Yes Virginia, Density Causes Sprawl—Lorax Edition

Among  all the wonderous myths of the density NIMBYs, surely “density causes sprawl” is king. Long ago Yogi Berra, of all people, nailed the illogic of that argument with his famous quip that “Nobody goes there anymore. It’s too crowded.”  (Mr. Berra also coined “it’s deja vu all over again,” a sentiment that seems all too fitting for another density post on this blog, but hey, it’s been a while.)

Like most specious myths, there is a grain of underlying truth upon which the broken ediface is built. Because yes, from the dawn of cities to the present, those with the means sometimes choose to escape the ills of the crowded city to find more favorable living conditions on the fringe.

But that is not the operative dynamic in a growing city like Seattle. Here, people opt for the fringe because they don’t have the means to afford Seattle. And that’s because demand for housing is high in Seattle, which is because there’s limited supply, which is because Seattle isn’t dense enough.

Yet somehow the myth persists that all those new, big, scary multifamily buildings filling up with people are actually driving people out of the city and increasing sprawl. Never mind considering where all those people would have gone to live if there were no new, big, scary multifamily buildings for them to move into.

There’s also a corollary myth regarding tree cover—that taking out trees to make way for new development creates sprawl because no one wants to live in a city that doesn’t have enough trees. Except, of course, all the people who are moving in to that new development that took out the trees. Pesky details.

But here’s the punchline of the post: the source of the tree corollary appears to be none other than the public servants of the City of Seattle itself. The City’s 2007 Urban Forest Management Plan states that,

Accommodating growth is important in order to preserve open spaces outside of the city. However, the loss of treed relief in our built environment reduces livability and further motivates sprawl.

and also that,

As the pressure to redevelop land within Seattle continues and the region’s population increases, density goals and development pressures need to be balanced with tree protection and planting goals. Finding the right balance is crucial to maintaining the city’s livability and encouraging new development within already developed areas rather than pushing it to the metropolitan fringe.

It sounds reasonable on the surface, and yes, trees are important for livability. But poke below that surface and say hello to bald-faced illogic: We must hold back development to prevent the loss of trees and preserve livability so that we can accommodate dense development that will cause loss of trees. Capiche?

And here’s another fun irony: If Seattle invests in expanding tree cover, it’s only going to make the City even more desirable. And that will further raise housing prices—a true generator of sprawl—and also increase development pressure.

What’s needed is some perspective. We all agree that trees have significant value on many levels. But if, for example, we think trees are important for carbon sequestration, we must consider how that fits into the big picture. The Urban Forest Management Plan estimates that Seattle’s existing trees sequester 52,400 Mg CO2/yr. How much is that? It’s 0.8 percent of Seattle’s total carbon footprint.  

But we also know that as density goes up, driving—and the associated carbon emissions—goes down. Just a two percent decrease in road transportation emissions would offset the sequestration provided by all of Seattle’s existing trees.

Same goes for stormwater management. The Plan places a $21 million stormwater mitigation value on Seattle’s existing trees. How does that compare to other mitigation strategies that can be integrated with dense development such as green roofs? And what about the impervious surface that is avoided with dense infill development—how much does that save us in terms of runoff pollution to Puget Sound, for example?

The list goes on. But the point is that planning decisions must be based on defensible analysis.  Does Seattle’s 30 percent tree cover goal meet that requirement?


Whether it’s about trees, ugly buildings, traffic, etc, there appears to be a fantasy scenario being invented in the minds of density NIMBYs in which people are fleeing Seattle because of all the terrible development that’s been happening.  But they’re doing no such thing. Plenty of people still want to live in Seattle—that’s why housing is so expensive here. 

Take Belltown, for example, often maligned for growing too rapidly without providing sufficient open space and schools. But somehow rents are still among the highest in Seattle. Maybe we should ask the people who choose to pay those rents whether or not the neighborhood is a success. And again, we’re faced with the gotcha: add more open space to Belltown and rents are going to go even higher (you may be feeling the pull toward a discussion of affordable housing, but we’re not going there now) .

