The limitations of locust preventive management faced with spatial uncertainty: exploration with a multi‐agent model

Abstract

BACKGROUND The spatial structure of locust outbreaks is a major aspect of preventive management that relies on where survey teams have to be sent if they are to react in time to any upsurge. The concentration of areas propitious to outbreaks has been documented for many species. Areas where preventive management fails to collect information because of insecurity or remoteness constitute other limits. We explored these conditions using a spatially explicit multi‐agent model representing a preventive management system. We simulated areas where field teams had limited or no access and areas where the probability of initial outbreaks was concentrated in hotspots. RESULTS A strong effort by the budget holder to maintain funding over time might be cancelled out with 5% of a territory having limited access. The larger the area of no access, the worse the proportion of plague years. Multiple no access areas generated more plagues than only one no access area of an equivalent size because more fronts must be controlled. Concentrating outbreaks in hotspots increased the probability of plagues. One hotspot alone was easier to control than several same‐sized hotspots. The period of the budget holder's cyclical behaviour between awareness and reduction in funding was longer with one hotspot than with several. CONCLUSION These results highlight the need to consider the spatial conditions and accessibility of locust species when planning the sustainability of management systems. Despite significant budgets to set in place a preventive management system, cyclical locust outbreaks may be related to these spatial conditions. © 2019 Society of Chemical Industry

Locusts and People: Integrating the Social Sciences in Sustainable Locust Management

“…This opens a space for discussion to include land management practices as a way to manage locusts, and thus to include farmers and their social environment (e.g., markets, policies) as key players. Within this family of systems studies, Gay et al [60,61] focus on the ability of the current preventive system to manage desert locust plagues. Using multi-agent systems that include both human (e.g., field teams, national control units, funding institutions) and non-human agents (e.g., locusts), they explore the role of funding institutions' awareness, budget cyclicity, and the lack of access to some areas due to insecurity.…”

“…Making an analogy with locust phase polyphenism, he characterized an alternation between two institutional phases: a motivation phase associated with important funding in the face of an emergency situation, and an oblivion phase during recession times when "the memory of the invasion fades, funding is reduced below an operational level, specialists are dispersed, and motivation wanes". This "vicious" cycle [60] thus refer to a situation in which one is locked in a complex chains of events that reinforce themselves through a feedback loop and that has detrimental results. It is typified by the desert locust but can also be observed in Madagascar for the migratory locust [14] and in the South American locust [89].…”

Adult Desert Locust Swarms, Schistocerca gregaria, Preferentially Roost in the Tallest Plants at Any Given Site in the Sahara Desert

“…Therefore, remote sensing techniques and historical survey data could be used in the future to predict night-roosting areas [27,34,[61][62][63]. As suggested by multi-agent models [19,64], the spatial conditions and accessibility of locusts should be considered to improve preventive control system.…”

“…Although desert locust management systems have been developed by the Food and Agriculture Organization of the United Nation (FAO), locust affected countries, and researchers by using chemical pesticides and biopesticides, swarms often occur at remote and inaccessible habitats due to geography and insecurity issues and then invade cultivated areas near human activity [17]. This may be one of the reasons why we still face desert locust problems in 2020 [18,19]. Therefore, improving control techniques and methods against swarms is important.…”

Importance of human capital, field knowledge and experience to improve pest locust management

“…Consequently, we recommend that all management systems maintain a sufficient budget between plagues to avoid any disruption in the management chain, the funders' perception of the crisis and the speed of their response, as well as to maintain good levels of skill among the prospectors. In the second version of ALM-MAS 44 we added spatial realism by including reproduction hotspots to reflect the field diversity and locust initial outbreak areas. We also adjusted prospectors' access to hotspots to reflect real field constraints.…”