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Holy cow! Dino flatulence may have changed ancient climate

May 7, 2012
Courtesy of Cell Press 
and World Science staff

Nev­er mind cows: di­no­saurs pass­ing gas could have re­leased enough cli­mate-altering meth­ane gas to warm the pre­hist­or­ic world, ac­cord­ing to newly pub­lished cal­cula­t­ions.

While many a stu­dent has snick­ered over the ob­serva­t­ion that flat­u­lat­ing live­stock con­trib­ute to the at­mos­pher­ic green­house gas­es blamed for glob­al warm­ing to­day, deal­ing with a hulk­ing ap­at­o­saur­us (a.k.a. bron­to­sau­rus) with in­di­ges­tion might have been no laugh­ing mat­ter.

The new re­search pub­lished in the May 8 is­sue of the re­search jour­nal Cur­rent Bi­ol­o­gy al­so sug­gests that this beast and its kin—giant dino­saurs known as sau­ro­pods—could have har­bored enough meth­ane-making mi­crobes in their guts to make a sub­stan­ti­al cli­mate im­pact.

“A sim­ple math­e­mat­i­cal mod­el sug­gests that the mi­crobes liv­ing in sau­ro­pod di­no­saurs may have pro­duced enough meth­ane to have an im­por­tant ef­fec­t,” said Dave Wilkin­son of Liv­er­pool John Moores Uni­vers­ity in the U.K. “Our cal­cula­t­ions sug­gest that these di­no­saurs could have pro­duced more meth­ane than all mod­ern sources—both nat­u­ral and man-made—put to­geth­er.”

Meth­ane and oth­er green­house gas­es tend to warm the cli­mate by trap­ping heat in the at­mos­phere, sci­en­tists say.

Dis­tinc­tive for their enor­mous size and long necks, sau­ro­pods were wide­spread about 150 mil­lion years ago. As in cows, meth­ane-producing mi­crobes aided the sau­ro­pods’ di­ges­tion by fer­ment­ing their plant food. Wilkin­son and study co­au­thor Graeme Rux­ton from the Uni­vers­ity of St An­drews, U.K. were stu­dying sau­ro­pod ecol­o­gy when a ques­tion dawned on them: If mod­ern cows pro­duce enough meth­ane gas to be of in­ter­est to cli­mate sci­en­tists, what about sau­ro­pods? They teamed up with meth­ane ex­pert Euan Nis­bet at the Uni­vers­ity of Lon­don to work out the num­bers.

“Clearly, try­ing to es­ti­mate this for an­i­mals that are un­like an­y­thing liv­ing has to be a bit of an ed­u­cat­ed guess,” Wilkin­son said.

Phys­i­ol­o­gists have stud­ied meth­ane pro­duc­tion from a range of mod­ern an­i­mals to de­rive equa­t­ions that pre­dict meth­ane pro­duc­tion from an­i­mals of dif­fer­ent sizes. It turns out those cal­cula­t­ions de­pend only on the an­i­mal’s weight. A me­di­um-sized sau­ro­pod weighed over 20 tons. Us­ing avail­a­ble es­ti­mates of popula­t­ion dens­i­ties, the sci­en­tists cal­culated glob­al meth­ane emis­sions from sau­ro­pods to have been 520 mil­lion met­ric tons year­ly, com­pa­ra­ble to to­tal mod­ern meth­ane emis­sions. 

Be­fore mod­ern in­dus­try took off, meth­ane emis­sions were roughly 200 mil­lion met­ric tons a year. Mod­ern ru­mi­nant an­i­mals, in­clud­ing cows, goats, gi­raffes, and oth­ers, pro­duce about one-fourth to one-half that amount. The stu­dy’s con­clu­sions not only show “just how strange and won­der­ful the work­ings of the plan­et are,” but al­so serve as a use­ful re­minder for the im­por­tance of mi­crobes and meth­ane for glob­al cli­mate, the re­search­ers wrote.


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Never mind cows: dinosaurs passing gas could have released enough climate-altering methane gas to warm the world, according to newly published calculations. While many a student has snickered over the observation that flatulating livestock contribute to the atmospheric greenhouse gases blamed for global warming today, dealing with a hulking apatosaurus (brontosaurus) with indigestion might have been no laughing matter. The new research published in the May 8 issue of the research journal Current Biology also suggests that this beast and its relatives—giants known as sauropods—could have harbored enough methane-making microbes in their guts to make a substantial climate impact. “A simple mathematical model suggests that the microbes living in sauropod dinosaurs may have produced enough methane to have an important effect,” said Dave Wilkinson of Liverpool John Moores University in the U.K.. “Our calculations suggest that these dinosaurs could have produced more methane than all modern sources—both natural and man-made—put together.” Methane and other greenhouse gases tend to warm the climate by trapping heat in the atmosphere, scientists say. Distinctive for their enormous size and long necks, sauropods were widespread about 150 million years ago. As in cows, methane-producing microbes aided the sauropods’ digestion by fermenting their plant food. Wilkinson and study coauthor Graeme Ruxton from the University of St Andrews, U.K. were studying sauropod ecology when a question dawned on them: If modern cows produce enough methane gas to be of interest to climate scientists, what about sauropods? They teamed up with methane expert Euan Nisbet at the University of London to work out the numbers. “Clearly, trying to estimate this for animals that are unlike anything living has to be a bit of an educated guess,” Wilkinson said. Animal physiologists have studied methane production from a range of modern animals to derive equations that predict methane production from animals of different sizes. It turns out those calculations depend only on the animal’s weight. A medium-sized sauropod weighed over 20 tons. Using available estimates of population densities, the scientists calculated global methane emissions from sauropods to have been 520 million metric tons yearly, comparable to total modern methane emissions. Before modern industry took off, methane emissions were roughly 200 million metric tons a year. Modern ruminant animals, including cows, goats, giraffes, and others, produce about one-fourth to one-half that amount. The study’s conclusions not only show “just how strange and wonderful the workings of the planet are,” but also serve as a useful reminder for the importance of microbes and methane for global climate, the researchers wrote.