'Ancient man harmed marine ecosystems'

Damage along coasts

In a recent article in the journal Science, anthropologists at the Smithsonian Institution and the University of Oregon cite evidence of sometimes serious damage by early inhabitants along the coasts of the Aleutian Islands, New England, the Gulf of Mexico, South Africa and California’s Channel Islands, where the researchers do fieldwork. “Human influence is pretty pervasive,” one of the authors, Torben C Rick of the National Museum of Natural History, part of the Smithsonian Institution, said in an interview. “Hunter-gatherers with fairly simple technology were actively degrading some marine ecosystems,” tens of thousands of years ago.
And, the researchers say, unless people understand how much coastal landscapes changed even before the advent of modern coastal development, efforts to preserve or restore important habitats may fail.
Rick’s co-author, Jon M Erlandson of the University of Oregon, said people who lived on the Channel Islands as much as 13,000 years ago left behind piles of shells and bones, called middens, that offer clues to how they altered their landscape.
“We have shell middens that are full of sea urchins,” Erlandson said. He said he and Rick theorised that the sea urchins became abundant when hunting depleted the sea otters that prey on them. In turn, the sea urchins would have severely damaged the underwater forests of kelp on which they fed.
“These effects cascade down the ecosystem,” Erlandson said. Today, coastal scientists argue about a similar cascade, which some attribute to sea otters being eaten by killer whales.

Abundance of shellfish
But not all the effects of early inhabitants were negative, scientists say, adding that when people in the Channel Islands hunted otters, they probably ended up increasing the abundance of shellfish.
The researchers also cite systems of walls and terraces that people in the Pacific Northwest built to trap sediment and create habitat for clams, which they harvested and ate.

Erlandson said anthropologists in general were not used to thinking that people exploited marine environments before 4,000 or so years ago, when sea levels that had been rising since the end of the last ice age more or less stabilised. Much of the evidence of earlier coastal settlements has vanished under the waves, he said.
And in places where such evidence remains, it is not always recognised for what it is, he said. “Anthropologists walked past those clam gardens for years without recognising them,” he said.

He said it was a coastal geologist who first exclaimed, “Wow, those aren’t natural!” Sea levels are on the rise today, fuelled by global warming, and Rick said anthropologists were rushing to excavate the most threatened coastal sites.
“This archaeological record is really important for helping us understand contemporary issues,” he said. “It’s a threatened resource.”