A new study in the Proceedings of the National Academy of Sciences suggests the last woolly mammoths died out because they didn't have enough water to drink. That happened about 6,000 years ago, on St. Paul Island off the coast of Alaska.
Russell Graham, a professor in Penn State's Department of Geosciences, joins Here & Now's Jeremy Hobson to discuss the new finding.
Interview Highlights: Russell Graham
On the study's findings
“We found that mammoths went extinct on an island about 5,700 years ago. This is an island in the Bering Sea. It's about 400 miles north of the Aleutian Islands and about 300 miles west of the Alaskan coast, so it's out in the middle of nowhere. The island was originally attached to the mainland on the Bering land bridge which was the area animals and people and plants could cross from Siberia to Alaska, and then with the melting of the glaciers, the sea level rose. The island became isolated, and on that island a group of mammoths were also isolated, and they persisted there until about 5,700 years ago, and then went extinct.”
On whether it was a naturally occurring event or one caused by man-made climate change
“It's a climate event that happened naturally. It was a climate that became warmer, and more arid for the island. It was a unique situation. As the glaciers melted, the island formed and it became smaller and smaller as the sea level kept rising, and this reduced the number of watering holes — that is lakes — that were available to the mammoths. There are no springs or creeks or rivers on the island. It's very small. With the drying of the climate, the mammoths congregated around the water holes and the water evaporated, and mammoths — probably like modern elephants — require a large amounts of water, 70 to 200 liters of water per day. So they really are dependent on the water, and with the depletion of fresh water, they became extinct.”
On what the research can tell people about the present
"I'm a paleoecologist, and I'm interested in how communities have reorganized themselves, mainly mammals in the past because of climate change. The other important aspect of this is that part of this was caused by the sea level rise itself in that the saltwater wedge penetrated the groundwater system of the island, and freshwater is lighter, so it floats on the saltwater. So as sea levels rose it pushed the freshwater up, effectively making it less and less in the water table. We're seeing the same thing happen on South Pacific Islands as sea level comes up. And in some cases people are going to have to leave those islands because they're not going to have enough freshwater to persist there.
This also may apply to Florida, and the same thing is happening there. We have a saltwater wedge, and so sea level is coming up, and as it does, it's reducing the amount of freshwater in the water table, and so everybody thinks about Florida, looking out and waiting for the sea to inundate them or flow over the state, but in reality they may be affected by this limitation of freshwater before that even happens, so it's really a critical factor to understand. And I think this really reinforces that we need to take a look at that."
Russell Graham, the study's lead author and a professor in Penn State's Department of Geosciences.
This segment aired on August 2, 2016.