Measuring the Benefits of Urban Forests

At a Casey Trees‘ conference on urban forestry, David Nowak, Ph.D, research forester at the U.S. Forest service, one of the world’s foremost experts on urban forests, and a member of the team that won the Nobel Prize at the Intergovernmental Panel on Climate Change (IPCC), said out of the 20 biggest cities in the U.S., 17 have declining urban forests. “Tree cover is going down.” For example, researchers have found that D.C.’s urban forestry cover decreased by 1 percent in the last 20 years, while impervious cover (hard concrete) grew by 20 percent. Now and in the future, the key to boosting urban forests may be to make better use of innovative Web applications like iTree, which “estimate value and benefits” of the tree canopy.

Nowak said to really understand urban forests you have to look at their extent or structure. You have to know “how many trees you have and where they are.” The structure of an urban forest also impacts the benefits. For example, where trees are placed impacts who receives the environmental, psychological, and social benefits.

Forests can be measured in either a “bottom-up” or “top-down” manner. Bottom-up approaches involve counting species on the ground and looking at species, tree health, and the various health risks. Nowak and his team at the Forest Service participated in developing iTree, a bottom-up tool that helps manage forests. Top-down efforts are usually satellite-driven and involve high-resolution imagery and photo interpretation.

In an examination of urban forests, Nowak found that some 30 percent of vegetation is planted, while the other two-thirds is “naturally regenerating.” There are also varying levels of natural vegetation within key spaces in cities. In residential areas, the share of naturally-regenerating nature is relatively low because people plant or mow, while in parks and open spaces, it’s higher.

Invasive plants are also on the rise across the country. In D.C., invasive plants may even be shifting the composition of the forests. “Frontier plants are changing things.”

To track all this change, Nowak said it’s important to use tools like iTree, which can help local urban policymakers, planners, and landscape architects “better understand the canopy and the true value of ecosystem services.” Nowak said anytime you’ve heard a number about the dollar value of an urban forest, it was probably based in an iTree estimate. Using “local variables such as energy, air, water quality, and climate,” iTree can put a value on an area’s trees and help local policymakers optimize the performance of the forest.

While landscape architects and others understand the inherent value of trees, local programs to protect trees from pests and fungus are expensive and budgets are tight, so “we need to build the financial case.” Without “data and tools, it’s hard.”

With 20 years of data available, there are a number of applications where you can run and test models. iTree Canopy uses Google Maps to create statistically-valid estimate of tree cover, while iTree Species helps users identify the specific ecosystem service benefits of one tree over another. The system has about 5,000 trees in its database. iTree Hydro looks at tree canopy and stormwater, while iTree Design, which Nowak called the Sim City of landscape design, helps landscape architects and designers figure out the benefits of certain tree sizes and types in a landscape design. In the same way, the tool could be used to figure out the amount of financial benefits that are lost when a tree dies.

iTree 5.0 will include some new features like Google Maps, web-based data collection using mobile devices, the inclusion of data on the volatile organic compound (VOC) output of trees, and “benefit forecasting.” There will also be more data on “the risks each tree type faces from insects and diseases” as well as risks from a given forest structure. For example, too many species in one place means that part of the forest could be simply wiped out with an infestation, creating a vulnerability in the overall structure.

On the value of having a tool like iTree itself, Nowak said: “This is really about urban forestry technology transfer” through a “credible, USDA-approved, public domain software.”

For more on the benefits of urban forests, see ASLA’s animation: Urban Forests = Cleaner, Cooler Air. Nowak was an expert advisor on the animation.

Image credit: Aerial View of Logan Circle, Washington, D.C. / Wikipedia

Bridging the Divide Between Man and Nature

The Cultural Landscape Foundation (TCLF) and Central Park Conservancy are hosting a conference on October 5 in New York City called Bridging the Nature-Culture Divide II: Stewardship of Central Park’s Woodlands. The conference will focus on the challenges involved in crafting a sustainable future stewardship program for Central Park’s woodlands, but also leap off into interesting debates about man and nature in urban parks, tackling issues at the heart of what landscape architects do.

The woodlands, writes TCLF, may appear “feral” but are actually a “historic designed landscape.” In today’s world, with the focus on climate change, TCLF and the Central Park Conservancy wonder what it means to sustainably manage such a seemingly wild place, a landscape Olmsted described as representing “the superabundant, creative power of nature” but found at the heart of a great city.

TCLF writes: “The 843-acre Central Park, originally designed by Frederick Law Olmsted, Sr. and Calvert Vaux, with a succession of additions and refinements by Samuel Parsons, Jr., Michael Rapuano, Gilmore Clarke and others, is also host to 230 bird species, along with turtles, fish, and countless species of butterflies, dragonflies, and other insects.” Focusing in on the park’s great man-made woodlands in particular, TCLF writes that they are “among the most historically significant designed landscapes in the country, they provide valuable refuge for wildlife, and they are a vital recreational resource for New Yorkers.”

But, given these places aren’t wild, how should they be managed? TCLF and the Central Park Conservancy see a new approach: “When we expand our definition of ecology to include people and cultural values and recognize that human activity is part of any ecosystem we touch, the question becomes not ‘how do we strike a balance between nature and culture?’ but ‘how to do we interact with nature in a way that is both meaningful and sustainable?'”  

The one-day symposium will feature panels of officials from New York and San Francisco along with landscape architects and environmental designers from the around the country. The discussion will zoom in on the specific challenges involved in woodland restoration and management in Central Park, but panelists will also look at other cases from around the U.S. exploring design, management, and stewardship, and “how their lessons can be applied to Central Park’s woodlands.” 

TCLF conferences attract some of the best landscape architects, both as speakers and attendees. Moderators and speakers include Christian Zimmerman, FASLA, Vice President for Design & Construction, The Prospect Park Alliance; Elizabeth K. Meyer, FASLA, Associate Professor, University of Virginia, School of Architecture, Landscape Architecture; Dennis McGlade, FASLA, President/Partner, OLIN; Margie Ruddick, ASLA, Margie Ruddick Landscape; and Keith Bowers, FASLA, Biohabitats. See what they will be discussing in more detail.

Register for the symposium on October 5.

