Landscape architecture studio Stimson used Pathfinder to develop a Sustainable Landscape Implementation Plan for Pennsyl­vania State University. Published earlier this year and prepared in collaboration with horticulture consultant Phyto Studio and Conrad’s Climate Positive Design, the study concentrates on the core of the school’s main campus, Uni­ver­sity Park, encompassing nearly 430 acres. It examined strategies for a transition from mostly manicured lawns (making up more than one-third of the study area) to landscaping that is ecologically healthier, with lower maintenance requirements.

Penn State’s groundskeeping staff has already incorporated many ecological practices into its maintenance regimen. For instance, crews use very little chemical fertilizer, and they do not irrigate. Even so, Stimson and its collaborator found that the study area is responsible for 72,750 kilograms of CO₂ emissions per year. The lion’s share (57.1 percent) are generated by the decomposition of lawn clippings, with almost all the rest stemming from equipment use, both gas- and electric-powered, such as mowers, clippers, and leaf blowers.

Image: © Sasaki

At Ellinikon (above), Sasaki evaluated the carbon implications of land use, programming, and design decisions, starting with early project phases (below).

Image: © Sasaki

The report determined that the university could cut biogenic emissions by 60 percent and increase carbon-sequestration potential by 40 percent if it expanded campus tree cover, reduced mulched areas, and converted underutilized lawns to higher-performing, lower-maintenance ground flora, among other practices. And it identified locations distributed throughout the core campus, nearly 85 acres in total, as prime candidates for the transition, including th¬ose that are not used for recreation, are not in front of an historic campus building, or are often shrouded in shade, explains Matt Langan, Stimson technical director.

To jump-start the transformation, the report includes designs for two pilot projects—a 15,000-square-foot “sun meadow” and a 20,000-square-foot “shade meadow”—each with a unique combination of flora that will thrive in the select setting and particular solar exposure and include flowering varieties to provide what Langan calls “pops of color or sparkle” throughout the growing season. Planned for highly visible locations on campus in order garner support from the university community, pilot-project implementation is slated for next spring, pending funding.

If such landscape conversions were adopted at Penn State at scale, along with a move to an all-electric equipment fleet and a university-wide switch to renewable energy, management of the school’s grounds could achieve net zero operational emissions by 2035 (its emissions would be less than the amount that the landscape could sequester). This equation does not take into account the embodied carbon associated with any future landscape construction projects, however. To help keep these emissions in check, the report includes recommended changes to the school’s landscape-construction standards, including prioritizing salvage and reuse, minimizing new paving, and eliminating or reducing PVC piping.

Sasaki, meanwhile, is using Carbon Conscience on its own projects, including Ellinikon, a park under construction on the former Kalamaki Airfield in Athens. It is projected to reach carbon neutrality within 35 years, meaning it will store at least as much carbon as is emitted, and continue to function as a carbon sink into the future. On the surface, the time frame might not sound impressive, but the scale is vast for a new park in such an ancient and densely populated city. Encompassing more than 650 acres, Ellin­ikon is larger than the city-state of Monaco; when complete at the end of the decade, it will single-handedly increase the amount of open space, per Athenian, by 44 percent.

The park is part of a larger redevelopment project master-planned by Foster + Partners on the land of the old airport, which was decommissioned in 2001 and subsequently used for sports venues during the 2004 Summer Olympic Games. The new development, organized into mixed-use neighborhoods, includes apartment buildings, hotels, and shopping malls, with buildings by Foster, Kengo Kuma, and BIG.

Image: © Sasaki

Sasaki came onto the project as landscape architect after the master-planning phase was complete, but by using Carbon Conscience and other tools the firm was able to convince the client to examine the character and scale of certain elements, moving the project toward what Michael Grove, Sasaki principal, calls a “true restoration ecology,” with re­established grasslands, riparian corridors, and freshwater wetlands.

Relying on Carbon Conscience as well as Pathfinder, and with carbon-analysis assistance from environmental-design consulting firm Atelier Ten, Sasaki and local landscape architect Doxiadis+ created a scheme that prioritizes maximizing sequestered and stored carbon and focuses on reducing embodied carbon. The team says that their design cuts embodied emissions by 45 percent, compared to a more traditional approach.

The park’s plants, more than 3.3 million of them—including trees, shrubs, geophytes, and herbaceous material—are being procured within Greece and were selected for their ecological benefits and adaptability to the site’s highly alkaline soil and its climate. They will be almost entirely irrigated with reclaimed water from a system comprising a stormwater-collection lake—repurposed from the former Olympic canoe and kayak venue—and a network of constructed wetlands, rain gardens, and bioswales. “We daylit as much of this infrastructure as possible, to avoid piping and channelization,” says Hardy, thereby conserving embodied carbon.

The project’s biggest carbon savings come from material reuse, including amending the existing soil rather than replacing it, and minimizing the employment of new concrete by salvaging the site’s considerable pavement. The former runways and tarmac, for instance, will be used as hefty monolithic slabs for new surfacing or broken up for aggregate in road base. The salvaged concrete will also to be incorporated into gabion walls and dry-stacked retaining walls. “It is gorgeous material, without rebar, and containing quartzite and marble,” says Grove. “It looks like terrazzo when polished.”

The design team’s considerations went beyond plants and materials. They also included energy modeling, which helped size an on-site solar array. With vehicles and equipment planned to be all-electric, the park should be operationally carbon neutral on day one. The multifaceted nature of the Ellini­kon, as well as that of the proposed revamp of Penn State’s campus, and the ongoing renewal of Houston’s Memorial Park, illustrate the level of analysis and thoughtful design needed to create low-carbon landscapes. When based in data and backed by science, the built environment beyond buildings can play a significant role in helping mitigate the climate crisis.

Supplemental Materials:

Designing with a Carbon Conscience V2: a web-based application to inform planning and urban design projects on potential carbon impacts, Sasaki Associates, Chris Hardy, Michael Frechette, June 2023. (Through page 13).