Parks protect water supply for downstream farms and cities

Garden Route National Park, South Africa

Collaborating with South African national park managers as well as academic researchers from South Africa and the U.S., we are investigating the positive impact of protected areas—in this case, a mountainous section of the Garden Route National Park—in maintaining consistent surface-water flows for downstream neighbors. These include farmers growing orchard crops, a major city on an estuary where the river meets the sea, and that city’s thriving tourism industry. We focus on park management’s clearing of invasive plants and its effects on water flow in the Keurbooms River. According to model projections, without plant-clearing, invasive species might have occupied up to 77% of the Keurbooms watershed and caused a 95% reduction in flow, nearly drying down the estuary’s freshwater contribution and putting the city’s drinking-water supplies at risk. Now we are finding out what happened on the ground: using statistical tools developed for impact evaluation – i.e. discerning the effect of programs or policies – we are measuring the benefits of a restoration project through comparisons with control watersheds without protected-area status or invasive-plant clearing.


Questions we're asking

  1. How much water is delivered to farmers, recreational users and urban households in the greater Keurbooms catchment in the presence of invasive-plant clearing programs?
  2. How would the absence of management have affected the water yield to downstream users?
  3. What is the value of those services to downstream users?

Problems we're solving

In South Africa and around the world, clean, consistent water supplies are at risk. The role of forested headwaters and the stewardship of protected areas – in this case removal of invasive plants – has not been sufficiently recognized and incorporated into water planning. South African National Parks, expected to finance themselves, are investing in vegetation management and clearing invasive species, thereby providing unrecognized value for downstream water users. Our work documents the parks’ vital contributions to watershed function and downstream flows.

Project participants: A. De Vos, Rhodes University, South Africa; J.L. Nelson, independent researcher; J. Smith, South Africa National Parks; M.M. Hanauer, Sonoma State University; D. LeMaitre, Council for Scientific and Industrial Research, South Africa.

Photo credit: JL Nelson 2015, Soetkraal region, South Africa