Ecoroofs: for the birds?

Photo by Brian Libby 

Two weeks ago I attended an open house at the Audubon Society of Portland, a chance to meet and see up close the organization's educational birds, those injured or otherwise unable to survive in the wild now used to teach about habitat and conservation - such as Jack the Sparrowhawk, Julio the Great Horned Owl, Aristophanes the Raven, and Ruby the Turkey Vulture.

Some of these are not birds ever likely to be common to urban landscapes, even those with a massive forest inside city limits like Portland. Even so, it was such an inspiring site to see these magnificent birds up close that it got me wondering about efforts to re-introduce nature and wildlife into the city through ecoroofs, bioswales and greenspaces.

Portland has become a national leader for ecoroofs, particularly ones that are designed to capture stormwater. But what if the city's collection of green roofs could, once expanded, go a step further and actually become a functional habitat for birds and wildlife - part of a green infrastructure in the city? Ecoroofs do a lot for buildings themselves, insulating them better and reducing energy bills, besides capturing stormwater to prevent runoff. But it wouldn't take much for them to be bird magnets as well.

As it happens, March is being promoted as "Ecoroof Month" by the City of Portland, the Audubon Society of Portland, and the Urban Greenspaces Institute. Events will include "Ecoroof Portland," a free two-day event this Friday and Saturday (March 12-13), as well as an ecoroof tour of South Waterfront on March 27, lectures on March 30 and 31 by London ecoroof expert Dusty Gedge, and an ecoroof tour of downtown Portland on March 31.

As Bob Sallinger, conservation director for the Audubon Society of Portland notes in the organization's wonderfully titled newsletter, the  The Warbler, there are already 200 ecoroofs in Portland, and the city has set a goal of increasing vegetated rooftops to cover at least 39 acres by 2013. An incentive program initiated by the city in 2009 provides property owners with up to $5 per square foot to install ecoroofs. According to the City's ecoroof website Buildings can also receive bonus FAR (floor area ratio) based on three ranges of ecoroof coverage in relation to the building’s footprint: 10-30%, 30-60% and 60% or greater earns one, two and three square feet of additional floor area per square foot of ecoroof respectively.

Multnomah County Central Library ecoroof, photo courtesy Jaysonphoto via Flickr 

Chicago is the only American city with more ecoroof area then Portland, with 534,000 square feet of ecoroof space compared to the Rose City's 423,000 as of 2009. But how are we doing compared to Europe, where ecoroof building leads the world and dates to the 1970s? We've got a lot of catching up to do.

For example, the metro area in Stuttgart, Germany, home of the exquisite Mercedes-Benz brand, has 10.7 million square feet of estimated ecoroof area. Dusseldorf, Germany's overall metro area has 7.86 million square feet. Basel, Switzerland - just the city, not its metro area - had 7.53 million square feet of ecoroof area as of 2007. London has 5.38 million, not including its suburbs and exurbs.

"Portland is particularly well positioned to learn from the European experience with ecoroofs and the emerging trend of biodiverse ecoroofs," writes Jim Labbe of the Audubon Society, also in The Warbler. "Efforts in the United Kingdom, Germany and Switzerland clearly indicate an ecoroof building boom is possible with the right public policies in place. These include adequate incentives and regulation to strongly encourage or require ecoroofs on new development where technically feasible. However we also need local research to help improve designs of biodiverse ecoroofs adapted to our unique climate, flora and fauna."

Photo by Brian Libby 

"By investing in and expanding biodiverse ecoroofs in Portland, we can dramatically expand urban habitat diversity, enrich our local and neotropical bird populations, and help keep nature nearby in our densest neighborhoods."

In 2006 I wrote an article for Metropolis magazine about Tanner Springs Park and its design by German landscape architect Herbert Dreiseitl, which was indicative of an an emerging philosophy regarding wild-life protection in a high-density urban setting. "Instead of just setting aside one or two larger parcels on the outskirts of the city, Portland planners favor also introducing small pockets of nature throughout," I wrote back then. “We’ve done a lousy job of protecting nature in the city until very recently,” added Mike Houck, urban naturalist for the Audubon Society of Portland and director of the nonprofit Urban Greenspaces Institute. “This is a new phenomenon.”

In seeking to become a sustainable capitol, can Portland also become an innovator for nature in the city? Sure, if the Europeans haven't beaten us there first. But Portland also boasts something these older European cities perhaps don't, or at least not in as much supply: enough space, and enough of a connection with the surrounding natural landscape, to enjoy a more substantial connection between city and nature. In that way, the urban growth boundary is as important as ecoroofs. But as with urban planning, it takes both macro and micro level design and implementation to make the unified whole work successfully - a unified plan for growth, and means to make it happen block by block, or in this case, roof by roof and park by park.

Comments

[Lyle]

Interesting Brian! Also, "Jack the Sparrow Hawk" might be better known as "Jack the American Kestrel." These beautiful birds are the most common found falcons in North America.

