HONG KONG — Swarms of desert locusts have devastated crops in East Africa, hit the Middle East and moved into South Asia. They’re breeding fast thanks to changes in global climate patterns that have brought about major cyclones and heavy rains, and they are feeding off human food supplies across continents. So far, India has managed to prevent a swarm of biblical proportions from spilling over into Bangladesh, Burma, and then China—where the coronavirus has already paralyzed much of the country’s activity. But it’s not clear how long that line will hold. Eastern Africa has been hit the hardest by the xanthic bugs, with fields in Tanzania, Kenya, Uganda, South Sudan, Ethiopia, Eritrea, and Somalia ravaged by 360 billion locusts. Swarms can be city-sized, and one of the largest—located in Kenya—covers about 37 miles by 25 miles. It is so dense that it turns ...