Introduction
The Birds Directive recognises that wild birds, of which many species are in decline, are mainly migratory and constitute a common heritage of the Member States - and that effective bird protection is typically a trans-frontier environmental problem. This requires maintenance or restoration of a sufficient diversity and area of habitats, making certain species subject to special conservation measures, regulating hunting and preventing commercial interests from exerting harmful pressure on exploitation levels.
Similarly, the Habitats Directive recognises that many natural habitats and wild species are seriously threatened, that they form part of the EU's natural heritage and that threats to them are frequently of a transboundary nature. This requires their maintenance and restoration through both site protection as well as through a general system of protection for certain species of flora and fauna, complementary to the Birds Directive, and allowing management measures for certain species, if their conservation status so warrants. 
In order to achieve this protection, over the last few years the European Union has built up a vast network of protected areas in all Member States, the so called Natura 2000. Based on information officially provided by Member States, the Commission and the European Environment Agency have developed a 'Natura 2000 barometer' that summarises progress on the establishment of Natura 2000 in each Member State. According to the latest barometer that summarises the situation until January 2016, Natura 2000 is comprised of 27 312 sites, covering 1 147 956 km². The terrestrial component covers 787 606 km² (more than 18% of the EU’s land surface) and the marine component 360 350 km² (estimated at about 6% of the EU marine surface). This represents the largest coordinated supranational network of nature conservation areas in the world.