For those who can’t make the conference but will be in NYC, there’s no excuse to miss out on TCLF’s free What’s Out There tours, which follow on October 6-7.  The 25+ tours in all five boroughs are led by landscape architects, designers, and other professionals. TCLF writes: “Some are places we see daily, while others are ‘hidden in plain sight.'” Some great ones include the Noguchi Museum in Queens; The Cloisters in upper Manhattan; Van Cortlandt Park in the Bronx; multiple Prospect Park tours in Brooklyn; and Snug Harbor in Staten Island. The Weekend is organized in cooperation with the New York City Department of Parks & Recreation, the New York chapter of the American Society of Landscape Architects (NY-ASLA), Archtober 2012, the Central Park Conservancy, the Municipal Arts Society, the New York Restoration Project, New Yorkers for Parks and Open House New York.

Image credit: Central Park Woodlands / TCLF

In D.C., New Eco-District Plans Unveiled

After two years of internal debate among 17 different federal agencies and the D.C. government, the National Capital Planning Commission (NCPC) released its long-awaited plans for a new Southwest Eco-District designed to undo the worst damage of the massive “urban renewal” projects inflicted on L’Enfant neighborhood over the past decades. Designed to transform the spooky, almost pedestrian-free area just south of the Mall into a highly sustainable, people-friendly cultural and business destination, the Eco-district plan means to take on many challenges at once. As Elizabeth Miller, ASLA, the intrepid landscape architect who is guiding the project, explained, this 110-acre, 15-square block project is meant to showcase “high performance buildings and landscapes” while creating space for 19,000 new federal workers and solving some of the worst pedestrian access problems.

At the beginning of the hearing today, NCPC Chairman L. Preston Bryant, Jr said the project can go a long way to “breathing new life into the city.” While the whole Eco-District may take 20 or 30 years to design and implement, “we have a once in a generation opportunity to make this happen.” He added that NCPC and its many federal partners are eager to move forward because there are some synergies that make the timing right: The Department of Energy (DOE) building is “coming to a lifecycle decision,” meaning that it’s ready to be torn down because it’s now highly inefficient in terms of energy and water use; the Southwest waterfront plans are moving forward, with $2 billion in private sector investment set; and the D.C. government-led Maryland Avenue redevelopment project is on its way.

Miller outlined a vision for an Eco-District that provokes the imagination, at least among sustainable designers. She said the new District will “capture, manage, and reuse water, energy, and waste” and work beyond a single building, leveraging clusters of buildings to create a new system. At the same time, the plan will take aim at the incredible lack of public access — the barriers, the highways, and grade changes — that keep people away, except for the federal workers that have to go there for work.

Diane Sullivan, sustainability planner for NCPC, said a sustainable mixed-use community will arise out of a set of new “guidelines, objectives” that will frame neighborhood development efforts and the creation of new environmental systems.

On developing the neighborhood, Sullivan said that a user survey of D.C. residents found that the lack of amenities was the overwhelming reason why people didn’t want to move down there or even hang out there. So the goal is create a new tree-lined 10th street (or L’Enfant Place) that can connect the Mall to the new Southwest waterfront development while also making that connection itself an exciting cultural destination, lined with 1.2 million square feet in new space for up to 5 new museums, along with farmers’ markets and other draws.

Better pedestrian access is also key to making all this work. In the new plans, Miller said Virginia and Maryland Avenues will re-appear, carving new paths through new buildings as park-like avenues for promenading. Sullivan said the new local street designs cutting up the mega-blocks are still being worked out. She asked, “which streets should be monumental? Which should be local?”

To better get those pedestrians — all those federal workers — to the area, a “better inter-modal system” will be put in place, with a revamped, solar roofed-L’Enfant station, offering both commuter rail and Metro. To ease pressure off Union Station, more commuter rail may be directed there somehow.

The saving grace of the scary L’Enfant Place now is the fountain in Dan Kiley’s Modern-era Benjamin Banneker park, with its dramatic overlook across the Washington Channel. Unfortunately, the rest of Kiley’s park was not well realized. With spaghetti loops of highways cutting through, it’s a matter of taking your life in your own hands to go from the park to the waterfront. In the new plans, Kiley’s park will be completely redone but the area will still serve as a monument to African American surveyor Banneker. The new, more sustainable park will more easily connect to the waterfront while providing a new visual identity for the “eco” part of the district.

Now, on the systems that will make the district more eco: First, many of the old federal buildings will go, getting a revamp so they meet the goals of Obama’s Executive Order 13514, which calls for federal agencies to reduce greenhouse gas emissions, water and energy use. The ones that stay, like the famed Brutalist HUD building, will be updated to be more efficient.

Sullivan said the goal is to have “zero-net energy district as measured in carbon.” Pretty near impossible unless fully renewable power is the rule for the new Eco-District. Sullivan said solar PVs and solar thermal systems (for hot water) will be added to the roofs of the new buildings wherever possible, while ground-source heat will also be tapped. A central facility run by GSA, which runs on natural gas, will still be used (but that won’t get them to zero emissions).

Heading down towards the water, the freeway that cuts off the connection between Benjamin Banneker park and the waterfront will be capped with a new layer covered in solar panels.

For water, the goal is to reduce potable water use throughout the Eco-District by 70 percent and manage all stormwater where it falls. All building greywater will be reused while blackwater will go to the new anaerobic plant. Rainwater will be caught by acres of green roofs (including edible ones), green streets, trees, and planters. What isn’t caught will be funneled into cisterns underneath 10th street and used later. Green infrastructure is then clearly a central part of the strategy. Permeable areas overall are to grow to 35 percent, while the tree canopy is to reach 40 percent (a solid target). (Right now, the barren area has just 8 percent tree cover). While we didn’t hear anything substantive about creating a wildlife-friendly landscape designed to attract diverse species, we hope that’s in the works.

There are more ambitious goals for waste reductions: Some 75 percent of construction materials for the new buildings will be reused, and 80 percent of everyday waste will be diverted from the landfill. A composting program will be put in place, too.

So, how will this all actually work? Sullivan sees some government buildings first getting a light rehabilitation and then others will undergo a full rehabilitation. Three federal buildings will be “re-purposed” as major infill development begins. Then, big redevelopment will start over the freeway. At the same time, critical projects like a new Banneker park and a new 10th street landscape will begin next year.

