Monitoring the modes and phases of global human activity development over 30 years: Evidence from county-level nighttime light

Abstract

The extent of human activity has expanded, and the intensity of human activity has increased, supported by a progressive economy and powerful technology. Compared with daytime remote sensing images or statistical data, nighttime light (NTL) remote sensing has the advantages of long time series, global coverage, objectivity, and quantifiability in observing the development of global human activities. Existing studies have focused more on the levels of human activity development at multiple points in time and less on overall patterns of human activity development during a period. We developed a non-parametric time-series curve morphology classification methodology combining trend analysis and change-point detection. We identified modes and phases of human activity development based on NTL datasets and analyzed the spatial and temporal patterns, modes, and phases of county-level human activity development globally over the past 30 years (1992–2021). We found that the level of human activity development is generally on the rise globally, with areas of significant growth mainly along the coast of China and in global ports. In more than half of the counties, the extent of human activity development is saturated. A significant increase mode was observed in most counties (71.5 %), while a few counties (1.1 %) saw a decrease mode. 10.1 % of global counties are in an anomalous phase, with low levels of human activity and slower or even stopped development. The new method has been validated in cases of different development modes and has the potential to generalize to the pixel level. Monitoring human activity development facilitates understanding development modes globally over a long time series, which can guide future policy formulation and socioeconomic progress. We recommend a greater focus on inequalities within and between countries.