Increase, decrease, or both: A systematic review of mosquito population response to floods

Tobias Röspel, Daniele Da Re , Damien Delforge , Pietro Coletti 

Floods are increasing in frequency and severity under the ongoing climate change and are widely reported to alter mosquito population dynamics. However, the direction, magnitude, and consistency of this effect across mosquito species and flood contexts remain poorly studied. This systematic review synthesizes empirical evidence on mosquito species population responses to disastrous flood events and identifies environmental and flood-specific factors that modulate these responses. Scopus,Embase, and PubMed were searched following PRISMA guidelines for English-language articles reporting empirical mosquito population data in relation to unexpected, disastrous flooding. Articles addressing seasonal, tidal, or controlled flooding were excluded, as were those reporting only mosquito-borne disease outcomes or indirect population proxies. Of 2,005 records identified, 28 studies met the inclusion criteria, spanning 1970–2025 (most published since 2020) and 12 countries, with a strong bias toward the USA (35.7% of studies) and no studies from South America or Southeast Asia. Most studies (78.6%) reported a population increase in at least one species following flooding, while over a third (35.7%) reported a decrease, and several documented both patterns across different species. Floodwater species showed comparatively consistent post-flood increases, whereas responses among non-floodwater species were inconsistent across studies. Flooding substantially affects mosquito abundance, species composition, and assemblage structure, but no single, generalizable direction of effect exists. Responses are shaped by species identity, flood properties, environmental context, vector control, and study design. Rainfall, temperature, and standing water were the most frequently implicated modulating factors, alongside flood depth and duration. Geographically diverse, standardized, high-resolution surveillance, combined with rigorous statistical and modeling approaches, is needed to better anticipate flood-driven vector risk under a changing climate.