An international marine preservation group says the creation of a marine park in New Caledonia is just the first step and a management plan will now be developed over the next three years.
Global Ocean Legacy, which is part of the Pew Charitable Trusts, works with communities and governments to establish large, highly-protected marine reserves around the world.
New Caledonia has set up a 1.3 million square kilometre park covering its entire exclusive economic zone.
The project manager of Global Ocean Legacy, Aline Schaffar, says if the area is not protected then its biodiversity will be lost.
"If we don't protect it one day there will nothing to look at, there will be no more coral reef, no more fish, no more migratory species, that's what the richness of our ocean is today, so if we don't protect it we are going to lose it."
Aline Schaffar says the park's management plan will identify the areas most important to protect and set out the different levels of protection.