An increase in management actions has compensated for past climate change effects on desert locust gregarization in western Africa

Herbillon Fanny, Piou Cyril, Meynard Christine N.. 2024. An increase in management actions has compensated for past climate change effects on desert locust gregarization in western Africa. Heliyon, 10 (8):e29231, 18 p.

https://doi.org/10.1016/j.heliyon.2024.e29231

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Url - jeu de données - Dataverse Cirad : https://doi.org/10.18167/DVN1/1FO9M6 / Url - jeu de données - Entrepôt autre : https://locust-hub-hqfao.hub.arcgis.com/ / Url - jeu de données - Entrepôt autre : https://chelsa-climate.org/timeseries/

Résumé : In response to high population density, the desert locust, Schistocerca gregaria, becomes gregarious and forms swarms that can cause significant damage to crops and pastures, threatening food security of human populations from western Africa to India. This switch from solitary to gregarious populations is highly dependent on favorable weather conditions. Climate change, which has been hypothesized to shift conditions towards increasing risks of gregarization, is therefore likely to have significant impacts on the spatial distribution and likelihood of outbreak events. However, the desert locust is intensely managed at large scales, which possibly counteracts any increased risk of outbreaks due to a more favorable climate. Consequently, understanding the changes in risks in the future involves teasing out the effects of climate change and management actions. Here we studied the dynamics of gregarization at the very early stages of potential outbreaks, in parallel with trends in climate and management, between 1985 and 2018 in western Africa. We used three different spatial scales, with the goal to have a better understanding of the potential effects of climate change per se while controlling for management. Our first approach was to look at a regional scale, where we observed an overall decrease in gregarization events. However, this scale includes very heterogeneous environments and management efforts. To consider this heterogeneity, we divided the area into a grid of 0.5° cells. For each cell, a climate analysis was performed for rainfall and temperature, with trends obtained by a harmonic decomposition model on monthly data. Analyses of gregarization showed only a few significant trends, both positive and negative, mainly found in western Mauritania where management effort has increased. To improve the statistical power, these cells were then grouped into larger homogeneous climatic clusters, i.e. groups of cells with similar climatic conditions and similar climatic trends over the study period. At this scale, gregarization events depend on the intersection between climate conditions and management efforts. The clusters where gregarization increased were also the ones with the highest increase of management. These results highlight the important effect of preventive management, which may counteract the positive effects of climate change on locust proliferation.

Mots-clés Agrovoc : changement climatique, surveillance des déprédateurs, Schistocerca gregaria, effets du changement climatique, distribution spatiale, densité de population, comportement sexuel, variation saisonnière, dynamique des populations, gestion du risque

Mots-clés géographiques Agrovoc : Algérie, Burkina Faso, Tchad, Libye, Mali, Mauritanie, Maroc, Niger, Sénégal, Tunisie

Mots-clés libres : Schistocerca gregaria, Climate Change, Pest management, Agricultural pest, Population dynamics

Classification Agris : H10 - Ravageurs des plantes

Champ stratégique Cirad : CTS 4 (2019-) - Santé des plantes, des animaux et des écosystèmes

Agences de financement hors UE : Food and Agriculture Organization, Agence Française de Développement, Commission de lutte contre le criquet pèlerin dans la région occidentale

Projets sur financement : (ITA) Consolider les bases de la stratégie de lutte préventive et développer la recherche opérationnelle sur le Criquet pèlerin en région occidentale

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