Biodiversity and ecosystemsConservation of biological diversity is the subject of Chapter 15 of Agenda 21, which was adopted by the United Nations Conference on Environment and Development, in 1992, in Rio de Janeiro. At the same Conference, the United Nations Convention on Biological Diversity (CBD), which has subsequently entered into force, was opened for signature. In 2002, the World Summit on Sustainable Development, in Johannesburg, addressed biological diversity in Chapter IV, paragraph 44, of the Johannesburg Plan of Implementation. The Johannesburg Summit also endorsed the target to achieve, by 2010, a significant reduction of the current rate of biodiversity loss at global, regional and national levels as a contribution to poverty alleviation and to the benefit of all life on earth, which had some months earlier been adopted by the sixth meeting of the CBD Conference of Parties (COP). Biodiversity has also been discussed by the Commission on Sustainable Development on several occasions and is one of the themes for discussion in the 2012/2013 two-year cycle. The Millennium Ecosystem Assessment released in March 2005 concludes that there has been a substantial and largely irreversible loss in the diversity of life on Earth due to human action. Among the outstanding problems are the dire state of many of the world's fish stocks, the vulnerability of the 2 billion people living in dry regions to the loss of ecosystem services and the growing threat to ecosystems from climate change and nutrient pollution.