When is an urban forest large enough?

Forested Canopy in Shenandoah National Park

In the 2007 Comprehensive Plan, the City of Charlottesville set for itself the ambitious goal of creating a 40% tree canopy. At least it seemed ambitious at the time. After performing an analysis of aerial photos this year, city officials realized that 46% of the area is actually already covered by trees. In response, a new Urban Forest Management Plan has been drafted that calls for yet more trees. City Council has reviewed the plan, and everyone who spoke wholeheartedly endorsed making this a reality.

The plan recommends several methods for increasing the scale of natural forest land within city limits, including protecting forested parkland and/or forested private lawns in perpetuity with conservation easements, increasing the tree planting requirements for all new development, and acquiring more public land to be converted into green space. To clarify, we're talking specifically about the 10 square miles within the limits of the City of Charlottesville.

I should stop here and make it clear that I love trees. I've spent two summers living in a national park, getting out into the mountains and forests as often as the opportunity allowed. Deforestation has been a major global problem for many years now, contributing to the rising levels of GhG in the earth's atmosphere due to loss in carbon sequestration potential. Street trees are a wonderful accoutrement to the urban fabric, enhancing the aesthetic value of streets, soaking up particulate matter, and providing energy-efficient shade. Trees are great.

From 2009 aerial-photo study (Enlarged Picture)

But ... and it's pretty obvious where this is going ... there are important differences between urban areas, rural areas, and wilderness areas. They each have their own ecological and economic function, form, and aesthetic properties. As enticing as it is may be to have the best of both worlds, with wilderness/rural/urban all mixed together across the landscape, this strategy of suburbanization has resulted in a number of unintended consequences throughout the 20th century. What was idealized as a rainbow of land types coexisting often turned out, in reality, to become a beige mush of none of the above. And acres of parking lots as a bonus.

Charlottesville happens to be an urban area, at least that's how it's conceived of by many of its residents. The current map of the urban tree canopy is pretty clearly an inverse of the population density map for the city, with the downtown the least treed and the more low-density residential districts showing more trees. Makes sense. More trees appear to mean less people. More forest would seem to mean less city.

So what's the right amount of trees for an urban area? There is a spectrum of options. Brooklyn, New York, recognized by many for it's tree-lined streets, has a 12% canopy coverage. So does Frederick, Maryland. On the other coast, The City of Vancouver has about 20% coverage throughout its jurisdiction. Portland, Oregon clocks in at 26%, mostly on account of its forested hillside parks west of downtown. As the Charlottesville plan notes, American Forests, a national forest advocacy group, recommends for towns and cities east of the Mississippi a 50% canopy coverage for suburban residential areas, 25% coverage for urban residential, and 15% coverage for the downtown.

This seems to me like a reasonable ideal to set. The more suburban a city would like to become, the closer to 50% tree coverage the better. The more urban a city would like to become, the closer to 15-25% tree coverage the better. But perpetual growth of the tree canopy with no limits would not seem to be a prudent way to plan for a city's future.

The National Building Museum and the mainstreaming of urbanism

The Green Community exhibit at the National Building Museum has been up since last October, but I just recently had a chance to stop in and check it out. As I perused the various displays, it occurred to me that the exhibit is a highly polished and fun way to communicate much of the same things I'm hoping to explore here. According to promotional material, it's a look at "how and why we plan, design, and construct the world between our buildings." It moves beyond advocating energy efficient green building practices to examining where the buildings sit in relation to each other. It moves beyond the hybrid car solution to asking whether gains in automobile energy-efficiency may simply be offset by allowing us to drive more. I won't go into all of the details, but if you're anywhere near D.C. before October '09, I'd recommend stopping in for a quick look.

What encourages me most about this exhibit is the fact that it exists. The National Building Museum is a private institution, not a part of the Smithsonian system. It's donor list consists of many of the major professional organizations of the fields of development, architecture, and planning. A lot of the big construction firms and trade organizations also support the museum. In other words, this is neither the manifesto of some fringe group nor a subversive government plot to control the masses. It's the aspirations of mainstream development.

This is the perfect segue into an insightful post by Robert Goodspeed in Planetizen entitled, "The New Normative Planning." Goodspeed sees a subtle shift in the language used by the American Planning Association. In the past the APA, like many large organizations, opted for neutral platitudes that were likely crafted to appease the broadest range of members. However, in recent years, many of the principles of urbanism, such as mixed-use development, density, and walkable scale, have more and more been accepted as normative by the profession. It's as if Jane Jacobs, once seen as a fiery voice against the establishment, has gradually (I think she would appreciate the gradualism here) worked her way into the profession she set out to attack.

