Prolonged monsoon in Indo-Pak region drove recent locust outbreak: Scientists

Emanating from Pakistan, the swarms of pests, three to four-km-long and one-km-wide, settled at the trees in border villages

The recent locust outbreak along the India-Pakistan border may have been driven by the longer-than-usual monsoon across the region, and frequent cyclones in the Indian Ocean, scientists say.

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In India, the outbreak—the biggest in 26 years—began late last year in Gujarat and Rajasthan, and recently Punjab was also affected.

Locusts, popularly known as ‘tiddi dal’, were earlier spotted in some villages of Fazilka, Muktsar and Bathinda districts. Emanating from Pakistan, the swarms of pests, three to four-km-long and one-km-wide, settled at the trees in these border villages. However, timely action against the attack ensured their elimination, claimed Punjab officials.

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 the country’s Punjab province.

“The current locust outbreak is the biggest in 25 years in Ethiopia and Somalia, 26 years in India, 70 years in Kenya,” Keith Cressman, locust forecasting officer at the UN Food and Agriculture Organisation (FAO) told PTI.

“The outbreak started after heavy amounts of rains over east Africa and the Arabian Peninsula,” Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology (IITM) in Pune added.

According to the FAO, locusts are the oldest migratory pests in the world.

These insects 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 the FAO.

The locusts, which are considered to be among 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 kilometre of swarm can contain up to 80 million adults, they said.

Koll noted 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.

Koll 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.

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,” Cressman said.