Idea #7

Plant Trees Strategically and Wisely

by Frederick Steiner

Design is how we articulate and visualize different possibilities for our future. Design can address mitigation, adaption, and transition in response to climate change. All three require that we follow Ian McHarg’s advice and “design with nature.” The Kentucky poet Wendell Berry tweeted about the power of nature on June 1, 2019: “Nature is a party to all our deals and decisions, and she has more votes, a longer memory, and a sterner sense of justice that we do.” We have designed against nature for too long.

To design with nature requires ecological literacy. We need to know how to read landscapes and to act on that knowledge. Ecological knowledge is what we can learn from our interactions with the natural and cultural worlds around us. The ecosystem services concept can help us understand the values we derive from nature and then to mitigate, adapt, and transition with the changing climate. These services account for the direct and indirect contributions of the natural world to human well-being.

The Green Business Certification Inc.’s SITES rating system is grounded in ecosystem services and should prove especially helpful in adapting built outdoor environments to change. The system enables designers to rate how different environmental elements – soil, water, and plants – are employed in the planning for a park, a campus, an office complex, a waterfront, a parking lot, or a cemetery. The SITES system addresses almost anything outside beyond the building envelope. Such places can be designed to contribute to ecosystem services, conserve energy, and reduce greenhouse gas production. SITES can be employed on projects with or without buildings.

Chazdon and Brancalion (2019) have identified an urgent need to replenish tree canopy cover to avoid the devastating effects of climate change. In a recent Science article, Bastin and colleagues (2019) note that tree restoration is among the most effective strategies for climate change mitigation. Trees alone can do much to mitigate climate change, especially in temperate regions and SITES provides guidance about how to use trees and other vegetation. Trees help reduce stormwater runoff, improve water and air quality, and absorb atmospheric carbon. Through absorbing carbon, trees lower greenhouse gases that contribute to global warming. Shade from trees cool areas, making them more pleasant, and minimizing urban heat islands. In addition, tree shading can help lower energy use in buildings. To take advantage of shade, the vegetation needs to be planted strategically. Trees are especially effective when designed to cast shadows on air conditioners, windows, and/or walls. Furthermore, their location on the side of the building receiving the most solar exposure can be useful. Rows of trees and shrubs can be deployed as windbreaks to improve the microclimate in some places.

With the SITES rating system, the emphasis is on conservation of plants as well as special status and native vegetation. Through the use of this system, site plans need to optimize biomass, reduce urban heat island effects, and minimize building energy use. For trees to flourish, they need good soil, ample water, and sunlight. SITES provides practical guidance about how to design these elements together. In addition to what we gain, other species benefit from vegetation as well. Through the use of the SITES system, the design team accumulates points for positive actions with plants.

Meanwhile, we should be aware that the trees, especially in tropical flooded areas, are a source of methane . Generally, trees store more carbon than the methane they emit. Overall, trees are generally good for the climate and have many other positive benefits. In addition, trees in temperate regions produce less methane then their counterparts in the tropics. As a result, we need different planting strategies for temperate and tropical regions. SITES, for example, was developed for temperate region site design. It should be redesigned for the tropics or a new system conceived entirely.

Designing with nature, including planting trees strategically and wisely, can help mitigate the effects of climate change as well as adapt to those fluctuations. More ambitiously, if we can apply ecological knowledge to all our designs and plans, we can transition to a future free from the deleterious consequences of climate change.

Frederick “Fritz” Steiner is Dean and Paley Professor at the University of Pennsylvania Stuart Weitzman School of Design.