What’s this all going to cost? Miller and Sullivan said an economic feasibility study only provided some high-level numbers, but they did say the federal government would make back its multibillion dollar investment over 20 years through reduced energy, water, and waste fees; increased revenues from private sector developers; and improved local tax gains.

While we hope this project is a sure thing, new governance structures and partnership and financing agreements will need to be worked out among all the partners, including the private sector developers who are key to making this all happen. Let’s hope this is not a protracted process. As the Eco-District gets moving, it can become an innovative showcase for how to revamp government hubs across the U.S.

Learn more about the bold plans. D.C. residents can attend a public hearing on the proposals on July 19. The comment period will be open for three months. Comments will be incorporated into a final plan ready to go by early 2013. By the end of next year, NCPC hopes to have design competitions launched for a new Banneker park and 10th street, its two priority public projects.

Image credit: ZGF Architects, courtesy of NCPC

D.C. Offers a Bold Vision for a More Sustainable Future

At a historic church in the Shaw neighborhood of Washington, D.C., Mayor Vincent Gray said there are either two future directions for the city: “The gaps between us could further divide our city,” or the city could become “greener, more equitable, and more prosperous” for all. Outlining a bold vision for a Sustainable D.C., Gray said he wanted the city to not only be the greenest in the U.S. but among all world cities. D.C. is currently ranked 8th in a recent ranking of North American cities by the Economist Intelligence Unit so the city has quite a ways to go to get to number one in this continent, let alone the world. In the near term, can D.C. beat New York City, Vancouver, or San Francisco? That’s a stretch and only possible with deep collaboration with the non-profit and private sectors.

Gray is giving the city one generation — 20 years — to accomplish his ambitious objectives, which weave in health, economic, employment, and environmental goals. The idea is that D.C. will not only become greenest but healthiest, with the most number of green jobs. On top of this, Gray wants to continue to grow the city’s population in a big way. Gray said “sustainability will need to be a continual process.”

In terms of carbon dioxide, the city wants to cut emissions by 50 percent by 2032. In presenting the goals, Christopher Tuluo, head of D.C.’s Environment Department, said “climate change is happening. If someone says it isn’t, they are flat out wrong.” A key part of achieving this goal will be reaching objectives on energy use and efficiency. The city seeks to cut district-wide energy use by 50 percent while increasing renewable energy use to 50 percent. Given some 75 percent of emissions come from buildings, the District will push for adaptive re-use of old buildings so they can become greener. The idea is to maintain and improve the current building stock and increase the number of LEED buildings (the city is already number one for that metric). Another way to fight the effect of climate change: strengthening D.C.’s already considerable urban forest, which stores much of the city’s carbon, reaching a 40 percent tree canopy by 2032. Here Tuluo added that “trees are important when it’s 100 degrees out because of climate change.”

Investing in more sustainable transportation systems is also key to both reducing transportation-related emissions and adapting to a carbon-constrained world. The district seeks to make 75 percent of all trips walking, biking, or transit in 20 years. Harriet Tregoning, D.C.’s planning director, said “this is a stretch goal but these trips already make up 50 percent of all trips right now.” She discussed how more young people may be moving to D.C. because the city’s transportation system is so affordable. This younger generation is so in debt with college loans they can’t afford cars. In fact, just 60 percent of D.C. residents own cars and that number is falling.

Sustainability means improving D.C.’s waterways, which are amongst the most polluted in the country. Gray wants 100 percent of District waterways to be fishable and swimmable, and 75 percent of D.C.’s green space to be used as green infrastructure that captures and filters rainwater for reuse. Tuluo wants the city to become much “spongier.” He wants the city to become “a much more natural place — not just for the environmental benefits. We want return on investment” in terms of stormwater management benefits.

The process for dealing with waste, which the Economist Intelligence Unit report said was among D.C. weak points, will need to be totally transformed if the city is going to reach zero waste in 20 years. Tuluo asked, “is zero waste a pipe dream?” Perhaps not. Organic waste is already turned into compost as a matter of practice in San Francisco, one of the best cities at dealing with waste. He sees D.C. residents “becoming urban farmers,” using their compost daily, and other waste consumed by digesters that turn other garbage into energy.

The front end of the reuse chain is local food production, which will also need to ramped up if the 75 percent of all food is to be grown within a quarter-mile of the population eating it. Tregoning argued that “it used to be really difficult to find a supermarket in the District.” While that has changed, improving the availability of local produce will be sped along by a network of food-productive roofs. She wants one million square feet of these vegetated roofs in place funneling produce to local shops and co-ops. (According to Gray, the city is already number-one in terms of green roofs so this may be possible). Getting local produce to D.C. residents seems to be a key focus. Health must be at the top of a sustainability agenda in a city where 22 percent of the population is obese. Gray wants to cut that rate in half in 20 years. 

D.C.’s plan won’t work without more equitable economic and employment growth. Right now, the unemployment rates in the city differ dramatically from ward to ward. In Ward 3, it’s as low as 2 percent, while in poorer parts of the city, like Ward 8, it’s 24 percent, among the highest in the country. Gray wants to boost the number of green jobs by five times — providing opportunities at all levels, from the PhDs experimenting with biofuels to the landscape architects designing parks, from the green roof installers to the maintenance crews keeping green infrastructure and waste reuse systems working.

Explore the plan. There are a few short, medium, and long-term actions listed. As Tregoning said, “the vision is a painting of what’s possible in the District.” A design and implementation strategy with hundreds of actions comes next. To see some actions that should be considered, explore ASLA’s 30-page set of recommendations: Becoming Greenest. One big focus of ASLA’s report was the need for a climate adaptation plan. If local species in D.C.’s great urban forest were to die off due to higher temperatures, none of the other goals related to water, air quality, or health will be possible.

