According to the San Jose planning department, “trees make the city a healthier, more beautiful place. They provide residents many benefits…shade, beautifying the city, and improving air quality.”
But our city’s tree canopy is at risk. The planning department reports that “citywide tree canopy cover has decreased from 15.36% in 2012 to 13.54% in 2018. That’s 2.7 square miles of tree canopy cover! Replacing lost canopy isn’t easy; it can take 30 to 40 years to replace a mature tree.”
The elimination of single-family zoning (i.e., SB9 ) will accelerate this loss of citywide tree canopy. By its very nature, SB9 spreads new construction horizontally across our city. It is a low-density addition to existing low-density neighborhoods, which will require the removal of many trees on existing single-family lots. Economically motivated developers will use their newly granted rights under SB9 to build out to the maximum footprint on every parcel they acquire for conversion to multi-unit use, trees be damned!
High-density Urban Villages, on the other hand, increase housing density vertically, not horizontally. This minimizes tree canopy destruction. Simply put, multi-story high-density Urban Villages maximize the number of new housing units per tree removed.
A comprehensive study using Google Earth imaging technology in Seattle, one of the few municipalities to implement an ordinance similar to SB9, confirmed that replacing single-family homes with duplex, triplex and fourplex units resulted in significant tree canopy loss.
Today single-family lots in San Jose account for less than 62% of all land use, but 70% of all trees. Under SB9, the conversion of these single-family lots into multi-unit dwellings will inevitably lead to accelerating tree canopy loss throughout the entire city. Even more concerning, the conversion of single-family lots to multi-unit use—and the resulting tree canopy loss—will be greatest in the most economically disadvantaged parts of our city where land purchase costs are lowest.
“High-density Urban Villages minimize tree canopy destruction while creating the population centers needed to support mass transit. Because they minimize the amount of land required for buildings and roadways, there is more room for trees; they are the very definition of smart growth,” explained Dave Poeschel, a conservation activist with the local chapter of Sierra Club. “The proposed citywide [...] ordinance is the opposite. It would expand low-density developments across the city and their building footprints, likely accelerating the number of tree removals in our city already woefully short of tree canopy, especially in East San Jose. Vertical growth clearly beats horizontal growth for environmental sustainability.”