• Post category:2021 / News
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1 June 2021 | By Alanna Rebelo

In a study of three South African river catchments (the Berg, Breede and uMngeni) that have received significant investment into ecological infrastructure (e.g. clearing invasive alien trees), the evidence base for the benefits of these investments was found to be empirically weak.

This work was undertaken as part of the Socio-Economic Benefits for Investing in Ecological Infrastructure (SEBEI) Project by researchers Alanna Rebelo, Petra Holden and Mark New, as well as Karen Esler from the C∙I∙B.

They asked the question: is there evidence that ecological infrastructure interventions are delivering the proposed benefits?

To answer this question, they drew together three approaches:

  1. The development of an ‘ecological infrastructure intervention – ecosystem services’ (EII-ES) framework which they used to hypothesize the effects of ecological infrastructure interventions on ecosystem processes and services.
  2. A review of peer-reviewed and grey literature in the three catchments.
  3. Integration of the hypothesized EII-ES framework with the evidence from the literature review into a conceptual diagram using causal loop diagramming principles.

The implication of this weak empirical evidence base of benefits of investing in ecological infrastructure is (1) that there is a need for better baseline data collection, and monitoring during and after ecological infrastructure interventions (like alien clearing) to establish evidence for the benefits, and (2) that governments make funding available to support focused, applied and local empirical research to build an evidence base for the benefits. This could help to attract or leverage private sector funding.

Our systems dynamic framework also is a good starting point for identifying the gaps where evidence is lacking in terms of quantifying the linkages between various interventions and their impacts (e.g. how ecosystem properties and processes relate to ecosystem services), specifically for these three South African catchments,” said Alanna Rebelo, lead author of the paper published in The Royal Society of Open Science.

Read the paper in The Royal Society of Open Science

Rebelo, A.J., Holden, P.B., Esler, K.J, & New, M.G. 2021. Benefits of water-related ecological infrastructure investments to support sustainable land-use: a review of evidence from critically water-stressed catchments in South Africa. The Royal Society of Open Science. https://doi.org/10.1098/rsos.201402

For more information, contact Alanna Rebelo at ARebelo@sun.ac.za

  • Ecological infrastructure: ‘the underlying framework of natural elements, ecosystems, and functions and processes that are spatially and temporally connected to supply ecosystem services’ (Dominati 2013)
  • Ecological infrastructure interventions: artificial or natural actions that aim to enhance chosen ecosystem services in intact to transformed landscapes, informed by an understanding of ecology. Examples of natural interventions include alien plant clearing and revegetation, and examples of artificial interventions include artificial wetlands, permeable pavements and erosion control structures (gabions and weirs).
Rose charts of the logn+1 of the number of cases per type of evidence given for the benefits of implementing each ecological infrastructure intervention in the study catchments according to the literature.
(a–l) Rose charts of the logn+1 of the number of cases per type of evidence given for the benefits of implementing each ecological infrastructure intervention in the study catchments according to the literature. The number of cases for each intervention is indicated on each plot (n), and for empirical and modelled evidence, an average certainty is given on the plot, ranging from 0 to 1. Ecosystem services are indicated on the plot using the following symbols: A = Aesthetics, AQ = Air Quality Regulation, B = Biodiversity, CR = Climate Regulation, DP = Drought Protection, FRR = Fire Risk Reduction, FA = Flood Attenuation, FP = Food Production, FFP = Fuel and Fibre Production, HP = Habitat Provision, HCBIA = Heritage, Cultural, Bequest, Inspiration and Art, NR = Noise Reduction, RT = Recreation and Tourism, SR = Sediment Retention, SQ = Soil Quality Regulation, S = Spiritual, W = Water Provision, WP = Water Purification and PC = Pest Control. IAPs = Invasive alien plants.
Conceptual framework of the impacts of ecological infrastructure interventions.
Conceptual framework of the impacts of ecological infrastructure interventions. The potential (not-exhaustive) relationships between ecosystem properties, processes and ecosystem services are shown for the South African case studies. The causal loop diagram shows linkages between native-invader dynamics (figure 5) and internal ecosystem properties (stocks in black boxes with green arrows), processes (black italics), ecosystem services (purple) and external anthropogenic factors (red). The climate system is shown in blue, and fire dynamics in orange (some elements adapted from Luvuno et al. [31]). Ecological infrastructure interventions (EII) are given in red, labelled EII1–10 (no boxes), demonstrating the impacts that investments in ecological infrastructure could have on various key ecosystem processes and services. Links (arrows) where empirical evidence exists to support the relationship between variables for these South African case studies are given in bold.