The recent locust outbreak along the India-Pakistan border may have been driven by the longer-than-usual monsoon rains across the region, and frequent cyclones in the Indian Ocean, scientists say.
In India, the outbreak—the biggest in 26 years—began late last year in Gujarat and Rajasthan, and recently Punjab was also affected.
In Pakistan, the government declared national emergency last week to eliminate the attacking swarms of desert locusts, which were destroying crops on a large scale in Punjab province.
'The current locust outbreak is the biggest in 25 years in Ethiopia and Somalia, 26 years in India, 70 years in Kenya,' Mr. Keith Cressman, locust forecasting officer at the UN Food and Agriculture Organisation (FAO), said..
'The outbreak started after heavy amounts of rains over east Africa and the Arabian Peninsula,' Dr. Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology (IITM) in Pune added.
According to the FAO, locusts are the world's oldest migratory pests.
These differ from ordinary grasshoppers in their ability to change behaviour, and form swarms that can migrate over large distances. The most devastating of all locust species is the Desert Locust (Schistocerca gregaria), according to FAO.
The locusts, considered the most dangerous pests known to humanity, reproduce fast—20-fold within three months, the FAO experts noted.
An adult locust can eat quantity equal to its weight daily, and just a single square kilometer of swarm can contain up to 80 million adults, they said.
Dr. Koll noted the heavy rains which drove the locust outbreak occurred due to intense storm activity sourced from the Arabian Sea during the last two seasons.
'Heavy rain triggers growth of vegetation in arid areas where desert locusts can then grow and breed,' he said.
He explained that recently climate change accentuated the phenomenon called the 'Indian Ocean Dipole', with warmer than usual waters to its west, and cooler waters to its east.
'On top of that, the rising temperatures due to global warming made the Western Indian Ocean particularly warm,' he said.
Mr. Cressman added that the current locust invasion in India by an unprecedented number of swarms originated in southern Iran from their breeding in spring last year.
'Summer breeding along both sides of the Indo-Pakistan border was much higher than normal due to the swarm invasion and the monsoon rains lasting one month longer than normal, allowing up to three generations of breeding,' he said.