Considering the value of nature in urban areas got me thinking about small moves that could lead to large impacts. We often think of parks and backyards as being the opportunities available to city dwellers for access to nature. The phenomenon of green roofs has been picking up traction in this arena, but generally provides private access rather than a public amenity. But all of these are destinations which means that we need to actively seek them out, they are not inherently a part of daily life.
Everyday we walk the sidewalks of the city, even if for a short trip to the car parked on the street or just around the corner to the bus stop. What if we rethought the sidewalk to create in these little journeys an opportunity to commune with nature? What if we could accomplish even more with that little strip of land?
Consider that the city of Seattle has 1172 miles of non-arterial streets. These streets generally have one or two lanes of travel, with two lanes of parking. That is, there is 100-200% as much emphasis on the right to park a car as there to drive a car. By reducing the parking provided on each block to a single lane we could free up 8 feet of space for creating an urban network of nature. That 8 feet has incredible potential.
First, to deal with the cars: by removing that parking lane and bring the curb out 8 feet there would be a traffic calming effect. While parked cars provide may provide the same service, they are largely missing in the middle of the day, creating a thoroughfare that is twice as wide and more inviting for speeding. With a concurrent ramping up of carshare capacity and the improvements planned for public transit, it is likely that the impact on people’s mobility (i.e. American Freedom) would be largely unaffected. 1172 miles of parking space, could easily account for the removal of about 200,000 vehicles (at 66% capacity and 20 feet per vehicle).
The other benefits could be wide ranging, the most obvious being the improvement in quality of life. I’ll let the cute picture of this mom and her daughter do the talking on that one.
Adorable right? But consider also the ground level air quality improvements that could do public health wonders for the city.
We can also expect functional improvements, and I got mathy on this one to help explain. We love talking about water here, and streets comprise a huge part of our impermeable land area. With an intense care for the water resources that surround us, addressing the quality of that runoff has become a big concern. This transition in parking lanes could equate to almost 2 square miles of new permeable surface, which equates to 3600 acre feet of rain water annually. If we were to assume another lane worth of water still falling on the streets could be diverted to the new permeable ground, the amount of runoff that could be properly filtered and stored is equivalent to the annual demands of 70,000 people.
But the effects of restoring plant and soil health go far beyond runoff. The ability to permanently sequester carbon is one of the newest realizations about the benefits of healthy soil. If we assume that the currently degraded and replanted soil had an ability to sequester only a third of its potential 1000 kg/ha/year that means that this new land area could sequester about 152 tons of carbon annually. As the ecosystem improved, this could likely increase over time. This does, however, mean a rethinking of what the area between the sidewalk and the curb can be. Currently the majority of these spaces are grass, with a decreasing prevalence of street trees. As with any monoculture, the benefits of grass are limited, but the potential of grasses is immense. By encouraging a diversity of different grasses, ferns and other plants, the benefits of this new system can be multiplied and the human experience proportionally enriched.
I would imagine that intense resistance to removing the fundamental right of parking will come at first, but I don’t think it would take long for people to feel the intangible benefits of being continually surrounded by nature. I also believe that it would not take long for the market to show that one side of the street was more valuable than the other.