Brown Roofs and Biodiversity

The key driving force behind the specification of brown roofs is the desire to encourage biodiversity. For this reason, brown roofs and biodiversity can be said go hand in hand - in fact, brown roofs are often described as 'biodiverse roofs.'

What is Biodiversity?

'Biodiversity' or 'biological diversity' can be defined as 'the totality of genes, species, and ecosystems in a region.' The Convention on Biological Diversity gives the following definition of 'biodiversity':

"The variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems."

It is widely accepted that the world is losing biodiversity as a result of human activity. This is generally regarded as a negative trend as biodiversity provides a number of important benefits:

  • Agriculture - High levels of biodiversity reduce dependence on individual strains of crops which might be attacked by disease (e.g. Irish potato blight).
  • Science and Medicine - Many important drugs have been synthesised from chemicals found in plants. High levels of biodiversity maximise the selection of plants that scientists can screen for potential new drugs.
  • Materials - A high proportion of materials are derived directly or indirectly from biological resources - e.g. timber, plastics, rubber, fabrics.
  • Ecosystem - Human activities that impact negatively on biodiversity can have a disproportionately large impact - e.g. due to the effect on animals further up the food chain.
  • Cultural and Aesthetic Value - The unmeasurable value of experiencing the world in which we live and helping to preserve it.

Government Initiatives to Encourage Biodiversity

Due to the widely-held belief in the necessity to encourage biodiversity Governments and organisations around the world have sought to introduce frameworks to encourage biodiversity. At the Rio Earth Summit in 1992 the "Convention on Biological Diversity" (CBD) was adopted and set the target of achieving by 2010 "a significant reduction of the current rate of biodiversity loss at the global, regional and national level as a contribution to poverty alleviation and to the benefit of all life on earth." There are a number of European and UK Government policies that have been adopted to try and meet the targets set in the CBD. In the UK the most important of these is probably the UK Biodiversity Action Plan, details of which can be found on the UKBAP website. Most local authorities in the United Kingdom also have their own local biodiversity action plans which are focused on local needs.

How do Brown Roofs Encourage Biodiversity?

Brown roofs are can encourage biodiversity in a number of different ways:

  • Compensating for loss of brownfield habitat: When a building is built on a brownfield site, soil and rubble can be set to one side and used as the brown roof substrate. This soil and rubble should be able to provide a rooftop habitat for the flora and fauna that inhabited the site before the construction of the building.
  • Selection:  The type of vegetation and features on the roof can be tailored specifically to the area or to a particular species of plant or animal
    if required.  This is particularly important in inner city areas and redeveloping areas where habitats are lost.
  • Protection:  Having a habitat on a roof means that any particularly vulnerable species are protected from animal or human interference on the ground.
  • Location:   Brown roofs can be used to introduce areas of vegetation to otherwise barren places, the perfect example being the inner city. Increasing biodiversity in inner cities has many benefits, including an improvement in air quality.