Improving access to family planning services and promoting sexual equality are the priority The 2009 state of the world population report from the United Nations Population Fund (UNFPA) tackles what UN Secretary General Ban Ki-moon has termed the greatest challenge facing humanity.1 2 The report, “ Facing a Changing World: Women, Population and Climate ,” is published just weeks before representatives of the world’s nations arrive in Copenhagen to forge a new climate treaty. The treaty will hopefully include agreements to reduce emissions globally and equitably, and ways of adapting and building resilience in countries most vulnerable to the effects of the changing climate. The UNFPA report should convince negotiators to pay more attention to women’s crucial role in mitigating and adapting to climate change and to ensure that population factors stay on the table—within the rights based framework of the programme of action of the 1994 International Conference on Population and Development. Women and men are affected and respond differently to the challenges of climate change. The UNFPA report highlights the vulnerability and …