Ecological impacts of traffication

Traffication. How cars destroy nature & what we can do about it. Donald, P. F. 2023. Pelagic Publishing, London, UK. 279 pp. £20.00 (hardcover). ISBN 978-1-78427-444-3.

A clouded leopard in the middle of the road. New thinking about roads, people, and wildlife. Jones, D. 2022. Cornell University Press, Ithaca, NY, USA. 272 pp. US$19.95 (paperback). ISBN 978-1-501763717.

The message of these books is more than shocking, even for advanced readers in ecology and biodiversity conservation because it shows how the network of roads destroys nature and human welfare. The overarching logic of both books is brilliant; all statements are supported by facts, analyses, and references. Traffication is theory oriented, whereas Clouded Leopard focuses on practical solutions to mitigate the effects of road traffic. The volumes prove that although the negative effects of roads on human health and biodiversity have long been known, road ecology is a neglected topic even among conservationists (Forman et al., 2003). The authors provide fascinating introductions to a novel term, road ecology, and the author of Traffication invented the term to describe the complex of phenomena of the effects of roads on humans and nature. (By traffication, the author means the expansion of road networks and the burgeoning of motorized travel along them.) We find detailed and highly informative introductions to the parallel histories of car driving and road development and to how the pioneers of road ecology recognized the devastating nature of road traffic. The authors show that more than 100 years ago, cycling started as the key means of human travel, not just an entertainment for the rich. Cycling was rapidly replaced by car driving—and we are now slowly recognizing what a big mistake it was. Astoundingly, the earliest road ecologists understood that road traffic affects wild populations to at least the same degree as natural processes.

We learn how road traffic changed our lives and what an immense cost we humans need to pay for road traffic, in terms of human lives and health. It is horrible to recognize that road accidents are the leading cause of death for people from 5 to 30 years of age. In spite of this, traffic intensity measured both in vehicle miles and top speed is continuously growing, without any sign of stopping or even deceleration. Consequently, field studies show that the number of dead animals on roads is just a small proportion of individuals killed by cars. I was shocked and astonished by the number of animals estimated to be hit by cars, both in absolute numbers and densities. The case is even serious for invertebrates—the number of roadkills is probably in the hundreds of billions in North America alone. It is a key conservation concern that endangered species, such as the Amur tiger (Panthera tigris altaica) and the southern cassowary (Casuarius casuarius), are threatened with extinction by road traffic. However, some species, such as corvids, can adapt to road traffic and benefit from roadkill.

These volumes nicely demonstrate that roadkill patterns can be modeled effectively based on species’ life-history parameters and ecology; road properties; traffic parameters; environmental predictors, such as the surrounding land cover; date; and weather. Thus, roadkills also provide ample material for investigations of the ecology, evolution, genetics, and diet of wild populations. The books show that roadkill patterns are also related to the road-crossing strategies of animals: blind-crossers, pausers, speeders, and avoiders. Road avoiders are the biggest losers of traffication. In considering the effects of fragmentation by roads, the theory of island biogeography (MacArthur & Wilson, 1967) applies, as illustrated by fragmented grizzly bear (Ursus arctos horribilis) and the Iberian lynx (Lynx pardinus) populations. Additionally, populations can be completely separated, which leads to genetic drift and divergence.

On one the hand, roads can function as highly effective barriers. On the other hand, they may facilitate movement of invasive species. For example, the cane toad (Rhinella marina) is rapidly spreading in Australia, which has led to morphological adaptations. Populations at the leading edge of spread have longer legs, which enables them to move faster. Similarly, common ragweed (Artemisia ambrosifolia), which causes extremely strong allergic reactions in many people, is traveling fast along roads by seeds transported by cars. A large number of plant species have their seeds dispersed by cars, and seed densities along roads are extremely high.

As shown in the books, road ecology influences our understanding of other major ecological phenomena. The effects of climate change interact with traffication, resulting in climate traps. Species surrounded by roads cannot follow their climatic niche, which can lead to extirpation. Road noise, a particular special feature of road ecology, has multiple negative effects on humans and animals alike, including increased stress levels, weakened immune systems, disrupted sleep patterns, and decreased cognitive performance. Noise also reduces hunting efficiency in several raptor species and affects health at even the genetic level (shortened telomeres in some animal species). The authors introduce an alternative name for car noise disturbance: soundscape pollution. Road noise generates a so-called landscape of fear that widens the nonpermeable zone for many species. In addition, bird songs get higher pitched as a result of soundscape pollution, and the quality of the song is reduced in a number of species. Corrupted versions of the original song are learned and become increasingly unrecognizable to conspecifics. Mammals, especially bats, exposed to traffic noise produce louder and higher pitched calls. Road noise eliminates the kangaroo rat's (Dipodomys sp.) ability to detect the foot-drumming of other kangaroo rats, which is their primary means of communication.

An astounding fact of traffication is that the key pollution problem has shifted from exhaust to particles generated by the interaction of tires and the road, which may be carcinogenic and include microplastics and chemicals that are toxic to many plants and their pollinating insects. Another form of the pollution component of traffication is salt on the road, which has significant impacts on aquatic life, especially amphibians; for example, it modifies sex ratio in frogs.

The reader is faced with the terrifying question: can roads be responsible for the disappearance of hundreds of millions of pairs of birds in Europe alone (Burns et al., 2021). The answer is difficult. Scientists are no longer able to measure the magnitude of road effects because there are so few road-free areas for comparison. The books provide a deep analysis of the road effect zone, listing many examples from around the world. Astoundingly, simple calculations show that road effect zones affect larger areas than agricultural intensification.

We learn that the beneficial effects of the COVID-19 phenomenon can partly be summarized as a so-called anthropause—the partial or complete halt of human activities outdoors—which induced near-immediate changes in distributions and behavior. An artificial road experiment in a forest showed the large role noise plays in generating road effect zones. Although we know little of traffication-free ecology, one of the side effects of COVID-19 resulted in the rapid return to normal behavior in terms of spatial movements and acoustic behavior in several wild animal species.

As shown in both books, traffication is in conservation's blind spot, even though it disrupts key ecological and evolutionary processes. The nature conservation lobby is unfortunately absent from the detraffication lobby. Considering the future of traffication, the authors demonstrate that traffic generates more traffic, which is called induced traffic. Additionally, electronic vehicles (EVs) encourage people to drive more and, due to their speed, produce more particulate pollution than slower vehicles. The authors conclude that we need specific engineering solutions to control the effects of traffication, for instance, new types of roads, tires, and headlights (the short-wavelength blue light interferes with many biological processes). We also need legislation to control the effects of traffication. The first signs of detraffication are already apparent: the proportion of young people not wanting to drive is increasing. Further, the first conservation-minded responses are appearing. Installations of wildlife over- and underpasses, canopy crossings, and bridges equipped with remote cameras are increasing. These systems are supplemented with animal-activated detection systems and radio-tracking-driven smart signs in some regions, which also greatly reduce collision probabilities for particular species. The authors also provide suggestions for detraffication at home.

I recommended these books for a broad range of ecologists, road engineers, and anyone who cares about ecological problems of roads and cars and need to drive a car.