As if helping to save the world from the worst effects of climate change were not enough, renewable energy may also curb workplace injuries and deaths.
That's because fossil fuels – as the term suggests – have to be dug or drained from underground, and mining is one of the deadliest of industries. Oil and gas extraction account for 100 deaths each year in the US alone, coal another 30, not to mention many more non-fatal injuries.
Carbon-sparing energy sources such as solar panels and windmills, on the other hand, are unlikely to take such a toll on the workers who build and maintain them, argues Steven Sumner, a physician at Duke University Medical Center in Durham, North Carolina. "Extracting the fuel, generating the power and distributing the power are more dangerous in fossil fuel energy than renewable energy."
That sounds like common sense, but there's little hard data on the health costs of producing green energy compared with extracting fossil fuels. One study, a 2005 European Union assessment of the external costs of different energies, found working with wind power was safer than working with coal or oil. And US Department of Energy researchers put solar's occupational health costs in the same ballpark as nuclear, though they ignored the potential for long-term harm from nuclear radiation and catastrophes such as meltdowns.
"We don't know very much," Sumner admits. But as green energy make up a ever-larger chunk of global power supplies, firmer data on workers' health should follow.
Beware biofuels
Vasilis Fthenakis, a photovoltaic researcher at Brookhaven National Laboratory in Upton, New York, agrees that greener energies are generally safer to produce than fossil fuels. Increased demand should make that difference even starker, as renewable energy manufacturing become more efficient and automated. "The picture keeps improving because the technology keeps improving," he says.
Not all green energies are inherently safer for workers than fossil fuels, though. "Rates of injury in agriculture are high, therefore we suspect that biomass energy that comes from crop production is likely to have high risks," Sumner says.
Friday, August 21, 2009
Chinese emissions could peak in 20 years
A THINK tank with links to the Chinese government has predicted that the nation's carbon emissions could peak in 2030. This conclusion, in the 2050 China Energy and CO2 Emissions Report released by the Energy Research Institute, is at odds with the government's insistence that the country's rapid economic growth will mean that emissions cannot decline before 2050.
If China adopts an "enhanced low carbon scenario" with very stringent policies, emissions could peak in 2030 and fall to 1.4 billion tonnes in 2050, equivalent to their 2005 level, the report says. This would be "difficult but doable", says lead author Jiang Kejun.
Pan Jiahua, director of the Chinese Academy of Social Sciences' Research Centre for Sustainable Development and the nation's leading climate economist, says that rapid progress in developing clean technologies means China could reduce emissions earlier than 2050. "But I would think it would be safer to set the peak time at 2035," he says.
Pan says the report could put pressure on the government to compromise on its refusal to adopt emissions cuts in the run-up to the UN climate negotiations in December.
If China adopts an "enhanced low carbon scenario" with very stringent policies, emissions could peak in 2030 and fall to 1.4 billion tonnes in 2050, equivalent to their 2005 level, the report says. This would be "difficult but doable", says lead author Jiang Kejun.
Pan Jiahua, director of the Chinese Academy of Social Sciences' Research Centre for Sustainable Development and the nation's leading climate economist, says that rapid progress in developing clean technologies means China could reduce emissions earlier than 2050. "But I would think it would be safer to set the peak time at 2035," he says.
Pan says the report could put pressure on the government to compromise on its refusal to adopt emissions cuts in the run-up to the UN climate negotiations in December.
Kenya's lions could vanish within 10 years
Kenya has been losing 100 lions a year for the past seven years, leaving the country with just 2000 of its famous big cats, says the Kenya Wildlife Service (KWS) – which concludes the country could have no wild lions at all in 20 years. Conservationists have blamed habitat destruction, disease and conflict with humans for the population collapse.
But Laurence Frank, a wildlife biologist at cat conservation group Panthera, thinks the KWS estimate is optimistic. "Lions are disappearing so fast from Kenya, as well as the rest of Africa, that I think they will disappear [from Kenya] in less than 10 years if action is not taken very quickly," says Frank, who runs several lion conservation projects in the country.
The IUCN suggests that large lion populations of 50 to 100 prides are necessary to conserve genetic diversity and avoid inbreeding.
