The fifth edition of IGRA´s prestigious congress series deals with the special challenges of Green Roofs in dry climates. More than one-third of the world population already lives in these expanding regions, without considering the global metropolitan areas which often are grappling with the same problems and referred to as “city deserts”. The performance of Green Roofs in these special environments is strongly connected with the availability and scarcity of water and the limited types of plants, which are able to tolerate these harsh weather conditions – therefore the water & plantation issue is a common thread of the congress presentations and discussions.