The Economics of Desertification, Land Degradation, and Drought

Figure 2.23—Relationship between fertilizer application and NDVI
Source: Author’s compilation based on simulation results.
Regression Analysis
Table 2.9 reports the results of the regression at both the global level and disaggregated across the major
regions to evaluate the robustness of the results. Oceania and North America are missing from the results
due to the small number of countries in the regions, which leads to low variability of the national level
explanatory variables and consequent problems with the estimation process. Due to the complex and
multidirectional relationship between NDVI and the selected variables, the results are to be interpreted
with extreme caution. Note that the results might not indicate a causal relationship but only an association
of NDVI with the selected biophysical and socioeconomic variables. The effects of changes in population
density are clearly less consistent across geographical areas. Generally, increases in population density
correspond to decreases in NDVI values. This is not true for East Asia and Near East and North Africa.
As expected, increments in precipitation are related to increases in NDVI. This is a result consistent
across all geographical regions. The results for the effects of changes in agricultural intensification appear
to be very robust. With the exception of the Near East and North Africa, agricultural intensification is
associated with higher values of NDVI. The results for government effectiveness are also consistent and
follow our expectations. With the exception of East Asia, greater government effectiveness is associated
with higher NDVI values. The relationship between GDP growth and NDVI is less clear. Contrary to the
environmental Kuznet curve, the GDP–NDVI relationship is U-shaped, suggesting that land degradation
first declines as GDP increases and then increases beyond a threshold. This type of result is observed in
only three regions: the European Union, Latin America, and the Near East and North Africa. In East Asia,
South Asia, and Sub-Saharan Africa, however, the relationship between GDP and NDVI follows the
expected environmental Kuznet curve.
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