Discovery News: Environmental

Nuclear Cooling

Today I wrote a story about how wildfire smoke acts to cool the Arctic by reflecting light back into space before it hits the surface.

I spoke with Alan Robock at Rutgers University who said, "I worry much more about nuclear weapons than I do about climate change in its effect on our climate."

Nuclear weapons could create plenty of cooling smoke, Robock says, even if used on a relatively small scale.

"We've calculated how much smoke you would get from a 'tiny' war between India and Pakistan, each using 50 Hiroshima-sized bombs," he said. "Even that would produce climate change to temperatures colder than in the Little Ice Age."

Robock's study found that the associated drop in agricultural productivity from global cooling could be enough to lead to famine. Other studies have suggested that a full-scale nuclear war could result in death of a majority of the world's population from such indirect causes.

I'm all for avoiding climate impacts from CO2 emissions and from nuclear fallout. Everybody with me?

(Photo courtesy of National Nuclear Security Administration / Nevada Site Office)

Shuffling Species

As the climate warms, many species may no longer be comfy in their habitats and become better suited to survival at higher latitudes or higher elevations where they can escape the heat. But how is a tree species that takes decades to reproduce going to migrate fast enough to keep pace with a rapidly changing climate? What if a major city lies between a critter's old habitat and where it needs to go to survive?

We might help. That's the idea behind "assisted colonization"--deliberately moving plants or animals from places where they're doomed to places where they might survive in the future. In today's issue of Science, a group of researchers published an article saying this is an approach we should take seriously. Read an article about it at Discovery News.

It's a horrifying prospect to some conservation biologists. They point to the long list of species introduced into new habitats by humans (like moving cane toads to Australia) that have gone terribly wrong. The authors of the new report agree that some introductions would be risky and should be avoided: moving polar bears from the Arctic to Antarctica would introduce a predator of penguins and seals and likely decimate those populations.

But other introductions seem less likely to cause a disruption. Most would be regional moves, not inter-continental. The authors point out that staghorn corals currently live over a range of latitudes and that those at low latitudes can tolerate higher temperatures than the ones further from the equator. Moving low-latitude coral into higher latitudes where cold-adapted corals are already dying off is unlikely to cause a problem, the authors argue.

The researchers discuss assisted colonization as a way to save species from extinction, but there might be other motivations.

For instance, here in Minnesota, we are at the southern tip of the spruce-fir forest range, which is likely to retreat into Canada in a warming climate, and our deciduous forests face threats, too. But having forests in the state is a big part of its identity. Can we be happy knowing that the forests exist to the north and learn to live without them here? Or, should we bring in trees from further south that will thrive in our new climate and keep us under a forest canopy?

It's not just a psychological issue: forests contribute to our industrial and recreational economy, so people may be reluctant to let the woods give way to savanna. Check out an earlier post about a conference here where they discussed the topic.

What do you think? Is this a good idea? When would you be willing to give a species a helping hand? Or, should we let nature take its course... whatever that means in today's world?

(Image: Flickr user *Micky, some rights reserved)

Antarctic Wildlife Feels the Heat

Today at Discovery News we reported on work by three researchers who study different aspects of the Antarctic ecosystem, and who decided to get together and tell the combined story of the changes they've seen over the last two or three decades as a result of climate change.

We thought we'd post it here so you could have your say. Do you care about what's happening in Antarctica? Are you ready to start marching for the penguins? What strikes you about the researchers' findings?

Also, stay tuned at the end of the post for some extra tidbits that didn't fit in the original story.

(Photo: Juvenile krill, Jim McClintock)

At Antarctic Peninsula, Fast Change
Jessica Marshall, Discovery News

 

July 10, 2008 -- From the tiny phytoplankton living under the ice to the penguins at the top of the food chain, the ecosystem of the Antarctic Peninsula is changing fast, driven by warming waters and a loss of sea ice.

