Effects of Community-Based Watershed Development on Landscape Greenness and Vegetation Cover in the Northwestern Highlands of Ethiopia

Siraw, Z. B., Degefu, M. A., 2019. Earth Systems and Environment

Original research (primary data)
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Abstract

This study assesses the effects of community-based watershed development (CBWD) on landscape greenness and vegetation cover in the northwestern highlands of Ethiopia. It also evaluates implications of results on ecological conditions and rural livelihoods. Paired-sites comparison approach was used, and compared landscape greenness and vegetation cover at conserved (Tija Baji) and non-conserved (Tata) watersheds for the period 2000�2015. Landsat images for 2000 and 2015 were the datasets used, and analyzed using geographic information systems (GIS). Normalized difference vegetation index (NDVI) was employed to detect landscape greenness. The results showed that landscape greenness represented by high NDVI value (> 0.02) increased in the conserved watershed and decreased in the non-conserved watershed during the study period. The observed change in landscape greenness in both watersheds was due to the change in shrub land and grassland covers. Shrub land and grassland covers increased by 20.6�ha and 22.5�ha in the conserved watershed and decreased by 50�ha and 49.3�ha in the control watershed, respectively. The decreasing change in landscape greenness in the control watershed was due to the conversion of shrub land and grassland into cropland and bare land covers. Cropland and bare land covers in the control watershed increased by 41.9�ha and 26.7�ha, respectively. In contrast, these land covers declined by 30.4�ha and 23.3�ha in the conserved watershed, respectively. The observed changes in landscape greenness, cropland and bare land covers in the conserved watershed have important implications for the improvement of soil fertility, biodiversity, soil erosion and flood control, ground water recharge, carbon sequestration and on rural livelihood systems.

Case studies

Basic information

  • Case ID: INT-264-1
  • Intervention type: Combination
  • Intervention description:

    "community-based watershed development: The Tija Baji micro-watershed has been under intensive CBWD work over the last 15 years (2000–2015), and di erent types of physical (terraces, cuto drain, waterways, check dams and trenches) and biological soil and water conservation measures (afforestation, re-for- estation, nursery established and area closure), water har- vesting structures, soil fertility and livelihood improvement activities have been implemented. The observed change in landscape greenness in both watersheds was due to the change in shrub land and grassland covers. Shrub land and grassland covers increased by 20.6 ha and 22.5 ha in the conserved watershed … The increasing change in shrub land cover in the con- served watershed was due to primarily the plantation of trees like Sesbania sesban, Acacia saligna and Acacia decurrens Protection of degraded areas (locally called Wunchilie) for self-regeneration (area enclosure) was also another factor for the enhancement of shrub land cover in the conserved watershed. The increased grassland cover in the conserved watershed is due to the e ect of CBWD. Due to the zero grazing practice as part of the CBWD practice, degraded and low productive croplands were converted into grassland as a source of feed for livestock. The implemen- tation of di erent management practices (e.g., area enclo- sure and plantation of grass and other plant species) has converted some bare land into grassland in the conserved watershed. "

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Loss of food production  Positive **Check if should code for agri prod as climate impact b/c by reducing erosion, increased productivity AC - yes, because the authors interpret that way as follows - "Reduction in soil erosion and addition of organic matter due to conservation measures also increased farmland productivity. Key informants also stated that the enhanced vegetation cover in the watershed has improved pasture and fodder for livestock. This in turn has increased the number and productivity of livestock and income generated from the livestock sector. "
    Soil erosion  Positive Not quantified outcome measure. Based on qualitative assessment of perceptions of effectiveness Soil erosion [Positive] “The local people in the conserved watershed reported that surface runo and the rate of soil erosion have declined in the recent years as compared to the pre-intervention period. They also con rmed that the conditions of rill and gully developments were reduced due to the planta- tion of trees and grass species over degraded areas and along gullies.”
  • Approach implemented in the field: Yes
  • Specific location:

    The study was conducted in two micro-watersheds, namely Tija Baji (conserved site) and Tata (non-conserved or control site), in the northwestern part of Ethiopia (Fig. 1), which cover 670.7 ha and 1079.5 ha, respectively. Geographically, Tija Baji watershed extends from 10°51′22′′ to 10°54′40′′N and 38°17′20′′ to 38°19′55′′E, while Tata extends from 10°50′55′′N to 10°55′30′′N and 38°17′00′′ to 38°19′02′′E. Tija Baji is a micro-watershed where CWDP has been implemented since 2000, whereas Tata is an adjacent micro- watershed without conservation and considered as a control watershed in this study

  • Country: Ethiopia
  • Habitat/Biome type: Created forest | Created grassland | Montane/Alpine |
  • Issue specific term: Community-based (general)

Evidence

  • Notes on intervention effectivness: "Focus group discussion and key informant interview were conducted to understand the environmental and livelihood implications of LULC changes and landscape greenness in the conserved watershed. " Erosion on the other hand linked to water causes. Did not code for experimental because biomass recovery investigated compared to control but relevant outcome measures reported through before-after method
  • 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?: Yes
  • Impacts on GHG: Positive
  • Assess outcomes of the intervention on natural ecosystems: Please select
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: Informants in the conserved watershed indicated that plant diversity in some conserved sites (area enclosure) increased due to regeneration of tree species from soil seed bank. Cal- purnia aurea, Buddleja polystachya and Brucea antidysen- terica were some of re-grown tree species in the conserved watershed. In addition to these, other tree species like Olea europaea subsp cuspidata, Rhamnus prinoides, Juniperus procera hochst, Grevillea, Cordia africana and Acacia sali- gena were planted to protect conservation structures, along hillsides and at homesteads. The local community and devel- opment agents also explained that di erent types of wild animals (e.g., hyena, fox, baboon and monkey) came back to protected areas and the population of these wild animals was increasing rapidly. However, local elders stated that, although the biodiversity has increased, it is still substan- tially lower as compared to the original natural forest of the area.
  • Assess outcomes of the intervention on people: Yes
  • Impacts for people: Positive
  • People measures: "Local economies conservation measures such as area enclosure has created an opportunity for bee keeping and income generated from this activity. Tree plantation in the conserved watershed has also cre- ated many opportunities for local farmers. Farmers generated additional income from selling of wood that they planted at their homestead and private lands. The CBWD practice has also signi cantly reduced seasonal migration of labor to urban centers in search of additional income as a coping mechanism. At present, income sources increased/diversified and the annual income of households improved as a result of conser- vation efforts. Basic needs Availability of wood that are used for construction purposes, e.g., bridges, fence water points and house construction increased. Furthermore, focus group discussion participants confirmed that the increased vegetation cover has reduced women’s work burden as they get firewood at the nearby location. "
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

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