What causes a locust swarm: An integrative multi-scale analysis of insect population dynamics

Locust swarms have plagued human history by posing significant threats to global food security. For example, the 2003-2005 desert locust (Schistocerca gregaria) swarm destroyed 80%-100% of crops in the impacted areas and cost over US $500 million to control as estimated by the Food and Agriculture Organization of the United Nations. To effectively predict and manage locust swarms, an integrative multi-scale approach much be taken, but rarely occurs. In this talk, I will synthesize our research from lab, field, and remote sensing approaches on the ecological causes of locust swarms in Australian plague locusts (Chortoicetes terminifera) and desert locusts. At the microhabitat scale, we show how clumping of nutritionally optimal food can induce gregarization of locust nymphs. At the field to landscape level, we show why locusts avoid woody vegetation and how suboptimal nutritional landscapes can dictate population distributions. Finally, we show that outbreak response to preceding vegetation growth differs between and within four spatiotemporal levels. This suggests that there are errors in modeling efforts if spatiotemporal hierarchy is not acknowledged. Therefore, by accounting for this spatiotemporal variation, the predictive ability of forecasting models can be increased dramatically. To better understand what influences locusts and more broadly insect population dynamics, there needs to be an acknowledgement of the spatiotemporal hierarchical nature both theoretically and if possible, statistically. Biological phenomena such as locust swarms are usually complex and require a multi-scale and multi-research-field integrative approach. Thus, the framework shown in this presentation can be applied broadly.