Gigantic animals which once roamed Australia were mostly extinct by the time humans arrived, according to a new study Tuesday which suggests climate change played the key role in their demise.

For decades, debate has centered on what wiped out megafauna such as the rhinoceros-sized, wombat-like Diprotodon, the largest known lizard, and kangaroos so big that scientists are studying whether they could hop.

German Chancellor Angela Merkel warned Monday that in the quest for binding international emissions targets to fight global warming, doing nothing is "not an option".

"I'm under no illusion that there is a long road ahead," Merkel said about efforts to reverse global warming, melting ice caps and rising seas.

Conservationists warned Monday that Hong Kong may lose its rare Chinese white dolphins, also known as pink dolphins for their unique color, unless it takes urgent action against pollution and other threats.

Their numbers in Hong Kong waters have fallen from an estimated 158 in 2003 to just 78 in 2011, with a further decline expected when figures for 2012 are released next month, said the Hong Kong Dolphin Conservation Society.

Japan, China and South Korea agreed Monday to continue cooperating in the fight against cross-border air pollution, despite strained relations between the neighbors because of territorial disputes.

The annual environmental meeting in Kitakyushu, southern Japan, on Sunday and Monday, came after acrid haze blanketing swathes of China earlier this year sparked health warnings in Japan as the smog spread across the ocean.

Alaska's Cleveland Volcano is undergoing a continuous low-level eruption following an explosion early Saturday morning, scientists from the Alaska Volcano Observatory and the U.S. Geological Survey said.

Satellites and cameras suggest low-level emissions of gas, steam and ash, scientists said, and satellites detected highly elevated surface temperatures at the summit. A faint plume of ash extended eastward below 15,000 feet (4,600 meters), but the Federal Aviation Administration said there were no flight restrictions as a result.

Millions of birds that stop at coastal wetlands during annual migrations could die as rising sea levels and land reclamation wipe out their feeding grounds, researchers warned Monday.

The study into the migratory habits of shorebirds predicted that a loss of 23 to 40 percent of their main feeding areas could lead to a 70 percent decline in their population.

Hundreds of people protested against a proposed chemical plant in southwest China on Saturday, state media said, while residents in another city accused authorities of preventing a similar protest.

More than 200 demonstrators gathered in the city of Kunming to protest plans for a factory which will produce paraxylene (PX), a toxic petrochemical used to make fabrics, China's official Xinhua news agency reported.

Australia insisted it was committed to protecting the Great Barrier Reef on Saturday after the U.N. warned that the natural wonder's world heritage status could be in downgraded in 2014.

UNESCO said little had been done to address concerns about rampant coastal development and water quality raised a year ago with the Australian government in a warning that its heritage status was at risk.

A Chinese fishing vessel that crashed into one of the Philippines' most famous reefs damaged almost 4,000 square meters of centuries-old coral, the marine park said on Saturday.

Some 3,902 square meters (42,000 square feet) of coral was destroyed after the boat became stranded in the Tubbataha marine park -- a UNESCO World Heritage-listed coral reef -- the park management said.

The first-ever manned airplane that can fly by day or night on solar power alone landed in the dark at a major southwestern U.S. airport, a live feed from the organizer's website showed early Saturday.

Solar Impulse, piloted by Swiss adventurer Bertrand Piccard, touched down at the Sky Harbor International Airport in Phoenix, Arizona at 0730 GMT after departing from California more than 18 hours earlier on the first leg of a cross-country journey.