The United States has joined more than 20 countries in creating 40 new marine sanctuaries around the world to protect oceans from the threat of climate change and pollution.
President Barack Obama designated the first US marine reserve in the Atlantic Ocean: 4,913 square miles (12,724 square km) known for underwater mountains and canyons off the coast of New England.
Britain said it would double the area of ocean under marine protection around its overseas territories to about 2.5 million square miles (6.5 million square km), an area greater than the landmass of India.
The various sanctuaries, unveiled at a high-level conference in Washington, limit commercial fishing, oil and gas drilling, and other human activities that affect ocean ecosystems.
Altogether, countries at the two-day oceans conference will announce new sanctuaries covering nearly 460,000 square miles (1.19 million square km) of ocean, an area around the size of South Africa.
The area designated by Obama includes canyons as deep as the Grand Canyon in Arizona and underwater mountains higher than any in the United States east of the Rockies, according to Environment America, a federation of state-based environmental advocacy organisations. Environment America said it and other groups were pushing for Obama to designate more land-based national monuments before leaving office in January.

