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Graphical abstract Highlights • Healthy wetlands had higher C uptake, N&P uptake efficiency & flood attenuation. • Their value coupled with marginal agriculture advocates more strategic use of wetlands. • High downstream demand for ES suggests potential for payments for ES scheme. • The rapid tool didn't adequately assess degraded wetland ecosystem services (ES). • Healthy wetlands were accurately scored for ecosystem service provision by the tool. Abstract Wetlands globally are highly threatened by agriculture, and damage associated with it, such as invasion by alien species and the impacts of fertilizers and pesticides. South African palmiet wetlands make an interesting case study to investigate this, as they are valuable valley-bottom, peat-forming systems, highly threatened by agricultural development. Currently most agriculture in these palmiet wetlands is marginal (low agricultural productivity) due to the challenges of farming a system that experiences severe floods and erodes rapidly, forming gullies, when wetland vegetation is disturbed. The current situation seems to be a lose-lose situation for nature and society. We aimed to assess this conflict between water-related services and agriculture objectively by comparing provision of fifteen ecosystem services by degraded and pristine sections of three palmiet wetlands using a rapid ecosystem service assessment tool (WET-Ecoservices). To validate this technique, we compared results to those obtained from examining three key ecosystem service complexes in slightly more detail. We found that pristine palmiet wetlands provide valuable ecosystem services to society, which are currently being compromised for private, marginal agricultural gain. These pristine wetlands sequester between 21 and 41 g.m−2 of carbon per year, have nitrogen and phosphorus uptake efficiencies of 62–85% and 16–89% respectively, and provide about 16 times more flood attenuation relative to degraded ones. The full impact of degradation on wetland ecosystem services was not entirely captured by the rapid ecosystem service assessment tool: WET-Ecoservices. We suggest some adaptations to this tool for the valley-bottom wetland hydro-geomorphic unit. Overall, these wetlands have high potential for incorporation into a Payments for Ecosystem Services scheme, due to the ecosystem services provided and their position above important municipal dams. We recommend collaboration between private landowners struggling with marginal agriculture, and decision makers in cities dealing with water shortages and debt to ensure the most efficient and judicious use of these palmiet wetland ecosystem services. [ABSTRACT FROM AUTHOR]

Despite the importance of water purification to society, it is one of the more difficult wetland ecosystem services to quantify. It remains an issue in ecosystem service assessments where rapid estimates are needed, and poor-quality indicators are overused. We attempted to quantify the water purification service of South African palmiet wetlands (valley-bottom peatlands highly threatened by agriculture). First, we used an instantaneous catchment-scale mass balance sampling approach, which compared the fate of various water quality parameters over degraded and pristine sections of palmiet wetlands. We found that pristine palmiet wetlands acted as a sink for water, major cations, anions, dissolved silicon and nutrients, though there was relatively high variation in these trends. There are important limitations to this catchment-scale approach, including the fact that at this large scale there are multiple mechanisms (internal wetland processes as well as external inputs) at work that are impossible to untangle with limited data. Therefore, secondly, we performed a small field-scale field survey of a wetland fragment to corroborate the catchment-scale results. There was a reasonable level of agreement between the results of the two techniques. We conclude that it appears possible to estimate the water purification function of these valley-bottom wetlands using this catchment-scale approach. [ABSTRACT FROM AUTHOR]