Three researchers who have spent decades studying Antarctica's denizens paint a picture of interconnected changes at the bottom of the Earth that are changing the ecology over just decades after some 30 million years of relative isolation.

"The changes are profound," said Hugh Ducklow of the Marine Biological Research Laboratory in Woods Hole, Mass.

He and colleagues James McClintock of the University of Alabama at Birmingham and William Fraser of Polar Oceans Research Group in Sheridan, Mont. compiled their findings from studying different aspects of the Antarctic ecosystem in an article in the current issue of American Scientist.

Nowhere on Earth is climate change happening faster than on the neck of land stretching north from the Antarctic continent more than 900 miles toward South America. The average midwinter temperature on the Antarctic peninsula has increased more than 10 degrees Fahrenheit since 1950, five times the global average.

The changes the researchers see begin at the base of the food web, with phytoplankton -- tiny photosynthetic organisms that, in Antarctica, are evolved to live in the sea ice. As the extent of sea ice has decreased, so has the amount of phytoplankton.

"Sea ice is not just ice," Ducklow said. "It's a habitat for organisms."

Indeed, juvenile krill, tiny shrimplike organisms that serve as the main food source for Adélie penguins and baleen whales, graze on the phytoplankton under the sea ice.

"Juvenile forms of krill are not as strong swimmers as adults," Ducknow said "By congregating on the underside of the ice, they get a shelter from predators, and it's where the food is."

Krill have been declining for decades, the authors note, although sea ice decline may not be the only reason.

With less krill to feed on, organisms at the top of the food chain like Adélie penguins suffer. Their populations have been decreasing in the central and northern Antarctic peninsula.

The Adelie penguins also rely on the sea ice directly. In winter, they use the sea ice to get out to hotspots of food. As this shrinks, their food will be too far away to swim to.

In contrast, two related species, the gentoo and chinstrap penguins, do not rely on sea ice for winter feeding. Their populations are rising on the Peninsula.

Meanwhile, another Antarctic community is poised to change because of rising sea temperatures.

Since the Antarctic Peninsula separated from South America 25 to 35 million years ago, Antarctica has been encircled by the Antarctic Circumpolar Current, a clockwise roundabout current that holds cold water near the continent and isolates it from the rest of the ocean.

Crabs and other predators that get prey by cracking shells with strong forces were excluded from the region once the current was established, because they cannot survive at such cold temperatures.

Without such predators to guard against, animals like snails and clams in Antarctica evolved delicate, thin shells. But as the ocean warms, crab predators may move in and have defenseless prey to capitalize on. A colony of king crabs was recently found in deeper waters off the peninsula.

"It's only a matter of time before they can move up into even shallower water," said lead author McClintock, who studies Antarctica's invertebrates. "When crabs get into those communities of clams and snails and brachiopods, they are going to be history."

McClintock notes that the reproductive cycle of invertebrates is also closely tied to temperature, and warming may lead to larvae hatching out of sync with the availability of their plankton food supply.

But, he adds, kelp-like macroalgae are likely to thrive with the greater availability of sunlight thanks to reduced sea ice. And jellyfish will probably also increase in number.

What is clear is that these populations are shifting fast in relation to one another, and the ecosystem that emerges will be different from the one that has existed in isolation for millions of years.

"People say, why Antarctica? Who cares about that?" Ducklow said. "It's a canary in the coal mine. We're seeing things happen rapidly there. It's a good wakeup call for us that there is climate change, and ecosystems really are responding to it."