None of this is to say that “livability” isn’t a critical ingredient of urban density (file under stupid-simple). Density advocates have expended an enormous amount of energy articulating their vision for how density can be livable, while at the same time helping us become more sustainable. If some folks disagree, that’s fine. But that disagreement is empty rhetoric if it isn’t backed with a credible alternative vision and plan. I’m still waiting.

29 Responses to “Yes Virginia, Density Causes Sprawl—Lorax Edition”

  1. Clayton

    Dan, Though the corollary you present may be a myth, and other specious arguments have been made, your post appears to present an either/or scenario for tree/open space preservation and increased density. We can have both, even adding open space along with density. Beyond carbon sequestration and storm water management, there are multiple benefits from trees and green space not as easily quantified.

  2. City Comforts


    I am so glad you have raised this issue of tree canopy.

    The City of Seattle claims that Seattle has lost a huge percentage of tree canopy since 1972-3 (I don’t have the exact quote handy but I think it is in The City’s 2007 Urban Forest Management Plan) and has been basing policy on that assertion.

    There is no factual basis for that assertion. The study on which the tree-cabaopy loss number is based was for the entire region from Everett to Tacoma and eastward well into the foothills.

    In fact, to those of us old enough to remember 1972 (I was working for the City in that era doing shoreline management and so was extremely aware of Seattle’s environment) there is little doubt that Seattle has MORE TREES NOW than then.

    The City, however, chooses to ignore the facts and sticks with its claim because, I assume, it make a better story and buttresses certain policies.

  3. MikeP

    If you want to be surrounded by trees, go to the forest. However, recognize that if you want the forest to remain the forest, you have to make the city ever more the city. You might have to live a little ways from a park and that park will probably look more like Cal Anderson than like Seward. What’s the big deal?

  4. City Comforts

    Putting it another way: Over the last 35 years Seattle has become more dense and Seattle has become more treed.

  5. ktstine

    let me know when i can go there about density and affordable housing…

  6. dan cortland

    Don’t city trees reduce summer air temperatures significantly? Wouldn’t that reduce the amount of energy expended on cooling?

    David Sucher, weren’t there two different studies done, one being limited to Seattle proper, and aren’t you confusing the two? Can you provide some data to support your claims?

  7. Clayton

    Mike P et al,
    A dense urban environment (I’m talking buildings, not just parks) could look a lot more like Seward park if we would think outside the proverbial ”box, via green streets, walls, roofs, etc.
    Its not either/or.

  8. Claude

    I agree with Clayton. We must have affordable, denser housing, and at least some trees and green space are important for healthy human existence, as pointed out in a number of studies – as well as making the city more attractive for families (Alex Steffen makes this point). But I don’t think Dan B. was saying cut down all the trees to make way for development. A balance can be struck.

  9. dan cortland

    “Number of trees” does not equal “canopy”. A few young trees planted in front of a townhouse six-pack replacing one or two mature trees on the SF lots is usually an almost total loss of canopy.

    From the American Forests study:

    American Forests conducted a Regional Analysis of the Puget Sound area to determine how the landscape has changed over time….This included 3.9 million acres..Within the regional study area a smaller urban growth area of 422,446 acres around Seattle was also analyzed…The regional trends in tree cover loss are equally pronounced in the 422,446 acre urban growth area.

  10. Nathanael

    Density goes well with trees.

    A high-rise next to a giant park vs. a large number of little houses? Think about it. This is exactly the advantage that most of downtown London has — huge parks, with dense buildings next to them. The Central Park scheme in Manhattan achieved similar types of benefits on a smaller scale.

    Unfortunately Seattle has largely failed to develop giant parks.

  11. City Comforts

    Dan Cortland.

    Yes there was a regional study.

    There is and was no study for Seattle — or if there was, the City of Seattle would not or could not produce it in response to my Public Disclosure Request.

    Of course there is no way for me to prove a negative and I have tried to find the source of the City’s statements but to no avail.

    As to your claim that trees don’t produce canopy, please explain.

