The methane emissions problem remains as acute, according to Richard Collins, who wonders, which creatures can help?
Bubbles of methane rise to the surface when you probe mud in stagnant pools. This ‘marsh gas’ is two dozen times more powerful, as a heat trapper, than carbon dioxide. The Arctic permafrost is melting, releasing vast quantities of methane into the atmosphere. Oil drilling and town dumps emit the gas. So do farm animals.
There are about 1.5bn cattle and 1bn sheep worldwide and their numbers are increasing. Vegetarian animals face a digestive challenge; stomach acids can’t break down plant-cell walls. Cattle sheep and deer evolved fermentation chambers, known as rumens, in which bacteria attack plant fibres.
Methane, which the animal belches into the atmosphere, is a by-product of the process.
Your typical cow produces around 200 litres of the gas daily. Up to 60% of the methane produced by human activity comes from livestock, so how will we keep global temperatures to within 2C of pre-industrial levels if current agricultural practices continue?
The situation is particularly acute here; a third of Irish greenhouse gas emissions come from agriculture. Unless we find a solution to the belching problem, we won’t meet our international obligations. There will be substantial fines.
During the 1970s, it seemed that an iconic animal from ‘down under’ might be able to help. Kangaroos, like our livestock, have ‘fore-guts’ in which plant cells are broken down, although marsupials don’t ‘chew the cud’. Their gut bacteria, however, produce mainly acetic acid which the hosts go on to digest. Very little methane was expelled, scientists thought. Wallabies seemed to produce 80% less of the gas than cattle.
Kangaroo meat is exported to more than 50 countries. “Using kangaroos to produce low-emission meat is an option for the Australian rangeland and could even have global application,” claimed a study by the University of New South Wales in 2008.
The world’s chefs could help solve the methane problem by producing tasty kangaroo-meat dishes to wean us off beef and mutton. Fast food outlets of the future might sell marsupial burgers, and kangaroo roasts could become the pièce de résistance on great occasions. Wallabies have survived on Lambay since they were introduced there decades ago. Could these aliens replace beef cattle in Irish fields?
Cattle and sheep are not to blame for methane production, however. The bacteria in their rumens are the real culprits, so researchers began examining the gassy guts of marsupials to identify them. The bacteria in the rumens of livestock, it was hoped, might be replaced by ones taken from kangaroos.
It was a tall order; the ancestral lines of the placental and marsupial mammals diverged around 140m years ago and the two have very different histories. Fore-gut bacteria are finely adapted to their hosts.
Introducing alien ones would mean undoing millions of years of refined adaptation but, with the global warming crisis deepening by the day and no other solution in sight, scientists seemed prepared to clutch at any straw.
Then a study carried out at Copenhagen Zoo put a spanner in the works. It seemed to show that the basis of the marsupial research was fundamentally flawed. Kangaroos, the Danish researchers claimed, produce just as much methane as cattle.
They don’t belch out the gas, they fart it. Ten kangaroos, placed in sealed rooms at the Fowler’s Gap Research Station in Australia, confirmed the finding.
When all the gases the animals produced, and those released from their dung, were measured, they were found to contain only slightly less methane than what normal livestock produce. “Kangaroos probably don’t have a unique micro-biome,” one scientist reluctantly concluded.
The research focus has now shifted again. It’s thought that methane production may not depend entirely on gut bacteria after all, but on how food passes through the marsupial stomach.
The methane emissions problem remains as acute as ever. Kangaroos can’t help, but is there another creature which can?
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