Reduction of the Urban Heat Island (UHI) effect
Dense urban areas are often 2 to 3 degrees centigrade warmer than the countryside that surrounds them. This is caused by materials which retain heat, such as tarmac, and processes which produce it as a bi-product, such as cars. Urban Heat Islands (UHIs) disrupt local climatic cycles, particularly the hydrological cycle. This stresses the local ecosystem and is detrimental to wildlife.
Traditional roofs experience extreme flux of surface temperature over a 24 hour period & fuel the UHI effect. Living roofs help to mitigate UHIs by regulating the surface temperature through absorption of sunlight. Reduction of temperature extremes also reduces the stresses on the waterproofing layer and extends their lifespan.
Image taken from: http://tools.decc.gov.uk/nationalheatmap/