Donald begins with an account of the early history of the motor car and with the three components of traffication: increasing numbers of cars, moving at higher speeds, on a more pervasive road network — 90% of England is now within 1km of a road.
Early attempts to evaluate roadkill involved simple counting, but it's not that simple — road-crossing rates and risks vary between species (and larger animals are much more likely to be recorded), between females, males and juveniles, and with the season and time of day, among other factors.
Roadkill is an immensely complicated phenomenon, and our understanding of its many ecological, behavioural, sociological and physical nuances remains poor. We know too little about how animals move around the landscape, how they decide whether or not to cross a road or what their chances of crossing safely are to be able to predict with any great accuracy where, when and how roadkill will occur.
The species not found as roadkill may indicate a bigger problem: they may have been driven to local extinction, or they may be avoiding roads completely. The latter results in severance of populations, breaking them up into small "islands", which may be prone to local extinctions and loss of genetic diversity. And there is the reverse problem, where roads act as "invasion highways", enabling rapid movement of invasive species.
For humans, the evidence is that "traffic noise is not simply annoying; it is extremely dangerous".
"Other animals suffer exactly the same sorts of health impacts from road noise as we do. A huge amount of research, from both the field and the laboratory, has shown that animals exposed to vehicle noise suffer higher stress levels and weakened immune systems, leading to disrupted sleep patterns and a drop in cognitive performance. They suffer an impaired ability to learn, solve problems or remember where things are, failings that in the brutally competitive world of wild nature usually mean the difference between life and death."Other harms include air pollution (including particulates), salination from gritting salt, and light pollution.
Donald argues that many of the effects attributed to agricultural intensification are probably due to traffication, and that traffication should rank as a "sixth horseman" of ecological destruction, alongside agricultural intensification, habitat destruction, invasive species, unsustainable resource utilisation, and climate change.
He touches briefly on how a few species can tolerate or even benefit from traffication, though that comes with a reduction in species diversity.
The "what we can do about it" parts of Traffication consider measures such as wildlife bridges, de-traffication by closing some country roads to through traffic, and, with growing awareness of the problem, behaviour change: reducing speeds, avoiding unnecessary car trips, and so forth.
Traffication is accessible and aimed at a broad audience, but Donald is a scientist with a concern for evidence and accuracy: he makes his case by careful argument, not by dramatisation or playing on the emotions. He brings into the light a hugely important but largely neglected threat to ecosystems in Britain and around the world.
There is some discussion of human health in Traffication, largely because the effects of air and noise pollution on humans have been better researched. But it is insightful to read Traffication while reminding oneself that humans are animals, and to think about the implications of a broader ecological perspective for transport planning. As with roadkill, the direct deaths and injuries caused by motor traffic get the most attention, but the other effects are actually bigger public health problems. These include noise pollution and air pollution, but also the damage to physical and mental health from inhibition of walking and cycling and loss of independent mobility, especially among children and older adults. Children not showing up in road casualty statistics is often an indication that they are simply not walking or cycling. And genetic isolation may not be a problem for humans, but community and social severance certainly are.
Many of the solutions are also similar. Closing some routes to through traffic reduces the pervasiveness of motor traffic, grade-separated crossings reduce road severance, and so forth. An ecological perspective offers a different perspective on all these schemes, and on urban planning and transport more generally.
November 2024