A chunk of Antarctic ice about seven times the size of Manhattan suddenly collapsed, putting an even greater portion of glacial ice at risk, scientists said Tuesday.

Satellite images show the runaway disintegration of a 160-square-mile chunk in western Antarctica, which started Feb. 28. It was the edge of the Wilkins ice shelf and has been there for hundreds, maybe 1,500 years.

This is the result of global warming, said British Antarctic Survey scientist David Vaughan.

The capital’s famous cherry trees are primed to burst out in a perfect pink peak about the end of this month. Thirty years ago, the trees usually waited to bloom till around April 5.

In central California, the first of the field skipper sachem, a drab little butterfly, was fluttering about on March 12. Just 25 years ago, that creature predictably emerged there anywhere from mid-April to mid-May.

The thickest, oldest and toughest sea ice around the North Pole is melting, a bad sign for the future of the Arctic ice cap, NASA satellite data showed on Tuesday.

“Thickness is an indicator of long-term health of sea ice, and that’s not looking good at the moment,” Walt Meier of the National Snow and Ice Data Center told reporters in a telephone briefing.

This adds to the litany of disturbing news about Arctic sea ice, which has been retreating over the last three decades, especially last year, when it ebbed to its lowest level.

The world’s coral reefs are under threat. Overfishing, unsustainable tourism, coastal development, pollution, the global aquarium trade and climate change are having a devastating effect on these fragile ecosystems, according to the International Coral Reef Initiative.

Meanwhile fellow conservation group, Nature Conservancy, warns that if destruction continues at its current rate, 70 percent of the world’s coral reefs will have disappeared within 50 years.

Global warming this century could trigger a runaway thaw of Greenland’s ice sheet and other abrupt shifts such as a dieback of the Amazon rainforest, scientists said on Monday.

They urged governments to be more aware of “tipping points” in nature, tiny shifts that can bring big and almost always damaging changes such as a melt of Arctic summer sea ice or a collapse of the Indian monsoon.

“Society may be lulled into a false sense of security by smooth projections of global change,” the scientists at British, German and U.S. institutes wrote in a report saying there were many little-understood thresholds in nature.