by Whit Gibbons

December 30, 2007

Global climate change has been increasingly in the news recently. (The Nobel Peace Prize is a sure-fire attention-getter.) Among the species that receive special notice when global climate change is discussed are polar bears. They are unique among bears in being the only solid white species. The adult bears are majestic and photogenic. The babies are cute and photogenic. The species is a natural in the role of poster child for the adverse effects of global climate change. Penguins, the celebrity species of the South Pole, are also indicators of what we could lose from the impacts of global climate change.

What sort of creatures lived in those icy climes back before humans inhabited the earth? We know that dinosaurs lived in temperate and tropical areas across the world. But what about the polar regions? Did dinosaurs live at the poles in the cold and darkness that would have prevailed?

The short answer is "yes," dinosaurs lived in both northern and southern regions that were decidedly colder than places where most reptiles live today. Fossil records from Alaska, southern Australia, and even Antarctica have revealed that about 100 million years ago, dinosaurs roamed the polar landscape. Interpreting what their lifestyles were involves a mix of geology, paleontology, and ecology, along with meteorology, physiology, and several other scientific fields. Even with the tools of modern science, many mysteries remain about these fascinating animals.

The importance of geology in reconstructing what animals lived where relates to where Antarctica and Australia were a million centuries ago. Geological history tells us that at that time these continents had not split apart; they were a single cold continent centered around the South Pole. Later, of course, Australia would break away, drifting northward toward the equator. However, back then dinosaurs, whose fossil bones have been found in the southern part of Australia, lived in a land of ice and snow far different from today.

Various calculations have been made of the age of the rocks where fossils have been found and where continental drift would have placed the world's land masses at the time. Scientists known as polar dinosaur hunters have also incorporated the tilt of the earth relative to the sun in estimating what conditions were like in winter and summer. Most agree that weather conditions were probably like parts of Alaska are today, with frequent below-freezing weather and half a year or so of winter darkness.

Part of the biological mystery is determining how a reptile could survive such conditions. Being warm blooded (technically, being an endotherm and producing heat internally) like polar bears and penguins would be one solution for living in such a climate. Some paleontologists believe that the closest relatives of dinosaurs were birds and that they were indeed warm blooded. However, being cold blooded (technically, being a poikilotherm and getting body heat from external sources) permits some modern reptiles to hibernate for several months without food or water. Also, the enormous leatherback sea turtles have been known to travel into the ice-cold waters of polar seas, indicating that large reptiles the size of small dinosaurs can survive at least short periods of polar weather.

Another proposal has been that the large dinosaurs living near the poles migrated toward more temperate climates during the winter, the way many birds and whales do today. With the paleontological evidence available today we can only speculate about how these animals survived cold winters. But just knowing that dinosaurs were present in cold climates as well as warm ones stirs the imagination.

So if polar dinosaurs once ruled the poles but are now extinct, why should we be concerned about other species disappearing? Because polar bears and penguins have evolved alongside us. They help make today's world what it is. They are not species of the past that we know only from fossils. Whatever caused the dinosaurs to disappear, it had nothing to do with the human race. The same cannot be said for any species that exists today.

We humans should vow to try our best to prevent any other species, plant or animal, from going extinct on our watch. That would be a worthwhile New Year's resolution.

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