Estimating the Environmental Effects of Green Roofs

Green Roofs are making a difference in Kansas City. JBC is pleased to have contributed to this new report. 

The EPA is excited to introduce a new case study demonstrating the environmental and health benefits of green roofs in Kansas City, Missouri, Estimating the Environmental Effects of Green Roofs. The case study lays out a replicable analytical framework that state and local decision makers can use to assess the multiple benefits of green roofs, including stormwater runoff reductions and public health improvements. 

Estimating the Environmental Effects of Green Roofs: A Case Study in Kansas City, Missouri (PDF)

Street Trees Really Do Make People Healthier

Jason G. Goldman

It’s easy enough to claim that being in nature makes people feel better. It certainly feels like it’s true. A weekend in the mountains, or even a few hours in a park after a long day at work, truly feels like it is somehow restorative.

There are some good reasons to believe that green space could have a causal relationship with health and happiness. For one thing, trees scrub pollution from the skies, allowing those nearby to breathe cleaner air. Exposure to nature has also been linked with reduced blood pressure and stress, and it seems to motivate folks to become more active and less sedentary. Then there’s the Japanese practice of shinrinyoku, or “forest bathing.” The Japanese believe that what essentially amounts to a nature walk promotes human health and wellbeing. Plants are also part of a complex food web that, together, provides things critical to our survival like oxygen to breathe, fresh water to drink, and food to eat. Even if all these things are true – and they probably are – that still doesn’t mean that it’s nature, per se, that’s having the apparent health benefit.

To make that claim we need real, quantifiable data. That’s where University of Chicago psychology graduate student Omid Kardan and University of Chicago professor Marc G. Berman come in. They and their colleagues looked to Toronto, Canada, a city for which there is plenty of satellite imagery (which allows them to measure green spaces) and self-reported health information through the Ontario Health Study. By using a set of common statistical techniques, the researchers were able to really see whether there’s anything to the idea that greenery makes people healthier.

But it wasn’t green spaces in general they were interested in; it was trees in particular. By leaving lawns and bushes out, the researchers hoped to zero in on what they thought was “potentially the most important component for having beneficial effects.” First, they took data on trees from two databases maintained by the city of Toronto: “Street Tree General Data” and “Forest and Land Cover.” Together, those databases provided information on street trees as well as those in parks and backyards. They chose Toronto in part to rule out the effects of health insurance; unlike in the US, Canadians are guaranteed universal publically funded healthcare, regardless of employment status or income level. Still, despite equal access, not all Canadians choose to avail themselves of healthcare in equal ways. Indeed, those with lower incomes and fewer years of schooling tend to see doctors less often, which is why the researchers made note of that sort of demographic data.

They found that those who live in areas with more street trees reported better health perception than those in neighborhoods with fewer trees. Regardless of their actual health, they felt they were healthier. But it turns out they were actually healthier too: they suffered from fewer cardio-metabolic conditions.

But that’s not all. To really drive the point home, Kardan reduced the findings to cold, hard cash.

His team found that by planting 10 more trees per city block, Toronto could improve health perception as much as if every household on that same block earned $10,000 more every year, or magically became seven years younger.

The results were even more striking for actual health. Planting just 11 more trees per city block would reduce cardio-metabolic conditions the same extent as if everybody living on that block earned $20,000 more each year or somehow became 1.4 years younger.

So what’s the secret? Kardan doesn’t know, and his study isn’t explicitly designed to get at the underlying mechanism. But a close look at the data offers up a suggestion. It wasn’t proximity to trees in a neighborhood that was the most important variable, but the number of trees on the streets. That suggests that it’s not necessarily that the trees are themselves providing important services (they do that, though that might not be what accounts for these health effects). Instead, it could be something as simple as peoples’ ability to literally see trees, and the most common place for most people to see trees is on the street. It’s also possible that street trees are disproportionately responsible for capturing street pollution, and that could be driving the team’s findings.

Maintaining a street tree for a year costs between $30 and $500, depending on where it is. In other words, planting ten or eleven trees per city block would be far cheaper than paying everyone $10,000-20,000 more each year. That should be good news for city planners.

http://conservationmagazine.org/2015/07/street-trees-really-do-make-people-healthier/

Stormwater Master Class Series at Forester University Expands

Jeffrey L. Bruce FASLA is now teaching Fundamentals of Green Infrastructure for the Post-Construction Stormwater BMPs Master Class Series at Forester University.

http://www.foresteruniversity.net/masterseries-postconstruction-Stormwater-BMPs.html

The Next Generation of Infrastructure

Shanghai, China. Image © Scott Muller

by Scott Muller

The next generation of urban infrastructure will not be built. This is to say, that a sustainable future will not come from new technologies. Urgent demand is already overwhelming adequate risk management and urban governance capacities. While indeed carbon-free light rail, driverless cars and desalination plants will be in unquenchable demand, none of it will happen successfully without a bankable environment that aggressively manages the social, political, financial and environmental risks of new infrastructure. The barriers to the next generation of infrastructure [1] are neither technical nor financial; rather they’re social and political. Effectively responding to the unprecedented need for urban infrastructure hinges on the successful process over the high-tech outcome.

New Urban Dynamics

Cities have replaced national governments as the de facto drivers of global economic growth and human development. In fact, 300 of the largest metro economies worldwide, containing just 19% of the world’s population, delivered nearly half of the global economic output in 2011 [2]. A recent analysis by the McKinsey Global Institute reveals that by 2025, more than two thirds of global GDP will be produced by just 600 cities – the majority of them in emerging countries [3].

But importantly, economic growth does not alone create stability. Spanning from the least to the most developed, the fate of cities is one of increasing vulnerability to climate change, resource scarcity and rapid population growth.

Hyper-Urbanization

By the year 2030 world urban population will increase to nearly 5 billion persons (1.35 billion more than present), increasing the planet’s urban area by an astonishing 150% in less than 20 years. Sixty percent of the area to be urban by 2030 has yet to be built [4]. Contrary to the trend of the 20th century, the majority of this urban growth (and commensurate economic growth) will occur in developing countries and mainly in second-tier and lower cities. From now to 2030, the world will need to build the equivalent of a city of one million people in developing countries every five days. Their intense demand for the rapid construction of new infrastructure threatens their already challenged risk management and urban governance capacities.

