Green Roofs - Living Architecture Monitor - Summer 2012 - (Page 32)

POLICY PROFILE A HOME FOR BIODIVERsITY ON gREEN ROOFs by: bRAD bASS, pH.D., TERRy MCGLADE & SCOTT TORRANCE TORONTO’S bIODIVERSITy DESIGN GUIDELINES, A NORTH AMERICAN fIRST! I n 2001, the City of Toronto published the City of Toronto Natural Heritage Study (NHS) –Final Report. Several findings of the report have important ramifications for how green roofs are designed and how they can promote biodiversity. According to the NHS although 13.5% of the total city area is covered by natural habitat, the “habitat is unevenly distributed, with most of the larger patches located in the Rouge River and Highland Creek watersheds.” Most natural habitat patches are small (less than five hectares), have convoluted rather than simple shapes, and are thus vulnerable to negative urban pressures. The City of Toronto’s Green Roof Bylaw requires the construction of green roofs on new building developments (commercial, institutional and residential) with a minimum Gross Floor Area of 2,000m². The percentage of green roof coverage area required is based upon the total gross floor area of the building, varying between twenty and sixty percent. The Bylaw was implemented to take advantage of the many benefits associated with green roofs such as combatting storm water management issues and reducing urban heat island effect. Using green roofs as a biodiversity strategy requires a unique set of design guidelines which were not included in the Bylaw. In order to facilitate the use of green roofs as part of an ‘urban biodiversity strategy’, a manual was created in 2011 to illustrate best practices for design, construction and maintenance, the first of its kind in North America. The manual focused on four design approaches or objectives: 1. Recreate specific, native habitats that exhibit microclimatic characteristics similar to green roofs; 2. Design to attract specific birds, bees and other insects by providing features that these fauna require on the landscape; 3. Design to support adjacent ecosystems in the city by specifying plants and textures to create an edge condition to act as a buffer around the ecosystem; 4. Design to support emerging urban ecosystems based on plants that have adapted well to the stresses inherent in most cities. In addition, design strategies to manipulate three structural factors – structures on the roof, substrate depth and substrate diversity – are illustrated to maximize the opportunities to implement biodiverse green roofs. Greater biodiversity provides a greater chance for urban ecosystems to survive because each community is in itself a strategy for surviving under the current climate. When one strategy fails, other plants in the community can assume different roles, reflecting a different strategy to cope with a new climate or other system pressures. The area of roof space in Toronto provides an opportunity to create new habitat in urban areas where other ground level strategies are restricted due to limited availability of space. The manual provides sufficient design alternatives to make biodiversity a feasible option for a widest possible range of roof tops in the City of Toronto. Although biodiverse roofs will contribute to several unique ecosystem goods and services in the City, they will also enhance those benefits – reducing the urban heat island, energy conservation, runoff control – that are typically associated with all green roofs. FinD OUT MOrE environment/pdf/natural_ heritage/natural_text1.pdf

Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Summer 2012

Green Roofs - Living Architecture Monitor - Summer 2012
Letter from the Chairman
From the Founder
New Standard on the Use of Lightweight Aggregate
Urban Agriculture Declaration Caps Amazing Summit Debut
Economics of Biophilic Design
Brad Rowe, David Spalding, Cornelia Oberlander, Paul Kephart
Green Roofing Industry Sees Triple Digit Growth
Green Roof Local Market Symposiums
Industry Professionals Weigh in on Growing Media Quality Control!
CitiesAlive in Chicago Oct 17th – 19th
Green Infrastructure Ontario Coalition Changes our Perspectives on Infrastructure
Improving Tax Abatement
10th Anniversary Commemorative Pull Out Section
Halifax Seaport Farmer’s Market
Leadership Knows No Bounds- Virginia Russell
Policy Profile- A Home for Biodiversity on Green Roofs
New Industry Products
Plant Profile: Chives Thrive on Green Roofs
Half a year, Full-Fledged Growth
In God We Trust – All Others Bring Data!
New Corporate Members
Professional Calendar
GRHC Buyers Guide
Green Supremacy by Zach Williams

Green Roofs - Living Architecture Monitor - Summer 2012