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 Chinook salmon that swim upstream to spawn in the fall, the most robust run in the Sacramento River, have disappeared. The almost complete collapse of the richest and most dependable source of Chinook salmon south of Alaska left gloomy fisheries experts struggling for reliable explanations — and coming up dry.

Whatever the cause, there was widespread agreement among those attending a five-day meeting of the Pacific Fisheries Management Council here last week that the regional $150 million fishery, which usually opens for the four-month season on May 1, is almost certain to remain closed this year from northern Oregon to the Mexican border. A final decision on salmon fishing in the area is expected next month.

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.

Last week the price of crude oil broke new records, running about $110 a barrel. That’s well above the previous record (in inflation-adjusted dollars) reached in 1980 after the revolution in Iran resulted in the nationalization of its oil.

Since tanks of crude are full to brimming, many traders in oil markets suspect that $110 could be the top price for now. But a growing number of oil-market analysts reckon the supply of oil to the world economy has reached a peak or is about to. The discoveries of new oil are now exceeded by the output of old oil. At some point, global oil output will start to decline, as happened in the United States in 1971.

The world’s food situation is bleak, and shortsighted policies in the United States and other wealthy countries — which are diverting crops to environmentally dubious biofuels — bear much of the blame.

According to the United Nations Food and Agriculture Organization, the price of wheat is more than 80 percent higher than a year ago, and corn prices are up by a quarter. Global cereal stocks have fallen to their lowest level since 1982.