Active volcanoes have long been recognized for both their hazards and their benefits. The extent to which a volcano is considered hazardous (or beneficial) depends largely on its proximity to human population. Realistic estimates of the number of people at risk worldwide is necessary to systematically evaluate regional volcanic hazard and categorize individual volcanoes for potential human impact in the event of an eruption. This study quantifies the spatial relationship between global distributions of human population (in 1990) and recent volcanism. We estimate that 8.8% (455 million people) of the world's population lived within 100 km of an historically active volcano and 12% within 100 km of a volcano believed to have been active during the last 10,000 years (the Holocene Epoch). Of the 1410 Holocene volcanoes considered, we estimate that 457 volcanoes (222 historically active) had more than 1 million people living within a 100 km radius while 311 were relatively uninhabited with average population densities less than 1 person/ We also find that average population density generally decreases with distance from these volcanoes (within 200 km). The land around the 703 volcanoes with recorded historic eruptions had a median population density of 23 people/ within 200 km as compared with the global median density of 4.3 people/ for all occupied land area.
Population density near volcanoes is not evenly distributed worldwide. The results of this study suggest that preferential population of volcanic regions may be influenced, in part, by climate. Volcanoes at high latitudes are generally uninhabited but at lower latitudes volcanic regions are often densely populated. In tropical areas, the elevation and fertile soils associated with volcanic regions can provide incentive for agrarian populations to settle close to potentially active volcanoes. In the tropical climates of AustralAsia, Africa and Central America, higher population densities occur in closer proximity to volcanoes. In more temperate climates, such as those of Japan and Chile, population density tends to increase with distance from volcanoes - in part ,because the climatic "advantage" of volcanic elevation is presumably less important in these regions.