Matching Urban Infill With Tree Infill

Seattle shows how new buildings and new trees can be added to a city simultaneously—in fact, neighborhoods adding new buildings are maintaining its urban tree canopy while static single-family neighborhoods are losing trees.
September 19, 2018, 9am PDT | James Brasuell | @CasualBrasuell
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Dan Bertolet shares news about Seattle's effort to grow and maintain its tree canopy even while building new residential and commercial buildings to keep pace with its rapid growth. There's a catch to the consequences of Seattle's population and economic growth.

Seattle’s best new data [pdf] on the change in tree canopy over time does show a 6 percent decline between 2007 and 2015. Here’s the catch, though: most of the confirmed tree loss happened on land reserved for detached houses, the single-family zones that cover over half the city but where population has barely budged for decades.

Meanwhile, the same study found no statistically significant change in tree canopy [pdf] where the growth actually has been happening: the land zoned for commercial buildings and multifamily housing that absorbed the vast majority of Seattle’s new apartments, offices, and stores.

Bertolet cites the data to build an argument against some opponents of development who would use trees as a prop in a narrative about he destructive consequences of urban infill as the city reconsiders its tree ordinance. "Tree preservation rules that would sacrifice new urban homes—that is, housing that can accommodate a lot of people on a small amount of land—becomes even more indefensible when you factor in the resulting shift of development pressure toward places where low-density housing construction obliterates far more trees," writes Bertolet.

The article then expands its purview to include analysis from Treepedia's Green View Index, which "quantifies how much tree cover a person at street level experiences," according to Bertolet. That tool allows comparisons between Seattle and other cities like Portland, Sacramento, Los Angeles, and Vancouver, British Columbia.

Bertolet's comprehensive, feature-length examination of Seattle's tree canopy didn't go unnoticed in Portland either. Rachel Monahan and Michael Andersen both picked up the story and applied its lessons to Portland.

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Published on Tuesday, September 18, 2018 in Sightline Institute
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