Change of vegetation cover in the US–Mexico border region: illegal activities or climatic variability?

Abstract

This study explores both human activities and climatic factors to examine the change of vegetation cover in the US Southwest border region—a region that is almost 2000 miles long and with rich natural resources but mostly a sensitive semi-arid/arid ecosystem. It is the first study that integrates large-scale remote-sensing data with multiple layers of socio-economic data and aims to inform critical policy issues related to natural resources management and border security enforcement in the region. A fixed effects panel data regression model is deployed to control for spatial heterogeneities and macro trends in vegetation cover distribution. The results show that both illegal and legal activities have statistically significant impacts on the border region vegetation cover between 2008–2017. Within a 3 mile buffer of the border, a one-standard-deviation increase in illegal border-crossings would lead the vegetation cover index (measured between 0–100) to decline by 4.1% of its standard deviation. A one-standard-deviation increase in border patrol agent staffing would lead the vegetation cover index to decline by 19.0% of its standard deviation. Employment density (a proxy for the dominant local economic activities) in the border county economies and growing season monthly mean temperature are also statistically significant in driving the change of vegetation cover. These findings provide important implications for natural resources management and border security policy in the region, as well as for the quality of life in the local border communities.