On a recent Saturday morning in the Lincoln Heights neighborhood of Los Angeles, the city's River Revitalization Corporation is showing off a plan to add green space to an area that's now dominated by heavy industry. And Lee Christie of architecture firm Perkins+Will is explaining some options.
"You'd be looking at more raised beds or more greenhouses," she says, "which really opens up the possibility for rooftops."
Rooftops have a lot of hidden potential. A new EPA study predicts that as cities grow hotter, replacing flat black rooftops with plants could cool the cities back down.
According to Phil Morefield, one of the co-authors of that study, "any sort of well-designed, well-maintained green roof will give some benefit for the building that it's installed on."
Those benefits include reversing urban warming, absorbing rain before it overburdens sewers, and providing habitat for butterflies.
There's just one problem: green roofs come with a big up-front cost. So now, some cities are experimenting with financial encouragement.
For example, Austin lets developers build more floor space if they include green roofs. And Seattle gives out credits and discounts for rooftop gardens.
"Properties that take advantage of that credit range from single family homes to a regional airport," says Seattle Urban Designer Dave LaClergue, "so they're very different in size and scale."
The gardens on top of the Chloe Apartments in Seattle. That's the Space Needle on the right.Courtesy of Dave LaClergue/City of Seattle
But it's been a learning process. Many of Seattle's first rooftop gardens died, since they were designed with assumptions based on what worked in east-coast cities. And a garden that cools one city might have less of an effect in another.
"There really isn't a 'one-size fits all' strategy," says Britta Bierwagen, another co-author on that EPA study. "And there are a lot of things to consider."
Financial incentives are similarly fickle. In Nashville, a credit of $10 per square foot of green roof hasn't attracted a single taker. But Portland, Oregon, got an overwhelming response to a credit of just half that much.
That's because green roofs need to be customized to what the market in each city wants, as much as to the weather. One market might respond best to grants, while another prefers tax credits.
Courtesy of Dave LaClergue/City of Seattle
For example, in Portland, the incentive amount was determined in part by the region's damp climate and sewers that combine wastewater with stormwater. "It was the amount that we could apply that essentially would cost less to manage a gallon with a green roof than it would with a pipe," explains Portland Environmental Program Coordinator Matt Burlin.
And green roof incentives aren't just for major cities. In tiny Saluda, North Carolina, the Polk County Community Foundation provided a $6,000 grant for a green roof on the new restrooms at Pearson's Falls.
On a recent afternoon, foundation President and CEO Elizabeth Nager stopped by to see how the plants are filling in. It's looking good: "The roof resembles the forest floor in the glenn below the waterfall," she observes. "There are smooth rocks that fill the space where you expect to see traditional gutters."
It's more than just a few rocks and sage bushes, of course. It's part of a national experiment that's happening right over our heads.
When couples find out they are expecting, they usually spread the news to family and friends as soon as possible. When Janet Vertesi, an assistant professor of sociology at Princeton University, found out she was pregnant, she made a very similar call to family and friends, but with very different intentions.
Those close to Vertesi and her husband were told not to post anything on social media sites that would reveal the couples' pregnancy. Vertesi had decided to take her pregnancy off the grid, not because she wasn't overjoyed, but because marketing bots that figure out when a woman is pregnant become relentless in their targeted advertising.
Vertesi says the project was inspired by the invasiveness of data driven marketing that seems to go unchecked. So for the last nine months, she and her husband have paid for all baby-related expenses in cash, avoided social media, and used Tor, a browser that lets you use the internet anonymously, to visit sites like Babycenter.com and Namberry.com.
"So many of those websites also have trackers and cookies that know that you’re visiting so they can follow you around with advertising afterwards," says Vertesi. What she noticed in hiding her pregnancy from marketing bots was that her activity looked more like someone involved in illegal activity than someone about to have a baby. Tor, for example, is notoriously used for drug deals.
While she wouldn't recommend the experiment to others, Vertesi says it raised some interesting questions:
"What I would recommend is thinking seriously about how and where you want your data to go...That doesn’t mean, 'Don’t participate in social networks' or 'Don’t buy anything online.' But it does mean it’s time to think seriously about how and where we want to engage in these kinds of transactions."