UK ECN site. Dstl Porton Down is located in Southern England on the Wiltshire/Hampshire border. It is owned by Defence Science and Technology Laboratory (Dstl) and is used to deliver high-impact science and technology (S&T) for the UK's defence, security and prosperity. It has been closed to the public for over 100 years, resulting in it missing out on the agricultural revolution which affected the rest of the country. This is why it constitutes the largest uninterrupted tract of semi-natural chalk grassland in Britain. Over 1500 hectares is designated as a Site of Special Scientific Interest (SSSI), a Special Area of Conservation (SAC) and a Special Protection Area (SPA). The ECN monitoring takes place at the heart of the site on the chalk downland and takes in some of the sites special features. The ECN protocols that are undertaken on the site include Atmospheric chemistry, Precipitation chemistry and Weather data. Ecological data includes Rabbits, Birds, Butterflies, Moths, Ground Predators and Spiders.