For decades, developers have blamed conservationists for contributing to the San Francisco Bay area’s notoriously high housing prices--the claim being that removing land from development ends up shrinking the supply of buildable land, which then drives up real estate prices. But a new study out of Stanford University suggests that the impact of conservation on the housing landscape over the past half a century has in fact been rather minimal.

The reason, researchers say, is that most of the acreage set aside by government and nonprofits as protected parks, forests, coastlines, and wildlife habitats is not suitable for residential development, due to steep grading conditions and high water tables.

To arrive at this conclusion, Stanford researchers married maps of housing development and land conservation patterns in Silicon Valley over the past 60 years. The spatial overlay was created using material from two preexisting databases (from the U.S. Geological Survey and the nonprofit GreenInfo Network, respectively) that had never been combined.

Modeling studies were then created to project what the density of the region’s current share of conserved lands (about 116,000 acres) might look like today had that land been available for development all along. Topographically similar areas of unprotected land left open to the free market were used as a point of comparison. 

“What we found is that the areas that were preserved were less likely to be developed anyway,” says researcher Jon Christensen, executive director of Stanford’s Bill Lane Center for the American West.  “At least they were less likely to be densely developed in a way that would result in a significant number of new housing units. These places were originally set aside with the intent of having open space and recreation for a reason.”

The research team estimates that had all that preserved land been made available for development, it would likely have added an extra 51,000 housing units to the landscape--a number equal to about 6.5% of the 790,000 homes in Silicon Valley today.

But not necessarily the kinds of homes that are needed most. Factoring in site constraints, the modeling studies found that even if protected land had been open for real estate development, it could only have supported homes at a density of 1.2 per acre, doing little to ameliorate the affordable housing shortage in an area where the median home price is $350,000.

“Our hope is that these findings will take old argument that pits housing against conservation off the table,” says Christensen, who developed the study in partnership with sociology grad student (and primary researcher) Carrie Denning, and Robert McDonald, a landscape ecologist with the Nature Conservancy. 

“We realize now that it’s more complicated than that and that housing development and conservation have really gone hand in hand in some very interesting and important ways. Historically, lands have been conserved for different reasons over time, whether the goal has been to create parks and recreation areas for people, to protect delicate ecosystems, or to preserve open space and foster biodiversity.  If we look at the past half century, we now have a full picture of what conservation means for people and nature, and that can lead to more integrated approaches to conservation and development going forward.  Nature is one of this region's most prized amenities.”

The study findings were originally published in the journal Biological Conservation.

Jenny Sullivan is a senior editor covering architecture, design, and land use for BUILDER. 


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