[[File:YorkU2.jpg|thumb|Detail showing the early root development through the mat to the granular planting medium.]]
[[File:YorkU2.jpg|thumb|Detail showing the early root development through the mat to the granular planting medium.]]
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Green roofs are primarily a practice used to partially achieve water balance and erosion control objectives.
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Green roofs are primarily a practice used to partially achieve water balance and erosion control objectives through interception and [[Evapotranspiration| evapotranspiration]] of precipitation.