Artificial lighting reveals human presence
This map dramatically illustrates the growing extent of human activity on planet Earth through the detection of lights at night.
Covering a 15-year period of night-time satellite observations, it illustrates the phenomenal growth and intensification of human impact, revealing a mosaic of human settlements (e.g. urban clusters), industrial activity, wildfires and human-induced fires lit to clear land.
In the early 1980s the first low-light nighttime images of the Earth’s surface were released from the United States Defense Meteorological Satellite Program (DMSP).
These data were originally designed to monitor cloud cover at night for weather forecasting.
By the mid-1990s, they were being used to help map human population distribution, estimate built area and impervious surfaces, identify maritime commercial activity (including offshore oil and gas exploration and fishing), map fires and estimate the impacts of human expansion on agricultural land.
Humans have transformed over half of the Earth’s ice-free terrestrial land surface into cropland and pasture. Agriculture has evolved to sustain ever-larger populations which, in turn, has led to the more intense use of lands for urban growth, industrialisation and energy extraction. Now, we see a world transformed by these processes. We can observe the phenomenal growth of urban regions by changes in patterns of city lights.
On this map, older more established urban centres are shown in white while the urban growth since 1992 is shown in cyan, yellow and magenta (see map legend). The Indian subcontinent and Asia in particular have seen huge urban and industrial growth between 1992 and 2006. Fires, both natural and agricultural in origin, can be seen over vast areas of Africa, South-East Asia, South America and northern Australia. While they span huge areas collectively, individual fires are not as massive as the image suggests because they occurred over the 15-year period of record. Also seen on this image are oil flares where extraction activities are being carried out. Along the coast of South Korea and the Sea of Japan, lights of fishing fleets can be seen plying the waters using their lights to attract squid and other fish.
Night-lights alone under-represent the impact of human activities. Persistent cloud cover obscures urban centres in the Congo and the Amazon, which is why they remain dark in the map. More importantly, many inhabited areas, often in arid areas, have a very thin scattering of lights that suggest low levels of infrastructure.
When combined with maps of population density, the density and brightness of night-light networks can be used to infer the relative level of development and human well-being.