******************************************

Now, here's the extra bit that I'll call

Amazing Antarctic Facts

• The reason that crabs have heretofore been unable to survive in Antarctic waters is that they cannot expel magnesium from their bloodstream. Magnesium acts as a narcotic whose effect is enhanced at low temperatures. So, until now, any crabs that decided to go strolling in too-chilly waters became immobilized and died.
• Another species that is threatened by changing sea ice is the Waddell seal. Female adult seals get a private, predator-protected birthing room by using their ice-chipping teeth to scratch open a hole in the sea ice from underneath. They pop through the hole onto the surface when they're ready to pop out their young. According to McClintock, "The price they pay for these teeth is that over the years they wear down the teeth and they starve." They live about half as long as other seals, he said, but more of their young survive.
• About 70 percent of Antarctic species are found nowhere else.
• The sea ice in midwinter is about as big as the lower 48 U.S. states, but with a lot fewer Starbucks.
• Antarctic ice holds almost 2/3 of Earth's freshwater.
• Climate change has brought more snowstorms to the Peninsula. These have also harmed Adélie penguins. When it snows in spring, the nests can flood, killing eggs and hatchlings.
• If warming trends continue, the average midwinter temperature will be above freezing (for seawater) by mid-century. Sea ice will no longer form.

Does a Dairy Hormone Make Milk Greener?

Green-minded eating of animal products just keeps getting trickier. A study published Monday in the Proceedings of the National Academy of Sciences says that cows given the hormone somatotropin to boost their milk production require less energy and release less methane to produce the same amount of milk as cows not given the hormone, commonly abbreviated on milk cartons as rbST.

The authors claim that 1 million cows on rbST save the greenhouse gas equivalent of taking 400,000 cars off the road, compared with the emissions from untreated cows necessary to make an equivalent amount of milk. The savings come largely because fewer cows need less food, which requires less ground to grow it on.

But Michael Hanson of the Consumers Union in New York told news outlets (here and here) that assuming  a cow making more milk can get by on the same amount of food as an untreated cow is unrealistic. Accounting for increased food needs would remove much of the gain suggested by the authors, he said.

One of the study's authors works for Monsanto, who makes rbST under the name Posilac, and another is a Monsanto consultant.

What to do? Will you dump the organic milk to save the planet or will your milk moustache remain rbST-free?

(Image: Flickr user karlfrankowski. Some rights reserved.)

Climate Scientists Talk Serious

We thought we'd post today's Discovery News story--which presents climate scientists' assessment of where we stand with climate change--here at EnvironMental Case, so you could weigh in and tell us what you think. Are you worried, very worried? Here's the story:

The Time Is Now, Climate Experts Warn

Jessica Marshall, Discovery News

June 27, 2008 -- Earlier this week, renowned NASA climate scientist James Hansen warned Congress of the dangers of climate change, exactly 20 years after he did so for the first time.

The message he delivered was almost the same as it was in 1988, but there was one key difference: "The difference is that now we have used up all slack in the schedule for actions needed to defuse the global warming time bomb," he said.

Hansen's message painted a stark and urgent picture of a world already past the point where significant damage would occur. Discovery News wanted to know if other scientists shared his view. Are we really in for it and at what point? What are our options for avoiding the worst?

Earth's Carbon Budget

Hansen argued this week that the "safe level of atmospheric carbon dioxide is no more than 350 ppm (parts per million), and it may be less." This recommended level is less than the amount currently in the atmosphere -- 385 ppm. It may also be less than the commonly discussed stabilization target of 3.6 degrees Fahrenheit (2 degrees Celsius) of temperature increase, which probably corresponds to an atmospheric CO2 concentration of about 350-400 ppm.

Already, he argued, arid lands are expanding, glaciers are receding, and Arctic sea ice is shrinking, driven by cycles of positive feedback, where melting leads to more warming of the exposed dark ocean water, which leads to more melting.

"As a result, without any additional greenhouse gases, the Arctic soon will be ice-free in the summer," Hansen said.

To forest ecologist Lee Frelich at the University of Minnesota, Twin Cities, Hansen's argument that a lower stabilization target is safer makes sense.

"If you look at the paleological record, in the last interglacial period 110,000 to 120,000 years ago, the world was thought to have a climate that was two degrees warmer than today," Frelich said. "The oceans were 20 to 25 feet higher, but CO2 was only 290 ppm. I've always thought that if a CO2 content of 290 could cause that, why won't it do it now? Maybe there's just a lag time."

