land). The land tenure system is largely based on kaitasi (extended family ownership). Foreign relations Tuvalu participates in the work of the Pacific Community (SPC) and is a member of the Pacific Islands Forum, the Commonwealth of Nations and the United Nations. It has maintained a mission at the United Nations in New York City since 2000. It is a member of the World Bank and the Asian Development Bank. Tuvalu maintains close relations with Fiji, New Zealand, Australia (which has maintained a High Commission in Tuvalu since 2018), Japan, South Korea, Taiwan, the United States of America, the United Kingdom and the European Union. It has diplomatic relations with Taiwan; the country maintains one of the two foreign embassies in Tuvalu and has a large assistance programme in the islands. A major international priority for Tuvalu in the UN, at the 2002 Earth Summit in Johannesburg, South Africa and in other international fora, is promoting concern about global warming and the possible sea level rising. Tuvalu advocates ratification and implementation of the Kyoto Protocol. In December 2009, the islands stalled talks on climate change at the United Nations Climate Change Conference in Copenhagen, fearing some other developing countries were not committing fully to binding deals on a reduction in carbon emissions. Their chief negotiator stated, "Tuvalu is one of the most vulnerable countries in the world to climate change and our future rests on the outcome of this meeting." Tuvalu participates in the Alliance of Small Island States (AOSIS), which is a coalition of small island and low-lying coastal countries that have concerns about their vulnerability to the adverse effects of global climate change. Under the Majuro Declaration, which was signed on 5 September 2013, Tuvalu has made a commitment to implement power generation of 100% renewable energy (between 2013 and 2020), which is proposed to be implemented using Solar PV (95% of demand) and biodiesel (5% of demand). The feasibility of wind power generation will be considered. Tuvalu participates in the operations of the Pacific Islands Applied Geoscience Commission (SOPAC) and the Secretariat of the Pacific Regional Environment Programme (SPREP). Tuvalu is party to a treaty of friendship with the United States, signed soon after independence and ratified by the US Senate in 1983, under which the United States renounced prior territorial claims to four Tuvaluan islands (Funafuti, Nukufetau, Nukulaelae and Niulakita) under the Guano Islands Act of