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What has been causing polar bears in the Arctic to drown in record numbers?

Global Warming's Effects On Plant And Animal Life

Michael Oppenheimer (Professor, Princeton University) gives expert video advice on: What has been causing polar bears in the Arctic to drown in record numbers?; Is global warming affecting a change in the seasons? and more...

What has been causing polar bears in the Arctic to drown in record numbers?

Polar bears hunt from ice flows. Those ice flows are sea ice. Unfortunately, as the Earth has warmed, and as the Arctic has warmed even more than the Earth as a whole, the summer sea ice pack has shrunk. The polar bears have to swim further and further from one icy formation to another, or from ice to land, because it's harder to find ice, so they're having trouble hunting. Some polar bears, it is said, have drowned because of their inability to get from one spot in the Arctic to the other; they get weak and eventually they succumb. Whether or not that's a significant trend yet, it is almost certain that if the ice pack continues to shrink, life will get tougher and tougher for polar bears. We don't know whether they'll become extinct, but there will be much fewer of them left. The populations of polar bears will shrink and they'll become much rarer.

Is global warming affecting a change in the seasons?

Global warming is affecting the seasons. Autumn and winter are coming later in many places; spring is coming earlier. If you look at a typical lake or maybe a stream in the far North it melts earlier in the spring and it freezes later in the fall. The very timing of the seasons is changing such that the food sources for some insects and birds are not in the places they are supposed to be when the migrations of these creatures arrive at the place where they are expected to be fed. And so, the very timing of nature and the seasons is being upset by global warming.

How does global warming expedite the extinction of animal life on the planet?

Most animals, like most plants, are adapted to live in the climate in which they evolved. They evolved slowly in response to climate changes in the past that occurred naturally and slowly. Now climate change is about to happen at a time scale which is much faster than animals can evolve. The ones that are fleet on the foot, so to speak, and can move, like birds, may do relatively well; and the species that are trapped in unique places, like corals, they can swim, but the coral reefs and all the fish and all the plants that they are adapted to living with, they would have to leave them behind and so probably won't do very well. Some species are not fleet, and they're not going to survive in a warming world, and there will be a grave loss of biodiversity due to global warming. Other species may be able to move, but they may move to places which don't have the resources that they need. The place with the right climate for a certain bird may not have the right food for a certain bird. We're throwing everything up and hoping it comes down in a place where everything will survive. That's not entirely likely, and I think we're going to lose a lot of species due to global warming.

What is a "coral reef"?

Coral are small animals which grow hard shells around them, and they live in communities which are essentially mountains of this calcified material. Corals live in symbiosis, or in co-operation, with certain other species called zooxanthellae, and these co-operative relations are very delicate. As a result, corals in coral reefs are very sensitive to small changes in temperature. Coral reefs have often been called the rain forests of the ocean because they are so diverse. They have so many creatures, so many beautiful creatures. Yet they are so sensitive to temperature that even a modest warming of a few degrees Fahrenheit may be enough to drive many coral reefs out of existence.

What is "coral bleaching"?

Coral bleaching occurs because the symbiotic algae that live with the coral are very sensitive to temperature. If it gets too warm, they leave the coral behind. That process causes the color to disappear from the coral. Coral reefs can withstand one season of bleaching, but if bleaching becomes an extended process, the coral itself eventually dies and the reef goes out of business. This coral bleaching is what's threatening to happen during this century to many of our reefs, even if the world only warms modestly.

How do carbon emissions get into the ocean?

Carbon dioxide dissolves with water. We're all familiar with this because we know that seltzer contains carbon dioxide; it's the bubbles that come out when you take the cap off. Unfortunately, carbon dioxide has an acidifying effect on the ocean. Gradually, as more carbon dioxide builds up in the atmosphere, it's causing the ocean to become more acidic. Critters that form shells like corals, clams, or other bivalves will have a harder and harder time forming those shells in an acidic environment because the acid dissolves the shells. So, we are actually starting a pervasive ocean-wide process which will make calcification very difficult, and we just simply don't understand what the effects of that will be. It could be devastating for many parts of the food chain and it would certainly make life for coral reefs harder, especially since corals are already under threat due to the warming itself, so it's a double whammy.

How will a decrease in coral life affect mankind?

Corals are not only aesthetically wonderful, but they support a lot of fish life, and those fish are part of the livelihood for many communities and many countries, particularly many island nations. If the coral reefs were to go out of business, big chunks of the marine food chain would be in trouble, and parts of humanity support themselves with that food chain. Of course, the tourist income, from people going to want to snorkel and dive in those reefs, is also important to the same communities. This is a very specific example of how undermining nature undermines mankind's society as well.