Leo horror scope
Frank says that the decline of the big cats is due to the inexorable growth in human population and consequent conflict with people over livestock, rather than disease.
"Vast areas of Kenyan rangelands that held lions 20 years ago are now devoid of nearly all wildlife," Frank says. "Predators have been poisoned and speared, herbivores have been snared for meat, and the rangelands themselves have been destroyed by massive overgrazing by domestic stock."
According to Nicholas Oguge, who works for environmental charity Earthwatch Institute in northern Kenya, people lace cattle corpses with insecticide in order to poison entire prides. This ends up killing hyenas and birds of prey too.
"In Kenya, the biggest threat to lion conservation lies outside protected areas," says Oguge. "This is because of increasing cases of poisoning by communities due to livestock loss through carnivore depredation. Typically, the communities use the insecticide Furadan by applying it on livestock carcasses."
Bribes and trophies
Those who kill lions illegally are rarely punished, says Frank. Killing tends to occur far from the influence of authorities and conservationists. In the rare cases of arrest for lion killing, Frank says that the accused may secure their release by the payment of small bribes.
Even the animal-welfare groups that seek to protect lions from trophy hunters may be unintentionally placing them at risk. Sport hunting is banned in Kenya, which has allowed lions to fare better there than in most other parts of Africa, but the prohibition could also contribute to their eventual demise.
"Under current policy, there is no way for rural people to benefit from wildlife," says Frank. "They get essentially no income from tourism, and the only other potential source of wildlife income – carefully regulated, high-paying trophy hunting – is prevented by the financial influence of American and British animal-rights lobbies."
Research by the University of Chicago's Field Museum of Natural History and KWS suggests that on average each lion eats livestock worth around $270 a year. "On the other hand, given the size of Kenya's tourist industry and the central importance of lions to tourist satisfaction, each of Kenya's 2000 surviving lions may be worth upwards of $17,000 per year in tourist revenues," says Bruce Patterson, curator of mammals at the museum.
The fact that Kenya is suffering a devastating drought isn't helping matters, says Zeke Davidson of the University of Oxford. "Kenya is experiencing a very severe drought at the moment and this is driving ever-increasing numbers of pastoralist communities into wildlife areas in search of grazing and water supplies for their herds of livestock," he says.
"Large herds of unattended cattle have been reported forming in northern Kenya, moving toward Ethiopia," Davidson adds. He says they have been abandoned by their owners, who have gone in search of refuge from the drought further south.
Across the continent, the future looks bleak for lions. "Only drastic action on many fronts – policy change, effective law enforcement, giving rural people an economic stake in their natural heritage, and a great deal of investment – will prevent the loss of wildlife in Africa," concludes Frank
But Laurence Frank, a wildlife biologist at cat conservation group Panthera, thinks the KWS estimate is optimistic. "Lions are disappearing so fast from Kenya, as well as the rest of Africa, that I think they will disappear [from Kenya] in less than 10 years if action is not taken very quickly," says Frank, who runs several lion conservation projects in the country.
The IUCN suggests that large lion populations of 50 to 100 prides are necessary to conserve genetic diversity and avoid inbreeding.
Leo horror scope
Frank says that the decline of the big cats is due to the inexorable growth in human population and consequent conflict with people over livestock, rather than disease.
"Vast areas of Kenyan rangelands that held lions 20 years ago are now devoid of nearly all wildlife," Frank says. "Predators have been poisoned and speared, herbivores have been snared for meat, and the rangelands themselves have been destroyed by massive overgrazing by domestic stock."
According to Nicholas Oguge, who works for environmental charity Earthwatch Institute in northern Kenya, people lace cattle corpses with insecticide in order to poison entire prides. This ends up killing hyenas and birds of prey too.
"In Kenya, the biggest threat to lion conservation lies outside protected areas," says Oguge. "This is because of increasing cases of poisoning by communities due to livestock loss through carnivore depredation. Typically, the communities use the insecticide Furadan by applying it on livestock carcasses."
Bribes and trophies
Those who kill lions illegally are rarely punished, says Frank. Killing tends to occur far from the influence of authorities and conservationists. In the rare cases of arrest for lion killing, Frank says that the accused may secure their release by the payment of small bribes.
Even the animal-welfare groups that seek to protect lions from trophy hunters may be unintentionally placing them at risk. Sport hunting is banned in Kenya, which has allowed lions to fare better there than in most other parts of Africa, but the prohibition could also contribute to their eventual demise.
"Under current policy, there is no way for rural people to benefit from wildlife," says Frank. "They get essentially no income from tourism, and the only other potential source of wildlife income – carefully regulated, high-paying trophy hunting – is prevented by the financial influence of American and British animal-rights lobbies."
Research by the University of Chicago's Field Museum of Natural History and KWS suggests that on average each lion eats livestock worth around $270 a year. "On the other hand, given the size of Kenya's tourist industry and the central importance of lions to tourist satisfaction, each of Kenya's 2000 surviving lions may be worth upwards of $17,000 per year in tourist revenues," says Bruce Patterson, curator of mammals at the museum.
The fact that Kenya is suffering a devastating drought isn't helping matters, says Zeke Davidson of the University of Oxford. "Kenya is experiencing a very severe drought at the moment and this is driving ever-increasing numbers of pastoralist communities into wildlife areas in search of grazing and water supplies for their herds of livestock," he says.
"Large herds of unattended cattle have been reported forming in northern Kenya, moving toward Ethiopia," Davidson adds. He says they have been abandoned by their owners, who have gone in search of refuge from the drought further south.
Across the continent, the future looks bleak for lions. "Only drastic action on many fronts – policy change, effective law enforcement, giving rural people an economic stake in their natural heritage, and a great deal of investment – will prevent the loss of wildlife in Africa," concludes Frank
Rat-eating plant discovered in Philippines
The plant is among the largest of all pitchers and is believed to be the largest meat-eating shrub, dissolving rats with acid-like enzymes.
The team of botanists, led by British experts Stewart McPherson and Alastair Robinson, found the plant on Mount Victoria in the Philippines.
They were inspired to search for the plant after word that it is existed came from two Christian missionaries who described seeing a large carnivorous pitcher in 2000 after they climbed the mountain.
Mr McPherson, of Poole Dorset, said: "The plant produces spectacular traps which catch not only insects, but also rodents. It is remarkable that it remained undiscovered until the 21st century."
The team, which found the plant in 2007 following a two-month expedition, published details of their discovery in the Botanical Journal of Linnean Society earlier this year following a three-year study of all 120 species of pitcher plant.
They decided to name the plant Nepenthes attenboroughii, after the wildlife broadcaster Sir David.
"My team and I named it in honour of Sir David whose work has inspired generations toward a better understanding of the beauty and diversity of the natural world," added Mr McPherson.
Sir David, 83, said: "I was contacted by the team shortly after the discovery and they asked if they could name it after me. I was delighted and told them, 'Thank you very much'.
"I'm absolutely flattered. This is a remarkable species the largest of its kind. I'm told it can catch rats then eat them with its digestive enzymes. It's certainly capable of that."
The team of botanists, led by British experts Stewart McPherson and Alastair Robinson, found the plant on Mount Victoria in the Philippines.
They were inspired to search for the plant after word that it is existed came from two Christian missionaries who described seeing a large carnivorous pitcher in 2000 after they climbed the mountain.
Mr McPherson, of Poole Dorset, said: "The plant produces spectacular traps which catch not only insects, but also rodents. It is remarkable that it remained undiscovered until the 21st century."
The team, which found the plant in 2007 following a two-month expedition, published details of their discovery in the Botanical Journal of Linnean Society earlier this year following a three-year study of all 120 species of pitcher plant.
They decided to name the plant Nepenthes attenboroughii, after the wildlife broadcaster Sir David.
"My team and I named it in honour of Sir David whose work has inspired generations toward a better understanding of the beauty and diversity of the natural world," added Mr McPherson.
Sir David, 83, said: "I was contacted by the team shortly after the discovery and they asked if they could name it after me. I was delighted and told them, 'Thank you very much'.
"I'm absolutely flattered. This is a remarkable species the largest of its kind. I'm told it can catch rats then eat them with its digestive enzymes. It's certainly capable of that."
Global warming could change Earth's tilt
Warming oceans could cause Earth's axis to tilt in the coming century, a new study suggests. The effect was previously thought to be negligible, but researchers now say the shift will be large enough that it should be taken into account when interpreting how the Earth wobbles.
The Earth spins on an axis that is tilted some 23.5° from the vertical. But this position is far from constant – the planet's axis is constantly shifting in response to changes in the distribution of mass around the Earth. "The Earth is like a spinning top, and if you put more mass on one side or other, the axis of rotation is going to shift slightly," says Felix Landerer of NASA's Jet Propulsion Laboratory in Pasadena, California.
The changing climate has long been known to move Earth's axis. The planet's north pole, for example, is migrating towards 79 °W – a line of longitude that runs through Toronto and Panama City – at a rate of about 10 centimetres each year as the Earth rebounds from ice sheets that once weighed down large swaths of North America, Europe, and Asia.
The influx of fresh water from shrinking ice sheets also causes the planet to pitch over. Landerer and colleagues estimate that the melting of Greenland's ice is already causing Earth's axis to tilt at an annual rate of about 2.6 centimetres – and that rate may increase significantly in the coming years.
Now, they calculate that oceans warmed by the rise in greenhouse gases can also cause the Earth to tilt – a conclusion that runs counter to older models, which suggested that ocean expansion would not create a large shift in the distribution of the Earth's mass.
Tracking sea levels
The researchers modelled the changes that would occur if moderate projections made by the Intergovernmental Panel on Climate Change – a doubling of carbon dioxide levels between 2000 and 2100 – were to become reality.
The team found that as the oceans warm and expand, more water will be pushed up and onto the Earth's shallower ocean shelves. Over the next century, the subtle effect is expected to cause the northern pole of Earth's spin axis to shift by roughly 1.5 centimetres per year in the direction of Alaska and Hawaii.
The effect is relatively small. "The pole's not going to drift away in a crazy manner," Landerer notes, adding that it shouldn't induce any unfortunate feedback in Earth's climate.
But he says the motion is strong enough that it needs to be taken into account when interpreting shifts in Earth's axis. Tracking the motion of the poles could help place limits on the total amount of sea level rise over decades.
"The oceans take up at least 80 per cent of the heat that is added from greenhouse gases," Landerer told New Scientist. "They have a huge heat capacity, so this effect is going to be there for quite a bit."
Faster spin
Maik Thomas of the German Research Centre for Geosciences in Potsdam, who was not affiliated with the study, says the new work overturns previous ideas. "Up to now, people had believed that height variations [from ocean temperature changes] gave no contribution to polar motion," he told New Scientist. "This is an effect that now has to be considered."
But Thomas notes that polar motion is unlikely to yield a good measurement of sea level rise, whose signal may be difficult to disentangle from a host of other factors that contribute to changes in Earth's tilt, from movements in Earth's crust and mantle to the periodic effects of El Niño, an oscillation of the ocean-atmosphere system in the Pacific.
And climate change can also affect the Earth's spin. Previously, Landerer and colleagues showed that global warming would cause Earth's mass to be redistributed towards higher latitudes. Since that pulls mass closer to the planet's spin axis, it causes the planet to rotate faster – just as an ice skater spins faster when she pulls her arms towards her body.
The Earth spins on an axis that is tilted some 23.5° from the vertical. But this position is far from constant – the planet's axis is constantly shifting in response to changes in the distribution of mass around the Earth. "The Earth is like a spinning top, and if you put more mass on one side or other, the axis of rotation is going to shift slightly," says Felix Landerer of NASA's Jet Propulsion Laboratory in Pasadena, California.
The changing climate has long been known to move Earth's axis. The planet's north pole, for example, is migrating towards 79 °W – a line of longitude that runs through Toronto and Panama City – at a rate of about 10 centimetres each year as the Earth rebounds from ice sheets that once weighed down large swaths of North America, Europe, and Asia.
The influx of fresh water from shrinking ice sheets also causes the planet to pitch over. Landerer and colleagues estimate that the melting of Greenland's ice is already causing Earth's axis to tilt at an annual rate of about 2.6 centimetres – and that rate may increase significantly in the coming years.
