Low-cost grass restoration using erosion barriers in a degraded African rangeland

Kimiti, D. W., et al., 2017. Restoration Ecology

Original research (primary data)
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Abstract

Rangeland degradation, typified by extensive bare ground and soil erosion, is a serious problem around the world. In sub-Saharan Africa, rangeland degradation threatens the food security of millions of people who depend on livestock and the region’s large mammalian wildlife diversity. We tested the ability of five simple, low-cost erosion barriers to promote grass and forb establishment in a bare ground-dominated rangeland in Kenya. These treatments were: (1) trenches with small berms; (2) bundles of branches; and bundles of branches with (3) elephant dung balls, (4) burlap sacking, or (5) nylon mesh sacking inside them. We also tested whether barrier performance depended on (1) supplemental seeding with the grass Cenchrus ciliaris and (2) whether a barrier was located next to existing vegetation patches versus in the open. Within months, the trench and nylon mesh barriers had accumulated 20–50% more sediment than other treatments and had greater grass and forb seedling establishment. Seeding with Cenchrus resulted in higher herbaceous cover but was not necessary for other grasses to establish. After 3 years, the trench and nylon mesh barriers had created patches of new vegetation averaging 18–63% larger than patches created by the other treatments. Barriers that were initially adjacent to existing vegetation had created new vegetation patches averaging 65% larger than those created by solitary barriers. Results suggest that all barrier types increase grass cover but that trenches—especially if placed next to existing vegetation patches—are a particularly cost-effective way to reduce bare ground and erosion in degraded rangelands.

Case studies

Basic information

  • Case ID: INT-087-1
  • Intervention type: Restoration
  • Intervention description:

    field assessment, no control. restoration techniques using five different types of erosion barriers, either: (1) trenches with small berms; (2) bundles of branches; and bundles of branches with (3) elephant dung balls, (4) burlap sacking, or (5) nylon mesh sacking inside them. We also tested whether barrier performance depended on (1) supplemental seeding with the grass Cenchrus ciliaris and (2) whether a barrier was located next to existing vegetation patches versus in the open.

  • Landscape/sea scape ecosystem management: No
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Loss of food production  Positive Initial Barrier Effectiveness: Measures of initial plant establishment included total percent cover, species richness, and biomass of different plant functional groups in the first 1m or first 2 m upslope of barriers Long-Term Barrier Effectiveness: the number of nonoverlapping 50 × 50 cm quadrats upslope of the barrier that had greater than 50% vegetation cover to estimate the total area of newly established vegetation (measuring the long-term effectiveness of barriers in forming large and lasting patches of herbaceous vegetation in previously bare areas)
    Soil erosion  Positive Initial Barrier Effectiveness: Measures of initial plant establishment included total percent cover, species richness, and biomass of different plant functional groups in the first 1m or first 2 m upslope of barriers Long-Term Barrier Effectiveness: the number of nonoverlapping 50 × 50 cm quadrats upslope of the barrier that had greater than 50% vegetation cover to estimate the total area of newly established vegetation (measuring the long-term effectiveness of barriers in forming large and lasting patches of herbaceous vegetation in previously bare areas)
  • Approach implemented in the field: Yes
  • Specific location:

    Mpala Conservancy in Laikipia, Central Kenya

  • Country: Kenya
  • Habitat/Biome type: Tropical and subtropical grasslands |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: look at effectiveness by monitoring changes over time (compare to baseline) but no control treatment (i.e. no restoration barrier) effectiveness measures relevant for ecosystem as well because framed also for ecosystem health + species richness + specify that measures reflect ecological resilience
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: Initial Barrier Effectiveness: Measures of initial plant establishment included total percent cover, species richness, and biomass of different plant functional groups in the first 1m or first 2 m upslope of barriers Long-Term Barrier Effectiveness: the number of nonoverlapping 50 × 50 cm quadrats upslope of the barrier that had greater than 50% vegetation cover to estimate the total area of newly established vegetation (measuring the long-term effectiveness of barriers in forming large and lasting patches of herbaceous vegetation in previously bare areas)
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: Yes
  • Economic appraisal conducted: Yes
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: