Night-time satellite images used to identify areas of poverty
Image credit: Dreamstime
Night-time satellite images can be used to determine economic wellbeing at locations across the globe, researchers from the International Institute for Applied Systems Analysis (IIASA) have said.
Despite successes in reducing poverty globally in the last two decades, almost one billion people are still living without access to reliable and affordable electricity, which in turn negatively affects health and welfare, and impedes sustainable development.
Researchers have been using satellite images of Earth at night to study human activity for almost 30 years and it is well established that these images – commonly referred to as night-time radiance – can help map issues like economic growth, poverty, and inequality, especially in places where data are lacking.
In developing countries, areas that are unlit at night generally indicate limited development, while brightly lit areas indicate more developed areas like capital cities where infrastructure is abundant.
An obvious example can be seen in satellite imagery of both North and South Korea where the South is brightly lit up along the whole stretch of the country while the North has only small amounts of light emanating from its largest cities.
Traditionally, researchers have been more interested in using the data gathered from the lit areas with unlit areas typically being disregarded.
But the latest study focused on the data from the unlit areas to estimate global economic wellbeing.
“Whereas previous work has focused more on the relationship between lit areas and economic development, we found that it actually also works the other way around and that unlit areas are a good indicator of poverty. By identifying those unlit areas we can target interventions for poverty alleviation and places to focus on to improve energy access,” explained study author Steffen Fritz.
The researchers used a harmonised geo-spatial wealth index for households in various countries across Africa, Asia, and the Americas calculated by the Demographic and Health Surveys program, which places individual households on a continuous scale of relative wealth from poorer to richer.
They then combined this data with data from satellite images of global night-time lights in these countries and found that 19 per cent of the planet’s total settlement footprint had no detectable artificial radiance associated with it.
The majority of unlit settlement footprints were found in Africa (39 per cent) and Asia (23 per cent). If only rural unlit infrastructure is considered, these numbers rise to 65 per cent for Africa and 40 per cent for Asia. In almost all countries, the results indicate a clear association between increasing percentages of unlit communities in a country and decreasing economic wellbeing levels.
“We were able to map and predict the wealth class of around 2.4 million households for 49 countries spread across Africa, Asia, and the Americas based on the percentage of unlit settlements detected using night-time light satellite images with an overall accuracy of 87 per cent. Surprisingly, there were also relatively large amounts of unlit settlements in developed countries, in particular Europe. There can be several reasons for this result, including the fact that the satellite overpass is after midnight, but it could also be due to conscientious energy- and cost-saving policies in Europe by homeowners, governments, and industry,” said research group leader Ian McCallum, who led the study.
The United Nations Sustainable Development Goals specifically include ‘access to affordable, reliable, sustainable and modern energy for all’ and while efforts are underway to achieve this goal, and substantial progress has been made over the past two decades, indications are that governments and industry will struggle to keep pace with expected population growth.
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