Now, they calculate that oceans warmed by the rise in greenhouse gases can also cause the Earth to tilt – a conclusion that runs counter to older models, which suggested that ocean expansion would not create a large shift in the distribution of the Earth's mass.
Tracking sea levels
The researchers modelled the changes that would occur if moderate projections made by the Intergovernmental Panel on Climate Change – a doubling of carbon dioxide levels between 2000 and 2100 – were to become reality.
The team found that as the oceans warm and expand, more water will be pushed up and onto the Earth's shallower ocean shelves. Over the next century, the subtle effect is expected to cause the northern pole of Earth's spin axis to shift by roughly 1.5 centimetres per year in the direction of Alaska and Hawaii.
The effect is relatively small. "The pole's not going to drift away in a crazy manner," Landerer notes, adding that it shouldn't induce any unfortunate feedback in Earth's climate.
But he says the motion is strong enough that it needs to be taken into account when interpreting shifts in Earth's axis. Tracking the motion of the poles could help place limits on the total amount of sea level rise over decades.
"The oceans take up at least 80 per cent of the heat that is added from greenhouse gases," Landerer told New Scientist. "They have a huge heat capacity, so this effect is going to be there for quite a bit."
Faster spin
Maik Thomas of the German Research Centre for Geosciences in Potsdam, who was not affiliated with the study, says the new work overturns previous ideas. "Up to now, people had believed that height variations [from ocean temperature changes] gave no contribution to polar motion," he told New Scientist. "This is an effect that now has to be considered."
But Thomas notes that polar motion is unlikely to yield a good measurement of sea level rise, whose signal may be difficult to disentangle from a host of other factors that contribute to changes in Earth's tilt, from movements in Earth's crust and mantle to the periodic effects of El Niño, an oscillation of the ocean-atmosphere system in the Pacific.
And climate change can also affect the Earth's spin. Previously, Landerer and colleagues showed that global warming would cause Earth's mass to be redistributed towards higher latitudes. Since that pulls mass closer to the planet's spin axis, it causes the planet to rotate faster – just as an ice skater spins faster when she pulls her arms towards her body.
World's ocean temps are warmest on record
Steve Kramer spent an hour and a half swimming in the ocean Sunday — in Maine.
The water temperature was 72 degrees — more like Ocean City, Md., this time of year. And Ocean City's water temp hit 88 degrees this week, toasty even by Miami Beach standards.
Kramer, 26, who lives in the seaside town of Scarborough, said it was the first time he's ever swam so long in Maine's coastal waters. "Usually, you're in five minutes and you're out," he said.
It's not just the ocean off the Northeast coast that is super-warm this summer. July was the hottest the world's oceans have been in almost 130 years of record-keeping.
The average water temperature worldwide was 62.6 degrees, according to the National Climatic Data Center, the branch of the U.S. government that keeps world weather records. June was only slightly cooler, while August could set another record, scientists say. The previous record was set in July 1998 during a powerful El Nino weather pattern.
At a full degree above the 20th century average of 61.5 degrees, "the global ocean surface temperature for July 2009 was the warmest on record," the center said.
Large portions of many continents had substantially warmer-than-average temperatures, the center stated.
"The greatest departures from the long-term average were evident in Europe, northern Africa, and much of western North America," according to the National Oceanic and Atmospheric Administration, which oversees the center. "Broadly, across these regions, temperatures were about 4-7 degrees F above average."
El Nino, emissions as factorsMeteorologists said there's a combination of forces at work: A natural El Nino system just getting started on top of worsening man-made carbon emissions tied to global warming, and a dash of random weather variations. The resulting ocean heat is already harming threatened coral reefs. It could also hasten the melting of Arctic sea ice and help hurricanes strengthen.
"Arctic sea ice covered an average of 3.4 million square miles during July," the center said. "This is 12.7 percent below the 1979-2000 average extent and the third lowest July sea ice extent on record, behind 2007 and 2006."
The Gulf of Mexico, where warm water fuels hurricanes, has temperatures dancing around 90. Most of the water in the Northern Hemisphere has been considerably warmer than normal. The Mediterranean is about three degrees warmer than normal. Higher temperatures rule in the Pacific and Indian Oceans.
