Rodent Boom: how climate change is leading to more rats in cities nationwide
By hola | Published | No Comments
Getting used to rats is a big part of urban living. Cities like New York have even incorporated these animals into their landscape and iconography. Having dealt with the pest for so long, associating rodents with big cities has become normal.
In the past few years, however, cities like Washington, D.C., San Francisco, New York, Chicago and Boston have seen rat populations rise. Researchers at the University of Richmond linked this to climate change and rising temperatures in a paper published earlier this year in the journal Science Advances.
Hola Cultura met with Dr. James Boulter, the chairman of the Department of Public Health and Environmental Studies, and Dr. Jennifer Smith, associate professor of biology and animal behavior at the University of Wisconsin-Eau Claire. Before discussing the conditions fueling the rise of rat populations, both experts addressed how climate is affecting cities and urban communities to explain how these two things are related.
What are the atmospheric and climatic factors driving the recent rise in temperatures, specifically in urban areas?
Dr. James Boulter: It’s all about increasing quantities of greenhouse gases, mostly CO2, but some other gases as well. Most of which are byproducts of our fossil fuel economy, right? All of this is about expanding consumption. But it also has to do with how our cities are built. They absorb more heat; they don’t have cooling mechanisms like forests do. And there are also sources of heat in cities, power plants and automobiles and industries that are actually emitting heat as well.
What specific behavioral adaptations have rodents developed that make them especially suited for city environments?
Dr. Jennifer Smith: Behavioral flexibility — and dietary flexibility in particular — has allowed rodents to succeed in cities. Rodents are typically nocturnal, small, social and clever at solving new problems. These attributes allow them to take advantage of surplus food and housing opportunities created by humans in urban environments. Most rodents have a long evolutionary history of living near humans and taking advantage of the opportunities created by humans.
How might increasing rat populations affect the overall health and quality of life for city residents, especially in densely populated or lower-income neighborhoods?
JS: My colleague, Dr. Chris Schell, at the University of California, Berkeley, has written on The ecological and evolutionary consequences of systemic racism in urban environments. His work, in collaboration with others, has documented that the impacts of non-human animals, such as rats, on the health and well-being of humans living in urban environments are unequal. In fact, they demonstrate [quoting from the paper] “how systematic racist practices such as residential segregation, enacted in part through redlining, have led to an unequal distribution of ‘nature’ within cities. These inequities continue to play out in both the ecological processes of cities and the welfare of their residents.” It would logically follow that the patterns would extend to include challenges associated with exposure to rats.
How do changes in land use, such as rapid urbanization or loss of green space, contribute to rising temperatures in cities globally?
JB: Globally, we’re becoming a more urban species. People are leaving rural areas to move to cities, and with the growth, these unplanned cities have very little, if any, infrastructure. No plumbing, no electricity, right? There are very few services, and those are very dangerous environments in a warming climate. Urbanization is going to be a big problem, because as more people move into the cities, the cities warm faster.
On the other hand, has there been an actual impact thanks to the recent trend of green building?
JB: Not enough, not yet. Green buildings are getting more attention, but what percent of the building stock in a given city is green? Probably not a lot. Maybe in some very wealthy cities, in Europe, primarily. I think the percentage of green buildings is just too small.
How, if at all, do urban ecology and recent efforts to make cities greener affect rodent populations and their movement patterns?
JS: Recent efforts to make cities greener benefit all animals, including rodents, by reducing their exposure to toxins associated with pesticides and herbicides. The addition of green spaces with trees helps to provide habitat for tree-dwelling rodents such as squirrels, but the cleaning up of trash can reduce opportunities for rodents to scavenge from human subsidies in urban settings.
What role do rats play in the broader urban ecosystem, and can their presence indicate something about the health of the city itself?
JS: Rats are an important food source for coyotes and birds of prey. They also consume and help to disperse seeds to promote green spaces and plant communities in cities.
Are there any ethical concerns we should consider when dealing with pest control?
JS: Many forms of pest control are unethical in terms of how they impose pain on their target hosts. Another concern is that poisons administered to rodents at lower trophic levels are, in turn, consumed by animals at higher trophic levels. These poisons can have unintended consequences for other wildlife, as well as human health, that can be more harmful than the original problem they intended to solve.
Looking ahead, what changes in urban planning or policy could help manage rat populations more sustainably?
JS: Rats are social mammals with an extraordinary capacity for learning, problem-solving and cooperation. Appreciating the intrinsic value of these animals and their importance in food webs for other wildlife will be key to maintaining a healthy balance in urban environments.
There has to be a healthy coexistence between rodents and humans in big cities. Both benefit from each other’s existence. While it can be shocking to see a rat running around while you order your morning coffee, there is a symbiosis that keeps the relationship between humans and other animals in balance. The goal is not to eliminate rats from cities, but to stay alert and regulate climate warming, which is dynamic and constantly changing. In the end, the rise of rats isn’t just about rodents, but a reminder that when the climate shifts, so does everything living within it.
This interview has been edited for length and clarity.
– Story by Jamie Orozco
– Copy edited by Samantha Golzalez, Elbia Vidal and Kami Waller
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