Nexus Issues

Incongruous to this rapid urbanization, is the reality that current growth is no longer supported by sustainable inputs, as we are already 50% in “overshoot.” In other words, human systems are presently using 50% more than the annual productivity and assimilating capacity of the planet’s ecosystems [5]. This unsustainable consumption of ecosystem services to subsidize the growth of cities is progressing ever farther along the urban-to-rural gradient. One result is an ominous energy-water-food nexus of demand confronting city, regional and national decision makers.

As urbanization reaches farther beyond its geopolitical borders to satisfy ever-greater metabolic demands, rural communities and families are linearly assimilated into “foreign” urban economies, with marked social and cultural impacts. Families with rural legacies can be insurmountably challenged by joining an urban economy yet remaining spatially disconnected from services. In the end, urban migration is more often not so much a quest for economic prosperity, as it is a survival strategy for the rurally displaced.

Climate Change

Continued urban development is made more complex by a third, interrelated, crosscutting element: climate change. Increasing climate disruptions are changing the fundamental rules of city planning and administration. Rapid climate change is altering both the risk (threats) and the fitness (responses) landscapes of cities. Unfamiliar risks and new statistical criteria have rendered historical “business-as-usual” strategies increasingly ineffective and detrimental with direct implications on safety, quality of life and the economic performance of cities. Uncertainty is now a fundamental core element of urban development, along with non-linear growth patterns, runaway positive feedback/ cascading failures, hidden thresholds and irrevocable tipping points. The rapidly reshaping insurance industry is but one example of shifting solutions – with increased disaster intensities and frequencies, the utility of insurance to guarantee major new infrastructure investments becomes increasingly untenable.

Manchay, Lima, Peru. Image © Scott Muller

The Managerial and Policy Challenge

As urban economies mature in developing countries, and as cities become increasingly more vulnerable, their decision-making power is rising and yet becoming more complex at the same time. The speed of urbanization and the new risk landscape present a profound managerial and policy challenge for municipalities. Cities and metropolitan governments are now obligated to deal with exponential rates of urban immigration; protect and conserve the surrounding landscapes and ecosystem services sourced outside their geopolitical boundaries; ensure sufficient energy supplies for their industry and residents; finance, construct and maintain hard infrastructure; respond to the pressing challenge of sea level rise; attract private industry and foreign investment; negotiate with multilateral development banks (MDBs) and engage with foreign government official development assistance (ODA).

Spanning from the least to the most developed, the fate of cities is one of increasing vulnerability to climate change, resource scarcity and rapid population growth. The fate of the world has become the fate of cities. There has emerged with great immediacy, a revolutionary worldwide discourse on how to best make cities more sustainable: building resilience, enabling transformation and de-risking the economy.

Addressing Vulnerabilities

The thoughtful development and management of new infrastructure is a powerful way to de-risk cities. But often overlooked in the speculative, investment driven rush to build, is the fact that infrastructure impacts the sustainability of urban systems in several ways; some of them less immediately apparent to elected officials.

Infrastructure’s impact on urban sustainability includes positive performance gains, but additionally, it can also create negative pathway dependencies and the commensurate loss of “optionality.” However, thirdly and most importantly, the demand for urban infrastructure creates a unique circumstance – when often disparate socioeconomic groups briefly share an orbit around an issue involving a public good or a common pool resource. This is a critical opportunity to generate and strengthen urban social capital – the key success attribute for the next generation of infrastructure.

Estimates suggest that US$ 53 trillion must be spent on infrastructure worldwide by 2030 to adequately manage the rapid growth of cities [6]. In 2011, the High Level Panel on Infrastructure for Recommendations to the G20 pointed out that the key constraint to infrastructure development is not a lack of funding. After all, financing can technically be created to support low-risk investments. Rather, they identify the principal barrier to rapid infrastructure development as the absence of a strong pipeline of bankable projects [7]. This is to say, infrastructure projects must be low-risk to qualify as “bankable.” Infrastructure in developing countries is an asset class highly vulnerable to political, regulatory and execution risk. Therefore, managing the social, political, financial and environmental risk of infrastructure projects should be the priority when pursuing the performance gains of new infrastructure.

The most important investment a city can make today is developing integrated, cross-disciplinary capacity within the “infrastructure development process,” and the commensurate tools and methods to mitigate the social, political, and financial risks. Building this systemic capacity allows successful urban development along a range of fronts, among them the “next generation” of infrastructure.

To create goal-seeking behavior towards sustainability and avoid the development of unsafe slums and unsupportable resource-intensive path dependencies, it becomes essential that all sectors of civil society have a seat at the table to participate in the selection, design, launch, management and perhaps ownership of infrastructure projects.

Collective Actions and Horizon Lines

Cities are Human-Environment Systems (HES), appreciably comprised of common pool resources and public goods. These interact in ever-shifting equations to one day ostensibly arrive at an equitable, circular economy.

HES are considered to be complex adaptive systems because they consist of influential, interacting smaller systems that self-organize as a whole. As they grow, the challenging issues of overuse and equity must continually be addressed. More specifically, growing cities are subject to social dilemmas and the problems of collective action and inter-temporal resource allocation. Collective action challenges in cities relate to the fact that individuals and subgroups make decisions based on particular desires without considering the impacts their decisions may have for others in society. Inter-temporal resource allocation dilemmas involve individuals and subgroups making decisions locally in time (short time horizon, or equivalently applying a high discount rate) without considering the long term/ global consequences of these choices.

As a complex adaptive system, HES can demonstrate goal-seeking behavior. So it is important to point out that the rapid expansion of cities is not impeded by the absence of adequate planning, transportation, housing, finance or attention to risks. Rapid urbanization occurs whether infrastructure is planned or not; “electricity and cable are first stolen and later gentrified” [8]. To create goal-seeking behavior towards sustainability and avoid the development of unsafe slums and unsupportable resource-intensive path dependencies, it becomes essential that all sectors of civil society have a seat at the table to participate in the selection, design, launch, management and perhaps ownership of infrastructure projects. Citizen access to and participation in public decision making, along with building coalitions and multi-sector partnerships will not only significantly increase the success of infrastructure projects, it will also unlock latent circular economies and subsequently advance the sustainability of the Human-Environment System.