Goodspeed sees this as the beginning of a workable consenus on principles,

"Many of the values of New Urbanism are becoming the profession's mainstream values. We are entering a new era of normative urban planning in America."

Housekeeping on Comments

It was just brought to my attention that I do not accept comments from non-Google users. Oops. This was certainly not an attempt to be exclusive or to discourage anyone from weighing in. I just hadn't revisited my settings for a long, long time.

I've now opened the comments up to anyone. I don't foresee myself getting on any power trips and squashing dissenting opinions - if anything, it would be great to get into some constructive dialog around here. I would enjoy that. But if you really just want to let me know how to make $75 an hour selling ads to Google, I'd like you to at least think of a creative way to weave it into the topic of discussion.

Keep the trail and the rail

I'm all about the mission of Rails-to-Trails Conservancy. I'm a member. I wear the T-shirt and everything. Yet, in the back of my mind, there has always been this voice saying, "what about the railroads?" The total railroad track mileage in the United States has dropped from a peak of 260,000 miles in the 1930s to under 100,000 miles today. I suppose as long as these are simply abandoned, multi-use trails are great alternative, particularly if they can serve important transportation corridors, but we may just need that track again if we need to put together a sustainable intercity transportation system.

That's why I've been getting more excited about the prospect of Rails-with-trails. This concept uses the valuable right-of-way leased to the railroad company to run a trail alongside the tracks. This is one way a trail can be get built in areas where land acquisition costs are prohibitively high, or there isn't much public interest in running easements through private property. Less commonly, this could occur if rail gets built alongside an existing trail. I believe many of the tracks donated by railroad companies to rails-to-trails come with some kind reclamation clause, in case adding more line becomes viable again. It would be good to be prepared for this occasion.

The unfortunate purple line dispute happening on the Maryland side of the DC metro area right now is essentially a question about rails with trails. Opponents of the line do not want to lose any of the Capital Crescent Trail, while purple line advocates respond that both can coexist.

The U.S. DOT conducted a pretty thorough study of rails-with-trails in 2002, in order to determine how safe they actually are and hammer out some design standards. Although liability is still a live issue for railroad companies, there are many strategies, such as fencing or creating a buffer, to mitigate the risk.

From the report:

"Based on the lessons learned in this study, it is clear that well-designed RWTs can bring numerous benefits to communities and railroads alike. RWTs are not appropriate in every situation, and should be carefully studied through a feasibility analysis. Working closely with railroad companies and other stakeholders is crucial to a successful RWT. Trail proponents need to understand railroad concerns, expansion plans, and operating practices. They also need to assume the liability burden for projects proposed on private railroad property. Limiting new and/or eliminating at-grade trail-rail crossings, setting trails back as far as possible from tracks, and providing physical separation through fencing, vertical distance, vegetation, and/or drainage ditches can help create a well-designed trail. Trail planners need to work closely with railroad agencies and companies to develop strong maintenance and operations plans, and educate the public about the dangers of trespassing on tracks.

Railroad companies, for their part, need to understand the community desire to create safe walking and bicycling spaces. They may be able to derive many benefits from RWT projects in terms of reduced trespassing, dumping, and vandalism, as well as financial compensation. Together, trail proponents and railroad companies can help strengthen available legal protections, trespassing laws and enforcement, seek new sources of funding to improve railroad safety, and keep the railroad industry thriving and expanding in its services (freight and passenger)."

Everything in its place

I stumbled upon an insightful little book written in 1977, Everything in its Place, about American zoning practice from an anthropological perspective. Judging by the fact that I bought it as a discarded library book for $3, it seems to be mostly forgotten. That’s too bad. Constance Perin, then a researcher at MIT, dug about as deeply into the suburban psyche as anyone I’ve heard from.

The question that launches her investigation is pretty familiar to many of us. How have American communities ended up with strict spatial separation of all different kinds of land uses? Why have we been willing to endure long commutes and social isolation simply to build buffers between ourselves and other kinds of people? The practice of zoning may have started as a simple application of common law nuisance provisions, but it has resulted in a precise mapping of our social class categories onto the built environment. It moved from protecting houses from smokestacks to separating different kinds of people by income, tenure, and age, and indirectly by race.

All of her interviewees, mostly developers, bankers, and planners, explicitly repudiated segregation, but in practice they found themselves passively oriented according to segregated land use patterns anyway. A primary motivation she found was the sheer weight of investment people are asked to place into their homes. Any financial advisor worth her salt will recommend a diverse portfolio, but almost all middle-class Americans do the opposite. They put all of their eggs into one basket – their home. Add to this the indisputable fact that the value of a property is tied up with the value of everything around it, and an element of fear is introduced into the equation. Every consumer of housing is also a producer of used housing, and this their entire product line is encapsulated in one particular property.

