In East Africa, the Middle East and South Asia, traveling locust swarms the size of Manhattan are putting potentially hundreds of millions at risk of starvation in what the UN has called the worst outbreak in a quarter of a century.

What it means: "Millions will starve because clouds of approximately 80 million desert locusts per square kilometer are voracious," writes Robert Rotberg, founding director of the Harvard Kennedy School’s Program on Intrastate Conflict.

"In one day they consume wheat, barley, sorghum, or maize crops that feed 35,000 people. Masses the size of cities can consume 1.8 million metric tons of vegetation every day – enough to feed 81 million people."

"The United Nations is to test drones equipped with mapping sensors and atomizers to spray pesticides in parts of east Africa battling an invasion of desert locusts that are ravaging crops and exacerbating a hunger crisis."

What's happening: The outbreak had been mostly confined to Kenya, Ethiopia and Somalia initially, but the UN Food and Agriculture Organization (FAO) says it’s now tracking 15 countries in Africa, the Middle East and South Asia affected by the locusts, Scientific American reports.

"The swarms have appeared in a swath hundreds of miles wide, from South Sudan in the west to parts of Pakistan in the east."

What's next: Authorities in East Africa are already undertaking a coordinated campaign of aerial pesticide spraying, "but experts say the scale of the infestation is beyond local capacity as desert locusts can travel up to 150 km (95 miles) in a day," the World Economic Forum notes.