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The impacts are then calculated as economic benefits that could be achieved from saved medical costs and productivity gains , and from people ’ s own willingness to pay to obtain these benefits . The series ran from 1830-1845 with 187 volumes in all , mostly by British authors . Coping capacity increases as you move from the state of vulnerability towards security and vice versa , along the continuum . For example , the underlying cause of much of Africa 's widespread poverty is the high rate of population growth , and it is poverty that forces people to overexploit their natural resources and thus degrade their environment . The Johannesburg Plan of Implementation , agreed at the World Summit on Sustainable Development in 2002 , includes commitments to diversify energy supply and to increase substantially the global share of renewable energy sources ; to improve access to reliable , affordable , economically viable , socially acceptable and environmentally sound energy services and resources ; and to establish domestic programmes for energy efficiency , among other things .