The Renewable Power of Shared Learning

One method to efficiently enable integrated capacity and multi-sector collaboration along the infrastructure development process is by creating peer learning environments among municipal government officials as well as civil society. Research demonstrates that the bottom-up accumulation of knowledge by professionals via peer-to-peer learning experiences is one of the most important factors in the types of projects and policies that make their way into successful strategic planning and policy proposals [9]. Peer learning builds capacities of all stakeholders and decision-makers, promoting effective functioning beyond a single project, including the next generation of infrastructure.

Over the past four years, the Institute for Sustainable Communities (ISC) has developed a methodology for creating shared learning environments, culminating in the organization of Sustainable Community Leadership Academies (SCLA) with the explicit purpose to accelerate urban climate adaptation and sustainability [10]. These intensive three-day academies bring together 10-15 multidisciplinary teams of 5 or 6 senior level practitioners and municipal government officials from cities and metropolitan areas. To date, teams from more than 400 cities have participated in these Leadership Academies, generating a wealth of results, tools, and networks that can accessed by anyone.

Seoul, Korea. Image © Scott Muller

This past April 15-17 in New Orleans, Louisiana, the Mississippi Sea Grant Consortium [11] and ISC kicked off an 8 month “Gulf Coast Community Resilience Program.” Utilizing ISC’s peer-learning methodology, leaders from 6 Gulf Coast communities created an informal network to advance and accelerate resilience. During the workshop, the practitioners shared experiences and tools, each identifying two to three key implementation ideas to apply in their communities over the summer. Tailored technical assistance within the informal network will help the participating Gulf Coast communities apply their resilience implementation ideas. In the fall, the same six communities will come together again for a follow-up Climate Leadership Academy (CLA) to share results and lessons learned, solidifying the informal network.

One highlight during the April CLA plenary was when Dr. Pam Jenkins of the University of New Orleans’ CHART [12] Program facilitated a community mapping clinic. Using a structured process, each community team identified coastal adaptation initiatives that led to “therapeutic” or “corrosive” communities. For example, after the recent Deepwater Horizon Oil Spill, factions with differing interests and opinions on financial settlement options led to a “corrosive” community atmosphere. On the other hand, after recent natural disasters, many teams sponsored “therapeutic” community celebrations that featured actionable dialogue on coastal adaptation strategies. As a result of the clinic, community leaders now have the tools to foster therapeutic approaches for the design of climate-adaptive infrastructure choices.

Internationally, another contemporary example of cities using peer learning to develop the next generation of climate-adaptive infrastructure is occurring in Southeast Asia. ASEAN [13] cities are some of the fastest growing in the world, and yet at the same time, some of the most vulnerable to climate change – forcing more adaptive approaches to urban development. As a result, city practitioners across the region are designing and building more resilient, ecologically integrated urban infrastructure, engaging their populations in inclusive decision-making, and collaborating across jurisdictions. These activities are generating innovations and investment opportunities that are shaping growth throughout the region. In a partnership between U.S. cities and ASEAN member states, ten teams of senior municipal officials from second- and third-tier cities will be participating in an SCLA on Urban Adaptation next August, [14] with a primary focus on sharing lessons of managing the social, political, financial and environmental risks of urban infrastructure. After the SCLA, a selection of cities will participate in partnerships with U.S. Cities to gain more exposure to innovative approaches, good governance tools and appropriate infrastructure technologies.

The results of ISC’s Leadership Academies across diverse cities and broad geographical range, support the research that concludes shared learning environments and exchange among practitioners can effectively overcome information overload as well as resource constraints, spawning innovation and greatly increase the likelihood of policy transfer [15]. What’s more, peer learning affords practitioners the ability to not only learn from their colleagues, but also to teach them – offering a sense of empowerment. Growing and strengthening the leadership capacity of these municipal leaders builds the overall profile of the profession – the resources generated from peer learning provides a core knowledge base for city sustainability practitioners and civil society organizations.

Going Forward

So while infrastructure is a key physical and technological asset of cities – representing critical capital investment – more important is the knowledge, shared ownership and collaboration that the next generation of urban infrastructure embeds in the Human Environment System. Successful public infrastructure is a legacy to the surmounted social dilemmas, collective action challenges and path dependencies resolved leading up to its construction.

The next punctuated equilibrium will not come from advanced or new technologies. Rather it will emerge from shared learning, multi-sector coalitions, integrated planning, public-private partnerships, the skillful advocacy of civil society and good governance. This is how to best reframe urban development and economic growth to include the capacity of the biosphere.

References

[1]  The next generation of infrastructure is defined by its service to urban sustainability.

[2]  Metropolitan Policy Program, Global Metro-Monitor 2012: Slowdown, Recovery, and Interdependence. (Report, Brookings Institution, 2012).  Accessible at http://www.brookings.edu/~/media/research/files/reports/2012/11/30 global metro monitor/30 global monitor.pdf

[3]  McKinsey Global Institute, 2012.  Urban world: Mapping the economic power of cities. (Report, McKinsey & Company, March 2011) Available at http://www.mckinsey.com/~/media/McKinsey/dotcom/Insights and pubs/MGI/Research/Urbanization/Urban world mapping economic power of cities/MGI_urban_world_mapping_economic_power_of_cities_full_report.ashx

[4]  Seto, Karen C., Burak Güneralp, and Lucy R. Hutyra. “Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools.”Proceedings of the National Academy of Sciences 109, no. 40 (2012): 16083-16088.

[5]  Wackernagael, M. et. al. 2002. “Tracking the ecological overshoot of the human economcy.” Proceedings of the National Academy of Sciences. July 9, 2002 vol. 99 no. 14

[6]  OECD, Strategic Transport, Infrastructure Needs to 2030.  (Report, OECD, March 2012) ISBN 978-92-64-16862-6.

[7]  Thiam, Tidjane -Chairman. High Level Panel on Infrastructure, Recommendations to G20 (Final Report. 26 October 2011).

[8]  Brand, Stewart. Whole earth discipline; an ecopragmatist manifesto. Atlantic Books, 2010.

[9]  Marsden, Greg, Karen Trapenberg Frick, Anthony D. May, and Elizabeth Deakin. “Bounded rationality in policy learning amongst cities: lessons from the transport sector.” Environment and Planning A 44, no. 4 (2012): 905-920.

