PES has also been touted as a tool for rural development. In 2007, the World Bank released a document outlining the place of PES in development. But the link between the environment and development had been officially recognized long before with the 1972 Stockholm Conference on the Human Environment and later reaffirmed by the Rio Conference on Environment and Development. However, it is important to note PES programs are usually not designed to be primarily poverty alleviation schemes, although they may incorporate development mechanisms.