An international treaty that is designed to preserve the unique environment of Antarctica by limiting development there. It was signed in 1959 by the seven countries (Norway, France, Australia, New Zealand, Chile, Great Britain, and Argentina) which claim sovereign rights over the continent, plus twelve other countries, and it dedicated the whole continent to peaceful scientific investigations. All existing territorial claims were suspended when the treaty came into effect in 1961. Since it was signed, international concern has grown over the prospect of renewed mineral prospecting in and around Antarctica, and there have been repeated calls for the continent to be designated a World Park and protected for ever against development. In 1991, 24 countries approved a protocol to the treaty (the Madrid Protocol) that would ban oil and other mineral exploration for at least 50 years.