    Your statement “A few young trees planted in front of a townhouse six-pack replacing one or two mature trees on the SF lots is usually an almost total loss of canopy.” may or may not be relevant. For one thing, we have to look at canopy over a period of years.

    For another, since you appear to be supporting the City’s claim, it seems to me that you might want to offer some hard numbers on how many trees have been lost etc etc.

    Part of the problem with this issue, generally speaking, is that a lot of well-meaning people seem to assume that a lot of the development that Seattle has seen in the past 30 years has been on lots which had a lot of trees. Just ain’t so. A lot of the development — most probably but then again no one has facts — has been on already developed sites or parking lots etc etc.

    I know it may be hard for people who have not been examining the Seattle environment for the past 40 years to realize, but there were no huge forests back then. It is physically impossible for Seattle to have lost the canopy some claim over the last 30 years as the city didn’t have that much treed area back then.

    Anyway, if you have facts, please bring them forth.

  12. Harry

    Density yes, trees yes, affordability absolutely!

    As said above, the question is not trees vs density, it’s how buildings and canopy relate in the built environment. Managing that relationship and still providing for affordability at significant levels is the true test for livability standards that will eventually marginalize the anti-density NIMBYs.

  13. Jarrett at

    The tree-saving equation is as much about the need for road space as for development footprints. Per-capita road space requirements go up with lower densities, so shifting growth to lower density areas, typically on the fringe, definitely reduces the amount of land that can be devoted to tree cover.

    It sounds like some of the ambivalence of the Seattle tree people is that they’re specifically charged with caring for trees inside the City of Seattle, so they are sensitive to tree loss for infill but not greater tree loss for sprawl on the outer urban edge, far from the city.

  14. dan cortland

    One can also argue that an urban tree provides greater per capita benefit.

  15. City Comforts

    “they are sensitive to tree loss for infill…”

    I think that the issue at hand (I think that is why Dan was posting) is in fact whether there has been any net tree loss from infill development in Seattle over the past 35 years. The contention is usually put something like this: “During the last 40 years Seattle’s urban tree canopy has seen a 50% reduction.” (That’s from Nick Licata.) My question, as soon as I heard that statistic, was to wonder “Where were those forests 40 years ago? Which ones in Seattle have been cut down?”

    I say that none have been cut down over the past 40 years.

    My contention is that the loss of trees and/or canopy from development of the very few vacant lots over the past 35-40 years has been far more than offset by planting of street trees specifically due to development, maturation of the constantly-aging canopy, park development (think Discovery and Magnusson as examples). protection of green belts and public street-tree planting such as during Forward Thrust.

    The City, on the basis of no discernible evidence, says one thing. I, based on memory and logic, say another thing: more development in Seattle has been accompanied by more trees and tree canopy.

    What is missing is a definitive study.

  16. Joshua Daniel Franklin

    Woodland Park Zoo claims to have quadrupled its tree canopy since 1987. They’ve built several new buildings in that time, they just have professional horticulturists taking care of the trees. The same can be said for UW.

    My only thought on the 1960s tree canopy mystery is that the single largest change since then has been more space for cars: new freeways, surface parking lots, wider streets for driving and parking, curb cuts for driveways and garages in Craftsman neighborhoods, and so on. None of that was infill development but it cost a lot of trees.

  17. City Comforts

    Joshua wrote:

    “My only thought on the 1960s tree canopy mystery is that the single largest change since then has been more space for cars: new freeways, surface parking lots, wider streets for driving and parking, curb cuts for driveways and garages in Craftsman neighborhoods, and so on”.

    The reference date used by the City in the loss of urban forest claims is 1973 which post-dates freeway building in Seattle by a decade. The rest of your ideas are plausible but for one thing: it didn’t happen that way. The city you see now was in its physical form the same one I saw in 1973. Few streets have gotten wider, curb cuts are inconsequential in number etc…

    Think about the claim the City makes: ONE HALF of the tree canopy has disappeared since the early-mid 70s. Try to imagine the scale of that change. If it were true it would be huge and would imply the cutting of a huge number of trees. Where were those trees? My assertion is that those trees existed only in the imagination of people too young to remember Seattle in the 1970s or people who simply weren’t here.

