AOSIS is a coalition of small island and low-lying coastal countries that share similar development challenges and concerns about the environment, especially their vulnerability to the adverse effects of global climate change. It functions primarily as an ad hoc lobby and negotiating voice for small island developing States (SIDS) within the United Nations system. AOSIS has a membership of 43 States and Territories, drawn from all oceans and regions of the world: Africa, Caribbean, Indian Ocean, Mediterranean, Pacific and South China Sea. Thirty-seven are members of the United Nations, close to 28 percent of developing countries, and 20 percent of the UN's total membership. Together, SIDS communities constitute some five percent of the global population. Member States of AOSIS work together primarily through their New York diplomatic Missions to the United Nations.