CREDIT Graphic created by Steven P. Brady using symbols courtesy of the Integration and Application Network, University of Maryland Center for Environmental Science (

Roads, one of the largest human artifact on the planet, have been blamed for the rapid evolutionary change in wild populations of plants and animals.

A study [PDF] published in Frontiers in Ecology and the Environment claims that roads impact the ecology of nearly 20 percent of the U.S. landscape alone, and globally, are projected to increase 60 percent in length by 2050; however, their impact on the evolution of animals and plants have largely been overlooked.

Roads have been blamed for a range of negative impacts on wildlife as well as environment including pollution and road kills among others, but scientists now claims that these human artifact are playing a major role in evolutionary changes in road-adjacent populations of wild plants and animals.

Scientists have found that over a short period of time on an evolutionary scale, some animals living in road-adjacent habitat are evolving higher tolerance to pollutants, such as road salt runoff; the common grass Anthoxanthum odoratum is one such example, the spotted salamander (Ambystoma maculatum) is another.

Despite this positive influence of rapid evolution, road-adjacent populations are not always able to adapt to life beside the road, at times becoming ‘maladapted,’ evolving lower tolerances to negative road effects.

Earlier fieldwork revealed that the survival rate for wood frog Rana sylvatica populations living by the road was 29 per cent lower than those transplanted from other areas. With the spotted salamander and wood frog, the fitness of each population had increased and decreased, respectively, relative to populations not living roadside, which demonstrates how local adaptive and maladaptive changes are occurring through natural selection among various species. Even though a population may experience local adaptation, the researchers point out that while evolution might decrease the chance of local extinction, it does not preclude it.

The evolutionary perspectives of road ecology is integral to understanding how roads are impacting our environment, and to planning for and implementing conservation efforts. As new roads and infrastructure projects are considered by local, state and federal municipalities, including the prospect of a new U.S. infrastructure program, an integrated policy approach that considers maximizing the connectivity of habitats, preserving genetic diversity and increasing population sizes, may help “mitigate the consequences of roads.”


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