NAIROBI • Billions of locusts swarming through East Africa are the result of extreme weather swings and could prove catastrophic for a region still reeling from drought and deadly floods, experts said.

Dense clouds of the ravenous insects have spread from Ethiopia and Somalia into Kenya, in the region's worse infestation in decades.

The United Nations' Food and Agriculture Organisation (FAO) estimated the size of one swarm in Kenya at 2,400 sq km, meaning it could contain up to 200 billion locusts, each of which is able to consume its own weight in food every day.

The locust invasion is the biggest in Ethiopia and Somalia in 25 years, and the biggest in Kenya in 70 years, according to the FAO.

If unchecked, locust numbers could grow 500 times by June, spreading to Uganda and South Sudan, and devastating crops and pasture in a region which is already one of the poorest and most vulnerable in the world.

This could lead to "a major food security problem", Dr Guleid Artan of regional expert group, the Climate Prediction and Applications Centre, told a press conference in Nairobi.

The locusts, he said, were the latest symptom of extreme weather conditions that saw last year start with a drought and end in one of the wettest rainy seasons in four decades in some parts - with floods killing hundreds across East Africa.

Dr Artan said the invasion had come after a year of extremes which included eight cyclones off East Africa, the most in a single year since 1976.

This was due to a warmer western Indian Ocean, a climate condition known as the Indian Ocean Dipole which has conversely led to severe drought in Australia that is experiencing its own extremes: bush fires, hail and dust storms.

"We know East Africa is one of the most vulnerable to climate change. We know this region will see more extremes," he warned.

Dr Artan said the pastoralists were just emerging from three years of drought, and that recovery from a dry spell usually takes them up to five years.

And if the locusts are not brought under control by the start of the next planting and rainy season - typically around March - farmers could see their crops decimated.

AGENCE FRANCE-PRESSE