[Linder]

Tanner Springs Park is a “small pocket” indeed. Unfortunately, it is too small to be much of a wildlife habitat. It is too bad the city and developers backed-off their plans to daylight the entire Tanner Creek. It would have been a nice natural break from all the glass and concrete, would have supported a much broader range of wildlife, and would have helped Portland ”become an innovator for nature in the city.”

As for ecoroofs is there any long-term cost / benefit analysis that take into account long-term maintenance?

Did you ask Mike Houck to comment on ecoroofs? Are ecoroofs good habitat for anything besides plants?

I understand that ecoroofs slow and filter run-off, but I imagine it would be more beneficial, if not as exciting, if the money were instead spent to divide our combined sewer system.

[Scott]

interesting. Looking forward to more dialogue on this topic.

[Mudd]

Linder,

I think the goal would be better to not even need to split the combined sewer system. If a site just simply uses it's own storm run-off, through harvesting for non-potable uses and percolating the rest, you wouldn't need to uproot the whole sewer system in the process. Let's stop investing so much in a storm sewer system that doesn't solve the real problem. Sure, likely there will need to be some overflow into the combined system but the attempt should be made to make this minimal. In Portland, we benefit from a very predictable stormwater season.

Mudd

[kyle]

Gardens as graphics on the roofscape of our buildings gives something back to not only the city, affording pleasant views rather than rooftop HVAC, but also provides habitat which supports attributes of biophilia. Habitat for birds could work on roofs, and we might even design them to promote it, BUT we will have to take care with the glass that is adjacent. That is the killer to the birds. Especially when they see a tree on the inside. Nice horizontal grill, or pattern on the glass surrounding these eco-roofs could prove to be a nice amenity to any city or building.

[Linder]

I like the look of ecoroofs, but I want to be sure that they are as green as they look.

Of the water that falls on an ecoroof in Portland, what percent is actually evaporated back into the atmosphere, and what percent is just slowed on its eventual path to the sewer? Given that Portland’s predicable storm water season has little sunshine, my guess is a large percent is just slowed on the way to the sewer.

There will always be storm water run-off from sidewalks and streets and from parking lots and roofs for years to come. Treating storm water and sewage the same is inefficient (not green) and so I think Portland will eventually divide the systems. It is too bad we are spending $1.4 billion on a “big pipe” to simply move storm water and sewage to North Portland instead of, as we will eventually have to do, dividing our sanitary sewer and storm water lines.

[Stephen]

Linder,
See here for one cost/benefit analysis: http://www.portlandonline.com/bes/index.cfm?c=50818&a=261053

And don't forget about transpiration - evaporation isn't the only mechanism vegetated systems provide to get water out of the system. It's not wholly sun-dependent.

Stephen

[Mudd]

Linder,

True green strategies strive to de-centralize as much as possible. Why depend on the electrical grid if you can make enough power on-site. Why pipe drinking water from Mt Hood when you can harvest it locally. Green roofs are the first step in de-centralizing our stormwater systems. Rather than spending a ton of money to provide a new stormwater sewer grid throughout the city, why not use that money to stimulate more robust green roof systems, rooftop planters and other common strategies at grade so that a site can truly be self-sustaining when it comes to rainwater?

[Matt]

Thanks for posting Brian. The event this weekend is described in detail at www.portlandonline.com/bes/ecoroofpdx , and Friday's sessions would be especially relevant to this discussion.

[Aneeda]

Dreiseitl's park in the Pearl has very little to do with ecology. It is nothing more than an energy intensive recirculating water feature and unusable open space that does nothing but put further pressure on other areas for open space and recreation. Dreiseitl sold the residence in that area a bill of goods with his fancy video presentation and blue jump suits. The park isn't even a very comfortable place to hang out, much less a thing of beauty.

[Brian Libby]

Aneeda, appreciate your opinion but I don't completely agree. I like the idea that not every open space is about recreation and tons of people spending time there. Given how solidly nearby Jamison Square Park fills that role, with kids frolicking and such, I appreciate that Tanner Springs Park is its opposite.

The ecology at Tanner is admittedly far more symbolic than literal. But symbolism isn't wholly without value either. Whenever I'm in this neck of the Pearl, I enjoy spending time sitting on the steps of Tanner and getting a little Zen moment in the center of the city.

[billb]

Mudd , good thoughts ! I might go one step further and require all new buildings to have water storage tanks built in , to capture 90 % - ish of all rainwater for re-use. Dream Big !

[Lyle]

Brian,
Your note about Tanner Springs Park above, could have been written by me. I'm glad that Jamison Park is popular but I really appreciate the tranquilty of Tanner Springs Park.
thanks,
Lyle

[Linder]

Mudd, I am in favor of decentralized treatment, which is one reason spending a ton of money on the the "big pipe" seems like a bad idea.