"I'm sympathetic to a more aggressive goal," said glaciologist Jay Zwally of NASA Goddard Space Flight Center in Greenbelt, Md. "The goal that people have adopted of keeping it to a total of two degrees [Celsius] rise since the preindustrial is still going to allow enough warming that we'll have an even more significant impact than we've already seen," he said.

While other scientists agree that 350 ppm is a safer target that increases the likelihood we will avoid many of the negative effects of climate change, some also think it's unrealistic.

"Three hundred and fifty is impossible," said climatologist Stephen Schneider of Stanford University in Palo Alto, Calif. "We're going to overshoot 350 and 450 and probably 550, though I sure hope not."

Schneider's hope is that while it might still be 20 years before actions to reduce CO2 emissions really have an effect, innovations over the next two decades will make it possible to dramatically reduce emissions.

"My cynical scenario is that there will be more Katrinas, massive fires, melting of the Arctic, and people will say, 'Oh my God, what have we done. We'd better undo this,'" he said. Such catastrophes could finally spark the dramatic change that's needed, he suggests, if we don't take action sooner of our own accord.

"I try not to talk about a threshold of two degrees," Schneider added. "At 1.8 the world is not fine. At 2.2, we don't turn into a climatic pumpkin. We just have more severe events. The object is not to get hung up on the numbers. The object is to get out there and get solutions."

Others agreed.

Nevermind the Tipping Point

"Time is of the essence here. I don't know if targets like 350 ppm are that useful," said John Harte of the University of California, Berkeley. "We can't make a regulation on something we can't control. We don't regulate temperature, and we don't even regulate the amount of CO2 in the atmosphere. However, we control what our automobiles look like. We control the efficiency of our devices. We control what our energy looks like."

"I'm not so enthused about the concept of the tipping point," he added. "My view is that we've probably passed some tipping points. We've entered some realms of irreversibility. There are probably many more, but we don't know where they are."

"We know that if we don't take action, it will be a disaster," he said. "That's all we need to know."

Whether they focused on thresholds or not, the scientists all agreed that the problem is urgent and that not doing anything will lead to disaster: rising sea levels, food shortages, spread of infectious diseases and extinctions.

Starting From Here...

Hansen argued that to achieve the target of 350 ppm, we need to put a moratorium on new coal-fired power plants and phase out burning coal without capturing and storing the carbon.

While scientists agree that coal is a huge part of the problem, they also emphasized the need to apply every available sensible strategy to address the problem.

"There seems to be an emphasis on coal and a distraction from other things we can be doing as well," NASA's Zwally said.

"Some people think that climate change is just about saving a few rare species, and it's just environmentalists making a fuss," Frelich said. "That's really not it."

"It's really about the quality of life for people," he continued. The Earth has been through many big changes before. There have been big extinctions, and new species have evolved to fill the ecosystems. It's not a big deal to the Earth's ecosystems, but it will be a really big deal for the quality of life of humans."

Frelich points out that right now the best soil for growing crops in the United States aligns ideally with the right climate for agriculture. But if the favorable climate moves north, it will be over Canada in an area where bedrock lies at the surface, stripped of soil by the last glaciation.

"If the best climate for growing crops lines up with the Canadian shield, that's an issue for people," he adds.

The scientists also pointed out that countries that tackle this most aggressively will be the winners, regardless of what other nations have committed to.

"The economic giants of the rest of this century are going to be the nations that are selling wind turbines and solar panels and efficient cars to the rest of the world," said Harte. "I would think we'd want to be the leader in that."

"Solving this problem is technologically and economically not that difficult," Harte added. "It's proving to be politically difficult."

(Image: "Wildfire Landscape" by Flickr user Clinton Steeds, some rights reserved.)

Toto, I Think We're in Kansas From Now On

There’s a map that’s tossed around a lot in these parts showing Minnesota shifted south and west a bit--right over Kansas--to illustrate what we should expect the future climate to be like.

