Transport Infrastructure, Climate Change and More Than Human Mobilities
Anoop C Choolayil, Indian Council of Medical Research, Vector Control Research Centre, India Muhammed Jabir MM, Indian Council of Medical Research, Vector Control Research Centre, India Uli Beisel, Freie Universität Berlin, Germany Carsten Wergin, Universität Heidelberg, Germany
Climate change and the resulting extreme weather conditions are often discussed in the context of how certain species are at risk of habitat loss with many species threatened by extinction. However, some species of flora and fauna gain access to and thrive in novel ecological niches due to climate change. This introduction and proliferation of so-called invasive (we prefer “mobile”) species to larger spatial planes blurs the lines of niche differentiation and generates impact across species. One of the most visible cases of such expansion and mobility are mosquitoes, particularly Aedes mosquitoes, that leverage human mobility and evolving climate dynamics.
The primary habitat of the more than 950 Aedes species used to be the tropics (Monteiro et al., 2019). Due to human travel, global trade and climate change, they now appear in places they have never before, most notably the Global North (Ma et al., 2022). As highly adaptable insects, Aedes thrive near people and turn the latter into efficient disease transmitters. As an interdisciplinary research team of anthropologists and entomologists from India and Germany, with further members from the Ifakara Health Institute (Tanzania) and the Universidad Nacional Autónoma de Mexico, we aim to understand how these mobile mosquitoes affect humans in India, Mexico, Tanzania and Germany.
We take Aedes as a paradigmatic case of how human and nonhuman mobility converge in contemporary societies. To do so, we monitor the presence and abundance of Aedes in and through human transport to highlight the socioecological dynamics that stem from entangled mobilities and investigate the role infrastructures play in the transmission of infectious diseases.
This article draws on the initial results of our sub-project in India, where research on the entangled mobilities of Aedes and humans spanned 300 KM of the Chennai-Trichy highway. We collected mosquitoes at various spots, such as in trains, buses and trucks, following a go-along methodology through which we engaged passengers and further stakeholders like train conductors and bus drivers. The Chennai–Trichy route was selected for this study due to its extensive transportation networks consisting of bus stations, railways, airports, and the Chennai International Seaport, facilitating significant human and cargo movement. The route also experiences high human traffic as it connects the two largest cities in Tamil Nadu with many industries, hospitals, and educational institutions. Additionally, the strong presence of Aedes mosquitoes and a general history of dengue outbreaks made it a suitable place for our study (Rodriguez-Barraquer et al., 2015). Based on our latest empirical findings, we argue that entangled human-mosquito mobilities paired with climatic factors can potentially serve as a catalyst for a substantial global public health problem in the near future.
Entangled Mobilities, a Changing Climate and Expanding Mosquito Populations
Aedes constitute one of the most common mosquitoes in India. They breed in human-made habitats, like rubbish tips, and leverage human transport infrastructures for mobility and expansion. The movement of mosquitoes fostered by human mobility can not only trigger outbreaks of Aedes borne infections but also introduce new pathogens into subpopulations of uninfected mosquitoes as well as new species to locations where they did not exist before (Adams & Kapan, 2009; Eritja et al., 2017). Our research focuses on how Aedes travel via public transportation, specifically buses travelling between Chennai and Tiruchirappalli (Figure 1). We conducted multiple bus trips with five teams making four journeys each at different time periods over the past year. On the buses, we used tools such as aspirators and specialized traps to collect and identify mosquitoes using genetic markers (Figure 2). The results indicated that public transport is a significant pathway for mosquito movement.
Figure 1: Map and bus routes between Chennai and Tiruchirappalli
Figure 2: In a bustling public bus in the city of Chennai, India, two entomologists are on a task to capture adult Aedes mosquitoes using a mechanical aspirator. Photo taken by authors.
However, the story of entangled mobilities does not simply end with this finding. Bus stations themselves turned out to be breeding grounds for mosquitoes, even during harsh weather periods. Overflowing taps, overgrown vegetation, littered plastic containers, and neglected building sites all provided a perfect breeding environment. This “mosquito haven” allowed Aedes to feed on thousands of passengers passing through, potentially transmitting diseases back and forth.
The even larger concern, however, rests with the question of what happens next. Our preliminary observations suggest these mosquitoes can travel long distances on buses, potentially carrying diseases to new locations while also finding new ecological niches. This again highlights the factor of shared mobility for the spread of mosquitoes and mosquito-borne diseases (Adams & Kapan, 2009; Eritja et al., 2017). Climate change exacerbates this further. Like many other places, Tamil Nadu has seen significant changes in temperature and rainfall patterns (Jeganathan et al., 2019; Rangarajan et al., 2022) that facilitate suitable conditions for mosquito populations to expand.