  18. serial catowner

    Well, why can’t it be both?

    The amount of tree canopy in Seattle is truly mindboggling to someone who watched the city develop between 1970 and 1995. In the 70s and 80s it was physically painful to see wooded land developed, not least because it happened in the city’s “greenbelts”, which were never owned by the city, but just marked on maps as places where they thought development was unlikely.

    Compared with 1970, Seattle is incredibly dense and developed- as is the tree canopy. Apparently a goodly number of trees grew up.

    I think if we could compare satellite photos from 1970 with today, we could quickly put the kibosh on the city claims. The potential problem is real, though, because trees are high-maintenance in the urban environment, and they can’t fight back when some bozo wants to improve his view or park on the sidewalk.

    In general, you can’t go far wrong if you fight like a tiger to protect greenspace. There will always be lots of people with money, many of whom don’t even live here, looking to make a quick buck. No harm in making them work a little harder and build their development up instead of out.

  19. dan cortland

    I think if we could compare satellite photos from 1970 with today, we could quickly put the kibosh on the city claims.

    …must resist clicking the link to the satellite-imagery-based study that is the basis for the city’s claim.

  20. Joshua Daniel Franklin

    DanC, the American Forests study you linked based on Landsat data looks really interesting. Unfortunately the report you link to only summarizes findings for the entire Puget Sound region (with one Bellevue neighborhood example). Looks like the findings are a product you can purchase (also require ArcGIS):
    If they really do have neighborhood-level data it would be interesting to see.

  21. City Comforts

    Once again: I asked the City via the Public Disclosure Law to provide the information to support its claims of tree canopy loss.

    It could not do so.


    Go ahead and repeat my experiment. If you get some hard facts which relate to Seattle, and/or which prove things one way or another, please share it.


    And let’s remember why this issue is important. It goes back to Dan’s critically-important statement that it is crucial to dissociate the idea that increased urban density means declining quality of the natural environment (in this case the urban forest.)

    My belief is that a fair-handed study of the Seattle situation will show just the opposite: that increased urban density is consistent with increased urban tree canopy and not just in theory — but in fact.

    Go get ’em, academic researchers in geography, urban planning, forestry. Let the facts fall where they may.

  22. Ross

    My guess is that we are within 5 or 10% of where we were in the early 1970s. Here is why:

    1) Big additions (as already mentioned) in Discovery and Magnuson Park plus a smaller addition due to Freeway Park.
    2) Losses due to bigger houses. Seattle is a nice place to live so wealthy people have moved here. Many of them have cut down old trees (on their lot) and expanded their house.
    3) Suburban style expansion. Much of the city is (or at least was) suburban in nature. Their was some old fashioned, suburban style growth in the North, South and West (Magnolia) end of the city. Not as much as Bellevue, certainly, but enough to move the numbers a bit (probably similar to the loss due to bigger houses).
    4) Conversion to apartments, condos, or multiplexes. As much as I believe in density, I have a hard time believing that we didn’t see a net loss of trees in, say, Ballard. A lot of houses with trees got replaced by condos and multiplexes with concrete. But here is where the same folks who complain about loss of tree canopy are dead wrong about their policies. It is the policies which lead to the concrete (for parking) not the density. The developers would have loved to save the trees (or plant some new ones) and not worry about the parking. The neighbors might have complained about the parking (eventually) but they wouldn’t have complained about the new development (since it would have been much nicer). The answer is obvious, get rid of the parking requirement; get rid of the restrictions on mother-in-law apartments; get rid of the restrictions on backyard cottages. All of those changes will be good for the trees (and homeowners and renters). Oh, and since we’ll have a lot more people in the city, we’ll be able to better afford a lot more park land. Perhaps we could make a nice big park downtown, by Westlake (oops — too late) or maybe a nice “public commons” by South Lake Union (oops, too late again). All kidding aside, the argument that increased density in Seattle will lead to a huge loss of tree canopy is rather absurd.

