Raising The Roof on Urban Landscape Design: Greenroof Future

As humans, we focus on what we see every day. It stands to reason that much of the discussion of urban canopy and landscape projects and developments take place at ground and subterranean level.

With each passing year for approximately the past 15 years, however, more and more design visionaries and their taskforces are raising their eyes upward…to our rooftops. With the massive amount of square miles taken up by buildings, re-purposing their roofs help us reclaim some of the lost land and create a whole other kind of landscape.

Diana Balmori of Balmori Associates, NY couldn’t agree more. “We need to create a different balance between the inert surfaces and the living surfaces,” Balmori said. With the exception of pockets of urban parks, cities have the sky, the earth, and stories of glass, metal, cement and rock between them. Watching how city dwellers flock to those park spaces, Balmori realizes that there’s a wealth of untapped, unutilized potential not only for the human city dwellers, but the flora and fauna grasping for a foothold in a gray world.

A robust example of the success a rooftop landscape is Balmori’s own 667 acre Public Administration complex in Sejong, Korea. Balmori Associates says, “We proposed a new approach to city-making, one that starts with landscape architecture. The master plan consists of a continuous linear park on a continuous roof joining all the ministries.” In conjunction to providing a reprieve for persons, the task of building a green roof with wildlife in mind requires a whole other set of considerations. “Creating biodiversity on a green roof or green wall is significantly different than restoring it on ground level. On a rooftop there is no preexisting ecology to enhance; everything is from scratch,” states the Green Roof Service webpage of Jörg Breuning, owner.

Given this, the plants, animals and insects are essentially living under an altered set of circumstances, which could affect their continuing habitation and ability to thrive under the new conditions, even with a perfect replication of a landscape indigenous to any particular area.

From an infrastructural standpoint, the installation of green roofs presents vast benefits, including prolonging the life spans of rooftop materials, decreased use and energy consumption of HVAC units, stormwater management, and significant moderation of the Urban Heat Island effect.

Green Roofs for Healthy Cities Community webpage states, “Through the daily dew and evaporation cycle, plants on vertical and horizontal surfaces are able to cool cities during hot summer months and reduce the UHI effect. The light absorbed by vegetation would otherwise be converted into heat energy.” With such evidence of benefits being discovered and explored from several standpoints: the human element, ecology, and infrastructure, a future with more green roof designs should be just on the horizon for landscape design experts, scientists, engineers, and others.

photo credit: Green Roof Gardner, CC

Nature Trails Detrimental to Urban Forests:

Being close to nature has its downside that is detrimental to the environment, according to a latest study by scientists from Curtin University and Griffith University.

Remnant urban forests are popular sites for recreational activities like hiking, biking, and motorised recreation. However, the study said this could result in the “formation of extensive trail networks, fragmenting vegetation into patches separated by modified edge effects and ultimately contributing to the degradation of the ecosystem as a whole”.

The study used a Geographic Information System (GIS) approach to assess the extent and diversity of trail-based fragmentation across 17 remnants of endangered urban forest in southeast Queensland, Australia (a total area of 829 hectares).

The study mapped out 14 different trail types totaling 46.1km of informal biking and hiking. More than 47 hectares or 5.7 percent of forest have been lost to trails and their edge effect, nearly equal to the area recently cleared for urban development.

“The degree of fragmentation in some remnants was in the same order of magnitude as found for some of the most popular nature-based recreation sites in the world. In localised areas, the fragmentation was particularly severe as a result of wide trails used by motorised recreation, but these trails were generally uncommon across the landscape (five percent). Spatial regression revealed that the number of access points per remnant was positively correlated with the degree of fragmentation,” the study said.

An article by Science Network Western Australia said experts from both universities and co-authors, Mark Ballantyne, Dr Ori Gudes and Professor Catherine Pickering, found these forest area trails result in changes to soil microbiology, compaction, erosion, the introduction of weeds and pathogens and wildlife disturbance.

“[All trail types] have an environmental impact. Each one has its own communities of animals and plants that rely on that area to live in. However, overall I fell the largest loss would be stress as they have a very limited trunk area and a large canopy, so for every tiny bit of trunk removed a large canopy [is also removed] so they’re not proportional,” Ballantyne told Science Network.

He added that the lack of planning plus the informal trails coming from tourists and park-goers leads to “networks of damaging trails that need to be structured and maintained for effectiveness”.

“We encourage more landscape-scale research into trail-based fragmentation due to its capacity to impact extensive areas of endangered ecosystems. Management should seek to minimise the creation of informal trails by hardening popular routes, instigating stakeholder collaboration and centralising visitor flow,” the study said.

A first national study by the United States Forest Service has revealed that trees are saving more than 850 human lives each year and preventing 670,000 instances of acute respiratory symptoms.

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The 202020 Vision and University of Technology Sydney has released the first ever benchmark report on urban tree canopy cover in Australia.

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