Ecosystem service evaluation of the Zandvlei Estuary Nature Reserve, Cape Town, South Africa

Abstract

Ecosystem services, encompassing both tangible and intangible benefits derived from natural processes, play a vital role in enhancing human well-being and environmental sustainability. Estuaries and wetlands, particularly those found in peri-urban areas, offer a unique blend of ecological services and are of paramount importance to our society. However, these crucial ecosystems face escalating threats due to urban expansion, resource exploitation, and pollution, underscoring the urgency for innovative management strategies. Ecosystem-based management (EBM) presents a holistic approach that integrates both ecological and human needs into decision-making processes. Valuing ecosystem services is pivotal in guiding sustainable resource management and making informed policy decisions. Traditional valuation methods have predominantly relied on quantifying economic values, often neglecting the less tangible social and environmental dimensions of ecosystem services. This partial assessment fails to capture the comprehensive worth of ecosystems and their services, leaving a gap in our understanding of their true value to society. This study investigated aspects of three ecosystem services of the Zandvlei Estuary Nature Reserve (ZENR): 1) Recreational Value: A comprehensive questionnaire survey, employing a travel-cost methodology, reveals that ZENR users contribute significantly to the local economy through expenditures on travel and recreational equipment and fees. Moreover, the study sheds light on the pivotal role that ZENR plays in enhancing the social and cultural well-being of its users, with a notable 95% of respondents acknowledging its value. Additionally, over half (56%) of respondents highlight the importance of ZENR to their livelihoods. Litter management emerges as a prominent concern, with 26% of respondents expressing apprehension. The user base varies, encompassing a wide range of activities from walkers and bird watchers to on-water enthusiasts like fishers, rowers, and canoeists. Notably, walking stands as the most popular activity, while picnicking ranks the least frequented. Walkers and picnickers tend to spend less, whereas yachters and fishers are the highest spenders. A majority of respondents reside in neighbouring areas such as Marina da Gama, Muizenberg, and Lakeside, but ZENR draws visitors from across the Cape Town metropole. 2) Water Purification Service: The study delves into the regulatory ecosystem service of water purification which occurs via the natural filtration processes within the Zandvlei Estuary, where pollutants and excess nutrients are absorbed and broken down by aquatic vegetation, sediments, and microbial communities, thereby enhancing water quality and supporting the overall health of the ecosystem. This analysis was performed utilizing data from monthly water quality tests conducted by the City of Cape Town over a decade (2009 to 2018). The analysis uncovers spatial and seasonal trends, shedding light on the estuary's vital role in reducing concentrations of pollutants such as nitrogen, phosphorus, and E. coli, particularly in the aftermath of events like sewage spills. However, some chemical and biological pollutants have shown an increasing trend over the years, potentially jeopardizing the estuary's health and its capacity to provide safe recreational waters. The study pinpoints the river inlets, especially the Sand River Canal, as critical areas of concern due to reduced dilution capacity, canalization, and exposure to pollutants from industrial, agricultural, and residential sources. Stormwater drains further exacerbate the contamination issue, emphasizing the need for the rehabilitation and protection of these inlets. 3) Aesthetic Value: An assessment of property values in six areas surrounding ZENR provides insights into the cultural service of the estuary's aesthetic value using hedonic pricing methodology and general regression analyses. The findings highlight the positive influence of ZENR on the surrounding property market, contributing significantly to its economic value. The hedonic pricing approach indicates a surplus of up to R174 million generated by ZENR between 2014 and 2018 in the residential property market. General regression analyses reveal a positive correlation between house prices and proximity to the estuary, extending beyond a 200-meter range in three of the six surrounding suburbs. However, these analyses are influenced by other factors such as proximity to the beach, railway lines, or roads. It is essential to recognize that the value of an ecosystem extends beyond its monetary contributions. Ecosystem services are interconnected, and a decline in one service can have cascading effects on others. To avoid double counting, it is imperative to distinguish final ecosystem service values from support services. Effective management is pivotal in maintaining the supply of ecosystem services, and decision-makers rely on research-based information and stakeholder engagement to make informed choices. In conclusion, this study highlights the need for comprehensive valuations of ecosystem contributions to human well-being, moving beyond conventional economic metrics and embracing holistic approaches like the System of Environmental-Economic Accounting. The ZENR case study illustrates the multi-layered benefits provided by estuarine ecosystems and the importance of sustainable management to ensure their continued provision of vital services to society.