WET-EcoServices Version 2: A revised ecosystem services assessment technique, and its application to selected wetland and riparian areas

Abstract

A rapid assessment technique, termed WET-EcoServices, was developed 10 years ago to help assess the ecosystem services that individual wetland hydrogeomorphic units supply. The technique requires the assessor to consider and score a suite of indicators (e.g., hydraulic roughness of the vegetation) which are then used to rate the ability of the wetland to provide 16 different ecosystem services. WET-EcoServices has become well entrenched in the South African context, with wetland specialists routinely using the technique to inform development planning, whilst it has also been used extensively in the wetland rehabilitation context. The technique has recently been revised, including the following key changes: (i) the technique is now more explicit in terms of distinguishing both ecosystem services’ supply and the demand for all ecosystem services assessed; (ii) the technique has been expanded to include non-wetland riparian areas; (iii) several of the indicators have been refined or replaced with indicators more relevant or appropriate for informing the rating of the ecosystem service or for which information is more readily available at a national level; and (iv) the algorithms used to integrate scores for the relevant indicators have been comprehensively refined so as to better account for the relative importance of the respective indicators. The aim of this paper is to present an overview of Version 2 of the technique and its underlying approach and then to demonstrate its application to 6 selected cases representing contrasting contexts, with a particular focus on the graphical representation of ecosystem service supply and demand for each case. Some of the key emphases and approaches applied by WET-EcoServices are then discussed in relation to other published techniques widely used for assessing wetland ecosystem services. After reflecting on some key limitations of WET-EcoServices, the paper concludes with recommendations on the technique’s potential contributions to operationalizing key broad imperatives of government.

Valley‐bottom wetlands as temporary buffers for source‐to‐sink dispersal of sediment and associated phosphorus in dryland landscapes

“…The general issue of spatial and temporal complexity in sediment trapping and total P removal efficiencies also poses a challenge in terms of generalisation and predictability of ecosystem services, especially when using rapid assessment tools (e.g., WET‐Ecoservices tool; Kotze et al, 2009, 2020). However, there are opportunities to improve the integration of indicators related to process geomorphology within South African wetland protocols for appraisal of ecosystem service provision.…”

“…The extent of these hydrodynamic mixing and dilution processes is mediated by the magnitude of rainfall events and longitudinal flux connectivity of surface water as well as particle availability (Ballantine et al, 2008;Owens & Walling, 2002) (Figure 9). The general issue of spatial and temporal complexity in sediment trapping and total P removal efficiencies also poses a challenge in terms of generalisation and predictability of ecosystem services, especially when using rapid assessment tools (e.g., WET-Ecoservices tool; Kotze et al, 2009Kotze et al, , 2020. However, there are opportunities to improve the integration of indicators related to process geomorphology within South African wetland protocols for appraisal of ecosystem service provision.…”

“…Fluvially-integrated wetlands, such as floodplains and valleybottoms, support diverse and highly valued regulatory ecosystem services including the attenuation of 'source-to-sink' dispersal of water, sediment, particulate organic matter and dissolved solutes (Johnston, 1991;Kotze et al, 2009;Phillips, 1989). The relative effectiveness of a given wetland type in mediating these material fluxes has been attributed to the complex interplay between catchmentscale hydrometeorological, geomorphological, ecological, biological and land-use conditions (Grenfell et al, 2014;Kotze et al, 2009).…”

“…As such, the fluxes and storage of phosphorus are typically closely associated with the dynamics of fluvial sediment and organic matter (Kronvang, 1992;Schwarz, Malanson, & Weirich, 1996). Consequently, factors influencing the dynamics of sediment trapping such as hydroperiod, vegetation density and sediment loading rates are also important in the dispersal and attenuation of fluvially-transported P within wetlands (Kotze et al, 2009).…”

Assessing Trade-Offs between Agricultural Productivity and Ecosystem Functions: A Review of Science-Based Tools?

“…They found that an important trade-off appeared to exist between the potential food provision of the wetlands and water-related ecosystem services, as well as with carbon storage. The tool appears relatively easy to apply in the field by non-experts, but it has a limited scope with its focus on South African wetlands [86]. However, after some adaptation, it could probably be scaled up to other areas with sub-tropical peat/wetlands.…”