KUNMING, China, Oct 11 (Reuters) - The world has now reached "a moment of truth" when it comes to protecting its vital ecosystems, U.N. biodiversity chief Elizabeth Maruma Mrema said on Monday as talks on a new global conservation treaty got underway in Kunming, China. Mrema, executive secretary of the U.N. Convention on Biological Protection, said during the opening ceremony of the talks that the world had not achieved the necessary breakthroughs from 2011-2020 and was not yet able to safeguard ecosystems that were key to human wellbeing. The first round of the "COP15" talks on biodiversity will last from Oct. 11 to Oct. 15. A post-2020 biodiversity pact is expected to be finalised during the second round in April-May next year.