[10]  “Sustainable Communities Leadership Forum,” Institute for Sustainable Cities. Accessed 5/22/2013 at http://sustainablecommunitiesleadershipacademy.org/

 [11]  NOAA, “Home” Mississippi-Alabama Sea Grant Consortium. Accessed 5/22/2013 at http://sustainablecommunitiesleadershipacademy.org/

[12]  “Center for Hazards Assessment, Response & Technology,” University of new Orleans. Accessed 5/22/2013 at http://sustainablecommunitiesleadershipacademy.org/

[13]  Association of South East Asian Nations

[14]  “A Climate Leadership Academy on Urban Adaptation: From Risk Barrier to Results,” ICMA, CityLinks and USAID. Accessed 5/22/2013 at http://icma.org/en/cl/news/events/climate_leadership_academy

[15]  McCann, Eugene. “Urban policy mobilities and global circuits of knowledge: toward a research agenda.” Annals of the Association of American Geographers 101, no. 1 (2011): 107-130.

http://landscapeurbanism.com/article/the-next-generation-of-infrastructure/

Jeffrey L. Bruce & Company Opens New Office in Iowa

NOAA Southwest Fisheries Green Roof, La Jolla, CA

 

We are pleased to announce that in order to better serve our rapidly expanding practice, JBC has opened an Iowa office. Des Moines has been a great location for us to grow and expand our business. There is an exceptional pool of local talent and a great network of businesses to work with and share ideas. We are looking forward to an exciting future and aim to continue growing our staff and services.

www.jlbruce.com

Condition of Vegetative Roofs Years After They're Exposed to the Real World.

In KieranTimberlake's extensive survey of roof gardens, it identified species that were planned, had thrived, or were rogue (l to r, respectively): prairie dropseed (Sporobulis heterolepsis); two-row stonecrop (Sedum spurium fuldaglut); moss pink, pink phlox (Phlox subulata) Credit: Bruce Peterson

It’s one thing to Photoshop a green roof into a rendering; it’s another thing to plant and sustain one. And it’s all but unheard of to go back and analyze the state of these living roofs years after their completion, as Philadelphia-based Kieran Timberlake did for its groundbreaking Green Roof Vegetation Study. The study responds to “a lack of long-term data on real buildings with diverse and dynamic plant communities,” according to the firm. Instead of concentrating on one engineering or horticultural aspect of green roofs, the firm looked at “how green roofs function as ecosystems and how they change over time.”

The jury highlighted two innovative aspects of the study: its comparative method and its ecological thesis. In 2011 and 2012, Kieran Timberlake surveyed six of its completed green roofs, ranging in area from 1,744 to 10,000 square feet, and designed between 2003 and 2011. Using the Relevé vegetation survey method and the Braun-Blanquet abundance scale to quantify its findings, Kieran Timberlake assessed the roofs’ vegetative cover, species richness, and species diversity in 2-meter-square sections. The researchers also interviewed facilities and grounds maintenance personnel at each site. Juror Bill Zahner praised the study’s “way of collecting the data needed rather than saying, ‘Well, let’s just put seeds down and keep our fingers crossed.’ ” Juror Jing Liu agreed: “What they’re doing is different. The research is to study the long-term dynamics of green roofs.”

The resulting report confirms that roof ecologies are indeed dynamic and that changes will occur spatially and over time from the original planting design. More importantly, it details the nature of those changes, and raises questions about what the changes might indicate for long-term resiliency. In many of the case studies, the prevalent species observed on the roofs in 2012 that were part of the initial planting design were accompanied by dozens of new or “emergent” species. Artemisia (commonly known as mugwort) at the Yale Sculpture Building and Melilotus (or sweet clover) at Cornell University’s Alice H. Cook House independently found their way to roof tops, took root, and eventually made themselves at home in the roofscape design. Roof biodiversity often increased, although the report cautions that the results of any single survey could be deceptive: “What appears to be major shifts in species composition may in fact be short-term fluctuations or cycles caused by unpredictable changes in experienced climate and environmental conditions.”

While the report rigorously maps the distance between design intent and material outcomes, it also sets the stage for even more radical research to be conducted on the interplay between landscape and architecture. Kieran Timberlake envisions deploying sensors on the roof to measure thermal and moisture conditions in relation to the building’s internal climate and energy consumption. The report also suggests that architecture “is responsible for the … vegetative dynamics and ultimate performance of the roof.” On the roof of a dining hall at Middlebury College, for example, the otherwise feeble grasses and forbs become lush and verdant around the skylight cones, whose shade presumably helps the soil retain moisture. “Architectural design creates microclimates across a roof, determining availability of sunlight, water, and nutrients,” the report states.

Kieran Timberlake is already putting its newfound knowledge to use on the forthcoming Penn State Center for Building Energy Education and Innovation at the Philadelphia Navy Yard, which itself will serve as an ongoing laboratory and teaching center for scientists, students, and professionals interested in eco-effective architecture. The firm has developed a proposal to create a green roof test bed on this building; currently, it is in the process of raising funds.

But documenting the consequences of a designed green roof subjected to unforeseeable or uncontrollable environmental forces has wider implications for architecture in general, juror Jing Liu said. “If you think of the green roof as an ecological system, you can have architecture as an ecological system,” she said.

In the messiness of the real world, architecture depends on dynamic variables. Buildings are never really complete. Rather, they are subject to the vicissitudes of client maintenance regimes, the inconsistencies of occupant behavior, and the unpredictability of weather. That is why post-occupancy studies—of both indoor and outdoor environments—must be as meticulous as they are fearless.

Project Credits 
Project Green Roof Vegetation Study 
Design Firm KieranTimberlake, Philadelphia 
Project Team Roderick Bates, Stephanie Carlisle, Billie Faircloth, AIA, Stephen Kieran, FAIA, Taylor Medlin, Assoc. AIA, Max Piana, James Timberlake, FAIA, Ryan Welch

 

 In 2005, when Kieran Timberlake planned the green roof of Cornell University’s Carl L. Becker House, in Ithaca, N.Y., the rigorous planting plan comprised three types of succulents (two-row stonecrop, tasteless stonecrop, and houseleeks), combined with strips of prairie dropseed. When Kieran Timberlake surveyed the roof in 2012, the vegetation was healthy and full, but there were a few surprises—54 of them, in fact. That is the number of new plant species that had taken root over the years.