Apparently, the phenomenon of being “house poor” is nothing new. She talks with homeowners who had put everything they had into their house, with not even enough left in the budget to fill it with furniture. Tax incentives and a feeling of social obligation compelled buyers to extend themselves as far as possible. Writing from the midst of white flight, she found that even white homeowners who immediately befriended the new black neighbors who moved in started to wonder if everyone else would take to the change as amenably as they had. Were they willing to gamble on it?

She makes the counterintuitive claim that zoning ordinances are actually mostly for the benefit of developers and bankers. As much as developers like to grumble about regulations, in reality these laws serve as an insurance policy for their investments. They do not necessarily enhance value, but they minimize risk. They keep the financial calculations uncomplicated and allow for the application of formulaic principles. Development plans that can isolate the existing conditions and surroundings are more easily replicable at a mass scale.

But it’s not all cold economic calculation. She noticed neighbors fighting against new low-income housing even when it was accompanied with extravagant improvements to the neighborhood. Not only do people identify with their family household but often the social identity spreads through the entire surrounding area. Certain neighborhoods can have status attached to them. Perhaps Glenmore will not evoke the same image if a large apartment complex is built right in the heart of it. And while privacy has always been an important human concern, the means of meeting this need shifted. She found that suburbanites expressed privacy through walls, while urbanites used social rules to maintain privacy.

The shape of land use is formed though a multiplicity of actions by developers and bankers, homeowners bound together as neighborhoods, and public officials responding to pressures from both groups. It has been the modern way to break down the whole into many discrete parts, and this expression has socially mapped itself out onto the metropolitan areas we live in.

Envisioning the next GM

If you're an American, you're now the proud owner of a car company - at least 60% of one. The official line from both General Motors and the Obama administration is that the federal government will not use its shareholder stake to influence corporate decisions. The government will just let the "new and lean" GM do their thing. Hands off. Everyone recognizes that this is not going to happen, but it's interesting to see how both sides of the aisle are laying out their predictions. Here are two public figures about as far apart as possible, on any scale you would measure with.

David Brooks is not very optimistic about the new arrangement:

"The end result is that G.M. will not become more like successful car companies. It will become less like them. The federal merger will not accelerate the company’s viability. It will impede it. We’ve seen this before, albeit in different context: An overconfident government throws itself into a dysfunctional culture it doesn’t really understand. The result is quagmire. The costs escalate. There is no exit strategy."

Michael Moore, who has a tangled history with GM all the way back to "Roger and Me," is much more optimistic:

"Just as President Roosevelt did after the attack on Pearl Harbor, the President must tell the nation that we are at war and we must immediately convert our auto factories to factories that build mass transit vehicles and alternative energy devices ... The things we call "cars" may have been fun to drive, but they are like a million daggers into the heart of Mother Nature. To continue to build them would only lead to the ruin of our species and much of the planet."

Given Brooks' belief that the Obama administration is already in too deep, and cannot possible handle the political fallout from dismantling a major corporation, what is the pragmatic way to proceed? Ought they grab the bull by the horns, as Moore suggests, and spearhead the transition of industrial infrastructure toward more sustainable ends building public transit? Or should they keep pumping more funds into GM so they can continue to produce cars, hoping that one day the company will get back on their feet and make responsible decisions for themselves?

Gladly paying for parking

Yesterday, I slipped my credit card into a solar-powered parking kiosk in the Baltimore neighborhood of Fells Point. Two dollars gave me a little receipt to put on my dashboard, which was good for two hours worth of parking in a prime spot on Broadway. I found the open spot within a minute. We enjoyed a walk around the harbor area and a nice dinner at a Fells Point restaurant.

This meter system has been in place in Baltimore for around five years, and it's been popular among business owners, the local government, and the public as a whole. There is only need for one machine per ten parking spots, which reduces street clutter. There's no more shuffling around for change. Meter collection theft is managed. Variable pricing could be a possibility. What's not to like about these new systems that are being installed in cities around the country?

That is if you believe that those who park should pay for their own parking. In some areas, many people still believe motorists have an inalienable right to have their cars stored for free (or at least really cheaply). Matthew Yglesias has an analogy for this particular form of government subsidy.

"It’s overwhelming conventional wisdom in the United States that price controls are bad. If I suggested that the city implement price controls on Diet Coke, people would say that it would lead to shortages. And if I proposed dealing with the ensuring shortages by saying that anyone who wants to build a new building needs to also provide millions of dollars worth of Diet Coke to people in the neighborhood, people would look at me as if I were insane. Creating the Diet Coke shortages is not a favor to anyone—neither fans nor haters of Diet Coke benefit—and the regulatory mandate is an absurd subsidy to Diet Coke drinkers with no conceivable policy justification. It’s bizarre."