Preventive locust management: humanitarian crises averted

A new study, published by scientists from CIRAD and INRAE, provides a state-of-the-art assessment of the risk of Desert Locust invasions in West and North Africa, by analyzing 40 years of field data and climate records. The study reveals that preventive management measures have been successful in countering the favorable effects of climate change on outbreaks of the pest. This finding underlines the crucial importance of preventive management in mitigating the impacts of climate change and its consequences for food security in the region.

At low densities, the Desert Locust(Schistocerca gregaria) behaves like other locusts and poses no problems. This is known as the "solitary" phase. But when insect density increases, they become gregarious, forming highly mobile swarms that devour crops and pastures, causing enormous damage. These swarms can rapidly threaten the food security of populations from Senegal to India, as demonstrated by the latest crises of 2003-2004 in West Africa and 2020-2021 in the Middle East and East Africa.

The transition from solitary to gregarious phase is highly dependent on favorable weather conditions, particularly temperature, humidity and rainfall. In West and North Africa, climate change is increasing temperatures and modifying rainfall patterns. Climate change is therefore likely to increase the onset of locust invasions and could alter their spatial distribution. Despite growing concerns about the impact of climate change on desert locusts, the researchers found that intensified management measures have been successful in countering these effects. These measures, which involve treating limited areas with insecticides (chemical or biological) at the very beginning of the outbreak process, are therefore effective in preventing large-scale invasions and crises.

This conclusion is the fruit of an analysis of trends over the last 4 decades in the frequency of signs of the start of a potential invasion, carried out at three different spatial scales: the scale of a 10-country region, a fine scale of space divided into 50km cells, and an intermediate scale grouping these cells into 6 homogeneous groups in terms of their climatic trends.

This work was carried out within the framework of the project "Consolidating the foundations of the preventive control strategy and developing operational research on the Desert Locust in the Western Region", led by the CLCPRO (Commission for Controlling the Desert Locust in the Western Region) of the FAO (Food and Agriculture Organization of the United Nations) with funding from the AFD (Agence Française pour le Développement ).

Reference

Herbillon, F., C. Piou, and C. N. Meynard. 2024. An increase in management actions has compensated for past climate change effects on desert locust gregarization in western Africa. Heliyon (2024), e29231. https://doi.org/10.1016/j­.heliyon.2­024.e29231