An aerial view of Cornell campus dormitories shows Kieran Timberlake's green roofs outlined in white; the Carl L. Becker House is at the right side of this image. Credit: Kieran Timberlake

According to KieranTimberlake's study, the most biodiversity was found in the Becker House's southernmost bay, where shading along the adjacent building edge minimized the effects of record droughts.

 

Various poplar species were found on the Becker House roof, despite not appearing in the original roof planting plan.

Credit: Kieran Timberlake

http://www.architectmagazine.com/green-building/green-roof-vegetation-study.aspx



Reconsidering the Underworld of Urban Soils

by Laura Solano

Look down. If you are in a city or large town, below you is a vast network of hidden systems that support your life: pipes that carry natural gas, potable water, stormwater, sewage, and communications wires. These pipes rarely come to mind, but we agree that their operation is for the common good, that survival is not possible without them, and that armies of workers should keep them running. Surrounding those pipes are soils that are equally critical to our existence but to which we give much less attention. If we truly understood the delicacy of soil as a dynamic living system integral to the health of our towns and cities, our neighborhoods and families, we would be more cautious about how it is perceived, treated, and protected. Healthy soil performs important functions such as sequestering CO₂, mitigating stormwater runoff, supporting plant life, and sustaining the microbial populations that form the basis for all living things. So essential and complex are the conditions for soils in more developed areas that a new branch of science has arisen and is now being intensively pursued: the science of urban soils.

The Challenges of Urban Soils

Urban soils are are naturally-occurring soils that have been disturbed by development in a way that affects their functioning and properties. Urban soils are distinguished by a number of similar features: Their horizons (the natural vertical order of soils) have become jumbled by excavation. This makes urban soil horizons confoundingly diverse; one layer may be hospitable, but adjacent layers may not be, creating abrupt changes that can cause impermeable interfaces. Soil structure (the balance of solids and pores) has been crushed out of existence by mechanical compaction that chokes off water and air exchange. Organic matter (the source of plant nutrients) is low or missing from lack of replenishment, and this imbalances the soil biological community (bacteria, fungi, nematodes, arthropods, earthworms, insects, and more). Soil volumes that are important for plant health decrease because of interruptions from urban debris such as construction waste and rocks. Finally, the predominance of pavement separates soils from natural inputs such as nutrient-rich leaf litter, and this separation causes the nutrient cycling system to slow or shut down.

In the urban environment, soils are likely to be sealed off from the agents that build healthy soil—including wind, precipitation, ice, temperature, gravity, and mineralization—which frequently have been replaced by anthropogenic processes detrimental to soil functioning. Urban soils often become defined by human activities and land use histories at a particular location rather than by the continuum of geologic processes. This disrupted order makes urban soils particularly challenging to analyze, manage, and construct.

Urban Soils in the Service of Stormwater Management

Urban soils have the potential to be an important partner in stormwater management, use, and protection. The Natural Resources Conservation Service has recognized that soils with good infiltration and permeability can significantly reduce stormwater runoff rates and volumes that might otherwise overwhelm and impair the performance of the chain of water bodies that sustain our water supplies and the ecosystems that are necessary for healthy living [1]. Good infiltration reduces runoff by letting water soak into soils before it builds up to damaging volumes and velocities that would erode topsoil and carry both silts and pollutants to waterways. Permeability influences how quickly absorbed water drains through soil to useful depths for plants and recharge. Water that reaches root zones reduces irrigation needs. Some soil can filter toxic compounds or excess nutrients by holding them, degrading them, or otherwise making them unavailable. All of these benefits are feasible when soil has adequate pore space, which is only possible when soil’s natural physical texture and structure have been preserved or created.

Over-compaction of soils is one of the greatest deterrents to implementing best practices for stormwater management, because crushed particles minimize pore space and prevent water and air from moving through. In a study by the University of Florida, soil compaction from construction vehicles reduced infiltration by 70 to 90% [2].  This is perilously close to impermeable pavement.While people recognize that reducing pavement is the primary way to improve stormwater management, few see the same connection with soil. It is not enough to substitute pavement with plant beds if nothing has been done to prevent construction compaction. Without a soil management plan that includes practices for dealing with compaction before, during, and after development, urban soils will continue to become, plot by plot, a decommissioned resource in stormwater management.

 A Partnership between Urban Soils and Vegetation

The greatest positive effect of healthy urban soil is most evident in plants, the workhorses of the environment that clean the air, absorb CO₂, abate high temperatures, support wildlife, slow stormwater runoff, and keep erosion in check. In recent years, there has been resurgence in support for increasing the vegetation and tree cover in American cities. We are well aware of the positive ecological, social,[3]  and economic value of plants for individual properties, community open space, and urban regions [4]. Ecologically, a single large tree in the city is said to be ten to twenty times more beneficial to the environment than a single tree in the forest [5]. Yet the health of urban trees is declining at a rapid rate. A recent study by the U.S. Forest Service looked at twenty cities and found that they are losing tree canopy cover on average by 3% per year [6]. While this loss may seem small, over time the cumulative effects are severe. For example, Washington, D.C. lost 64% of its acreage-coverage from 1973 to 1999 at an average annual rate of 2.5% [7]. Still we continue to ignore the most basic need of trees: healthy soils. On most urban sites, fertile topsoil is absent, plant roots are restricted, air and water movement is suppressed, and nutrients cannot be exchanged. All this puts plants at an extreme disadvantage. The evidence of poor soil is all around, telegraphed by unhealthy plants. So if trees are to become “beautiful utilities” as urban tree expert Henry Arnold [8] suggests, then soil must also be treated in projects as an essential utility: analyzed, engineered, budgeted, scrutinized, and maintained.

Advocating for Soil

There are sound economic reasons to invest in good soil. As one of the core infrastructural materials in every urban landscape project, soil needs only to be tended more carefully to make it a viable component of stormwater management. Using soils to store and retain water as part of the stormwater management system can reduce costs for piping, drainage structures, runoff storage tanks, irrigation systems, and infrastructure maintenance and can provide more flexibility in design, since hard systems can add horizontal and vertical complexity that limits design options. Plants (especially street trees) with well-functioning soil are more able to start and sustain the nutrient cycling system without big infusions of maintenance after establishment and in maturity. When they do get maintenance, they are more likely to respond. Healthy soils beget trees that live longer and grow bigger, enabling them to cast more shade, and absorb more CO₂, and runoff. Even asphalt benefits from healthy trees, since shade improves its performance and durability [8]. Last, trees in good quality soil are far less prone to infection and pests, virtually eliminating the need for chemical treatments [9]. Investing in soil is critical for the long-term health of urban trees and by extension for the success of sustainable landscape projects and green infrastructure programs.

