Study investigates impact of road ecology
Former Dartmouth postdoctoral fellow Steven Brady published a paper in mid-February on the evolutionary impact of roads on wild populations of plants and animals. This study of road ecology will appear on the cover of the upcoming March 1 print edition of scientific journal Frontiers in Ecology and the Environment.
Brady said that a key message of the paper is that roads have significant evolutionary consequences for plants and animals.
“In some cases, that means they develop a higher tolerance to the nasty conditions of roadside dwelling, and that’s when we see rapid adaptation,” he said. “For conservation, that’s potentially a useful thing — populations that aren’t doing so well over time may have a chance to do better over evolution.”
He added, however, that the same process of evolution can also lead to maladaptation in certain species, which end up “developing lower tolerance over time.”
There is a universal theme that roads cause problems, and they cause populations to become different from each other through evolution, Brady said.
The paper cites the fact that globally, roads are projected to increase 60 percent in length by 2050, according to a 2013 International Agency study. Brady said that it becomes crucial to understand how roads are impacting the planet due to their abundance.
“The evolutionary piece is really important for the way we think about managing landscapes,” he said. “There is a lot of effort that goes out into protecting species and trying to create healthy ecosystems or restore systems, but that message about evolution still isn’t really picked up in applied conservation.”
He added that he hopes the paper will prompt people to think about designing roads in a way that facilitates adaptation or reduce selection pressures. When people think about roads as driving evolution, other strategies might emerge for helping to sustain these systems in healthy ways, Brady said.
Brady added that he was intrigued by the impact of salt applied to roads in the winter.
“I thought for sure that this world would’ve been saturated with research when I got to grad school, so I didn’t really put my eye on it too closely,” he said. “When I started thinking about it more and looking around, I noticed there wasn’t a ton of information on it. It seemed like an area to start asking questions.”
Biology professor Ryan Calsbeek said that salt washing off of roads and entering the water can have big evolutionary impacts. Some animal species can better adapt to salty environments than others, he said.
There is a lot of research on road ecology and how roads affect plants and animals, but not as much work done specifically on their evolutionary impact, Brady said.
“Other fields of conservation, or disciplines, [that] are dealing with climate change, invasive species and overfishing, have all considered evolutionary consequences,” he said. “In road ecology, it just hasn’t been picked up that much.”
Brady said his work in graduate school at Yale University focused mainly on the interaction between environmental changes and evolution. He principally studied roads and runoff but also examined disease emergence in the context of urbanization, looking at how landscape changes can cause new diseases to emerge in wildlife.
Prior to pursuing research at the College, Brady was a postdoctoral researcher at the Northeast Fisheries Science Center, the research arm of the National Oceanic and Atmospheric Administration. During his year there, he used passive acoustic techniques to monitor whales.
In 2014, Brady came to Dartmouth to work in Calsbeek’s evolutionary ecology lab and collaborate with him. Calsbeek had just transitioned into working with wood frogs, a species that Brady had worked with in the past.
“We study how natural selection shapes the evolution of wood frogs in this area,” Calsbeek said. “We study interaction with predators, competitive interactions, female mate choices.”
He added that the wood frog is the only amphibian found north of the Arctic circle and is even capable of living while being frozen solid.
“We’re watching right now as the temperature climbs this week; wood frogs should start emerging,” Calsbeek said, adding that the wood frog is one of the first types of amphibians to emerge for breeding when the snow melts.
He said that he and others in his laboratory will soon begin catching wood frogs and recording their mating calls.
“The most exciting thing is really working with the frogs because they’re really cool little animals,” Calsbeek said, adding that they are also well-known creatures to the local townspeople.
He added that as he is working locally in Hanover, it is much easier to involve other members of the community in scientific research. The lab has worked with undergraduates, high school students and even fifth-grade science classrooms at Windsor Elementary School, Calsbeek said.
Since leaving Dartmouth in May 2015, Brady has worked at the University of Vermont, developing an open source R software package for wildlife harvest data analysis. It was during this time that he wrote the road ecology paper, he said.
Brady now works with a group of scientists for the King County government in Washington state. He is part of a program that monitors the health of streams.
“We have almost 200 sites throughout the country that we monitor every year,” he said. “We go and collect samples from the streams and write reports about how efforts to restore these streams are doing.”
Brady added that he maintains a working relationship with Calsbeek.
Brady’s interest in the impact of roads on evolution started early on in his life, he said. When he learned about evolution in grade school, he said he wondered if squirrels were evolving into faster runners because of the threat of cars.
Brady mentioned this idea to Calsbeek, who suggested that they “get a radar gun and go measure the sprint speed of squirrels darting across the road.”
Roads also have significant impacts on the environment from a non-biological aspect. Roads negatively change the albedo — the amount of light that a surface reflects — of the surface of the earth by absorbing, rather than reflecting, heat from the sun, Thayer School of Engineering professor Benoit Cushman-Roisin said.
Cushman-Roisin said that bigger road networks further disperse human populations, creating suburbs and even “exburbs,” a term coined to refer to areas beyond suburbs.
“People drive more because it’s possible,” Cushman-Roisin said. “As they drive more, they burn more fossil fuels and they contribute to the greenhouse gas effect.”
Freight transportation by trucks also generates significant CO2 emissions in the U.S., especially compared to Europe, where most freight is transported by electric train, Cushman-Roisin said. He added that distances are also much shorter in Europe, so even if transportation were done by trucks, energy consumption would still be lower compared to the U.S.
Not only does the presence of roads adversely impact the environment, but Cushman-Roisin also said that even the building and maintaining of roads emit large amounts of CO2.
Cushman-Roisin said that short of reducing the number of miles of paved roads, it is difficult to produce a solution that would mitigate the adverse environmental effects of roads.