Minnesotans seem to have mixed feelings about that future. I’m sure a person from Kansas would, too, if they saw their state plunked somewhere in west Texas (and so forth). We all have a sense of loyalty to place that has something to do with what sorts of plants and animals we expect in our surroundings, and how we live our lives because of them.

Late last week, I spent some time at a conference on climate change adaptation and biodiversity conservation at the Minnesota Landscape Arboretum.

Forest ecologist Lee Frelich of the University of Minnesota, Twin Cities, laid out his predictions for the future of forests in the state: pine beetle + emerald ash borer + invasive earthworms + deer overpopulation + climate change (including boreal forest moving 300 miles north, soil drying out, and more fires) = no trees (mostly).

Then he pointed out that there is a small stand of ancient forest further south in the state that’s composed of trees that should do well in a warmer climate.  So, he and others are wondering, should we start thinking about moving some of these species further north to make sure there will still be forests in Minnesota? Are there other plants and animals from further south that we should think about moving?

These are questions with no easy answers. One the one hand, a bit of foresight could preserve woods—which provide economic, recreational and psychological benefits to the state. Careful relocation might save some plant species from extinction. Many won’t be able to move north fast enough to keep up with climate change, Frelich predicts.

On the other hand, many scientists hope and expect some of the native species will survive here without intervention, so maybe we should wait and see what they can do. Or, maybe it is OK for boreal forests not to reach into Minnesota anymore, but rather for us to be satisfied that they continue to exist further north in Canada, and to take what comes naturally here. Frelich noted that we might end up with savanna—a rare type of ecosystem in North America. So maybe there will be some perks.

In any case, the researchers argued, now is the time to start doing studies to figure out what approaches might work. Biologists don’t even know how to germinate the seeds of many of the plants that might be candidates for assisted migration, so for such an approach to work will require plenty of research, and soon. Trees can take decades to reproduce.

(Map: Union of Concerned Scientists)

How Green Is Your Hometown?

The Brookings Institution today released a report ranking the nation’s 100 biggest metropolitan areas by their residents’ average carbon footprint—the amount of CO2 they are responsible for releasing based on vehicle transportation (including freight and personal) and home energy use.

City living is greener overall: Although two-thirds of the U.S. population lives in the 100 biggest urban areas, they are responsible for only 56 percent of the carbon emissions. These urbanites’ footprint is 14 percent less than the country average.

So… who are the winners and losers?

Here are the 10 metropolitan areas with the lowest carbon footprint…and the highest (per capita CO2 emissions in metric tons in parentheses):

BEST
1.  Honolulu, HI (1.356)
2.  Los Angeles-Long Beach-Santa Ana, CA (1.413)
3.  Portland-Vancouver-Beaverton, OR-WA (1.446 )
4.  New York-Northern New Jersey-Long Island, NY-NJ-PA (1.495)
5.  Boise City-Nampa, ID (1.507)
6.  Seattle-Tacoma-Bellevue, WA (1.556)
7.  San Jose-Sunnyvale-Santa Clara, CA (1.573)
8.  San Francisco-Oakland-Fremont, CA (1.585)
9.  El Paso, TX (1.613)
10. San Diego-Carlsbad-San Marcos, CA (1.630)

WORST
91.  Knoxville, TN (3.134)
92.  Harrisburg-Carlisle, PA (3.190)
93.  Oklahoma City, OK (3.204)
94.  St. Louis, MO-IL (3.217)
95.  Nashville-Davidson--Murfreesboro, TN (3.222)
96.  Louisville, KY-IN (3.233)
97.  Toledo, OH (3.240)
98.  Cincinnati-Middletown, OH-KY-IN (3.281)
99.  Indianapolis, IN (3.364)
100. Lexington-Fayette, KY (3.455)

Here in Minneapolis-St. Paul we rank 45th.

