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

BACKGROUND: A poorly organised risk management system may dysfunction when used. The consequences can be dramatic for those supposed to be protected. Since the 1960s, preventive control strategies, with field officers as living memory, have been developed to monitor locusts. Preserving their experience of past plagues is consequently essential. Wrong use of their knowledge can disrupt the whole management chain. We explored these conditions using a multi-agent model representing a preventive system. We simulated how the field teams' tendency to repeatedly visit past outbreak areas (hotspots) by allocating them an attraction weight can help in preventing plagues. RESULTS: When field teams' attention remained constant over time, there was dramatic decrease in the number of plagues, with increasing interest in hotspots, as long as interest was less than 2.5 times more than elsewhere. When the field teams were only attentive during recession times, plagues were better controlled using a low weight for hotspots. The spatial structure of hotspot distribution had an effect: the more frequent and the bigger the hotspots, the lower the optimal hotspot weighting needed to reduce plagues. CONCLUSION: Orienting surveys towards hotspots particularly during recession times reduces plagues. The spatial structure of locust habitats may influence the way they are managed. Habitats located outside the multiple hotspots of species such as the desert locust should be visited more frequently than those with only one hotspot, such as the South American locust. The decline/loss of the field officers' experience highlights the need to save, capitalise and disseminate this knowledge. © 2021 Society of Chemical Industry.

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

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.

Improving preventive locust management: insights from a multi-agent model.

BACKGROUND: Preventive management of locust plagues works in some cases but still fails frequently. The role of funding institution awareness was suggested as a potential facilitating factor for cyclic locust plagues. We designed a multi-agent system to represent the events of locust plague development and a management system with three levels: funding institution, national control unit and field teams. A sensitivity analysis identified the limits and improvements of the management system. RESULTS: The model generated cyclic locust plagues through a decrease in funding institution awareness. The funding institution could improve its impact by increasing its support by just a few percent. The control unit should avoid hiring too many field teams when plagues bring in money, in order to ensure that surveys can be maintained in times of recession. The more information the teams can acquire about the natural system, the more efficient they will be. CONCLUSION: We argue that anti-locust management should be considered as a complex adaptive system. This not only would allow managers to prove to funders the random aspect of their needs, but would also enable funders and decision-makers to understand and integrate their own decisions into the locust dynamics that still regularly affect human populations. © 2017 Society of Chemical Industry.

Climate-driven geographic distribution of the desert locust during recession periods: Subspecies' niche differentiation and relative risks under scenarios of climate change.

The desert locust is an agricultural pest that is able to switch from a harmless solitarious stage, during recession periods, to swarms of gregarious individuals that disperse long distances and affect areas from western Africa to India during outbreak periods. Large outbreaks have been recorded through centuries, and the Food and Agriculture Organization keeps a long-term, large-scale monitoring survey database in the area. However, there is also a much less known subspecies that occupies a limited area in Southern Africa. We used large-scale climatic and occurrence data of the solitarious phase of each subspecies during recession periods to understand whether both subspecies climatic niches differ from each other, what is the current potential geographical distribution of each subspecies, and how climate change is likely to shift their potential distribution with respect to current conditions. We evaluated whether subspecies are significantly specialized along available climate gradients by using null models of background climatic differences within and between southern and northern ranges and applying niche similarity and niche equivalency tests. The results point to climatic niche conservatism between the two clades. We complemented this analysis with species distribution modeling to characterize current solitarious distributions and forecast potential recession range shifts under two extreme climate change scenarios at the 2050 and 2090 time horizon. Projections suggest that, at a global scale, the northern clade could contract its solitarious recession range, while the southern clade is likely to expand its recession range. However, local expansions were also predicted in the northern clade, in particular in southern and northern margins of the current geographical distribution. In conclusion, monitoring and management practices should remain in place in northern Africa, while in Southern Africa the potential for the subspecies to pose a threat in the future should be investigated more closely.