A Global-Scale Assessment of Water Resources and Vegetation Cover Dynamics in Relation with the Earth Climate Gradient

Changes in the terrestrial climate and the rapid growth of the world population cause pressures on water resources and natural vegetation covers. Given the importance of these resources for the survival of both human communities and the terrestrial ecosystems, it is critical to envision research-based strategies for their preservation. However, studies that assessed changes in vegetation and freshwater resources have preferentially focused on the marginal role of human, precipitation, and temperature, while neglecting the connection with global climate gradient. Yet, a full understanding of the ongoing changes in the terrestrial vegetation and water resources is needed to develop effective strategies for preserving these resources. In an effort of contributing to the understanding of these changes, this study investigates the actual patterns in the terrestrial land water masses and vegetation covers in relation with the earth climate gradient. Especially, climate aridity indices are estimated and used to highlight climate classes. Trends analyses of monthly leaf area index and land water storage anomalies show different signals depending on the earth latitude bands. Results show 36.5% of the continental lands have experienced a decrease of water resources, but these areas do not necessarily encompass regions with decreasing trends of vegetation cover. Chi-square statistics indicated significant connections between climate classes and vegetation cover trends as well as climate classes and land water storage trends. This study concludes the global climate gradient marginally regulates the dynamics of water resources and vegetation covers. Yet, examples show human-induced changes can supersede this overall connection in certain regions of the globe.