More than 190 countries have reached a landmark deal for protecting the biodiversity of the world’s oceans, agreeing for the first time on a common framework for establishing new protected areas in international waters.

The treaty, whose text was finalized Saturday night by diplomats at the U.N. headquarters after years of stalled talks, will help safeguard the high seas, which lie beyond national boundaries and make up two-thirds of Earth’s ocean surface. Member states have been trying to agree on the long-awaited treaty for almost 20 years.

Environmental advocacy groups heralded the finalized text — which still needs to be ratified by the United Nations — as a new chapter for Earth’s high seas. Just 1.2 percent of them are currently environmentally protected, exposing the vast array of marine species that teem beneath the surface — from tiny plankton to giant whales — to threats such as pollution, overfishing, shipping and deep-sea mining.