## Linear regression coefficients

Coefficient No POP term Linear Parabolic
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R^2 0.513 0.542 0.561
LOG(ELEVATION) 0.316 0.261 0.239
(ANNUAL TEMP)^2 0.365 0.276 0.210
LOG(ANNUAL PRECIP) 0.235 0.193 0.168
LOG(POP) 0.193 0.712
LOG(POP)^2 -0.523

A few of the standardized (beta) coefficients for three linear regression models. The second column shows that elevation, temperature, and precipitation are all positive determinants of vegetation that together account for over 50 percent of the variance of the dependent variable. When the population is added to the model, each of the other coefficients declines, suggesting a significant influence of human development on regional vegetation. When a parabolic population term is added to the model, the other coefficients decline further and the beta coefficients for population become large, suggesting a strong nonlinear effect of human development on vegetation in this region.