Why then do urban soils get so little attention when they are such a critical part of our environmental infrastructure and, ultimately, of human well-being? Some of the unawareness stems from societal and governmental ignorance. While keeping water and air usable is an unquestioned necessity, few people have the same association with city soils. For the most part, urban soil is considered mysterious, complex, and costly. Design professionals have an important role to play in dispelling unwarranted concerns and helping solve tangible problems: They should lead the way, project by project, educating their clients, agencies, and others about the need for healthy soil. Before that happens, designers must step up their own soil education. My interactions with colleagues suggest a dearth of understanding of basic soil science and the need for soil management in landscape projects. Often other landscape architects reach out for soil advice only when something has gone wrong. Designers do however have a thirst for this information as is shown by the increasing number of packed sessions in soil education at the annual meeting of the American Society of Landscape Architects (ASLA), the professions’ largest organization. Perhaps the neglect is also due to the fact that soil is not yet a hip topic; it has no visual presence. For many, design attention is reserved for visual effects; the hidden, infrastructural elements of landscape have long been considered the domain of engineers and scientists.

In my work as a landscape architect at Michael Van Valkenburgh Associates, soil discussions begin early, sometimes in the concept phase and always by schematic design. Soil is always an item on the design checklist. Just as all practitioners request surveys to locate utility lines, we request USDA soil tests to understand what we have to work with. Partnering with soil scientists, we have learned to interpret laboratory tests so we can ask the right questions and frame discussions. We keep up with developments in soil science (biology is the big topic now), often consult allied professionals, incorporate quality control practices into our specifications, and closely monitor sourcing, blending, and installing of soils during construction. We consider soil rigorously, as we do any other product or system in our projects.
I don’t mean to imply that assuring good soil is obvious or easy; it is neither, even for a firm that has been attempting it for twenty years. Every project brings unique soil challenges and clients with different agendas. The client may be unfamiliar with non-traditional stormwater approaches and therefore reluctant to consider soil-dependent systems. Brownfield properties often have contaminated soil or no useful soil at all. In other kinds of properties, existing soils could be reused if amended, but space may be too limited to manage soil-blending operations. Sometimes soil chemistry is limiting. For example: elevated pH from concrete or limestone rubble can interrupt nutrient exchange and narrow plant selection; high salinity in soil near tidal waters wreaks havoc on water uptake and cellular structure in plants. Local contractors often have no experience with installing designed soils. In my experience, construction managers show little tolerance for any aspect of landscape construction that is dynamic, an inherent characteristic of soil in particular and landscapes in general. Unless we have a repeat client, the process of educating, convincing, and making monetary tradeoffs to get good soil starts anew on every project. Sometimes we battle the sins of others’ projects in which someone tried but failed to improve soils. Projects with unsuccessful or difficult soil processes often produce rumors that the landscape architect specified unrealistic soils that cost too much and slowed the schedule, even if the problem was caused by the laxity of a member outside the design team.

Repositioning Soil as Infrastructure

How can we begin a campaign for good urban soil? We can start by talking with city hall, one of the biggest makers of landscapes and planters of trees, about the importance of soil. How many of the thousands of landscapes planted every year include soil improvement? Atlanta, Detroit, Denver, Los Angeles, and many other cities have tree-planting programs. Ambitious past and current mayors like Richard Daley and Michael Bloomberg launched campaigns to plant a million trees. Despite current commitments to increasing urban vegetation through tree planting, under current practices the mortality rate for young street trees is shockingly high: Some studies have found that over twenty-five percent of newly planted trees die within two years of installation [10,11], wasting already strained public funds and leaving behind a depressing reminder of failed nature. Wouldn’t it be more strategic to forgo planning one million trees in poor soil and instead plant 500,000 trees in good soil? [12]

To be stewards of urban soils, we need to ask pointed questions early in and throughout projects and insist on satisfactory answers that ensure positive long-term results for stormwater and planting. When zoning requires developers to add or replace trees, we need to ask for more than in-kind caliper inches and to require a soil management plan. When contractors install soil, they need to treat it like the valuable commodity it is or bear the cost of remediation. State and municipal specifications (which are used by contractors defensively instead of proactively) already define which dirt is suitable for backfill—why not extend this thinking to include requirements for the type, procurement, handling, and installation of planting soil? Landscape architects and anyone else who works with the landscape need to heed these too. Such guidelines should not be overly technical or onerous. Plant species should be matched to soil conditions, especially its pH and water supply. Trees should be planted at the right elevation to expose the root flare so soil doesn’t suffocate the tree. Adequate soil volume (800 to 1400 cubic feet per tree) and shared root space to encourage root spread should be provided [13]. Soils should be arranged to mimic the horizons in nature in which the top is rich in nutrients, the middle has the correct structure to encourage root growth, and the bottom is drainable. To resist compaction and maintain water and air exchange, soils higher in medium-to-coarse sands (rather than easily compactable fine sands and loam) should be used, and limits on density should then be set. Wet or frozen soils should not be moved or installed. To promote water and air exchange, rootball zones in tree pits should be exposed and at least half of the surface area of a plant bed should be left open, or a simple aeration system should be installed. Well-aged compost should be used to to provide 5% to 10% organics to the top layer of soils. And last, utilities should be placed at least three feet from trees.

There are more technical elements and specifications to consider, especially for sites with no soils, but as Stuart Shillaber the superintendent of horticulture at Boston’s Rose Fitzgerald Kennedy Greenway Conservancy advised me recently about introducing organic maintenance, “be happy when someone can implement 60% of the program. The rest will come when clients see results.”

The installation and upkeep of our existing “hard” utility systems requires substantial public and private investment. Creating well-functioning soils would not require large funds from the public since this work can be achieved project by project.  Upkeep of hard utilities is costly and disruptive; not so for soils that can be tended several times a year with substantially less trouble. The ASLA estimates that every year nearly 4.6 million acres are affected by public and private landscape projects [14]. Making headway on a quarter to third of that amount would start a revolution.

