News Brief

Pathfinder Tool Helps Landscape Designers Sequester More Carbon

Even a garden or park can take decades to become carbon positive. With a little effort, it doesn’t have to be that way.

Two designs for a city plaza are contrasted; both contain a large water feature and a concrete sidewalk, but one integrates many more trees and shrubs.

Adding 14 trees, converting 20% of concrete path to shrubs, and substituting wood for concrete site walls help cut the number of years it will take this plaza to be carbon positive from 194 to 20. 

Image: Climate Positive Design
Life-cycle assessments and embodied carbon are gradually becoming a bigger focus in the architecture world. But even for project teams that carefully track carbon impacts, rarely does the accounting include the site’s landscape design. A new tool called Pathfinder helps teams fill that gap and create projects that sequester more carbon in the process.

“Landscape designers have not had a seat at the table for the discussion about life-cycle assessments,” Pamela Conrad, the creator of Pathfinder and principal at CMG Landscape Architecture, told BuildingGreen. That’s a problem because ignoring the landscape distorts both sides of the carbon ledger. Omitted are the carbon emissions embodied in retaining walls and pathways, as well as those associated with mowing, fertilizing, and maintaining lawns. But also forgotten is the carbon sequestration provided by the trees and vegetation. “As a result, we have not been harnessing the sequestration power of landscapes,” says Conrad.

Pathfinder allows landscape designers to better understand these climate tradeoffs and to design projects that will be carbon positive in a short amount of time. The tool relies on datasets from the Indiana Impact Estimator and the U.S. Forest Service to estimate the embodied carbon, operational carbon, and sequestered carbon of a given landscape design. It then reveals how many years it would take for the designed landscape to sequester more carbon than it took to build and maintain.

Conrad has also rolled out the “Climate Positive Design Challenge,” which asks that by 2030, all landscape designers design their projects to be climate positive within a certain timeframe—twenty years for streetscapes or plazas, and five years for all other projects. The Pathfinder tool recommends strategies for meeting these targets. For example, it may recommend using decomposed granite instead of concrete or stone to reduce embodied carbon.

Currently, using the Pathfinder tool automatically registers a project as a contributor to the Challenge. However, after 2020, projects will have to actually meet the targets to be recognized as a Challenge contributor, according to Conrad. If all landscape design projects met the targets, by 2050 they would sequester one gigaton of CO2 more than they were responsible for emitting, she said.

Pathfinder is meant to be used in early design to compare the climate impacts of different designs and materials. Conrad still encourages project teams to use other tools like Athena and Tally to get a highly accurate inventory of greenhouse gas emissions that accounts for embodied carbon from material installation. The GHG Planting Calculator should be used to calculate precise  sequestration by plant species.

For more information:

Climate Positive Design
https://climatepositivedesign.com

Published October 7, 2019

Add new comment

To post a comment, you need to register for a BuildingGreen Basic membership (free) or login to your existing profile.