services were the most valuable at $43,299 per hectare, contrasting sharply with other categories and previous studies of Costanza et al. (2014), which reported higher due to outliers. This study aligns more with De Groot et al. (2020), recognizing a broad spectrum of coastal systems, including dunes and mangroves. Notably, including diverse ecosystems and the observed increase in service values since 2014 suggest rising prices due to decreasing natural resources. This report emphasizes the need for precise valuation comparisons and future studies to address these discrepancies and understand the global economic impact of these biomes.
Table 2 shows a trend of decreased ecosystem service values from 1994 to 2020. This is concerning for environmental and economic reasons, as the surface area and value per hectare have decreased. Compared with the global GDP in 2022, which is estimated to be Int$164.5 trillion, the economic contribution of these ecosystems seems minor. However, the implications for future sustainability are profound, indicating a potential decline in quality of life for future generations if current trends persist.
Table 2. Global flow rate for coastal wetlands.
| Value of ecosystem services per year
(in trillions of Int$) |
|||||
| Year | Area (millions of ha) | Total Average Int$/ha/year | Total Median Int$/ha/year | Value-based on average price | Value-based on the median price |
| 1994 | 165 | 18,455 | 3.05 | ||
| 2011 | 128 | 228,613 | 15,182 | 29.26 | 1.94 |
| 2020 | 35.1 | 86,743 | 11,897 | 3.04 | 0.42 |
Conclusion
Coastal wetlands are fragile yet economically valuable ecosystems, offering numerous ecological benefits and services to the communities. Coastal reclamation has fragmented and damaged these areas, impairing their ecological functions (Liu et al., 2020). Additionally, the rapid spread of artificially introduced vegetation (e.g., salt marshes) encroaches on native habitats, further degrading the natural environment and its services (Liu et al., 2023). Losses to coastal wetlands and river delta areas can be attributed to natural processes and human activities. Human-induced factors such as land use changes, population growth, and economic development have significantly impacted these ecosystems. The expansion of agricultural land, urban sprawl, and industrial areas has led to the exploitation and conversion of coastal wetlands into farmland and infrastructure, resulting in the loss of biodiversity and ecosystem services (Yu et al., 2016; Ma et al., 2019). Moreover, anthropogenic activities such as sediment deposition, flow-sediment regulation, and coastal reclamation have had detrimental effects on the structure and function of coastal wetlands in river deltas (Zhang et al., 2022). Excessive reclamation activities can destroy original habitats and lead to wetland degradation, impacting these areas’ ecological value (Zhao et al., 2023).
This study emphasizes the significant economic and ecological role of coastal wetlands and river deltas in providing ecosystem services essential to addressing climate change and preserving biodiversity. Despite their value, these biomes face striking threats from land use change, urbanization, and climate change, substantially losing their surface area and functionality. This report found a decrease of 78.72% in surface area of coastal wetlands between 1994 and 2020. This is also reflected in the global flow rate, with lower value of ecosystem services per year in 2020 than in 2014. The results of this study support the need for more robust conservation laws and environmentally friendly land management techniques to save and rebuild these essential ecosystems. Comparing this valuation with earlier research reveals a need for an increasing recognition of their values, necessitating immediate action to protect them.
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