91视频

There’s more to green roofs besides stormwater retention and energy savings, and Portland State University graduate student Sydney Gonsalves is looking into it.

She is researching the biodiversity of Portland green roofs to prove that they also provide viable urban habitat. Her efforts to collect, count and identify beetles residing atop eight Portland buildings are part of a global study 鈥� led by the Zurich University of Applied Sciences in Switzerland 鈥� that could influence green roof design to maximize habitat potential.

Researchers in San Francisco and Mexico City are conducting similar studies to compare biodiversity on green roofs in different climates.

鈥淭here has been a lot of research on the stormwater benefits and energy benefits, but in Portland we haven’t done a lot of research of the habitat benefits,鈥� she said.

Gonsalves, who is seeking a master’s degree in environmental science management, said hard data from the study of the habitat value of green roofs will provide yet another incentive for building owners to install them.

鈥淲e know that the urban environment is very complex, but there is a large amount of biodiversity in small patches,鈥� she said. 鈥淲e want to encourage more businesses to do this so we can provide more habitat. We also want to show there is value 鈥� that it’s providing habitat value in the city.鈥�

Her research compares the impact of irrigation on insect diversity and plant growth on different types of green roofs. Along with insect counts, the study will analyze irrigation and temperature data collected with soil sensors. Initial findings indicate that it may not be necessary to irrigate green roofs 鈥� a potential cost savings for building owners, Gonsalves said.

鈥淚 have one roof that doesn’t have irrigation and it looks great,鈥� she said. 鈥淚f the vegetation looks just as good and the beetles look just as good, why (irrigate)?鈥�

To conduct her research, Gonsalves gained permission from Portland green roof owners to place small cups in the soil that trap insects when they fall in. Traps on the ground near the buildings serve as the control.

When Gonsalves started pursuing a master’s degree at PSU last fall, she wanted to do research on green roofs. She reached out to Casey Cunningham, a landscape architect with the Portland Bureau of Environmental Services. He told her he was seeking a graduate student to participate in the Zurich University of Applied Sciences research, and then helped her gain access to many of the Portland green roofs used in the study.

Roofs in the study include the Oregon College of Oriental Medicine, Tri-City Water Pollution Control Plant, Central Wine Warehouse and Hamilton West apartments.

BES staffers have researched biodiversity on green roofs to encourage more to be built in Portland, but the Zurich University study will be far more comprehensive, Cunningham said. In Switzerland, such research has already led to changes in green roof design to provide habitat for an endangered bird species. The impact could be similar in Portland, he said.

鈥淚t could influence how we design eco-roofs in future,鈥� he said.

Gonsalves started testing Portland green roof biodiversity in April and intends to wrap up data collection this month. She hopes to conduct a similar study next summer, during the height of insect activity, with more Portland green roofs included.

Comparing insect counts on different green roofs will help determine which designs make ideal wildlife habitat, Gonsalves said. The eight green roofs in this summer’s study are divided in half between ones with thick soil and high vegetation and others with thinner, gravelly soil and smaller succulent plants.

Research by PSU and other institutions is invaluable to the green roof designers, builders and suppliers, said Elizabeth Hart, market manager of green roofing for roofing materials supplier Tremco. The data will help Tremco staffers tweak green roof designs, soil blends and plant selections to create more effective installations that support habitat and other goals, she said.

鈥淲e’re huge on performance-based metrics,鈥� Hart said.

Gonsalves said she monitors beetles because their presence is often a sign of a healthy habitat. She’s already encouraged by the presence of rove beetles on many of the green roofs in the study.

鈥淎 normal soil system would have them,鈥� she said. 鈥淭hat’s a good sign that the roofs are being colonized by the right kinds of (insects).鈥