The Future of Urban Soils

From my vantage point, prospects for improving urban soils are good. In my thirty-year career as a landscape architect, there has never been a time of greater interest, research, and resources for managing urban soils and as many successfully constructed projects using urban soils. Advocacy for higher quality soil is rising nearly forty years after Dr. Phil Craul (professor emeritus at SUNY) and his colleagues started the field studies on urban soils that led to his 1992 publishing of the seminal Urban Soil in Landscape Design. Today, the USDA’s National Resources Conservation Service has substantial mapping, literature, and research on urban soils [15]. Ted Hartsig, a division chair of the Soil Science Society of America, tells me that the organization recently formed an urban soils division and committee whose focus is issues of urban soils including morphology and classification, the relationship of chemicals and nutrient quality, physics, biology, and structure, as well as the restoration and management of these soils. Urban soils studies are proliferating at public and private universities like Johns Hopkins and Kansas State.

Most critically, the public is starting to understand at the personal level of their gardens that the old adage “better to put a $5 tree in a $50 hole than to put a $50 tree in a $5 hole” is correct. Remember that until professionals and individuals teamed together to demand action, climate change was downplayed. Landscape architects and other professionals must play a part, whether through projects, lobbying our government, writing articles, lecturing, self-education, or speaking up in any propitious situation. We can be plausible leaders in the discussion to invest in another underworld utility, the first that is purely for the public good.

References

[1]  Soil Quality Information Sheet. Soil Quality Indicators: Infiltration”, Natural Resources Conservation Service, USDA, January 1998 http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_019144.pdf

[2]  J.H. Gregory, M.D. Dukes, P.H. Jones, and G.L. Miller, “Effects of urban soil compaction on infiltration rate,” Journal of Soil and Water Conservation, Volume 61, Number 3. http://abe.ufl.edu/mdukes/pdf/stormwater/Gregor-et-%20al-JSWC-compaction-article.pdf

[3]  Geoffrey H. Donovan, David T. Butry, Yvonne L. Michael, ScD, Jeffrey P. Prestemon, Andrew M. Liebhold, Demetrios Gatziolis, Megan Y. Mao, American Journal of Preventive Medicine, “The Relationship Between Trees and Human Health: Evidence from the Spread of the Emerald Ash Borer,” Volume 44, Issue 2, pp. 139–45, http://www.ajpmonline.org/webfiles/images/journals/amepre/AMEPRE_3662-stamped_Jan_8.pdf

[4]  “Statistics on the Economic Value of Trees,” Conservation Montgomery, http://conservationmontgomery.org/resources2.html

[5]  “Study: Nations urban forests losing ground; New Orleans, Albuquerque, Houston losing Trees.” News Release, USDA Forest Service, February 23, 2012, http://www.fs.fed.us/news/2012/releases/02/urban-forests.shtml

[6]  Stephen C. Fehr, “Mayor Working To Keep It Green; Williams Pleads For More Trees,” Washington Post, November 17, 1999, http://caseytrees.org/wp-content/uploads/2012/02/02.01.1999-original-article-washingtonpost.pdf

[7]  Henry Arnold, “Sustainable Trees for Sustainable Cities,” Arnoldia, Volume 53, Number 3, 1993, http://arnoldia.arboretum.harvard.edu/pdf/articles/1993-53-3-sustainable-trees-for-sustainable-cities.pdf

[8]  E. Gregory McPherson and Jules Muchnick, “Effects of Street Tree Shade on Asphalt Concrete Pavement Performance,” Journal of Arboriculture, Volume 31, Number 6, November 2005, 303, http://www.fs.fed.us/psw/publications/mcpherson/psw_2005_mcpherson001_joa_1105.pdf

[9]  “Basics of Organic Maintenance”, UMass Extension, Center for Agriculture, http://www.extension.org/pages/62978/basics-of-organic-landscape-maintenance

[10]  “New Research Survey Suggests Urban Trees are On the Decline,” Public Radio International, March 16, 2012, http://www.pri.org/stories/science/environment/new-research-survey-suggests-urban-trees-are-on-the-decline-8967.html

[11]  Jacqueline W.T. Lu, Erika S. Svendsen,
Lindsay K. Campbell, Jennifer Greenfeld, Jessie Braden, Kristen L. King, and Nancy Falxa-Raymond, “Biological, Social, and Urban Design Factors Affecting Young Street Tree Mortality in New York City,” City and the Environment, Volume 3, Issue 1, 2010, http://digitalcommons.lmu.edu/cgi/viewcontent.cgi?article=1069&context=cate

[12]  “As City Plants Trees, Some Say a Million Are Too Many,” The New York Times, October 18, 2011, http://www.nytimes.com/2011/10/19/nyregion/new-york-planting-a-million-treestoo-many-some-say.html?pagewanted=all

[13]  James Urban, Up by Roots: Healthy Soils and Trees in the Built Environment, International Society of Arboriculture, 2008

[14]  “What is Landscape Architecture?” American Society for Landscape Architects, http://www.asla.org/nonmembers/LicPac99.htm

[15]  Soil Quality Information Sheets, Soil Quality Institute in cooperation with the National Soil Survey Center, NRCS, USDA; and the National Soil Tilth Laboratory, Agricultural Research Service, USDA, http://soils.usda.gov/sqi/publications/publications.html#utn

Suggested Reading

Timothy A. and Philip J. Craul, Soil Design Protocols for Landscape Architects and Contractors, Jon Wiley & Sons, 2006.

James Urban, Up by Roots: Healthy Soils and Trees in the Built Environment, International Society of Arboriculture, 2008

“Standards for Organic Land Care, Practices for the Design and Maintenance of Ecological Landscapes”, NOFA Organic Land Care Program publication, Northeast Organic Farmer’s Association, 2011. http://www.organiclandcare.net/sites/default/files/upload/standards2011.pdf

“Landscape Performance Series: Benefits Toolkit, Fast Facts Library, Scholarly Works”, Landscape Architecture Foundation, http://lafoundation.org/research/landscape-performance-series

http://landscapeurbanism.com/article/reconsidering-the-underworld-of-urban-soils/

German 'Algae Experiment' Powers Houses

Can you imagine a house powered not by sun, wind or coal, but by living algae? A group of graduate students at the University of Cambridge can … and their idea has won them international recognition. Practising what they call “algaetecture,” the students designed an “Algae House” they say could provide a model for future energy-efficient living. In such a model, the house’s residents would get the energy they need from the hydrogen and bio-mass created by the cultivation of algae.

