During the Vietnam War, the United States dropped more than 8 million tons of bombs and sprayed 74 million liters of Agent Orange and other herbicides in Vietnam, Cambodia, and Laos. Nearly 50 years after the war’s end, the deadly impacts of these campaigns persist: Unexploded ordnance continues to maim and kill, while hot spots of dioxin, a potent toxin in the herbicides, might still be contributing to cancers and birth defects today. Now, using declassified military satellite photos, scientists have identified the likely locations of these hidden dangers, which could help direct remediation and cleanup efforts.
The research, presented this week at the annual conference of the American Geophysical Union (AGU), offers “a powerful tool for decision-makers to assess and mitigate residual risks,” says Đức Nguyễn Văn, deputy manager of the database unit at Vietnam’s Quang Tri Mine Action Center.
Identifying these risky areas in the modern landscape is challenging. Tenacious vegetation growth has long since hidden the scars of war, and historical records of bombing and herbicide spraying are both incomplete and imprecise.
That’s why Philipp Barthelme, a graduate student in geoscience at the University of Edinburgh, and his colleagues turned to declassified satellite photos from the KH-9 HEXAGON and KH-4a/b CORONA missions, which were sharp enough to reveal details as small as 0.6 meters.
Although the satellite data alone cannot identify unexploded bombs, the researchers surmised they are most likely to be found in regions that were heavily bombarded. The craters from the exploded bombs stand out in the satellite images as bright white splotches. The researchers used machine learning, a kind of artificial intelligence, to pinpoint more than 500,000 such craters in Vietnam’s Quang Tri province, which was the most heavily bombed during the war, as well as a region near the borders of Vietnam, Laos, and Cambodia.
In collaboration with the nonprofit Conflict and Environment Observatory, Barthelme also used satellite data to study herbicide spraying in southern Laos. The U.S. sprayed these compounds in secretive wartime campaigns to destroy crops and improve visibility by defoliating the lush jungles. However, the dioxin in the herbicides killed and debilitated hundreds of thousands of people. Since 2007, the U.S. has provided financial support for victims and remediation in Vietnam. But Laotians have largely been overlooked, and uncertainties linger about the extent and impact of spraying in Laos.
The zones of defoliation from the herbicides appear in satellite data as bright, sinuous lines, which Barthelme manually outlined to provide a more accurate and precise account of herbicide spraying in Laos. The results could help guide sampling on the ground necessary to quantify the past impacts and lingering risks from dioxin.
Satellite data can also help track the impact of modern conflicts, says Sergii Skakun, a researcher at the University of Maryland who uses satellite imagery to track how the ongoing war in Ukraine is damaging agricultural lands and crop production. Skakun, who presented a poster at the AGU meeting, identified more than 3.8 million artillery craters in his analysis of some 31,000 square kilometers of Ukraine in 2022 imagery. Civilian drones are banned from the region, Skakun notes, which means commercial and publicly available government satellite imagery is the only way to monitor impacts in real time.
The footprints of war that can be quantified in satellite imagery—such as bomb craters, forest loss, or destroyed buildings—are each a proxy for many other broader impacts of conflict, says Corey Scher, a graduate student using remote sensing to study conflict at the City University of New York. For example, the destruction of buildings can foreshadow human migration or signify potential hazards such as toxic dust, Scher notes.
Using satellite data to examine the footprints of war is still an emerging field—but could boost public understanding of the breadth and extent of conflict, Scher says. “It also could be valuable for saving people’s lives.”
More: https://www.science.org/content/article/declassified-satellite-photos-reveal-impacts-vietnam-war
