More than one in three species of trees are at risk of extinction worldwide, threatening life as we know it on Earth, according to a report. Issued to coincide with the UN's COP16 summit on biodiversity, held in the Colombian city of Cali, the report states that over 16,000 tree species are at risk of extinction. Megan Barstow, who compiled the studies, points out that "trees are essential for life on Earth" and "we need to save tree species because they will protect everything else if we save them." IMAGES AND SOUNDBITES