Large-scale climatic patterns forcing desert locust upsurges in West Africa (original) (raw)

Chiara Vallebona*, Lorenzo Genesio, Alfonso Crisci, Massimiliano Pasqui, Andrea Di Vecchia, Giampiero Maracchi

ABSTRACT: The desert locust represents a serious threat to food security in many African, Middle Eastern, and Southwest Asian countries. Desert locust breeding, maturation, and diffusion are strongly influenced by local environmental parameters, mainly rainfall, temperature, wind, and related features such as soil humidity and vegetation development. The recurring simultaneous occurrence of outbreaks and seasonal breeding over wide regions suggests the existence of large-scale forcing due to climatic anomalies. Even if the connections between climate anomalies and desert locust upsurges have been hypothesized in the literature, no inference has been demonstrated for large-scale climatic processes, allowing their potential use as predictors. In the present study we assessed a historical data series on desert locust population dynamics by integrating several data sources. A climatic analysis was carried out on a monthly basis covering the period 1979–2005 using the global NCEP-DOE Reanalysis dataset. The Wilcoxon non-parametric test was used to establish whether identified West African atmospheric patterns in upsurge years present significant differences compared to recession years. The analysis suggests a significant role of a weaker easterly flow at the core of the African Easterly Jet during spring, coupled with stronger westerly moisture advection. These climatic features may indeed explain meteorological conditions supporting many contemporaneous outbreaks, eventually developing into an upsurge (i.e. widespread rainfall events over key areas).

KEY WORDS: Desert locust · West African climate · African Easterly Jet