Image credit: City Center, Washington, D.C. / SWF Institute

You Can’t Fool Mother Nature but You Can Understand Her

James Urban, FASLA, noted soil and tree expert, recently gave his talk, You Cannot Fool Mother Nature but You Can Understand Her, at the Arsenal in New York City. Urban is a prolific writer and lecturer on the subject of tree planting and the conditions needed to improve tree performance in urban environments. Urban focused his talk on “eight simple ideas,” all basic steps to yield more productive growth in urban trees. The ideas were driven home by a slideshow containing images from his recent award-winning planting guide and bookshelf mainstay, Up By Roots: Healthy Soils and Trees in the Built Environment. It was refreshing to know that the lecture did not fall on deaf ears as heads of the NYC Parks Department, the ASLA NY Chapter, and New York Restoration Project were all in attendance. If anyone needs to hear Urban’s talk, it would be them.

To Urban, planting trees is “all about the science.” Take a walk down your street and notice the adolescent trees stuffed into the recently curb-cut sidewalk. According to Urban, that is our fatal mistake. “We try all the time [to fool nature] but we never win.” The space below the ground is competing with other urban systems: stormwater structures, utilities, urban compaction systems. These obstacles severely hinder the performance of those adolescent trees, many of which were not even properly selected in the first place. Urban shared his understanding of this paradigm: “Once we have a hypothesis, we tend to give extra weight to any information that supports that hypothesis.” To Urban, this kind of thinking leads to many street trees being planted incorrectly.

Over the past thirty years, Urban has been instrumental in the development of both structural soils and structural cells for use under sidewalk pavement. However, his message has remained and his eight guiding principles to planting trees have as well:

1. Trees need dirt!
2. Plant trees that are native to their urban ecosystem.
3. Can you resolve the conflict between the politics of trees and the planting of trees?
4. There is no free lunch.
5. Get just one tree right.
6. More soil volume please.
7. Harvest stormwater.
8. Improve the nursery stock.

1. Trees need dirt!
According to Urban, New York is actually a relatively easy place to grow trees. To become a functional, mature tree in an urban environment, a tree needs between 800 and 1,200 cubic feet of “good-quality loam soil.” Urban believes that New York City has the space but not the soil.

2. Plant trees that are native to their urban ecosystem.
To further understand this concept the audience was pushed to buy Peter Del Tredici’s, Wild Urban Plants of the Northeast: A Field Guide. No longer are we harking back to the Manahatta planting plan for advice on what to plant on Queens Boulevard. Urban, the consummate pioneer of the urban environment tried to incite the crowd. “Let’s get into it and start figuring it out!” Urban also warned us that in ten years or less we will all be calling nurseries to purchase Ailanthus.

3. Can you resolve the conflict between the politics of trees and the planting of trees?
Urban took this opportunity to speak of the role of the arborist. Currently, certification is relatively easy to obtain. However, as the profession of arborists progresses it needs “serious restrictions.” Making certification more difficult to acquire would promote the profession, putting them on the political map. Arborists could then better join broader political discussions and highlight the importance of trees.

4. There is no free lunch.
Here Urban stressed the idea of compost. His example that “two tons of raw wood only produces one ton of compost” is telling in that he believes there is room to explore this area. He further explains this idea by bashing “the hot item right now,” Bio-Char. After describing Bio-Char as “really bad,” he lightened the assault by clarifying that “it is only good for small amounts of soil.” I wonder if this “simple idea” was an idea at all, or an excuse to diminish the popularity of the charcoal-based soil amendment.

5. Get just one tree right.
In a checklist for tree design, one requirement is to understand the root area index (RAI), the calculation determining the correlation between the root and the surface area. To explain this, Urban used an image of a wine glass standing on a dinner plate. The dinner plate, representing the soil volume and the wine glass base, the trunk flare, are basic visuals of how simple a successful planting can be.

6. More soil please.
Again Urban stressed the importance of understanding soils and the surroundings. Soil can be understood as the community of vegetated and urban systems surrounding the planting site. Urban explained the efficiency of his structural cells compared to that of constructed soils (Cu soils). One attendee, an expert and supplier of Cu soils, vehemently disagreed. He argued that the structural rock matrix that makes up the load bearing component of Cu soils do not inversely affect the performance of tree roots as Urban suggested. Not wanting to get into a fight over the success of his inventions, Urban explained, “I’m almost done with the Cu slide…actually, I’ve been done with the Cu slide since 2003.”

7. Harvest stormwater.
“When designing systems it’s important to allow nature to guide us in protecting our natural systems from floatables, hydrocarbons, chemical pollutants, and runoff toxins.” In the green infrastructure overhaul of New York City, large trees will play an important role in the solution and have the ability to “store and process massive amounts of stormwater both in their roots and leaves.”

8. Improve nursery stock.
Nursery stock, in the age of the New York City’s Million Trees Project, have become a hot topic. Tree growth can be determined before a tree is even planted if a basic understanding of the stock is obtained. There are many issues concerning healthy plant growth at nurseries. Proper limbing, pruning, watering, drainage, sunlight, soil volume, and basic organization are all things to consider when visiting a nursery for healthy plants. However, the number one issue is container plants. “We need to stop buying container trees. It’s an unfixable problem!” The girdling of roots has no remedy and their trees have no chance of reaching their potential.

Much of what James Urban discussed in his lecture seems to touch on the ideas of publicity. Yes, the science of tree planting is essential to success but so are “politics.” Urban reiterated this idea by empowering key figures in the crowd.”The Parks Department, the City of New York, and New York Restoration Project need to put pressure on nurseries!” It’s Urban’s hope that New York City will become the benchmark for intelligent street tree planting.

This guest post is by Tyler Silvestro, a master’s degree candidate at the City College of New York (CUNY), and writer for The Architect’s Newspaper.  

Image credit: Silva Cell / Deeproot

Nature and Structure Are One

When we think of paths through nature, we may first think of somewhat muddy trails carved out willy-nilly through the trees, covered in leaves. But a few landscape architects and architects have been showing how paths can be designed, set-apart, yet also enhance the experience of being surrounded by nature while carefully protecting natural habitat.

Reed Hilderbrand, a landscape architecture firm, created a narrow 2,700-foot wooden boardwalk through a previously “unreachable and unknowable” 50-acre wetland near their client’s house in West Stockbridge, Massachusetts. While the path did cut through undisturbed nature, the idea was to create environmentally-sensitive access to improve the stewardship of the unexplored land, 70 percent of which was made up of re-growth forest.

