Changes

[[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.]]  

Green roof performance has not been reported to reduce over time. Controlled studies have instead indicated that maturing green roofs may have improved water retention properties <ref>Simon De-Ville, Manoj Menon, Xiaodong Jia, George Reed, Virginia Stovin, The impact of green roof ageing on substrate characteristics and hydrological performance, In Journal of Hydrology, Volume 547, 2017, Pages 332-344, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2017.02.006.</ref>.

Controlled studies have indicated that maturing green roofs may have improved water retention properties <ref>Simon De-Ville, Manoj Menon, Xiaodong Jia, George Reed, Virginia Stovin, The impact of green roof ageing on substrate characteristics and hydrological performance, In Journal of Hydrology, Volume 547, 2017, Pages 332-344, ISSN 0022-1694, https://doi.org/10.1016/j.jhydrol.2017.02.006.</ref>.

The key hydrologic benefit which green roofs have over other forms of LID is the proportion of the water returned to the atmosphere through evapotranspiration.   

The key hydrologic benefit which green roofs have over other forms of LID is the proportion of the water returned to the atmosphere through evapotranspiration.