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The Economics of Desertification, Land Degradation, and Drought

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Results<br />

Correlation Analysis<br />

Consistent with past studies (for example, Grepperud 1996), Table 2.8 shows a negative correlation<br />

between change in population density <strong>and</strong> NDVI in all regions except Sub-Saharan Africa (SSA), the<br />

European Union (EU), <strong>and</strong> Near East <strong>and</strong> North Africa (NENA). This is contrary to Bai et al. (2008), who<br />

observed a positive correlation between NDVI <strong>and</strong> population density on a global scale. Consistent with<br />

Bai et al. (2008b), however, population density was positively correlated with NDVI in the SSA, EU, <strong>and</strong><br />

NENA regions. In SSA, population density is highest in the most fertile areas, such as mountain slopes<br />

(Voortman, Sonneveld, <strong>and</strong> Keyzer 2000). This leads to the positive correlation between NDVI <strong>and</strong><br />

population density even in areas south <strong>of</strong> the equator, which have seen severe l<strong>and</strong> degradation (Bai et al.<br />

2008b). Figure 2.20 also shows that there was a positive correlation between population density <strong>and</strong><br />

NDVI in central Africa, India, North America, <strong>and</strong> Europe. We also see an increase in NDVI<br />

accompanied with negative population density in Russia (Figure 2.20). Our results show that in all<br />

regions, GDP changes are positively correlated with NDVI changes (Table 2.8). Figure 2.21 also shows<br />

an increase <strong>of</strong> both GDP <strong>and</strong> NDVI in North America, Russia, India, central Africa (north <strong>of</strong> the equator),<br />

<strong>and</strong> China. This suggests the role ecosystems could play in economic growth.<br />

Table 2.8—Correlation <strong>of</strong> NDVI with selected biophysical <strong>and</strong> socio-economic factors<br />

Variable<br />

East<br />

Asia<br />

European<br />

Union<br />

Latin<br />

American<br />

Countries<br />

Near East<br />

<strong>and</strong> North<br />

Africa<br />

50<br />

North<br />

America Oceania<br />

South<br />

Asia<br />

Sub<br />

Saharan<br />

Africa<br />

Δ Population<br />

density -0.03* 0.002 -0.01* 0.04* -0.01* -0.01* -0.02* 0.01*<br />

Δ Precipitation -0.02* -0.04* 0.17* 0.23* -0.01* 0.09* 0.24* 0.13*<br />

Δ Agricultural<br />

intensification 0.06* -0.01* 0.20* 0.01* -0.14* -0.10* 0.14* -0.01*<br />

Δ GDP 0.06* 0.17* 0.03* 0.28* 0.14* 0.10* 0.21* 0.09*<br />

Δ Government<br />

effectiveness 0.09* -0.04* 0.24* 0.23* -0.14* 0.10* 0.08* 0.10*<br />

Source: Author’s calculations.<br />

Notes: Statistical significance codes: *significant at the 5% level. Δ = Change from end line to baseline period.<br />

Figure 2.20—Relationship between change in NDVI <strong>and</strong> population density<br />

Source: Author’s compilation based on simulation results.

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