How dense the city is, how much home heating and cooling the city requires, and whether the city uses primarily coal or a less carbon-intensive form of energy all contribute to where it sits in the green rankings.

Check out the whole report here (click on "Download"), and the complete rankings, clicking on "Download  Per Capita Footprints Supporting Material."

Atmospheric Scientists: To Study CO2 Is to Spew It

Here’s a curious article from the Annals of Irony: “The travel-related carbon dioxide emissions of atmospheric researchers.”

Andreas Stohl of the Norwegian Institute for Air Research (NILU) in Kjeller, Norway calculated the CO₂ emissions from all business travel for the institute's scientists, who study air pollution, including climate change.

More than 90 percent of the emissions came from air travel. The annual total for business travel alone came to 4.3-6 tons per scientist, compared to the global average annual total per capita CO₂ emissions of 5 tons.

"The travel-related CO₂ emissions of a NILU scientist, occurring in 24 days of a year on average, exceed the global average annual per capita emission," Stohl pointed out.

Incredibly, the Norwegian average annual total per person is 21 tons, among the highest in the world, Stohl reported, mostly because of oil industry emissions.

However, he concluded in his abstract (which was actually published in Atmospheric Chemistry and Physics Discussions), “If the emissions per NILU scientist derived in this paper are taken as representative for the average Norwegian researcher, travel by Norwegian scientists would nevertheless account for a substantial 0.2% of Norway's total CO₂ emissions. Since most of the travel-related emissions are due to air travel, water vapor emissions, ozone production and contrail formation further increase the relative importance of NILU's travel in terms of radiative forcing.”

As someone who works from home and sometimes gets a little stir crazy, I can see the benefits of face-to-face contact, and if these researchers' flights are going to help solve the climate problem sooner, then they're probably worth the CO₂. But video conferencing is getting more and more sophisticated—and is being used more as fuel and flight prices go up.

Should we be pushing for more telecommuting or do we need to meet in person? Let us know about your telecommuting successes and failures.

(Photo: NOAA via Wikimedia Commons)

Meat, Meat, Meat

The take home message from everyone I’ve been speaking with recently is that meat--especially beef--is just no good for the environment.

First, Christopher Weber at Carnegie Mellon University published findings showing that shifting a quarter of the average American’s red meat consumption to other foods saved as much greenhouse gas emissions as going entirely local, i.e. red meat has a really big carbon footprint.

Then, I spoke with researchers highlighting the importance of considering our “nitrogen footprint”, too. “Meat is one of the main drivers of acceleration of the cycle,” said Alan Townsend of the University of Colorado at Boulder. “To have meat diets under modern agriculture takes a lot of nitrogen. You end up having to have a lot of fertilizer and a big chunk of field to grow a few cows or pigs.”

Finally, the Stockholm International Water Institute issued a report about water… You guessed it: meat production takes lot of water. Their report estimates that about 50 percent of calories grown in fields never make it to the table, and about half of that loss is animal feed that doesn’t end up as a calorie on a cow, pig, chicken, or other edible critter. Growing those lost calories takes a lot of water.

For the most part, each of these impacts comes from the same cause: growing a pound of meat requires (much) more than a pound of grain. A pound of beef, for instance, requires eight. (The conversions are better for other types of meat, but never 1:1).

This inefficiency amplifies the demand for nitrogen fertilizer and irrigation, and leads to more of the greenhouse gas emissions associated with growing crops. These emissions come from energy for making fertilizer and release of nitrous oxide (N2O)—a super greenhouse gas almost 300 times more potent than CO2—by bacteria acting on fertilizer in the soil.

With cattle, greenhouse gas emissions also result from methane (23 times more potent than CO2) released by digestion, and nitrous oxide production from manure. 

