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/sq.km. 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/sq.km within 200 km as compared with the global
median density of 4.3 people/sq.km 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.