Sunday, January 23, 2011

Green Roofs, Biodiversity & Endangered Species

There are many, many reasons to construct a green roof, including;
  • Cleaning Stormwater
  • Reducing Heat Island Effect
  • Creating Sense of Place
  • Providing Habitat for Urban Core Wildlife
  • Preserving Biodiversity
  • Sequestering Carbon
  • Producing Oxygen, and more.
There are many other, less expensive roofing technologies capable of;
  • Cleaning Stormwater, and
  • Reducing Heat Island Effect
However, besides Green Roofs, there are no other roofing technologies with the benefits of;
  • Providing Habitat for Urban Core Wildlife
  • Preserving Biodiversity
  • Sequestering Carbon, and
  • Producing Oxygen
 In the long term Green Roofs may well be recognized as most responsible for preserving the heritage of our endemic biodiversity.

Because of the potential for Green Roofs to provide refuge to native plants, particularly those threatened and endangered by real estate development pressures, and endemic wildlife especially dependent on those native plants we must consider carefully those plants we specify into a green roof design.

With open space disappearing within the Urban Core, vegetated rooftops provide an opportunity to ensure native and endemic plants continue to thrive within the city.

Passiflora incarnata, Drought tolerant native plant for Florida Green Roofs
Soil media and mixtures can be formulated to mimic many of the site existing soil characteristics, such as mineral content and pH.

Gaillardia, Blanket Flower is a Florida Drought Tolerant Native Plant Perfect for Green Roofs
Research has shown local wildlife need certain types of common plants for foraging, larval food while other wildlife are specialized and actually required by the endemic plants for successful pollination.

The Monarch butterfly's, Danaus plexippus larvae feed on Asclepias spp., Milkweed plants.  Adult Monarchs will reportedly only breed where Asclepias grows.  Once proliferate across Florida, Asclepias has rapidly diminished in populations numbers due to loss of habitat in the Urban Core.

Monarch Larvae Feeding on Asclepias

 Asclepias or Milkweed is a hardy native species and grows well on Green Roofs.  The plant will enter a dormant stage during cold winters though and should be only one of the many native species comprising a native plant based green roof design.

Milkweed when blooming provides vibrant colors to a green roof planting scheme.
Monarch Larvae Feeding on Asclepias

Furthermore, native plant species tend to be more adaptable to the harsh conditions of a green roof, more so than many non-native or monoculture type landscape plants.

Wildlife are immediately attracted to green roofs with native plants.

Gulf Fritillary Butterflies Flying to Reach Green Roof Flowers

Gulf Fritillary Readily Forages on Green Roof Plants

 The saying, 'You Build It and They Will Come' is true with respect to green roofs, native plants and wildlife.

Over the years we have witnessed green roofs attract tree frogs and lizards initially, along with other smaller species.

The initial influx of lizards (we call them anoles in Florida) and tree frogs promotes a form of integrated nature-based pest management.  The lizards and tree frog devour pest insects like flies, termites and roaches.

Soon, larger animals such as birds and snakes arrive to forage on the lizards and tree frogs.

Not surprisingly, after the snakes arrive so do raptors such as hawks, kites and eagles.

You build it and they will come.

Yet not only do green roofs promote biodiversity by providing habitat for native and endemic species and also provide communal and foraging habitat for wildlife, they also provide another very important function with respect to endangered wildlife.

Cuban Tree Frog, Osteopilus septentrionalis
One of the fiercest and most invasive wildlife species in Florida is the Cuban Tree Frog, Osteopilus seeptentrionalis.

The Cuban Tree Frog has a voracious appetite.  One of its favorite prey is the native American Green Tree Frog, Hyla cinerea.

Hyla cinerea needs vertical green - greenery growing above 2 meters high to escape the larger, slower, heavier Cuban Tree Frog.

Green Roofs provide a refuge, a place of escape and safety for the American Tree Frog.

Biodiversity, habitat for plants and wildlife, carbon sequestration, oxygen production are all benefits of plants growing on the rooftop.

TPO and other innovative and eco-friendly roof materials cannot provide all vegetated roofs give.

Biodiversity may be the real reason Green Roofs are remembered in the future.

Remember.  No monocultures on a green roof.  Think native plants.  Think lots of native plants. 

As always, Happy green roofing!


1 comment:

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