LAGOS, Nigeria – Fast-growing countries are generally seeing sharp increases in air pollution as their populations and economies expand. But a new study of air quality in Africa published on Monday found the opposite: one of the liveliest regions of the continent is becoming less polluted.
The study, published in Proceedings of the National Academy of Sciences, found that levels of hazardous nitrogen oxides, a by-product of combustion, declined sharply in northern sub-Saharan Africa as wealth and population in the area increased. .
“The traditional paradigm is that as middle- and low-income countries grow, more emissions are seen, and that a different kind of orbit is very interesting,” said Jonathan Hickman, a researcher at the NASA Goddard Institute for Space Studies. , said. lead author on the study. “It’s nice to see a decline if you were to expect pollution to increase.”
According to researchers, the reason that the increase in pollution by industry and transport in the studied area – from Senegal and Ivory Coast in the west to South Sudan, Uganda and Kenya in the east – was offset by a decrease in the number of fires. was established by farmers.
Although not a major industrial polluter like Asia and North America, Africa has long been the place where biomass burned during the dry season.
Burning vegetation is considered an inexpensive and efficient method of clearing soil in preparation for planting time, and combustion has the advantage of retaining mineral nutrients in the soil. But the consequences for human health and global warming are potentially serious. Land management fires can combine with urban pollution to produce toxic air. And fires send carbon dioxide that warms the earth into the atmosphere.
Brush fires tend to evoke images of outdoor flames in places like Australia or the western United States, but Northern Equatorial Africa, according to researchers, is the region with the largest area of biomass fires in the world, with about 70 percent of the world burned country.
The new study used NASA satellite data and images to measure dangerous gases in the region’s air and determine fire trends between 2005, when the NASA records began, and 2017. At the height of the fire seasons, nitrogen dioxide levels were, or NO2, a harmful gas produced by road traffic and other combustion of fossil fuels and linked to respiratory problems, decreased in the lower atmosphere by 4.5 percent.
The decline was so significant, said dr. Hickman said this has resulted in a net decrease in pollution in the region.
The finding is important because the growing population of Africa, currently 1.2 billion, but which is expected to increase to two billion in 2040, is rapidly urbanizing. Pollution has surpassed AIDS as the leading cause of death on the continent. But governments often prioritize economic growth over the environment, which means that little emphasis is placed on collecting air quality data or implementing clean air policies.
The new study ‘provides an important tool to fill some of these gaps in Africa, where there is a shortage of air pollution studies at various levels’, said Andriannah Mbandi, an environmental researcher in Kenya and affiliated with the Stockholm Environment Institute . “It would be great if the follow-up work from this article would quantify these levels into health and economic measures, which are useful to policymakers.”
Although fires may decrease, pollution is still increasing.
Emissions from the burning of fossil fuels in Africa are expected to rise significantly. Despite an African Union commitment to green energy in 2015, 80 percent of the power generated on the continent comes from coal or other fossil fuels. More and more used cars are being imported, which increases the emission of transport.
This could cause a reversal in the positive trend identified in the study on Monday, especially in populous, wealthier countries such as Nigeria.
“As you increase GDP, you see a decrease in the amount of NO2, but it only follows up to a certain point,” said dr. Hickman said and the analysis describes what the team did while tinkering with the wealth and pollution levels within the model.
“At the highest levels of this GDP measure, the air pollution levels were almost back to the levels when we started,” he said. “What this suggests is that this decline we are seeing is likely to slow down and may change due to the increasing use of fossils.”