Losing Our Past: Climate Change and Island Archaeology

Climate change is here, now. Record droughts, increasingly severe storms, rising average temperatures, and a growing disconnect between ecological processes all point to the damage that increased greenhouse gas emissions are having on our world's climate.

We are just beginning to realize the effect that climate change will have on our lives, what we can do to reduce them, and what it's going to cost us. One cost of climate change, however, can't be measured in currency, jobs lost, or property damage. It is the loss of our shared human heritage. Climate change's effect is being felt on archaeological resources around the world, particularly on coastal sites that contain some of the oldest records of humankind.


Archaeology and Sea Level Rise

Humans have long lived where the land meets the water, surviving on the bounty of the world's oceans. Most evidence of prehistoric settlements are gone - lost to changes in sea level after the last glaciation event about ten thousand years ago caused water levels to rise hundreds of feet.

Today human-caused climate change is threatening what little we have left of this prehistoric past. As islands, the Channel Islands are particularly vulnerable; according to the US Geological Survey (USGS), half of the 250 miles of shore line on the Channel Islands were at risk of being damaged by the rising seas.

Losing the thread: the Channel Islands and the earliest Americans

Archaeological sites on the Channel Islands tell the story of the earliest sea-faring Americans and could be key in understanding how humans first came to the Americas. (See last week's post for more information on this.) Archaeologists like Jon Erlandson from the University of Oregon and his colleague are working feverishly to learn what they can about this history before it's taken by the sea.

He and his team are surveying and inventorying known sites before they erode beneath the waves. They are also looking for previously unknown sites -- and finding plenty of them. But it's a big job -- for example, San Miguel Island covers 9500 acres and contains 700 known archaeological sites. Some of these sites date to 11,500 years before present - among the oldest in North America.  They offer clues about the lives of our ancestors: what they ate, where they traveled, how they made their tools, and how they buried their dead. Middens, one of the most common sources of information about our unwritten past are goldmines of information about prehistoric diets and tool use. Ones near the shores - where many human settlements were located - are badly deteriorated, having lost 10-15 feet of material within the last decade.

How much has the sea risen?  Climate change scientists estimate that over the last 100 years, sea level has increased by seven inches. This relatively small change, coupled with increased severity and frequency of winter storms. The predicted change over the next 90 years? Forty inches.

Indeed, the race is on to document the prehistory of the Channel Islands, before it is washed away.

Sources:

Chang, A. 5 April 2009. Climate change threatens Channel Islands artifacts. USA Today.

Curry, A. March/April 2009. Climate Change: Sites in Peril. Archaeology vol. 62.