What’s more, car owners are predicted to cut back on driving in order to save money. Together, these changes in consumer behaviour could make an important dent in the US contribution to global warming, reducing annual carbon dioxide emissions by tens of millions of tonnes per year. The impact will be dramatic, says Chris Knittel, an economist at the University of California, Davis, who was involved in one of the studies.

The changes are being driven by record fuel prices in the US, where, at the end of April, the average price of gasoline stood at $3.65 per gallon, 20 percent more than in January and treble the price of a decade ago. Until recently, these increases did not seem to be having a consistent effect on the car market and fuel use. Though sales of SUVs in the US have been falling over the past few years, this decline has come on the back of years of rapid growth, and overall gasoline consumption has been increasing every year since 1991.

That could be about to change. Knittel and colleagues looked at data on 1.4 million car purchases over the past 10 years, comparing sales patterns with gas prices. They found that sales of the least fuel-efficient cars, such as SUVs and pick-up trucks, fell by 13 percent for every $1 per gallon increase in the price of gasoline. The biggest SUVs suffered the most, with sales dropping by over 25 percent for every dollar by which the gas price rose. And for every $1 hike in gas prices there was a corresponding 17 percent sales boost for the most efficient vehicles, such as compact cars and hybrids. Knittel estimates that over about a decade, such changes in buying habits could cut the amount of gasoline used by US drivers by around 7 percent for every $1 increase in its price.

Knittel’s findings, presented last month at the University of California Energy Institute in Berkeley, are in broad agreement with those of economist Kenneth Small of the University of California, Irvine. Small looked at data on US fuel consumption and prices over the past 40 years, and projected last year that the recent doubling in fuel prices would quickly lead to a 4 percent drop in the total mileage covered on the roads. In the longer term, as drivers continue to react to rising prices, he projects the size of the reduction will grow to around 20 percent (The Energy Journal, vol 28, p 25).

This would lead to a substantial reduction in carbon emissions. Small says that a $1 per gallon rise in gasoline prices, roughly that seen over the past two years, will result in motorists using 14 percent less fuel in the long term. That would avoid the release of some tens of millions of tonnes of CO2 per year, equivalent to roughly 2 percent of the country’s greenhouse-gas emissions for 2006. That is a hugely significant drop, close to the level of cuts that some nations are required to make under the Kyoto protocol.

Small’s prediction comes with major caveats, however. Gasoline prices are not expected to return to the lows of a decade ago, but could fall by 10 or 20 percent in coming years. And any US economic recovery will boost fuel consumption, partly through raising incomes, which would dilute the pressure on motorists to drive less. So while expensive fuel will rein in consumption, Small and other economists question whether this will be enough to cause an overall fall in emissions from cars.

It is also possible that politics will intervene before any of these effects has a chance to kick in. Presidential hopefuls John McCain and Hillary Clinton have reacted to consumer protests over soaring fuel prices by declaring that they would suspend federal gasoline taxes. “It’s a fantastically stupid idea,” says Roberton Williams, an economist at the University of Texas at Austin.

“But people don’t like high gas taxes, so it’s popular.”

[Claire Bowles @ New Scientist]

Professor Downing found that constructed ponds and lakes on farmland in the United States bury carbon at a much higher rate than expected; as much as 20-50 times the rate at which trees trap carbon. In addition, ponds were found to take up carbon at a higher rate than larger lakes.

“Aquatic ecosystems play a disproportionately large role in the global carbon budget,” Downing said. “Despite being overlooked in the past, it’s small bodies of water that are important because they take up carbon at a high rate and there are more of them than previously thought. The combined effect is that farm ponds could be burying as much carbon as the world’s oceans, each year.”

Ponds capture carbon in two main ways:

The research estimated there are 304 million natural lakes and ponds in the world, covering an area of 4.2 million square kilometers, twice the area previously thought. As many as 90 percent of these water bodies are one hectare (two acres) or less in area.

Downing’s research team published its most recent findings in the Feb. 15 issue of the journal Global Biogeochemical Cycles in a paper titled, “Sediment organic carbon burial in agriculturally eutrophic impoundments over the last century.” The team included members from Europe, the United States and Canada. The work was sponsored by the National Center for Ecological Analysis and Synthesis and the Iowa Department of Natural Resources.

Downing has presented invited seminars on this research to the International Society of Limnology, the American Society of Limnology and Oceanography, and at several major research institutions in North America and Europe. Most recently, he was invited to discuss his research by the Pond Conservation, a charity in the United Kingdom dedicated to creating and protecting ponds and the wildlife they support. He will spoke today at University College London. An upcoming presentation is scheduled for the annual meeting of the European Pond Conservation Network in Valencia, Spain.

Jeremy Biggs, Pond Conservation director of policy and research, said the research has exciting implications. “It may be that ponds will be the modern equivalent of the swamps that formed coal in the past. But before we all rush into making ponds to trap carbon we need to do some basic research here in the UK. If the rate of carbon uptake in ponds in Europe is the same as that found in the USA study, we may well have discovered an important new natural way of trapping carbon,” he said.

Downing’s ongoing research, partnering with the United States Geological Survey, and his contributions to the Iowa Lakes Survey will investigate the role of small Iowa lakes in the absorption of atmospheric carbon dioxide and other important gases such as methane.

[John Downing @ Iowa State University]

Denise Jackson had such success with her first book that she was inspired to write another. via WBIR-TV

Scene: The 2008 RALPH Awards, held at a highly secret location somewhere in the Northern Hemisphere. via Reno Gazette-Journal