Assessment of the long-term response to rehabilitation of two wetlands in KwaZulu-Natal, South Africa

Abstract

Assessing the ecological outcomes of wetland rehabilitation activities is an important need recognised by the 'Working for Wetlands' programme in South Africa. An assessment of ecological response was conducted in the Killarney and Kruisfontein wetlands, KwaZulu-Natal, in 2005 prior to rehabilitation in 2006, and again in 2011 and 2012, respectively, following rehabilitation. The assessment criteria included an evaluation of changes in ecological integrity, the supply of ecosystem services, and vegetation composition. Improvements in hydrological and geomorphic integrity were recorded in both wetlands, resulting in improved ecosystem delivery. However, investigation of vegetation composition using the wetland index value and floristic quality assessment index indices showed that, seven years after rehabilitation, Killarney's vegetation composition had improved, but Kruisfontein's vegetation was still largely dominated by pioneer species and appeared to be stable, but in a severely transformed state. The response of these wetlands has shown that sites for rehabilitation should be screened before work begins, and wetlands requiring intensive management of vegetation recovery should be assessed in terms of the objectives and the anticipated benefits of the project.

Assessing, with limited resources, the ecological outcomes of wetland restoration: a South African case

“…In at least one of the HGM units, namely Eselfontein valley bottom, an alternative stable state appears to have been entered which strongly related to invasive species in the unit, including the exotic grass Pennisetum clandestinum and indigenous shrub Elytropappus rhinocerotis . As shown by Cowden et al () for a channeled valley bottom wetland in KwaZulu‐Natal, South Africa, restoration interventions resulted in a significant improvement in the hydrological condition of the wetland, but vegetation showed little improvement, even after more than 5 years. At both sites invasive plant species already present at the site appear to be constraining vegetation recovery, as observed by Galatowitsch and van der Valk () for native sedge meadow wetlands in the North American prairie pothole region and by Tererai et al () for riparian areas along the Berg River, Western Cape, South Africa.…”

“…The approach developed in this study applies existing methods, notably WET‐Health, WET‐EcoServices, and hectare equivalents of Cowden et al () across multiple sites, from which key trends are identified and lessons distilled. As far as is known, the study is the first of its kind in Africa.…”

“…The spatial extent of the wetland in hectares was multiplied by the overall condition score to derive what is referred to as hectare equivalents, as described by Cowden and Kotze () and Cowden et al (). Hectare equivalents can be used as a “currency” for measuring the contribution of restoration interventions to overall ecological condition.…”

“…An approach has been developed for rapidly assessing the outcomes of wetland restoration (Cowden & Kotze ; Cowden et al ) in which WET‐Health (Macfarlane et al ) plays a central role, and WET‐EcoServices (Kotze et al ) a supporting role. This study seeks to further develop this approach, specifically by using a case study to extend its application within the context of a national wetland restoration program.…”

Landscape Connectivity in the Upper Mzimvubu River Catchment: An Assessment of Anthropogenic Influences on Sediment Connectivity

“…Extreme cases have been reported where buffers have been destroyed, such as wetlands that were purposefully drained to expand agricultural activities (e.g. Cowden et al, ). More general cases of ploughing on steeper slopes and the subsequent development of features such as sheet erosion, rills and gullies are examples where hillslope–channel connectivity has been increased (Kakembo & Rowntree, ).…”