To complement ongoing “woodlot management, edge restoration, and meadow extension” efforts, Reed Hilderbrand proposed a circuit trail that would loop through the wetland. It took nine months working with “conservation biologists, permit specialists, contractors, the property manager, and conservation commissioners to ensure adequate protection of the resource and mitigation of limited construction disturbance.” According to the firm, the only way the team could get permission was if there was a careful evaluation of the “hydrologic and biotic” characteristics of the site, low-impact construction technologies, and design elements that enhanced the wetland. 

“Path alignments were studied in plan from air and then thoroughly tuned on site to navigate among trees and snags, woody thickets, beaver impoundments, significant perennial stream courses, and wildlife corridors,” writes Reed Hilderbrand. Invasive species were removed, to the benefit of local flora and fauna. Overall, the new boardwalk actually supports local habitat: “Since completion, beneficial plant communities including speckled alder and silky dogwood have responded favorably, improving shade cover and food sources. A corresponding increase in wildlife has been observed.”

Another project, Stone River, in eastern New York state, uses stones instead of wooden boardwalks to create a subtle, new way to experience nature. Landscape architect Jon Piasecki, ASLA, Housatonic, writes: “I joined the path itself to the pre-existing stonewall and woods in an attempt to offer the visitor the opportunity to experience a sense of fusion with nature. The goal of this project is to join culture to nature.”

Piasecki, a master with stone, actually moved each stone down the path in a small wood cart and hammered each stone joint into place. “I transferred tens of tons of gravel and sand as a setting bed with a wheelbarrow and I moved nearly 400 tons of stone in the wall and as paving over the 800-foot length of the path. I opened the existing stonewall, chose the course of the path within it and rejoined the residual wall stone in such a way that the path appears to have grown organically within this stonewall where it resides. I was able to personally lay stones so as to avoid individual clumps of ferns, standing trees, fallen logs and existing stones with mossy growths in the wall.”

The silver stone (a mica schist) used in the project is a highly sustainable material because it will last so long. To further cut down on carbon dioxide emissions from the quarrying and cutting process, Piasecki used machines running on vegetable oils. 

The poetry of the landscape is only enhanced by Piasecki’s gentle intervention: “In this instance by joining stone and by making a path into the woods with great sensitivity, I am working to heal, in a small way, the rift between culture and nature that is intrinsic to our modern relationship to the land.”

Lastly, one Japanese architecture firm, Tetsuo Kondo Architects, wound a path through the tree tops in a temporary 3-month project in Tallinn, the capital of Estonia last summer. In the Kadriorg forest, which is located in the center of the city, trees have grown there for three centuries, around a palace built for the Czar of Russia. To provide a startling new look at the trees, a 95-meter-long elevated path was created.  

According to Landezine, the elevated path is made of steel pipe and sheet steel, with no columns touching the forest floor. In places, the paths seem to lean on trees for support (apparently, both the city’s park managers and structural engineers signed-off on this).

The architects write: “Instead of looking up at the trees from the ground, people will be strolling near the leaves, making their way between the branches. A structure made for the forest, a forest that exists for the structure. With no change in the shape of the forest, it will seem that the structure and the forest are one.” 

In these instances, man-made structures complement nature and even enhance the experience of being immersed in nature. These contemporary yet environmentally-sensitive paths help renew these places.

Image credits: (1-3) Half-Mile Hand Built Line: Berkshire Boardwalk, Andrea Jones, Garden Exposures Photo Library, (4-6) Stone River / Jon Piasecki and John Dolan, 2010 (7-9) A Path in the Forest. Reio Avaste / LIFT11

Why Use Ipe When You Can Have Black Locust?

Michael Van Valkenburgh, FASLA, and his fellow speakers got multiple rounds of spontaneous applause at the 2011 ASLA annual meeting for hosting a session on a topic near and dear to many design professionals and wood experts: how to end the unsustainable harvesting of Ipe wood and scale up the use of sustainable alternatives. The real alternative may be Black Locust (Robinia pseudoacacia), which Van Valkenburgh and other progressive landscape architects, architects, engineers, and wood manufacturers have already been using for some time. In addition, domestically-grown Black Locust may offer new opportunities for local sustainable forestry businesses. The trees grow fast and are hardy (in fact, in many areas, they are treated as invasives) and can even take root in urban areas, so they can provide a new source of employment in cities like Cleveland and Detroit, where populations are collapsing and landscapes aren’t as productive as they could be.

Ipe is a tropical hardwood often used in outdoor decks and furniture because it’s so resilient to rain, insects, and weather changes. It’s special properties also mean that it lasts a long time. However, there is a dark side to this wood, which is all too often still used in park and residential projects. Just a few Ipe trees are found per acre in dense, lush tropical forests, which means foresters must wreck havoc on the forest to extract and process those single old trees. Van Valkenburgh and others argue that there must be alternatives.

Why Black Locust?

Stephen Noone, ASLA, senior associate, Michael Van Valkenburgh Associates, said Black Locust lasts just as long as Ipe. He said it’s a “pioneering, not invasive” plant that “takes root on sites that other plants don’t like.” Unlike Ipe, the tree grows together in densely planted areas. In Europe and Asia, it’s already treated as an acceptable crop. In fact, a number of countries are moving forward with planting large groves for wood production, a business that, oddly, has failed to take root in the U.S. 

A research project by Michael Van Valkenburgh Associates’ interns found a plantation in Hungary producing a range of different quality Black Locust woods, including top quality woods. They found that Black Locust can “only be planted in marginal areas where Oak can’t be established.” In a smart move, a local forestry research organization and local wood producers aforested a massive area. Now, 8,500 hectares of dense Black Locust forests are being harvested in just one area there.

Black Locust has “high natural durability, is heavy and hard, but has a tricky kiln drying process,” said Noone. It’s “not going to rot and is insect resistant.” Noone delved into the details of moisture content, and the process needed to achieve the desired content levels. There is a complex multi-step process that involves lettting the freshly cut wood air-dry to reduce moisture and then using a “dehumidifier kiln.” Noone said “the process is very strict,” and “dilligence is required on the part of the drier.” There’s also a long lead time for landscape architects: 40-50 days until the wood can be used. But it’s worth it: Beyond the sustainability benefits, Black Locust is also cost-effective. In bulk, it’s $5.44 per square foot, while Ipe is more than $7 per square foot.

