Landscape Architects Are Key to Increasing Carbon Drawdown

Central Park Open Space Plan, Denver, Colorado / Andropogon

“To quote Vaclav Smil: ‘human societies are nothing but subsystems of the lithosphere, the Earth’s thin veneer of life, which is ultimately run by bacteria, fungi and green plants,'” said José M. Almiñana, FASLA, Principal, Andropogon Associates, and ASLA Climate Action Plan Task Force Member at Greenbuild in Washington, D.C.

Within this system, there is a “sticky substance that holds soils together.” It is called glomalin, and it’s a protein produced by mycorrhizal fungi. “It’s responsible for sequestering 27% of the carbon in soils,” Almiñana explained.

Humanity will decide what happens to the future of this thin veneer. If we preserve and regenerate landscapes, we will ensure they store more carbon. If we use a “place-based approach,” we will also help communities better connect to restoration efforts.

For example, the Central Park Development Plan* in Denver, Colorado reimagined a former airport landscape that was “polluted and decimated.” A new open space plan proposed by Andropogon in the mid 1990s enabled the restoration of a buried creek and the landscape (see image above).

“Once the decision was made to protect open space and recover the creek, all sorts of productive opportunities became a possibility.”

Almiñana’s point was that carbon sequestration must start with the landscape. And improving the health of landscapes will not only yield more carbon storage, but also provide more climate resilience and other important human health benefits.

Much of the conversation about climate change and the built environment has been focused on “how to do less bad” by reducing carbon-intensive materials, said Katie Riddle, ASLA, Director of Professional Practice at ASLA.

This is important work, but among the design professions, only “landscape architects can also do more good” by increasing carbon drawdown in the landscape.

Riddle highlighted a 2017 study from The Nature Conservancy, which found that “increasing carbon sequestration in plant biomass has the greatest potential to reduce net carbon emissions and slow the effects of climate change.”

These kinds of ecological strategies form the foundation of the ASLA Climate Action Plan, Riddle said.

Chris Hardy, ASLA, Senior Associate, Sasaki; Founder, Carbon Conscience; and Co-Chair, ASLA Climate Action Committee Subcommittee on Climate Drawdown and Biodiversity, has also focused on helping landscape architects do more good.

He is interested in increasing the “climate literacy” of landscape architects. This is crucial because “developers and clients increasingly expect it.”

Hardy led the development of Sasaki’s Carbon Conscience tool to help landscape architects, architects, planners, and others better understand the climate impacts of their design proposals. It’s for early phase design work when there is the greatest opportunity to reduce carbon and increase sequestration.

He wants to see more analysis of site carbon opportunities woven into projects, shifting from a model of whole building lifecycle assessments to whole site lifecycle assessments.

Whole site lifecycle assessment / Sasaki

“There are lost opportunities if we don’t factor in the landscape. For example, California’s updated building code, which regulates embodied carbon in buildings, ignores biogenic carbon in the landscape.”

“We need to expand the spatial boundaries of lifecycle assessments. The living environment is the only viable way to sequester carbon,” Hardy said.

Role of biogenic carbon. Carbon Conscience / Sasaki

But he also cautioned that “not all sites and not all ecosystems are equal.” This is why it’s important to work with a landscape architect to figure out the carbon storage potential of a site.

The Sustainable SITES Initiative (SITES) is another tool for reducing emissions and increasing sequestration in the landscape, said Danielle Pieranunzi, SITES Director, Green Business Certification Inc. (GBCI). “70 percent of SITES credits contribute to improving carbon drawdown.”

SITES is similar to LEED but is designed for landscapes that may or may not have buildings. Now, 336 projects in 41 states and D.C. and 20 countries, spanning over 1.2 billion square feet, participate in SITES.

The U.S. General Services Administration, which manages federal buildings, has required SITES certification for its projects. The State of Rhode Island and recently the City of Austin, Texas followed suit.

“SITES requires an integrative design process, which creates an opportunity to be climate and nature positive,” Pieranunzi said. She noted how the ASLA Climate Action Plan builds from SITES and is closely aligned with its goals.

“SITES shows how important soils and plants are. It’s also about reducing embodied carbon, conserving what is healthy and functional, and restoring landscapes.”

Almiñana shared other projects by his firm that show how landscape architects can increase carbon sequestration.

For the Greenville Courthouse in Greenville, Mississippi, Andropogon increased the diversity and quantity of trees and plants in their design proposal.

Greenville Courthouse sequestered carbon, Greenville, Mississippi / Andropogon

Using Climate Positive Design‘s Pathfinder tool, they were able to increase carbon sequestration through the landscape and modify materials so that it would take 32 years to reach a climate-positive state — in which more carbon is stored than emitted.

Greenville Courthouse, Greenville, Mississippi / Andropogon

For the new net water- and energy-positive Yale Divinity School Living Village in New Haven, Connecticut — which is also being certified as part of the Living Building Challenge — they planted more than 230 new trees and significantly increased permeable surfaces. “We doubled the landscape’s capacity to sequester carbon.”

Yale Divinity School Living Village, New Haven, Connecticut / Andropogon

*Almiñana noted that the name of the Central Park neighborhood was changed from the Stapleton neighborhood in 2021. The community had been named after the decommissioned Stapelton airport that once comprised the site, which in turn was named after former Denver Mayor Benjamin F. Stapleton. Community association members voted to change the name of the community after learning Mayor Stapleton had been a member of Klu Klux Klan in the 1920s and in the wake of protests after the murder of George Floyd. The Denver City Council unanimously approved the name change.

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