Several certification schemes and sustainability programs exist with direct or indirect links to urban green and NBS. The main value of such certifications is that if incorporated well, they stand for objectivity, transparency and trustworthiness and are perceived as beneficial by most parties (private, public and citizens). Examples of existing certification systems which include NBS-specific criteria are BREEAM, LEED (building sector). Furthermore, cities have also been working with more organisation-related certification schemes such as EMAS, The Natural Step, or agreements such as the Aalborg Commitments to push sustainable and green practices more generally. Cities can encourage local actors to utilise such systems by providing incentives for them to do so.