Building a Bridge in Brooklyn

A new pedestrian bridge made entirely of Black Locust and designed to move people from neighborhoods in Brooklyn into Van Valkenburgh’s Brooklyn Bridge Park (see earlier post) is now taking shape. Ted Zolli, HNTB, said in this case, “black locust is better than concrete in terms of its compression, strength, and flexibility” and an “incredibly viable structural material.”

Zolli showed how timber bridges aren’t a new thing. Some 20 percent of current bridges are made up of wood and some are more than 100 years old. This 400-foot long bridge is comprised of pre-fabricated pieces created off-site and the delivered and installed in BK. Some parts of the bridge span 120 feet. All together, there’s about 30 tons of wood. He said for this gangway, Black Locust was the right way to go.

HNTB purposefully tested how vulnerable the wood is to fire and found that it doesn’t lose its strength as it burns. “It’s better than steel and will do better in a fire than the cable wires we are using.” For him and his firm, the real challenge was getting a hold of longer planks and finding the right connector systems for the bridge components.

The Properties of Black Locust

Don Lavender, Landscape Forms, a man Van Valkenburgh called a “national treasure,” discussed the opportunities and challenges in scaling up a domestic Black Locust industry. He said there is great potential for the tree in the U.S. but it’s about “obtaining prime examples and taking selections.” Lavender said the best trees are found in the Appalachian region.

Black Locust was originally given to settlers by the government during the early expansion of the U.S. because it’s very fast growing. Within 15-20 years, the material can be cut down and burned. At 30 years old, it can be used for materials in homes. Lavender said the best of these trees “competed for sunlight with other trees.”

The tree can be used for many products, and even lesser-grade woods aren’t wasted. “100 percent of the tree can be purposefully used.” Lavender said lower grades can be used for mulch, biomass fuel, parquet, and greenhouse poles. The higher grades, #1 grade, premium and premium plus (the top 5 percent), are the result of a more challenging “kiln drying process” that requires “patience.” The wood is tough and resistant to drying for the “same reason it’s so resistant to decay.”

Once dried properly, it can easily be “cut, sawed, drilled, sanded, and shaped.” No outdoor finishes are needed and its screw retention is good. Its Janka hardness also compares favorably with other woods. At 1700, it’s better than Red Oak (1290), but a bit less than tropical hardwoods like Jarrah (1910) and Ipe (3684).  It’s also difficult to glue. But biologically, Black Locust is “remarkably decay resistant.”

Scaling up Cultivation and Production in the U.S.

Van Valkenburgh said the U.S. is falling further and further behind globally. “The country is losing its edge.” Currently, there are 5 million acres of Black Locust under cultivation worldwide, but “virtually zero in the U.S.” Korea has 1.2 million acres, China has another 1 million, while Hungary has 270,000 acres. “This is something that has the potential to be an economic engine in many parts of this country.”

Instead of being viewed as an invasive, as it is in many parts of the U.S., Van Valkenburgh said it should be grown in set-aside areas. Lavender added that the Amish, who “don’t waste anything,” has been using Black Locust for ages. The Amish, who have perfected techniques over generations, are in fact a perfect model for Black Locust production: “proper kiln drying is not something you just get into one day. It takes generations to learn this.” He added that a number of firms have “blundered into kiln drying” and ended up with kindling. “It needs to be done methodically” if an industry is going to bloom here.

Van Valkenburgh is currently using Black Locust imported from Hungary. A firm in Massachusetts is importing containers from Hungary and “taking it upon themselves” to expand the domestic market. While using this wood puts him out of the 500 mile range the Sustainable Sites Initiative (SITES) calls for in sourcing sustainable materials, he said “we have to think bigger about sustainability. The lifespan of these woods is several multiples higher than others.” Still, he wants to see the woods grown domestically. 

The Black Locust market in the U.S. is “still in its infancy” despite the advocacy efforts of Van Valkenburgh and others. Hopefully, some smart city officials will see an opportunity. As one audience member said, Detroit and other cities could not only turn their abandoned lots into forests, but Black Locust forests. Van Valkenburgh went even further: “Planting on reclaimed sites is a great idea.”

Van Valkenburgh, Noone, Zolli, and Lavender kindly shared their 84-page presentation (8MB) full of rich content, photos, and data. Download and help spread the word.

Image credit: (1) ASLA 2006 General Design Honor Award. Small is Beautiful. Michael Van Valkenburgh Associates / Elizabeth Felicella, (2) Walkway into Brooklyn Bridge Park / HNTB

Becoming Greenest: Recommendations for a More Sustainable Washington, D.C.

Washington, D.C. leadership has requested input from a range of organizations as it develops a new “unified vision” and “comprehensive framework” for a more sustainable Washington, D.C. The end goal: to connect sustainability with economic development and become the number-one, most sustainable city in North America. Washington, D.C. is currently ranked eighth in a recent Economist Intelligence Unit report sponsored by Siemens.

As part of this process, the American Society of Landscape Architects (ASLA) polled members from its Potomac, Northern Virginia, and Southern Maryland chapters and incorporated their input into a set of bold recommendations in the priority areas identified by the city government. Because the categories of recommendations will be evaluated by different D.C. agencies, recommendations are repeated when appropriate and relevant. Among them:

Energy: Reuse brownfields as solar energy farms. Through revised building codes and local tax incentives, expand use of smart tree placement and green roofs and walls. Reduce building energy use through green infrastructure. Incentivize the use of rooftop solar panels. Read research and recommendations >

Climate Change / Mitigation: Reduce total greenhouse gas (GHG) emissions by expanding urban park land, further improving bike and pedestrian infrastructure, incentivizing the growth in the number of bicycle and pedestrian commuters, creating highly walkable pedestrian-only areas, and introducing new innovative forms of public space such as parklets and underpass parks. Read research and recommendations >