The heat is most noticeable near the Arctic, where water temperatures are as much as 10 degrees above average. The tongues of warm water could help melt sea ice from below and even cause thawing of ice sheets on Greenland, said Waleed Abdalati, director of the Earth Science and Observation Center at the University of Colorado.
Breaking heat records in water is more ominous as a sign of global warming than breaking temperature marks on land, because water takes longer to heat up and does not cool off as easily as land.
The water temperature was 72 degrees — more like Ocean City, Md., this time of year. And Ocean City's water temp hit 88 degrees this week, toasty even by Miami Beach standards.
Kramer, 26, who lives in the seaside town of Scarborough, said it was the first time he's ever swam so long in Maine's coastal waters. "Usually, you're in five minutes and you're out," he said.
It's not just the ocean off the Northeast coast that is super-warm this summer. July was the hottest the world's oceans have been in almost 130 years of record-keeping.
The average water temperature worldwide was 62.6 degrees, according to the National Climatic Data Center, the branch of the U.S. government that keeps world weather records. June was only slightly cooler, while August could set another record, scientists say. The previous record was set in July 1998 during a powerful El Nino weather pattern.
At a full degree above the 20th century average of 61.5 degrees, "the global ocean surface temperature for July 2009 was the warmest on record," the center said.
Large portions of many continents had substantially warmer-than-average temperatures, the center stated.
"The greatest departures from the long-term average were evident in Europe, northern Africa, and much of western North America," according to the National Oceanic and Atmospheric Administration, which oversees the center. "Broadly, across these regions, temperatures were about 4-7 degrees F above average."
El Nino, emissions as factorsMeteorologists said there's a combination of forces at work: A natural El Nino system just getting started on top of worsening man-made carbon emissions tied to global warming, and a dash of random weather variations. The resulting ocean heat is already harming threatened coral reefs. It could also hasten the melting of Arctic sea ice and help hurricanes strengthen.
"Arctic sea ice covered an average of 3.4 million square miles during July," the center said. "This is 12.7 percent below the 1979-2000 average extent and the third lowest July sea ice extent on record, behind 2007 and 2006."
The Gulf of Mexico, where warm water fuels hurricanes, has temperatures dancing around 90. Most of the water in the Northern Hemisphere has been considerably warmer than normal. The Mediterranean is about three degrees warmer than normal. Higher temperatures rule in the Pacific and Indian Oceans.
The heat is most noticeable near the Arctic, where water temperatures are as much as 10 degrees above average. The tongues of warm water could help melt sea ice from below and even cause thawing of ice sheets on Greenland, said Waleed Abdalati, director of the Earth Science and Observation Center at the University of Colorado.
Breaking heat records in water is more ominous as a sign of global warming than breaking temperature marks on land, because water takes longer to heat up and does not cool off as easily as land.
Ancient Man Hurt Coasts, Paper Says
The idea that primitive hunter-gatherers lived in harmony with the landscape has long been challenged by researchers, who say Stone Age humans in fact wiped out many animal species in places as varied as the mountains of New Zealand and the plains of North America. Now scientists are proposing a new arena of ancient depredation: the coast.
In an article in Friday’s issue of 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.
Dr. 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,” Dr. Erlandson said. He said he and Dr. Rick theorized 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,” Dr. Erlandson said.
Today, coastal scientists argue about a similar cascade, which some attribute to sea otters’ being eaten by killer whales.
But not all the effects of early inhabitants were negative, the 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.
Dr. 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 stabilized. 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 recognized for what it is, he said. “Anthropologists walked past those clam gardens for years without recognizing 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, fueled by global warming, and Dr. 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.”
In an article in Friday’s issue of 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.
Dr. 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,” Dr. Erlandson said. He said he and Dr. Rick theorized 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,” Dr. Erlandson said.
Today, coastal scientists argue about a similar cascade, which some attribute to sea otters’ being eaten by killer whales.
But not all the effects of early inhabitants were negative, the 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.
Dr. 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 stabilized. 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 recognized for what it is, he said. “Anthropologists walked past those clam gardens for years without recognizing 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, fueled by global warming, and Dr. 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.”
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