The world's first international treaty to protect the high seas is due to be adopted Monday at the United Nations, a historic environmental accord designed to protect remote ecosystems vital to mankind. "It will be a huge accomplishment, one that we've already celebrated with the finalization of the text in March. But the adoption formalizes that, and really sets the pathway for the next steps," Liz Karan, of the NGO Pew Charitable Trusts, told AFP.