by Carl Carlson
Green roofs have been growing in popularity in the last few years with the recent push towards low impact design. They help mitigate environmental impacts of the built environment by offering storm water sequestering, reduced urban heat island effect, and providing superior insulation for buildings. The idea of putting plants on roofs is nothing new, but up until now the vast majority of green roofs have used non-native plants that are able to survive in the tough conditions of urban roof tops. These roofs can be very effective, however they can also be difficult to establish and maintain properly. Once they are established they usually don’t offer significant habitat opportunities due to the types of plants that are installed. The staff and students at my Alma Mater SUNY, ESF got creative and designed a green roof that thrives instead of survives and fits within the ecological context of northern New York State.
The Landscape Architecture firm Andropogon and the Landscape Architecture and Biology departments of SUNY ESF, collaborated to design and build a highly functioning green roof by recreating habitats that could be found naturally in the northern New York ecosystems.
After studying solar, wind and precipitation patterns they determined that there were two very rare ecosystem typologies that would likely survive well on their Syracuse roof top, Great Lake Dune and Alvar. The Great Lake Dune ecosystem is a very unusual habitat that exists along a 17 mile stretch of Lake Ontario shoreline. The very dry and windy environment of the dunes mirrors the conditions found on top of the building. East of the Great Lake dunes towards Watertown, NY is the Alvar ecosystem. Alvar communities only exist in a few concentrated areas on northern New York. They are high stress plant systems that have very shallow soils on top of limestone substrate. The soil and growing conditions are remarkably similar to what would be found on a typical green roof in Syracuse. The conditions of these ecosystems seemed perfect for adaptation.
As with most construction projects, significant challenges arose after the project started, especially asthis was the first time anyone had created Great Lake Dunes or Alvar ecosystems on a building’s roof. The plants were almost impossible to source and many are protected species in New York State. Using seeds collected from a private land owner students experimented with germination and propagation in their research greenhouses. Using test plots on their roofs, the students were able to study the best combination of soil depth, plant spacing and plant variety.
After a year of research the green roof was installed on ESF’s brand new Gateway building. Styrofoam was used to create “topography”, real limestone flagging was brought in to help mimic the habitat and soil was carefully placed to proper depth. The plants were only watered during the first few weeks after installation to help with establishment. Now, the roof relies solely on rainwater for irrigation. Overall the natural community green roof is a great success. The roof will continue to be studied and monitored as an ongoing research project. Students are continuing to collect data on insects, birds, and the spread of the seed bank on the roof. Future goals are to set up systems to study the stormwater infiltration and runoff rate from the roof. Although the habitats selected for the Gateway green roof are not appropriate for all regions of the United States, their systems can be used to find other native habitats that will provide the same benefits.
The Gateway green roof project was highlighted during the recent American Society of Landscape Architects (ASLA) annual conference as one of the latest trends and techniques in landscape design. It demonstrates the significant value of integrating science and design, the core practice of Great Ecology. Using scientific processes to influence and enhance design goals is crucial to the long term sustainability and success of projects.