Wolves, transport infrastructure and ‘trophic cascades’
Monday, August 06, 2018
What have wolves got to do with railway lines?
A video that has gone viral on YouTube tells the story of so-called "trophic cascades" through the reintroduction of wolves into Yellowstone National Park — a small-scale change that set off a chain reaction of responses in the park’s complex ecosystem that had the extraordinary impact of physically changing the course of the rivers.
Yellowstone Park may seem a far cry from the transport infrastructure of our biggest cities.
However, the same processes set in action by the wolves can help to better understand how we should approach planning our highways, railways and streets. And how we can better understand how cities really work, rather than how we would like them to work.
A trophic cascade is an ecological concept — one with a number of technical definitions but which rewilding advocate George Monbiot describes as a process that "starts at the top of the food chain and tumbles all the way to the bottom."
It relies on the complexities of predator-prey interactions and the knock-on effects of introducing small changes into the food chain that have far-reaching impacts. The story of Yellowstone’s wolves is the archetypal narrative that brought the obscure concept to public attention.
Understanding trophic cascades has helped to reveal the depth of the complexity of the natural world — one that evades the control of the most qualified ecologists and explains why even small interventions can have unpredictable and dramatic implications.
A similar lens can help us to understand our cities. It is becoming more common to understand cities through complexity theory — which tries to explain how millions of small interactions in the urban space can accumulate to shape life in the city without any "guiding hand."
Transport is a complex sociotechnical system, and an area where (often heavy) investment decisions are made all the time…to splurge on high speed rail or electrify exiting rail lines? To build a new highway or redirecting those funds to a new system of cycle lanes?
These decisions are not merely about serving demand. They provoke consequences that carve out whole new growth patterns, whole new districts, possibilities of movement. They create new urban fabrics and reinvent patterns of life.
A glance at historic maps of our cities proves that their form by no means happens by accident. The walkable centers of the medieval towns of Europe were built for pedestrians, on dense, walkable grids, creating the close-grained fabric many preserve until today.
In English cities, the "wild infrastructure projects" of the Victorian era attempted to ease uncontrolled urbanization and sprawl, but did much more than move the growing masses of people from A to B — they altered the very shape and growth trajectories of Victorian cities, creating compact walkable neighborhoods around rail nodes whose legacy still remains today.
By the mid-20th century, the rise of the "car era" not only catered to increasing demands for travel but exploded the urban form and gave birth to the mazes of car-centric cul-de-sacs that shaped the neighborhoods many readers of this article live in today, and the "suburban" lifestyles they nurture.
The way we move around the city can affect so many more things than simply getting from A to B. Many of these ambitious interventions have also had unintended consequences.
Just as scientists have found that changes to ecosystems can make infectious diseases more common, the cumulative effects of transport behavior on public health are becoming more clear. The suburban patterns prompted by transport infrastructure since the 1960s have also affected how we interact with each other socially, and have been linked to increasing levels of social isolation.
Transport interventions reshape the physical and social fabric of the city, just as the wolves did the landscapes of Yellowstone.
Moving on from 'predict and provide'
Traditionally, the business-as-usual approach to transport planning has been "predict and provide" — engineers carefully poring over the data and efficiently providing infrastructure that caters to projected demand. However, that approach fails to take account of the complex feedback loops that are inherent in planning.
Today, progressive city planners are using transport infrastructure as a more active tool to nudge us onto more sustainable pathways. But those policies must be carefully recalibrated, with an acceptance of complexity.
Looking at cities this way requires much greater comfort with uncertainty than most planners can muster — a recognition of the "irreducible uncertainties" of planning.
Conclusions: the whole is more than the sum of its parts
That certainly calls for a move from "predict and provide" to a more strategic shaping of the transport environment. But we might also think of policies that shift us away from cars to walking and cycling as the transport planning equivalent of rewilding — a recognition of what we have lost through our interventions in the urban space, and how we can restore the ecosystem to an earlier, more sustainable form.
However, whether we are speaking about wolves or rail lines, this strategy requires an understanding of the whole system rather than the parts.
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