The Power of Overlap
Edmonton, my home city, sits in Aspen Parkland—a transitional ecosystem between the great plains to the south and the boreal forest to the north. Not quite prairie, not quite forest, it is a classic ecotone: an area of overlap that is richer and more diverse than either ecosystem alone.
Ecologists describe ecotones as transition zones where two or more ecosystems meet. These places are greater than the sum of their parts, often containing the biodiversity of each overlapping system plus unique species that only thrive at the intersection. Think of a shoreline: aquatic life meets terrestrial life, and in the mix, you find mollusks, crabs, and shorebirds that exist only in that rich overlap.
In ecosystems, health is measured by connections—the more connections, the more resilient the system. The potential for connection is highest where different systems meet. Ecotones are dense with potential. In human terms, they are rich in opportunity.
Eco[tone]city: Reframing Urban Connection
In his book Ecocities: Rebuilding Cities in Balance with Nature, Richard Register calls cities “places for maximizing connections.” Cities exist to create proximity: to work, to play, to learn, to stumble upon the unexpected. When designed well, streets, neighbourhoods, and districts facilitate these chance encounters. That is their purpose.
But modern urban design often gets in the way. We divide land into zones and rely on single-use vehicles to move between them. This approach removes the ecological equivalent of a shoreline. It severs the connective tissue that allows diverse systems to collide and generate new possibilities.
Instead of fostering interaction, we ask the metaphorical crab to drive from the beach to the water.
Opportunity Likes Squiggles
The more contact between two systems, the more potential for connection. One way to achieve this is to extend the edge or encourage meandering.
Comedian Demetri Martin has this great line: “Culture is attracted to squiggles.” It’s a joke that contains truth. Ecotones aren’t straight lines. They bend and weave, creating moments of friction and synthesis. If ecotones increase opportunities, it follows that people would be attracted to geographical ecotones such as oceans, rivers, and mountain ranges.
Broadway As Ecotone
Unlike the grid that defines most of Manhattan, Broadway cuts diagonally through the city. Originally a natural trail used by Indigenous groups—the Wickquasgeck—it predates colonial planning.
“The Manhattan Indians used the Wickquasgeck name for the path they took through the center of the island to [the] northern reaches. Coming south along it, Indians of various tribes reached the Dutch settlement at the southern end of the island. The Europeans could likewise follow it north—through stands of pin oak, chestnut, poplar, and pine, past open fields strewn with wild strawberries … crossing the fast running brook that flowed southeast from the highlands…to empty into a small bay on the East River—to hunt in the thick forest at the island’s center and to fish the inlets that penetrated the eastern coast.”
– Anthropology in Paradise, Walking the Wickquasgeck Trail
This original trail created a jagged edge through the city’s otherwise rectilinear grid. And with it, an abundance of urban ecotones: triangular plazas and intersections like Times Square, the Flatiron Building, Greeley Square, and Herald Square. What might have been awkward leftover spaces became iconic gathering places.
Flatiron Plaza as Ecotone made possible by the Meandering of Broadway. Photo: New York DOT
Cities As Ecotones
How magical would incorporating Wickquasgeck’s original ecology into Manhattan’s built environment be? Imagine stands of pin oak, chestnut, poplar, and pine, with open fields strewn with wild strawberries, woven into the heart of the United States’ largest city.
If people are drawn to ecotones, a good starting point is to stop paving over or restricting existing ones. A more ambitious goal would be to cultivate, expand, and integrate ecotones—natural and otherwise—throughout the urban fabric.
I firmly believe cities are natural. Like ecosystems, cities form connections, cycle matter and energy, and create niches. Consciously designing urban/nature ecotones can preserve the strengths of both systems while generating new opportunities that only exist in the overlap. One system produces excess runoff; the other excels at slowing and absorbing water. One traps excess heat; the other cools and shades.
A Call for Connection
What if every sidewalk, boulevard, or stormwater channel was seen not as infrastructure but as edge habitat? What if the design goal was not separation but connection?
Let’s build squiggles into our cities. Let’s maximize the margins. Because it’s in the overlap—in the ecotone—where life gets interesting.