  23. David

    Seattle’s tree canopy is not only smaller than it was in the 70s AND in the early part of the last decade, it is less functional for all the things that make tree canopy important. (For the person who did the PDR, Seattle did not do the 1970s satellite work, so they would not have those data in hand. You PDRed the wrong agency. )

    Seattle’s tree canopy is less functional because we have replaced evergreens with deciduous street trees and lost most of the value of our tree canopy in the process.

    Deciduous street trees, in our weather area:

    1. Have 50-60% less stormwater retention
    2. Fail at scrubbing small particles from the air during the winter when we most need that service because of climatological patterns
    3. Fail at wind screening, which is the most important energy saving aspects of trees in our area because they have no leaves during our highest power usage times.

    If you’re inclined to read the science in this area, I’ll give you a free tip: You have to read both the methodology and the measurement method in urban forestry scientific papers. Most of the errors I read above are due to well-meaning people not getting past abstract or summary data.

    For example, almost all of the stormwater retention data comparing deciduous to evergreen concludes the difference between the two is minor. The error in applying this to Seattle is the bulk of our rain comes when there are no leaves on the trees. SPU has a most excellent summary scientific review on this subject that is worth reading as a first step before reading other scientific papers on the subject.

    Every city in our area, and international favorites mentioned here often, have stronger tree regulations than Seattle. Stronger tree regulations are not a barrier to density. To the contrary, strong tree regulations make it more likely people want to live and shop in our urban villages because it preserves tree canopy. The scientific data on this are very clear.

    That urban tree preservation is a NIMBY issue is a flat-out falsehood. Sure, some NIMBYs use trees to argue against development but that does not make tree preservation a NIMBY goal.

    Take the Roosevelt/Cicely property example. There was no reason to take down the significant cedar there. Shrink the unit sizes by single digit percentages and reduce parking and the mature specimen cedar gets to live. Smaller units are cheaper and more energy efficient. No parking is needed at that location because it is blocks from the Roosevelt light rail station.

    Saving the Roosevelt tree would have made the resulting MF development less auto-centric, more energy friendly, and likely more affordable (by unit rent and/or cost to maintain over time).

    1. Less auto centric
    2. More energy friendly
    3. More affordable

    If I understand correctly, those are three pretty important urbanist goals.

    Yet people decried those trying to save that tree as “NIMBYs”.

  24. Transit Guy

    Kudos to David Sucher and others here questioning the conventional wisdom about Seattle’s shrinking tree canopy. I came here about the same time David did, when Wes Uhlman was elected mayor — a new ideas Democrat replacing the conventional businessmen Republicans who had held the office up until then. Before Uhlman, Seattle had NO street trees, save for the Olmstead boulevards and what a few individual homeowners chose to plant.

    In the last 40 years, tens of thousands of street trees have been planted, in some neighborhoods producing canopy that covers the entire street right of way. Yes, we’ve lost some greenbelt acreage and trees on vacant lots have been cut down, but it’s hard to imagine that those loses are not more than offset by the tremendous number of trees now lining city streets and arterials.

  25. Ross

    Very good points, David. I really like the last couple of paragraphs (which go along with what I said). Specifically;

    “…reduce parking and the mature specimen cedar gets to live.”

    To a large extent, this is the cause of much or our urban canopy problem. The rules that require parking have knocked down mature evergreen trees and made the new development really ugly. I applaud the efforts by the developers of the last ten years. They have managed to create relatively nice places despite the stupid rules. But the development that took place in the 80s and 90s was really ugly. We got density, but we got a lot of concrete with it. We lost trees and nice landscaping. This made for neighborhoods that are no longer nice to wander. Much of the “anti-density” attitude started with such eye sores.

    I’ve said it once and I’ll say it again: this should be a high priority for the new administration. Much of what we would like the city to do will require money. However, changing the development rules will actually help homeowners, developers and renters:

    1) Allow more mother-in-law apartments
    2) Allow more backyard cottages
    3) Ease up on the parking requirements for new developments

    At a minimum, perhaps we should try and kill two birds with one stone: How about easing the parking requirements if trees are preserved (or planted). That would have made perfect sense for the example given.

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