The “Cost Benefit Evaluation” to which Stephen linked (thank you Stephen) seems to indicate more data is needed. Under the “Certainty of Information” section, the evaluation states, “Many reports describe costs and benefits qualitatively or without documentation. Furthermore, limited information exists on Portland-specific performance, cost or benefits.”

Given that is evaluation represents a possible rosy scenario, so to speak, the report states that an ecoroof can reduce run-off by 56% in the summer and 47% in the winter. A larger percent than I would think, but that still leave half the water needing further treatment.

[Linder]

Most of the cost saving in the Cost Benefit Evaluation comes from an assumed longer life span of an ecoroof (40 years) over a conventional roof (20 years). The evaluation states, “Not needing to replace or significantly improve the conventional roof twice would provide an avoided cost of $600,000.” Wouldn’t the ecoroof only save one replacement, as at the end of the 40 years the ecoroof would also need to be replaced? Am I missing something?

The evaluation does not indicate how much more an ecoroof would be to replace on an occupied building or repair compared to a conventional roof. The evaluation seems to only take into account the original new installation cost of the ecoroof.

Furthermore, under “Ecoroof Construction Costs” the evaluation states, “Ecoroofs vary greatly in cost.” and “For the purposes this evaluation {sic}, a simple ecoroof that represents the bare minimum components that will function effectively in Portland’s climate”.

[Mudd]

Yeah, yeah. Sure, Linder, sometimes the math doesn't add up perfectly. Luckily, the design world isn't made up of mathematicians making all of the decisions.

Green design cannot exist without beauty.

However, since you keep it up with the math, that other half of the stormwater could easily be consumed via additional synergistic strategies related to water. The only way we will ever get truly green buildings and sites is by looking at everything as inter-related. In this case, consume the other 50% of your stormwater thru rainwater harvesting for the occupants' non-potable needs as well as for productive gardens or other things that people can enjoy. Definitely, don't just put it in an expensive pipe in the ground.

[Stephen]

Linder,
I agree that more data is always a good thing, and the report I linked to is only one story. But if you're focusing on the separation of the sanitary and storm systems, which according to you we will "eventually have to do", some corrections are in order. The report states that the 56% reduction is average annual volume reduction, not the summer reduction as you described. The actual number stated for summer volume reduction is 86%. But perhaps most importantly, the peak flow reduction - or the reduction of flow at the highest flush of a storm - is 96%. As far as the combined sewer system is concerned, this is a very important number that bears mentioning.

[Linder]

Stephen, you are right to point out that the peak water flow reduction is one of the most important environmental benefits of an ecoroof, and sorry about misquoting the summer water data.

However, the implication of this post is that ecoroofs provide some type of improved habitat for wildlife, and help "to re-introduce nature and wildlife into the city" but to date I don't think that is the case. I would like to see ecoroofs that actually focus on creating habitat with native plantings, perhaps attempting to recreate an oak savanna.

So much habitat restoration work needs to be done in Portland's existing opens spaces, work with a proven record of accomplishment. I feel money spent on existing habitat restoration will yield wildlife that is more diverse if that is the goal.

As a birder in Portland for the last 18 years, I know we have been losing habitat and wildlife diversity in the city, though there are a few bright spots of restoration work.

[Linder]

Urban Habitats has a relevant report “Space for Urban Wildlife: Designing Green Roofs as Habitats in Switzerland,” by Stephan Brenneisen here:

http://www.urbanhabitats.org/v04n01/wildlife_full.html

The report outlines the importance of increased and varied substrate depth and natural substrate composition in support diverse pant, insect and bird life.

The paper quotes studies that “clearly showed the limitations of the roofs for supporting certain species” that could do reach the roof or could not survive the harsh dry summer conditions on a roof. In addition, “The size of the replacement habitat provided by green roofs is also a limiting factor. In the recent study (Brenneisen & Hänggi, 2006), the shunting yards cover several hectares and are thus in a different order of magnitude to a typical green roof”.

Given the increased requirements of a diverse habitat supporting ecoroof and the relative abundance of natural habitat in Portland in comparison to Basel or London, I am convinced that investing limited money in restoring our existing natural habitats would have a much greater impact on wildlife for years beyond the limited life of an ecoroof. In addition, the best opportunities for ecoroofs would appear to be on very large roofs on the outskirts of the city, such as the Swiss rail “shunting yard” or the Stucki Shopping Center in Basel, which is “roughly half the size of all the greenroofs in Portland.”

[[name removed - spam]]

Don't you envy the freedom of birds, that they can fly without mechanical assistance? And no ticket needed!

[[name removed - spam]]

I need information on Eco roofs like the cost and everything?
If u have a normal roof (slanted at points) can you still have an eco roof and can you plant vegetables or flowers on it? How much would the whole thing cost? You would have to get the plants changed in winter right? How much would that cost?