By Kat Harrold
Photo by ~ Jorg Breuning
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. In most cases the growing media is drastically different from the soil down below which in turn dictates what ecology can be supported. Accessibility, high winds, and proximity to the sun can also be challenging issues for organisms.
Studies show that plant selection and depth of growing media have a greater influence on the biodiversity of a green roof than height. In the translation of research covering the biodiversity of green roofs, “Where the Beetles are Crawling and the Honeybees are Humming,” the biodiversity found on green roofs as tall as 400 feet were comparable to that of lower green roofs.
Tray or modular green roof systems create the visual impression of a green roof by placing a series of planters close together. The history of German trays, introduced in 1978, show that in most cases the performance of pre-planted boxes fail to meet performance and maintenance expectations. The composition of a modular system simply does not provide the right set-up to reliably enjoy the 30 to 50 year lifespan expected from a built up equivalent system. Additionally there tends to be incredible amounts of species die back during the first 5 years creating a sparsely vegetated monoculture setting. These factors create a very poor and unreliable environment for biodiversity to take place.
Visit us next week for more information on bio-diverse intensive green roofs!