This is where things get complicated. If mosquitoes travel long distances but arrive in unsuitable environments, they may struggle to survive. However, since climate change helps provide favourable conditions, mobile species can easily establish themselves in new areas. This interplay between the entangled mobilities of mosquitoes and humans with climate change is not unique to India. Studies in Europe by Giunti et al. (2023) and Schaffner et al. (2013) as well as our own research in Germany, Mexico and Tanzania all demonstrate similar patterns, where, generally speaking, a combination of travel and a changing climate has unforeseen consequences for human health.
Figure 3: Under the bright sunshine in the city of Chennai, India, at a public bus station, two entomologists are hard at work. As passengers board a waiting bus, one entomologist kneels near a pool of standing water under debris, carefully collecting mosquito larvae, while the other records their findings diligently. Photo taken by authors
Figure 4: In a corner of the busy public bus station in Chennai, India, two entomologists, are deeply engrossed in their task. Surrounded by a clutter of waste materials discarded by passengers, they inspect for mosquito larvae. Photo taken by authors
The crucial point is that mobility infrastructures are indeed shared by significantly more than just human actors. Bus stations maintain an environment favourable for the breeding of mosquitoes, including overflowing taps, overgrown vegetation, littered plastic containers, and neglected buildings. From these sites, mosquitoes enter vehicles and travel long distances to novel environments, introducing and transmitting pathogens. Climate change is a significant driver within these shared infrastructures, as invasive species find more favourable conditions that facilitate survival and proliferation in places they might otherwise have struggled to adapt in. The first autochthonous transmissions of dengue in Paris and at Lake Garda in Italy during Summer 2023 are cases in point (Brem et al., 2024). The pairing of studies on climate change and more-than-human mobility also sheds light on the European context (Giunti et al., 2023; Schaffner et al., 2013), as climate change and entangled mobilities continue to induce adverse health outcomes.
Figure 5: At the Chennai International Sea Port, an entomologist stands beside a boat parked on land. Holding a larvae collector in her hand, she carefully inspects the interior of the boat for mosquito larvae amidst scattered debris strewn around. Photo taken by authors
Tackling Climate Change and Entangled Mobilities
As the COVID-19 pandemic has shown, extensive travel and global connections see events in one place quickly ripple across the globe. This poses a significant threat to public health, particularly so if viewed through the lens of entangled, more-than-human mobility. Our research makes evident how travel networks provide “novel niches” —new homes— for mosquitoes. The latter would not reach new territories without hitching a lift in planes, ships, trains and buses. Meanwhile, climate change creates ideal conditions for mosquitoes to thrive in previously unsuitable regions.
The future holds even more movement, on trains and flights, paired with a rapidly changing climate. These compounding factors pose a serious threat: the spread and intensification of mosquito-borne diseases like West Nile, Dengue and Zika across the globe, including the Global North. So, what can we do? Integrated Vector Control Measures (IVM) offer a potential solution. These involve tackling mosquitoes at various stages of their life cycle, targeting breeding grounds within transportation infrastructure—think overflowing water tanks at airports or neglected puddles near bus stations. By disrupting opportunities to travel or settle, we can make it harder for mosquitoes to establish themselves and thus limit the risk of new diseases. Understanding this network of transportation, climate change, and entangled mobility requires interdisciplinary work that brings social science research and entomology into conversation. Crucially, questions around human cohabitation and travel with mosquitoes, socio-political conditions (e.g. decaying infrastructures) as breeding spots, and citizen science and community participation as tools for understanding and controlling mosquitoes need to be investigated more closely if we are to develop proactive strategies to fight vector-borne diseases and protect public health in our shared world.
The research reported here has been made possible through generous funding from the Volkswagen Foundation for the project “Mobile Mosquitoes – understanding the entangled mobilities of Aedes mosquitoes and humans in India, Mexico, Tanzania and Germany” (Grant Number 9B366). We would like to further acknowledge and thank our colleagues AN Shriram, KHK Raju, Bhavna Gupta, Manju Rahi (Indian Council of Medical Research), Ashwani Kumar (Saveetha Institute of Medical and Technical Sciences, Chennai) as well as the anonymous reviewers of Weather Matters for invaluable comments on previous versions of this article.