Ecological restoration by afforestation may increase groundwater depth and create potentially large ecological and water opportunity costs in arid and semiarid China

Lu, C. X. Z. et al., 2018. Journal of Cleaner Production

Original research (primary data)
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Water scarcity is a global environmental problem that jeopardizes human safety and socioeconomic development. Since 1952, China has implemented a large-scale tree-planting program in the country’s arid regions to combat desertification. However, there is a serious risk this program will exacerbate water shortages and lower the groundwater table: the trees selected for this program were not chosen based on local environmental constraints, and their evapotranspiration exceeds the regional precipitation. However, no data on the afforestation’s effects on the groundwater table is available. This is problematic because any loss of groundwater will severely constrain socioeconomic development in China’s arid and semiarid regions, which already face severe water shortages. The economic concept of a groundwater opportunity cost could be used to guide socioeconomic activities to improve the sustainability of groundwater use and mitigate the potential problems caused by the Chinese afforestation program. In this paper, seven evapotranspiration models were used to provide the first estimate of the opportunity cost created by afforestation’s adverse effects on the groundwater resource. The results showed that the groundwater table declined yearly throughout the study area, with mean water opportunity costs in 2011 ranging from 0.04 x 10(9) RMB to 11.1 x 10(9) RMB under nine provinces in arid and semiarid China. This study provides the first solid evidence that afforestation in arid and semiarid northern China will exacerbate the groundwater decline while creating enormous opportunity costs. Thus, the afforestation program must be urgently reassessed and the water-use efficiency of vegetation must be considered when planning future ecological restoration both to make the restoration more cost-effective and to protect the ecosphere.

Case studies

Basic information

  • Case ID: INT-227-1
  • Intervention type: Created habitats
  • Intervention description:

    Since 1952, China has implemented a large-scale tree-planting program in the country's arid regions to combat desertification. China has invested huge sums of money to implement the largest tree-planting program in history, with one-third of the world's total area of plantation forest now growing in China Most of these programs have been implemented in the arid and semiarid regions of northern China to combat desertification and to control the dust storms that threaten densely populated areas to the south and east Under these programs, 28 106 ha of forests were planted from 2000 to 2005 alone (Chazdon, 2008). China's afforestation managers aim to increase the nation's forest cover to 26% of the total land area by 2050 (Wang et al., 2007).

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Reduced water availability  Negative They looked at maximum and actual potential groundwater cumulative change caused by afforestation; see methods. The predicted impact on the water table is inferred (for each province) from models suited for the Chinese context which rely on evapotranspiration measures, precipitation, and soil porosity. As per our definitions, landscape scale modeling exercises are not coded as scenario modeling because they do not predict impact in the future. The input variables are empirical and measured. Economic outcomes Opportunity costs – water loss Compares consumption of water by afforested lands with natural vegetation that the forests replaced To estimate the water opportunity cost of ecological restoration by afforestation, the analysis assumed that the forests would have been replaced by this potential natural vegetation, and that the water saved by this replacement could potentially be used for other purposes. Because the seven ET models have their respective advantages and disadvantages, and have not been individually parameterized for each of the nine study areas, the average of the seven model outputs was used to compare the forest plantations with the natural vegetation.
  • Approach implemented in the field: Yes
  • Specific location:

    the present study focused on nine provinces and provincial-level regions (Beijing, Hebei, Henan, Shanxi, Shaanxi, Ningxia, Inner Mongolia, Gansu, Xinjiang)

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


  • Notes on intervention effectivness: comparing water use by trees after afforestation with water use based on the conservation of natural vegetation. This isn’t a comparison though, because their model exercise compares the change that occurs from the natural vegetation to an afforested state models provided estimates of the annual water consumption caused by afforestation at a provincial level; using the same models to estimate water consumption by the region's natural vegetation provided a basis for comparison (i.e., a benchmark). Note methodology - Because no data was available on the changes in groundwater caused by afforestation, and obtaining this data for large areas of China would be prohibitively expensive and time-consuming, the effect was evaluated using seven previously published evapotranspiration models that have been tested in China and confirmed to be valid under Chinese conditions. Note the assumption - the assumptions that there were no groundwater exchanges with adjacent areas outside of the afforestation plots and that precipitation was the only water source for vegetation but this is not a serious concern because while “groundwater from surrounding plots with a higher elevation or a shallower water table will flow into these areas to compensate… water table in adjacent plots would decline by an amount roughly proportional to the inflow of water into the afforestation plots” For the opportunity cost measure they do not consider fluctuations in prices as the groundwater is depleted.
  • 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: 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: 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: