Let’s unpack each side of this hyphenated term. According to Kambites & Owen(Kambites & Owen, 2006: 483), green infrastructures (GIs) involve '…connected networks of multifunctional, predominantly unbuilt spaces that support both ecological and social activities and processes.’ Originating from landscape architecture and ecology, GIs aim to maximize the inclusion of green spaces in planning and as a means of increasingly urban livability while delivering short- and long-term resilience, sustainable development, economic growth and natural capital(Landscape Institute 2011.). GIs are part of the so-called nature-based solutions (NBS) trend in European cities, where they are understood to act as projective ecologies(Reed & Lister 2014) that explore potential paths forward for robust urban design thinking.
GIs within landscape architecture expands the traditional set of landscape planning and design strategies towards a multifunctional, highly performative system. It is important to recognize the difference between GIs as a concept influencing urban planning and GIs as a process maximizing benefits of green spaces (hubs and corridors) (Benedict and McMahon, 2006), ecosystem services(CNT, 2010) (Lovell & Taylor, 2013) and urban storm water management. In a stormwater context, GIs can be used to retain and treat stormwater through green roofs, trees, bio-retention, permeable pavement, etc.(Fletcher et al., 2014). GIs can provide additional social benefits in regards air quality, biodiversity, urban livability, etc.
Blue, or aquatic, ecosystems are inherently complex and characterized by constant variations (e.g., daily, seasonal) and interactions between different natural and societal processes and conditions(Roeffen, 2013). The growing awareness of the possibilities of exploiting the synergistic interplay between water and ‘green’ systems has led to the development of new ‘blue’ and ‘green' ways of managing water even in dense urban areas. Or, more frequently, a mix of (often existing) grey infrastructure with newly built or ‘hybrid’ Green-Blue environments. The EU defines GBIs as(EU, 2014) ‘strategically planned network of natural and semi-natural areas with other environmental features designed and managed to deliver broader array of ecosystem services' that incorporate ‘green spaces (or blue if aquatic ecosystems are concerned) and other physical features in terrestrial (including coastal) and marine areas.'
For example, Lake Văcărești, in Bucharest (Romania), is a 189-hectare reservoir project abandoned after the collapse of the Ceaușescu regime. Since then the swampy landscape of the surrounding area bounded up by dikes has developed a level of biodiversity unprecedented in urban environments(Forgaci & van Timmeren, 2014b), including several plant species and 94 protected species of fauna(Lascu, 2012). Known by locals as the ‘delta between the blocks’, Lake Văcărești has recently been declared a nature preserve(Forgaci & van Timmeren, 2014b).