Economic costs of invasive rodents worldwide: the tip of the iceberg

Abstract

Abstract Rodents are a notorious group of invaders worldwide. Their invasions have substantially impacted native ecosystems, local infrastructure, and human health and well-being. However, a lack of synthesized estimation of their economic impacts hampers effective management interventions at relevant scales. Here, we used the InvaCost database – the most up-to-date and comprehensive synthesis of reported monetary invasion costs – to assess the economic costs of invasive rodents globally. Our conservative analysis showed that reported costs of rodent invasions reached at least US$ 3.28 billion between 1930 and 2018, and were significantly increasing through time. The highest species-specific costs were reported from Ondatra zibethicus, Rattus norvegicus and Castor canadensis, with over 90% of the total costs damage-related, principally impacting agriculture, and predominantly reported in Asia (65%) and Europe (20%). Although minimal compared to damages, the majority of management investments were made on islands, with post-invasion spending always dominant. Importantly, managements expenditures to prevent rodent invasions were entirely absent from mainland areas. However, only approximately one quarter of the 48 known invasive alien rodents had reported costs, highlighting clear taxonomic biases. Obvious cost reporting gaps were also evidenced across different areas, sectors and contexts, suggesting a great underestimation of the costs incurred by invasive rodents globally. Greater and integrative research effort on the direct and indirect costs of rodent invaders – particularly the distinction between native rodent pests and invasive rodents’ impacts, or from indirect impacts on human health – would be crucial for bridging these gaps. Ultimately, this would support proactive and sustainable management strategies.