The Algae House design, created by graduate students in the university’s Departments of Architecture and Engineering, was awarded first prize in an international design competition run by SASBE2009 — the third CIB International Conference on Smart and Sustainable Built Environments. The competition challenged students to propose a concept of a small home that produces enough sustainable energy to equal out energy consumption.

The Cambridge team’s winning design uses in-built algae tubes and a photo bio-reactor to generate hydrogen. A glazing system and water pool are incorporated into the design to mitigate — reflect and cool — the sunlight the algae need to thrive. According to the students’ estimates, the house would produce 4,100 kilowatt-hours of hydrogen and bio-mass per year — enough to drive an electric MINI E car from London to Beijing and back twice over .

“Algae and people may not present themselves as obvious bedfellows, but through this project we hope to show that the integration of algae as an energy generator within a house is not only feasible, but that it opens up many exciting architectural possibilities for green living,” said Karuga Koinange from the Department of Architecture.

The competition, held at Delft University of Technology in the Netherlands, was organised and sponsored by the International Council for Research and Innovation in Building and Construction (CIB), the Passive and Low Energy Architecture association (PLEA) and the International Initiative for a Sustainable Built Environment (iiSBE). The students presented their work throughout the week-long proceedings to a variety of conference attendees, including the Dutch Crown Prince, Willem Alexander.

http://www.greenbang.com/the-house-that-algae-power-built_10676.html

New York's Green Roofs Are Crawling With Fungi

Demand for green roofs might plummet if they became known as "fungal roofs." But that is what they are, at least in New York – and contrary to what it may sound like, it's not a bad thing.

The world just became a little more aware of the hidden-but-teeming biomass of green roofs thanks to the intrepid work of researchers from Barnard College, Columbia University, Fordham and the University of Colorado. Recently, these guys found themselves wondering if the gardens in the sky might support different kinds of life than the stuff at dog-pee level. It's a realm into which few scientific minds have tread. While green roofs as heat-island dampeners and rainwater-runoff plugs have been widely discussed, the extent to which they serve as urban "biodiversity reservoirs" (in the researchers' words) is something of a mystery.

So in the summer of 2011, the team set out to test the soil composition of 10 green roofs stationed at recreation centers throughout the five boroughs: Using soil corers, they hunted for fungi, because fungal communities play a key role in a roof garden's health and longevity. For comparison's sake, they also took samples from five city parks near some of the roofs, including Central Park and the High Line. A little magic from "inductively coupled plasma atomic emission spectroscopy" at Alabama's Auburn University Soil Testing Laboratory, as well as a dollop of phospholipid fatty-acid extraction and Illumina-dye sequencing, and they had their results, which were published this month in the journal PLOS ONE.

So what were the conclusions? For one, these sun-kissed carpets of gray goldenrod and smooth blue aster are absolutely crawling with fungi. The researchers logged an average of 109 types of fungi per roof, such as Glomus, Acaulospora, Rhizophagus and Funneliformis, suggesting that green roofs can indeed contribute to urban biodiversity. As they explained:

"We found that green roofs supported a diverse fungal community, with numerous taxa belonging to fungal groups capable of surviving in disturbed and polluted habitats. Across roofs, there was significant biogeographical clustering of fungal communities, indicating that community assembly of roof microbes across the greater New York City area is locally variable. Green roof fungal communities were compositionally distinct from city parks and only 54% of the green roof taxa were also found in the park soils."

In other words, the roofs are home to fungi not typically given to squelching around in normal parkland. They also seem to be better for growing stuff you might, you know, put in your mouth: While the soil in New York's parks showed a greater biomass of microbes, it also tested higher for heavy metals, a scourge of urban gardens that can be unhealthy if consumed in larger quantities.

Here's a comparison the researchers put together illustrating how the roofs stacked up against the parks, in terms of the abundance of fungal phyla:

Needless to say, this is hardly the first news of green roofs supporting life. The elevated gardens are routinely patrolled by insects and in some cases much larger fauna. In Australia, for instance, the Adelaide Zoo maintains several grassy roofs that are designed as homes for urban plants and wildlife, like reptiles, insects and bats.

And an immense green roof in the U.K., mounted on a wastewater treatment facility near Brighton, attracts seagulls and crows that pluck at its quaking grass in search of food. To fight those hungry birds, the roof's overseers have released even more animals over the roof – ferocious goshawks, a golden eagle and even a great horned owl.

http://www.theatlanticcities.com/neighborhoods/2013/03/new-yorks-green-roofs-are-crawling-fungus/4960/

Net Zero Water Introduction

Learn basic technical and economic information on the design and performance of a fully integrated site and building water management system based on the "Net Zero Water" concept by Jeffrey L. Bruce FASLA, LEED, ASIC, GRP. This approach promises to significantly reduce the consumption of potable water in buildings, reduce discharge to municipal waste water systems, and save on municipal energy by reducing the amount of potable water treated at municipal facilities.

http://www.youtube.com/watch?v=sJXkNDPg2Xo&feature=g-user-u

Soft Waterfront Infrastructure to Protect NYC From the next Big Storm

Thanks to climate change, we've experienced some wild storms the past couple of years, culminating in Hurricane Sandy,  which hit the city with record devastation. To make matters worse, NYC is slowly succumbing to rising sea levels, which threaten to sink coastal neighborhoods throughout the boroughs. In light of a possible environmental disaster, a group of architecture firms have united to tackle these issues with innovative green design. Taking lessons from levee design flaws in New Orleans during Hurricane Katrina, these architects have created "soft infrastructure," a design concept based on priming the city to "deal with storms instead of fortify itself against them" by using natural resources like coastal marshlands and building more sustainable infrastructure like green roofs.

Read more: Architects Propose 'Soft Waterfront Infrastructure' to Protect NYC From the Next Big Storm | Inhabitat New York City

http://inhabitat.com/nyc/architects-propose-soft-infrastructure-to-protect-nyc-from-the-next-big-storm/