Vegetation changes in recent large-scale ecological restoration projects and subsequent impact on water resources in China’s Loess Plateau

Li, S. L. et al., 2016. Science of the Total Environment

Original research (primary data)
View External Publication Link

Abstract

Recently, relationship between vegetation activity and temperature variability has received much attention in China. However, vegetation-induced changes in water resources through changing land surface energy balance (e.g. albedo), has not been well documented. This study investigates the underlying causes of vegetation change and subsequent impacts on runoff for the Northern Shaanxi Loess Plateau. Results show that satellite-derived vegetation index has experienced a significantly increasing trend during the past three decades, especially during 2000-2012. Large-scale ecological restorations, i.e., the Natural Forest Conservation project and the Grain for Green project, are found to be the primary driving factors for vegetation increase. The increased vegetation coverage induces decrease in surface albedo and results in an increase in temperature. This positive effect can be counteracted by higher evapotranspiration and the net effect is a decrease in daytime land surface temperature. A higher evapotranspiration rate from restored vegetation is the primary reason for the reduced runoff coefficient. Other factors including less heavy precipitation, increased water consumption from town, industry and agriculture also appear to be the important causes for the reduction of runoff. These two ecological restoration projects produce both positive and negative effects on the overall ecosystem services. Thus, long-term continuous monitoring is needed.

Case studies

Basic information

  • Case ID: INT-213-2
  • Intervention type: Created habitats
  • Intervention description:

    Three Norths Shelter Forest System Project (~1978 to 2000); Natural Forest Conservation project and the Grain for Green project (after 2000); look at ecological restoration data of each county including returning cropland to forest/grassland, afforestation of barren land

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Biomass cover loss  No effect change in NDVI mapped over the intervention area
  • Approach implemented in the field: Yes
  • Specific location:

    The Northern Shaanxi Loess Plateau (35°21′-39°34′ N, 107°28′- 111°15′E), is located in the middle of the Loess Plateau with an area of 83,990 km2

  • Country: China
  • Habitat/Biome type: Created forest | Created grassland |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: determine effectiveness by monitoring change in outcome measures over time over the area where the interventions took place in show there was no significant increase during that time and "these costly efforts have yield little success in improving vegetation coverage (Fig. 1a). This can be interpreted as vegetation restoration is largely controlled by soil water availability in arid and semi-arid regions (Porporato et al., 2002; Chen et al., 2010), and artificial trees can consume more water than nat- ural native species (Wang et al., 2008)."
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS
  • 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: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures:
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • 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: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic:

Basic information

  • Case ID: INT-213-1
  • Intervention type: Mixed created/non-created habitats
  • Intervention description:

    Three Norths Shelter Forest System Project (~1978 to 2000); Natural Forest Conservation project and the Grain for Green project (after 2000); look at ecological restoration data of each county including returning cropland to forest/grassland, afforestation of barren land, and mountain closure (e.g. prohibition of fuelwood collection and grazing) Mixed created/non-created because mountain enclosure later referred to has switching focus to natural rehabilitation therefore coded as restoration but other interventions are created

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water availability  Negative Runoff coefficient (Rc) for individual catchment was derived by runoff dividing corresponding precipita- tion.
    Biomass cover loss  Positive change in NDVI mapped over the intervention area
  • Approach implemented in the field: Yes
  • Specific location:

    The Northern Shaanxi Loess Plateau (35°21′-39°34′ N, 107°28′- 111°15′E), is located in the middle of the Loess Plateau with an area of 83,990 km2

  • Country: China
  • Habitat/Biome type: Created forest | Created grassland | Montane/Alpine |
  • Issue specific term: Not applicable

Evidence

  • Notes on intervention effectivness: determine effectiveness for biomass cover loss by monitoring change in outcome measures over time over the area where the interventions took place in "Therefore, the recent ecological restoration projects such as the NFC project and GFG project put more emphasis on natural rehabil- itation (Fig. 2). In addition, the warming climate extends the length of the growing season and may intensify maximum rates of productivity (Shen et al., 2015). As a result, the satellite-derived vegetation index (NDVI) observed a significantly increasing trend in the most recent de- cade (Fig. 1a). However, precipitation and temperature, which are key climatic factors determining vegetation growth, changed slightly during the same period (Fig. 1c and d). Therefore, we speculate that recent large-scale ecological restoration, especially the NFC project and GFG project, is the primary driving factor for vegetation coverage increase." effectiveness for water availability determined by assessing change over time + performing correlation analyses to test the relationship between water runoff and NDVI, Daytime surface temperature, evapotranspiration (all associated with intervention-induced vegetation growth). Although other factors such as precipitation changes contributed to changes in the outcome measure, conclude veg restoration had contribution to its decline because of significant negative correlations between the above variables "A higher evapotranspiration rate from restored vegetation is the primary reason for the reduced runoff coeffi- cient. Other factors including less heavy precipitation, increased water consumption from town, industry and ag- riculture also appear to be the important causes for the reduction of runoff. ... NDVI in all catchments presented an obvious increasing trend while Rc presented an opposite trend of 2000–2012 (Fig. 3). The positive correlation between NDVI and ET (Fig. 5) can be the possible reason for runoff reduction. "
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Another NbS
  • 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: No
  • Impacts for the ecosystem: Not reported
  • Ecosystem measures:
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • 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: Quantitative
  • Is it experimental: No
  • Experimental evalution done: Not applicable
  • Non-experimental evalution done: Empirical case study
  • Study is systematic: