Oscar Warmerdam is the founder and CEO of Sempergreen, USA, the largest green roof company in North America. Oscar is a strong advocate for utilizing green infrastructure to improve the sustainability and habitability of cities. With over 25 years of green roof and horticulture experience, he founded Green Roof Diagnostics as a research institute to focus on improving the stormwater performance of green roofs, and structured GRD to operate independent from Sempergreen and other commercial interests. Oscar is working to elevate the role of replicable science in the design, selection, and implementation of green infrastructure, so that green infrastructure may become the engineer's first choice for stormwater management and a range of other ecosystem services.