According to the European Cities Monitor 2010, Stockholm is the best city in terms of freedom from pollution. Surrounded by 219 nature reserves, Stockholm has around 1,000 green spaces, which corresponds to 30% of the city's area. Founded in 1995, the Royal National City Park is the world's first legally protected "national urban park". For a description of the formation process, value assets and implementation of the legal protection of The Royal National Urban Park, see  Schantz 2006 The water in Stockholm is so clean that people can dive and fish in the centre of the city. The waters of downtown Stockholm serve as spawning grounds for multiple fish species including trout and salmon, though human intervention is needed to keep populations up. Regarding CO2 emissions, the government's target is that Stockholm will be CO2 free before 2050.