2008 marked the first year in human history that more than half the world’s population lived in cities. By 2030, about 5 billion people will reside in urban areas. Humanity’s migration to a handful of key population centers will test our knowledge of urban development, and force innovators to find more efficient ways to build and grow our cities. In this two-part series, we’ll examine the coming evolution of the metropolis. Today’s guide is Kristina Hill, associate professor at the University of Virginia, who lectured at the Harvard Museum of Natural History on March 18.
Our own Emerald Necklace, the seven-mile array of green spaces winding its way through the southern part of the city, was “the most significant American contribution to urbanism,” according to Hill. In the century since its completion, few cities have attempted anything on the scale of Olmsted’s park system.
In Boston and countless other coastal cities, our development has blocked paths of migration for many native species, altered fragile tidal habitat, and polluted waterways leading to the sea. “If most of our coasts are going to become urban, we have to do something,” Hill said.
Luckily, these changes are reversible. Hill described several changes cities have made to account for the welfare of their non-human residents. Using the principles of “ecological urban design,” we are building structures intended to support biodiversity.
If it’s not too far a hike, go out to Quincy Market and sit outside with a bag of chips. (We’ll be here when you get back.) If you actually did it, you discovered that people do a great job of attracting “nuisance” animals, like pigeons, which have adapted to living in our shadows. In Portland, one particularly urban critter was found taking the light rail! The problem in Seattle, where Hill formerly worked at the University of Washington, was crows—they flock to urban settings, like outdoor cafes, and commonly attack the nests of native songbirds. To let the birds nest in peace, she proposed a system of “exclosures” which allow them to come and go, while keeping nest predators out: a small, simple, and effective solution.
On a much larger scale, many cities in Europe have built ecoducts—“animal highways” that provide paths from the coast to undeveloped areas outside the city. In some ways, this represents the 21st century evolution of the Emerald Necklace—a long, connected set of greenways running all the way through the city. While Hill said that she would love to see an ecoduct in an American city, for now the best examples can be found in Stockholm and Antwerp. However, an article in the March 2009 National Geographic proposed an even larger ecoduct, which would give jaguars an unimpeded path between South America and the US–Mexico border.
Another crucial step in redesigning urban environments requires protecting coastal waterways. Often refuges for juvenile fish, these areas have been disrupted by polluted storm runoff and removal of submerged aquatic vegetation. To handle the first issue, Hill says that we can “make the city function less like an umbrella, where all the water is shed, and more like a sponge.” She proposed a system of "unconventional development," which filters urban runoff and gradually releases it back into the watershed.
Seattle has one example of "unconventional development" already in place—its prototype SEA Street. The edges of the street are designed to collect water, not divert it directly into storm drains and into the path of fragile wildlife. The improvements which produced SEA Street were actually cheaper than the city’s usual sidewalk repair, and reduced runoff by 97%. Hill’s next challenge is convincing a port city to artificially restore its aquatic vegetation, completely reversing the habitat loss caused by human development.
Finally, while the extent of sea level rise in the 21st century is of course uncertain, coastal areas are beginning to guard against its effects. In Rotterdam, a storm surge barrier called the Maeslantkering was completed in 1997 to protect the Dutch coast against severe sea level rise. Similar tide barriers may be necessary in the United States. However, Hill cautions that the barriers must account for the important fisheries off the Eastern Seaboard.
The ecological problems of conventional development are being counteracted by innovative design, a trend which will continue in the coming decades. Though we will never be perfect stewards of the land we use, future cities will be better equipped to lessen our impact on fragile habitat. Today, we find it incredible that densely packed cities had to survive without sewer systems. Our children will be similarly shocked by today’s needlessly destructive practices. They’ll look out over manmade wetlands in the wake of bustling shipping lanes, astounded that we had once let this environment slip away.
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