Climate Change / Adaptation: Increase coverage of street trees for shade and expand use of green and cool (white) roofs in order to adapt to higher average temperatures along with more varied temperature fluctuations within the District. Improve building and landscape water efficiency measures. Develop resiliency plans for Washington, D.C.’s plant and animal life within parks and green spaces, including the introduction of wildlife migration corridors and heat and drought-tolerant plants. Read research and recommendations >

Water: Develop a comprehensive green infrastructure plan that leverages existing grey infrastructure. Use Sustainable Site Initiative™ (SITES™) guidelines to improve water efficiency measures, require the use of appropriate plant species in public and residential landscapes, and enable rainwater capture and filtered or treated greywater (and even blackwater) reuse for landscape irrigation. For stormwater management, require the use of green roofs for new buildings exceeding a minimum size. In addition, approve the use of rainwater cisterns for irrigation of green roofs and other green infrastructure. Improve the permeability of the District’s park surfaces and their ability to capture and store water. Create multi-use infrastructure, or rain gardens or bio-retention systems in District parks, turning them into green infrastructure and water treatment systems. Increase the use of bioswales near transportation systems, and add in permanent green street corridors and green alleys. Continue to expand urban tree canopy and preserve larger trees to manage stormwater runoff. Spread use of tree boxes and permeable pavements for stormwater capture. As part of a public education campaign, parks and public green space should follow the highest water efficiency standards. Read research and recommendations >

Transportation: Expand bike and pedestrian infrastructure. Create safe bicycle infrastructure. Connect the Metro system with bike infrastructure and bikeshare stations. Require secure bike parking within office and residential buildings. Incentivize the growth in the number of bicycle and pedestrian commuters. Create highly walkable pedestrian-only areas, and introduce new innovative forms of public space such as parklets and underpass parks. Read research and recommendations >

Waste: Set clear, ambitious targets and deadlines for achieving zero waste in the District and measure progress against targets. Ensure all building materials are reused in new buildings (if the materials are non-hazardous). Use Sustainable Sites Initiative™ (SITES®) guidelines for park maintenance and eliminate grounds waste generated from Washington, D.C., parks through composting. Read research and recommendations >

Built Environment: Invest in turning more brownfields into parks. Apply bio-remediation and other safe environmental remediation technologies during park development. Develop an Internet-accessible inventory of all brownfields in the city to enable easier remediation and redevelopment of derelict sites by local developers. Create a certification program for remediated brownfields to facilitate faster reuse. Invest in retrofitting older school buildings to make them LEED Platinum and also integrate green school redesign activities into school curricula. Ensure all schools apply Safe Routes to Schools design guidelines. Read research and recommendations >

Nature: Develop a biodiversity and environmental education action plan based on the concept of biophilia. Recreate wetlands along riverfront edges and reintroduce native wildlife. Reduce the mortality rate of trees and extend their lifespan by enabling them to grow in larger tree pits with structural soils and under permeable pavements. Use appropriate trees grown locally for urban forestry campaigns. Experiment with growing trees in park nurseries. Read research and recommendations >

Food: Develop a comprehensive urban agriculture plan. Evaluate all available empty lots (including brownfield sites) as potential opportunities for commercial and community urban agriculture. Develop new codes enabling local food production. As a priority, target food desert communities with high numbers of brownfields. Allow local residential food production. Develop new soil testing and clean-up requirements for growing food in former brownfield sites. Allow and also increase tax incentives for rooftop food production. Read research and recommendations >

Green Economy: Invest in bicycle and pedestrian infrastructure improvement projects to boost job growth. Use green infrastructure systems, including green roofs, to increase number of local, non-exportable green jobs. Launch a comprehensive green jobs program, training chronically unemployed and former convicts in brownfield remediation, green roof installation, and other tasks. Launch a national campaign in an effort to lure the best green talent to the District. Read research and recommendations >

Governance: Organize watershed councils at the local level and appoint ward-level sustainability advocates to help implement and align SustainableDC initiatives. Use Sustainable Sites Initiative (SITES) guidelines as a management tool for achieving high-performing landscapes across the district. Read research and recommendations >

Go to the report Web site and explore the recommendations in detail, or download the PDF version of the report.

Also, be sure to add your comments below on how D.C. can become greenest.

Image credit: ASLA 2011 Professional Design Honor Award. Monumental Core Framework Plan, Washington, D.C. AECOM, the National Capital Planning Commission, and the U. S. Commission of Fine Arts, Washington, D.C.

Urban Forests = Cleaner, Cooler Air

Watch an animation from ASLA’s “Designing Our Future: Sustainable Landscapes” online exhibition that explains how urban forests fight air pollution and the urban heat island effect. See how cities can add in millions of trees, while ensuring the trees themselves live long, healthy lives.

Poor air quality has led to an explosion of asthma cases and other health problems among vulnerable populations including children, the elderly, and low-income residents. Each year bad air causes two million deaths worldwide. Also, in the U.S., there have been 8,000 premature deaths from excessive heat over the past 25 years. Urban heat islands, which are caused, in part, by sunlight being absorbed by paved surfaces and roofs, lead to higher surface temperatures, up to 90 degrees. Atmospheric air temperatures are also higher: in the day by up to 6 degrees, and at night, by up to 22 degrees. Vulnerable populations also face greater risks of heat exhaustion.
(Sources:  Heat Island Impacts, U.S. Environmental Protection Agency (E.P.A.), World Health Organization (WHO))

Increasing the tree canopy in cities is one way to fight both poor air quality and urban heat islands. Research shows significant short-term improvements in air quality in urban areas with 100 percent tree cover. There, trees can reduce hourly ozone by up to 15 percent, sulfur dioxide by 14 percent, and particulate matter by 13 percent. U.S. trees remove some 784,000 tons of pollution annually, providing $3.8 billion in value. Furthermore, a single large healthy tree can remove greater than 300 pounds of carbon dioxide from the atmosphere every year. In fact, New York City’s urban forest alone removes 154,000 tons of CO2 annually. Through their leaves, trees also provide evaporative cooling, which increases air humidity. Shaded surfaces may be 20-45 degrees cooler, and evapotranspiration can reduce peak summer temperatures by 2-9 degrees. (Sources: Heat Island Mitigation: Trees and Vegetation, U.S. Environmental Protection Agency (E.P.A.), “Sustaining America’s Trees and Forests,” David J. Nowak, Susan M. Stein, Paula B. Randler, Eric J. Greenfield, Sara J. Comas, Mary A. Carr, and Ralph J. Alig, U.S. Forest Service.)

