The UN General Assembly, through resolution 57/245 adopted on December 20, 2002, designated December 11 as International Mountain Day, with annual observances beginning in 2003. The day built on momentum from the International Year of Mountains in 2002, cementing mountain issues as a permanent item on the UN's agenda. Mountains cover roughly 27% of Earth's land surface, host immense biodiversity, and supply more than half of the freshwater humans use, while directly sustaining the livelihoods of about a quarter of the world's population. Yet mountain ecosystems face growing threats from climate change, melting glaciers, and unsustainable development. Countries and international organizations mark the day with field events and awareness campaigns on protecting mountains, initiatives supporting sustainable livelihoods for mountain communities, and scientific programs monitoring the impact of climate change on glaciers and mountain ecosystems around the world.