The SIWI report points out that demand for meat is rising fast. Here are some meat consumption numbers for different parts of the world:

--Southeast Asia: ~88 lbs/person/year in 2002, a sevenfold increase from 1961, when it was 13 lbs.
--India: Projected at 22 lbs/person/year in 2050 (Thanks to a largely vegetarian population.)
--China: Projected at 183 lbs/person/year in 2050
--US: 200 lbs/person/year in 2005, up 22 lbs from 1970

It’s also worth pointing out that dairy creates these impacts, too, though not to the same extent as meat.

Is Grass-Fed Beef Better?
So grain-fed beef is no good… but what about grass-fed? If you read Michael Pollan’s book, The Omnivore’s Dilemma, you might have been convinced, like me, that eating a bit of grass-fed beef was fine--even good. When cows eat grass, they’re converting plant calories that we can’t eat (i.e. grass) into calories that we can. This is an efficient way to harness the energy from the sun in food form in places that aren’t suitable to grow crops.

But, how much does the greenhouse gas footprint change when you switch to grass-fed beef? Then you don’t need those eight pounds of grain. Christopher Weber kindly did some math to help answer this question (Thanks, Christopher!). He cautions that these numbers are approximate and un-reviewed, but here they are:

“By switching to grass fed, you remove around 20% of the CO2 and 60% of the N2O in the supply chain of making and delivering grain to the farms.
So, if there is no increase in methane and manure emissions (of CH4 and N2O) are not being captured at the feedlot, there's approximately a 25% reduction in life cycle greenhouse gas emissions in grass fed vs. grain fed.”

But don’t stop reading. Studies have shown that grass-fed beef produces more methane than grain-fed beef. (Though at least one study has reported the opposite, Weber said.) This offsets some of the gains:

“If the grass-fed has 15% more methane, which is around the number I've seen cited, then grass fed is only 20% better.”

So, while there may be other advantages to eating grass-fed beef over grain-fed, it’s still not a climate-neutral choice. And, as Marshall Burke of Stanford University pointed out, if everyone switched to grass-fed beef, there wouldn’t be enough pastureland to go around.

To the climate conscious: learn to love lentils.

(Photo: Grant Hutchinson)

Don't Self-Sequester Carbon

Doing its part?

If you were thinking of sequestering carbon yourself—like, on yourself—by fattening up, you’d better skip it. Of course it’s bad for your heart and your brain and whatever else—but it’s also bad carbon counting.

There’s a letter published this week in The Lancet by Phil Edwards and Ian Roberts of the London School of Hygiene and Tropical Medicine arguing that competition for fuels and food—now widely discussed thanks to the surge in demand for biofuels--is not a new phenomenon. Both agriculture (making fertilizer is energy intensive) and transportation are heavy users of fossil fuels, so rising oil prices affect both.

But the authors also argue that our over-consumption of both food and cars is making us obese, and conversely, that obesity is contributing to climate change and the food crisis.

They write:
Compared with the normal weight population, the obese population consumes 18% more food energy.  Additionally, more transportation fuel energy will be used to transport the increased mass of the obese population, which will increase even further if, as is likely, the overweight people in response to their increased body mass choose to walk less and drive more.

It’s not the first time researchers have made these points. Roberts makes it here and related work is here, but it gets me thinking because I've written about food recently, and come across the statistic that it takes eight pounds of grain to make one pound of cow. Researchers have estimated that the greenhouse gas impact of red meat is 2.5 times greater than chicken or fish.

So I wonder: what’s the carbon footprint of every extra pound we pack? Of course, it depends on whether we’ve made it via beef or beans, but as the authors note, that pound consumes daily metabolic energy, and we drive it around and fly it places. A 2004 study found the average 10 lb weight gain of Americans during the 1990s cost airlines $270 million and released 3.8 million additional tons of CO2 in 2000.

So if I’m going to avoid beef because of its carbon footprint, I’d better cut back across the board, because making an extra pound of me is probably not any greener.

…Now, I also want to know, could carbon offset companies start selling offsets through health clubs or individuals who lose weight and keep it off?

(Photo: James Phelps)