Intensity of Human Activities and their Spatiotemporal Evolution in the Border Regions of Iran

Abstract. The surveillance of human activities along border zones is often complicated by the inherent intricacy of geographical landscapes. As a nation possessing one of the most extensive terrestrial boundaries globally, Iran presents a vital context for this type of investigation. This research introduces a Human Activity Intensity (HAI) index, formulated by integrating land cover data, population density metrics, and nocturnal light imagery acquired from satellites. We computed the HAI at a spatial resolution of 1 km within a 50-kilometer corridor flanking Iran's entire land frontier for four distinct time points: 1992, 2000, 2010, and 2020. Our findings reveal that nearly 90 percent of this border zone is characterized by low levels of human activity. A comparative analysis shows that HAI values are consistently greater on the Iranian side relative to adjacent nations. Furthermore, within Iran's borders, there has been a marked escalation in land-use intensity over the study period. Among the neighboring countries, Iraq exhibits the highest HAI and the most rapid rate of increase. The temporal dynamics of the HAI delineate four distinct patterns: a concurrent decrease observed in both Iran and Turkey; asymmetric growth favoring Iran over Turkmenistan; a persistent, steady rise within Afghanistan; and a coupled increase shared by Iran and Afghanistan. A subsequent hotspot analysis unveiled three distinct modes of spatiotemporal progression: expansion occurring on a single side, bilateral outward growth, and the eventual merging of transboundary clusters. The analysis clearly demonstrates the presence of both "border effects" and "aggregation effects" within these areas. These fluctuations in HAI have implications that extend beyond environmental concerns, significantly impacting geopolitical relations and geo-economics strategies. Consequently, the proposed HAI index proves to be a valuable instrument for policymakers, facilitating informed decisions regarding cross-border environmental protection, regional security measures, and the regulation of commercial exchange.