A possible plague? Locust infestations in the southern hemisphere

Locust infestations are currently affecting countries across eastern Africa, the Arabian Peninsula, the Middle East and South Asia. The infestations are destroying large volumes of crops in the affected areas, increasing food insecurity in regions where food supplies are already precarious.

The current cycle of infestations has been linked to the effects of climate change. The primary cause of the current infestations is the extreme weather conditions seen in the regions in 2018 and 2019. The regions affected by the infestations are often also combatting the effects of other weather-related issues, such as: drought; flooding and resultant landslides; successive cyclones making landfall; and declining water availability.   

Certain species of desert locusts pose a threat to food sources across the world. Of over 7,000 species of grasshopper, a minority possess the ability to become gregarious. This means that they gather in large groups to form swarms, changing their colour and shape when they do so. Swarms of locusts can travel up to 150km a day, and a swarm covering 1 square km can eat the same amount of wheat, corn and sorghum as that needed to feed 35,000 people.

Swarms of locusts are referred to as ‘infestations’ when they affect food supplies and ‘a plague’ when multiple regions are affected by locust swarms in increasingly large numbers over a period of several years. It is possible that the current infestations may be labelled a plague event in the coming months.

East Africa

Locust infestations are not uncommon in Africa. The last cycle of severe locust infestations occurred in 2003 to 2004, affecting 23 African nations. However, more damaging locust swarms have been linked to a hotter climate. Richard Munang, the United Nations Environment Programme (UNEP) expert on climate and Africa, noted that Africa is disproportionately affected, as global temperature changes have led to an increase in the conditions required for locusts to swarm and cause damage to crops.

The Food and Agriculture Organization of the United Nations (FAO) recently issued a report on the ongoing infestation of desert locusts across the Greater Horn of Africa, calling for action to combat “the worst infestation in decades”. Eight countries in the region are currently affected by infestations of locusts. There are 20.2 million people facing “severe acute food insecurity” in Ethiopia, Kenya, Somalia, South Sudan, Uganda and the United Republic of Tanzania. The ongoing threat posed by the locust swarms to food supplies has become cause for international concern, with affected countries calling for aid from the international community.

Iran and Yemen

The latest update from the FAO’s Locust Watch programme noted that the situation in Iran and Yemen was becoming “increasingly worrisome”. Swarms of locusts have laid eggs along a 900km stretch of the Iranian coast in the south western region of the country which borders Pakistan, threatening further swarms in both countries.

In Yemen, the civil war has stalled the response to locust swarms. Desert locusts are often present year-round in Yemen, but the locust control centres devoted to tracking and responding to locust swarms before they damage crops cannot coordinate a response due to the ongoing war. The locusts breeding in now-inaccessible parts of Yemen have moved to the Horn of Africa, to the Saudi Arabian desert and Iran. It is expected that the lack of a coordinated response in Yemen means that the infestations elsewhere will last longer.

Pakistan

The Pakistani government declared a national emergency on 1 February 2020 after crops in the Punjab region were affected by locust swarms. The other three provinces of Pakistan have also seen locust infestations since. Two weeks after the declaration, the FAO dedicated $500,000 to a support programme allowing national experts to benefit from FAO technical expertise.

In late February, the Chinese government announced that it was sending a team of experts to Pakistan to develop a response to the infestations. A possible response discussed by Chinese experts was the deployment of 100,000 ducks, as they can eat up to 200 locusts a day and be more effective than pesticides.

Tackling locust infestations to prevent plagues

The response to the locust infestations involves forecasting the movement of locusts using data. The latest models used are possible in part due to technology funded by UK aid via its Weather and Climate Information Services for Africa programme.

Once the movement of the swarms is modelled, the areas likely to be affected can be sprayed with pesticides. This is done via crop dusting planes, vehicles on the ground, and by hand. In Uganda, the army was mobilised to spray affected areas with pesticides and destroy locust eggs. Pesticide use can harm plants, and requires evacuation, so researchers are suggesting that biopesticides such as the Metarhizium anisopliae fungus be used to target locust populations. However, these biopesticides are difficult to get hold of in large quantities, or at short notice.

Drone technology is also being developed and tested in Mauritania, which could be used in the future to provide early warning of future infestations of locusts.

Image by FAO – Sven Torfinn.