(CNN)Nearly 200 countries have agreed to a legally-binding "high seas treaty" to protect marine life in international waters, which cover around half of the planet's surface, but have long been essentially lawless.
The agreement was signed on Saturday evening after two weeks of negotiations at the United Nations headquarters in New York ended in a mammoth final session of more than 36 hours -- but it has been two decades in the making.
The treaty provides legal tools to establish and manage marine protected areas -- sanctuaries to protect the ocean's biodiversity. It also covers environmental assessments to evaluate the potential damage of commercial activities, such as deep sea mining, before they start and a pledge by signatories to share ocean resources.
"This is a historic day for conservation and a sign that in a divided world, protecting nature and people can triumph over geopolitics," Laura Meller, Oceans Campaigner at Greenpeace Nordic, said in a statement.
The high seas are sometimes called the world's last true wilderness. This huge stretch of water -- everything that lies 200 nautical miles beyond countries' territorial waters -- makes up more than 60% of the world's oceans by surface area.
These waters provide the habitat for a wealth of unique species and ecosystems, support global fisheries on which billions of people rely and are a crucial buffer against the climate crisis -- the ocean has absorbed more than 90% of the world's excess heat over the last decades.
Yet they are also highly vulnerable. Climate change is causing ocean temperatures to rise and increasingly acidic waters threaten marine life.
Human activity on the ocean is adding pressure, including industrial fishing, shipping, the nascent deep sea mining industry and the race to harness the ocean's "genetic resources" -- material from marine plants and animals for use in industries such as pharmaceuticals.