Some other benefits: Urban forests reduce energy use by providing shade in the summer and wind breaks in the winter, reduce stormwater runoff, remediate soils, and provide animal and plant habitat. Trees have economic benefits: they increase property value. Lastly, trees have positive cognitive effects and may even help improve moods. (Sources: Does Looking at Nature Make People Nicer?The Dirt, “The Restorative Effects of Nature in Cities,” The Dirt, “Sustaining America’s Trees and Forests,” David J. Nowak, Susan M. Stein, Paula B. Randler, Eric J. Greenfield, Sara J. Comas, Mary A. Carr, and Ralph J. Alig, U.S. Forest Service.)

In the U.S., cities take up just three percent of land but contain 80 percent of the population. Cities may take up a relatively small share of all land now, but are projected to consume an area the size of Montana between 2000 and 2050. Two-thirds of the planet is expected to live in cities by 2050. With rapid urban growth, it’s essential that trees remain, whether along streets, in small pocket parks, or big green spaces. A 40 percent tree canopy is a challenging but worthy goal for every city to reach. (Sources: American Forests Tree Canopy Goals, “Projected Urban Growth (2000-2050) and Its Estimated Impact on the U.S. Forest Resource,” David J. Nowak and Jeffrey T. Walton, U.S. Forest Service, “Sustaining America’s Trees and Forests,” David J. Nowak, Susan M. Stein, Paula B. Randler, Eric J. Greenfield, Sara J. Comas, Mary A. Carr, and Ralph J. Alig, U.S. Forest Service.)

Scientists Estimate Planet Has 8.7 Million Species, Give or Take 1.3 Million

A new study published in PLoS Biology, a scientific journal, estimates that there are 8.7 million different species on Earth, give or take 1.3 million. Previous estimates have ranged from 3 million to nearly 100 million. According to The Guardian (UK), this study finds that some three-quarters of all species are on land, and a majority of these are insects. Only one quarter reside in the oceans, even though 70 percent of the Earth’s surface is covered in water. As famed biologist E.O. Wilson explored in The Future of Life, estimating the number of species is incredibly difficult, largely because a huge share of species are still undocumented. Attempting to put a number on our collective ignorance of the world’s biodiversity, the report argues that some 86 percent of all plant and animal species and 91 percent of ocean species have not been “named and cataloged.” Climate change make things even worse: Scientists estimate mass extinctions of up to 10 percent of all species, meaning that many unknown species will die off before they are even identified.

Dr. Camilo Mora of the University of Hawaii and Dalhousie University in Halifax, Nova Scotia told The Guardian that counting all species accurately is important for setting a base line: “Scientists have been working on this question of how many species for so many years. We know we are losing species because of human activity, but we can’t really appreciate the magnitude of species lost until we know what species are there.”

The researchers analyzed data on 1.2 million species, and used Carl Linnaeus’ taxonomical “tree-like” system to determine “patterns between […] hierarchical groupings which they could use to infer the existence of missing species that scientists have not yet described. That allowed them to use data from higher orders – such as anthropods, where there is a lot of data – to predict the number of creatures at the species level.” Their final estimate: 7.8 million species of animals; almost 300,000 different types of plants; more than 600,000 different species of fungi, mushrooms, and molds; some 36,000 species of single-celled organisms; and 27,000 species of algae. The authors didn’t delve into bacteria.

Robert Mays, a UK government advisor, said the findings were realistic: “It is sort of saying that the trunks and lower branches of the tree seem similar from group to group. At one end of the thing, you have birds and mammals that really are completely known. At the other end, you have just got a handful of branches and twigs. But if you do the big assumption the trees are similar, then it seems sensible.”

However, others are critical of the estimate, arguing that if the methodology was changed, an entirely new estimate could easily be calculated. For example, other approaches have tried to classify the Earth’s species based on patterns derived from the size of species or their location, or their relationships with other species. According to The New York Times, Robert May, an evolutionary biologist at the University of Oxford, argued in the late 1980s that the diversity of land animals grows as they shrink in size. “He reasoned that we probably have found most of the species of big animals, like mammals and birds, so he used their diversity to calculate the diversity of smaller animals. He ended up with an estimate 10 to 50 million species of land animals.”

Terry Erwin, a carabidologists or beetle expert, found more than 1,100 species of beetle from a single tree in the rainforest of Panama. He estimated more than 30 million species of insects in tropical rainforests alone. On the approach taken in the new study, Erwin told The Guardian: “These guys base these on classification of animals, and classification of animals are human constructs. The reason it is predictable is that humans are predictable, especially in the scientific field. What they are measuring really is human activity. It is not real activity out in the wild.” Also, a specialist focused on fungi, David Pollack at University of Colorado, agrees and argues that there are far more fungi out there, up to 5 million (not the 600,000 estimated in this paper’s approach). Lastly, microbiologists argue that the diversity of microbes will only dwarf animals. “A single spoonful of soil may contain 10,000 different species of bacteria, many of which are new to science.”

The Guardian writes that one problem is that identifying and cataloging new life forms is “expensive and slow,” with only 14 percent of life forms represented in databases. Scientists point to a lack of funding. “At the current pace, it would take 300,000 specialists 1,200 years to go through the laborious process of describing the new discoveries in scientific journals, and then entering them in electronic databases.” The lack of funding may be due to a lack of interest in these efforts among the public given most of the species to be discovered will be very small, and concentrated in remote areas.

Still, scientists are making big finds almost every day. “Last week, scientists at the Smithsonian Institution reported the discovery of a primitive eel in a reef off the coast of the South Pacific island nation of Palau. The new species, Protoanguilla palau, bore little relation to 19 other forms of eel currently in existence and some of its characteristics – such as a second upper jaw – were more in line with fossils from 65m years ago.”

Read the article and the study.

Image credit: Cristalino State Park, Alta Floresta, Mato Grosso, Brazil / Daniel Beltra Conservation Photography