Landscaping the future

It has long been acknowledged that the built environment sector is the largest contributor of greenhouse gas emissions globally. This has precipitated intense efforts to reduce both embodied and operational carbon emissions. However, the landscaping associated with buildings is frequently overlooked. Recently there has been more conversation around landscape architecture and its influence on the sustainability of the built environment it complements.

Where’s the problem?

“Landscaping” may seem innocuous in terms of the environment, but the reality is that urban landscape design often uses materials similar to those of the buildings themselves, with the same kind of embodied carbon concerns. Landscape designs generally incorporate various hard surfaces, structures and urban furniture. Estimates show that around 75% of emissions related to landscape designs are from embodied carbons in materials, while the balance relates to operational emissions from irrigation, lighting, security and maintenance functions.

Although quick to point out that he is not technically a landscape architect, Marc Sherratt, managing director of Marc Sherratt Sustainability Architects (MSSA), has been very involved in landscape design as part of his sustainable building projects. According to Sherratt, “Landscape [design] has largely been undervalued in its impact and role in green buildings in South Africa.” He further explains that GBCSA has noted this and included an Ecological Regeneration credit in Version 2 of its Green Star New Build rating tool, currently in its pilot stage.

Quantifying the impact

Landscape interventions can have their “cradle to grave” carbon footprint measured in a similar way to buildings. This Whole Life Carbon Assessment (WLCA) takes into account material make-up, including carbon emissions generated by their extraction or manufacture, transportation and installation.

perational emissions can also be measured as part of the same assessment process. There are various tools available to quantify carbon content of common materials, and declaration labels explaining the material’s origin and content may also be available. Materials such as concrete and steel have high WLCA figures (although the latter less so), while locally sourced, natural materials have a lower environmental impact than imported, high-energy manufactured materials. Also important is how clean the electrical grid is that’s used in the material manufacture. Reused, recycled or reclaimed materials are also helpful contributors towards lowering carbon.

“Carbon capture and storage technology remains unproven at scale and very expensive, and vegetation remains our best ‘technology’ to remove carbon dioxide from the atmosphere,” says Sherratt. That means protecting existing forests, grasslands, wetlands and peatlands, and then “rewilding” areas damaged by development. The amount of carbon sequestered (stored) by plants, and therefore not released into the atmosphere, can be measured in different ways. Sherratt explains that wetlands and peatlands store their carbon in the soil, which can easily be sampled and tested in laboratory conditions. Forest carbon is commonly stored in the trees themselves. Sherratt adds that, generally, the higher the biodiversity, the better the carbon sequestration figures. So, indigenous, locally sourced, bio-diverse landscapes should be targeted.

Dr Peta Brom, senior sustainability consultant and certification operations manager at Ecolution Consulting, adds that “At the ecosystem scale, scientists are finding that wetlands punch well above their weight in carbon sequestration, and that, counterintuitively, fire in grasslands expedites carbon sequestration. While, historically, biomass has been a rough measure of the capacity for carbon sequestration, we know today that even different species of the same size metabolise – and therefore sequester – carbon at different rates. As we learn more about how landscapes interact with carbon, it is changing both our designs and landscape management practices.”

Tanya de Villiers, director of CNDV Landscape Architects, warns that planting alone will not balance the carbon sums, however. Landscape architects need to first reduce the high carbon materials rather than try to offset them after the fact. She also believes that carbon should be considered at a building or precinct level as a whole: “Reducing the carbon footprint is a team effort. We once tried to add enough trees on a project to make the entire precinct carbon neutral. That was, unfortunately, impossible.”

South African context

De Villiers notes that local landscape architects are well aware of the requirements for creating a sustainable, carbon-neutral landscape – factors such as topsoil conservation; water conservation; material reuse; on-site composting; reducing invasive species; low-water plant selection; and the use of local, low maintenance and long-lasting materials. Planted roofs expand the area available for planting, and trees provide natural shading and cooling. The Green Star New Build V2 rating tool will also be able to provide a useful guide for creating and monitoring landscape designs.

“Landscape architects straddle architecture, spatial planning, civil [engineering] and environmental aspects,” De Villiers says. “They’re able to bring [everything] together as a whole.” She expresses some frustration that landscape architects are often brought on too late in a project programme and presented with a fait accompli design, and that quantity surveyors are generally not trained to accurately cost landscape aspects and often allow for too little in the budget, forcing designs to be squeezed even further.

Another issue, as highlighted by Sherratt, is that along with other professionals, landscape architects’ fees are often negotiated and discounted to a point where very little research and development can be implemented. De Villiers elaborates: “Clients are often unwilling to take risks or allow any different strategies to be implemented. [They’re only] willing to add something if there is a proven precedent. Innovation, therefore, is difficult.”

Local pioneers

The first GBCSA-certified Net-Positive Ecology: Level 2 – Operational Ecology project in South Africa was the offices of dsm-firmenich in Midrand. A leading global producer of sustainable nutrition, health and beauty solutions, dsm-firmenich holds positive climate and nature impact requirements as part of its vision statement, and targeted four net-positive certifications for its offices: Carbon, Water, Waste and Ecology. The Ecology rating tool stipulates that around 15% (about 1 500m²) of the site be regenerated landscaping. Marc Sherratt, who was invited to collaborate on its landscape design, established that the site’s native landscape would have been Egoli Granite Grassland. He set about replacing the existing kikuyu lawn and other exotic planting with ethically sourced indigenous species that would have previously been endemic to the region.

As part of its 6-Star Green Star Sustainable Precinct accreditation, Stellenbosch residential development Newinbosch set out to achieve “Ecological Connectivity” as a credit related to “Innovation”. The team explored “connectivity” and what it would mean for the site. Ecolution Consulting’s Dr Peta Brom considered both structural and functional connectivity by mapping its location in relation to other biodiverse, natural habitats in the area. Structural connectivity was possible via an existing stormwater culvert to the Plankenbrug river, a waterway running near the site.

Tanya de Villiers was the landscape architect responsible for the associated philosophy and design interpretation. A landscaping palette was developed by referencing the local ecosystems within a 2km radius of the site to foster functional connectivity through ecological “stepping stones”.

The historic habitat type for this site would have been a lowland, shrubby environment called Swartland Shale Renosterveld, which can evolve into a low-growing woody forest. Thus, the ecologists and designers set out to create a regenerated combination of these habitats. The result is a desirable housing estate that is set in the context of a biodiverse and sustainable landscape.

What next?

Landscape architecture can have a larger effect on the carbon emissions of a project than we may think, so it is far better to harness that effect for good. For this to be achieved, the landscape architect needs to be brought onto the project early and allocated a reasonable budget. Designers should then try to reduce high carbon-releasing materials by reducing infrastructure first and then selecting natural, local and recycled materials.

Sherratt reiterates that concentrating on an indigenous and connected natural ecosystem will assist with storing carbon, away from the atmosphere, for at least the lifespan of the building. Expanding beyond a single site, Sherratt emphasises that “focus should be on clever, affordable ways for landscapes to be connected over/under roads, through walls and across buildings, so cities can support indigenous species migration.”