Burgers may not shrink in the near future, but cattle might, erasing billions of dollars of profit from the agriculture sector. Photo by Mark H. Anbinder/flickr.
July 4, 2013
A study of bison in the U.S. predicts that wild and domestic cattle will drastically shed weight as the climate warms – compromising food security and stripping billions from farm profits
By Tim RadfordClimate News Network
The nation's cattle herds will shrink – not in number, but in weight and yield – as the climate warms, according to new research that delivers an ominous warning for farmers.
Animals from warmer, drier grasslands weigh considerably less on average than those from cool, wet ranges.
600 pounds lighter
Kansas State University researcher Joseph Craine reports in the Public Library of Science journal PloS One that he analyzed weight, age and sex data from 290,000 bison in 22 herds throughout the United States.
It all lines up to suggest that climate change will cause grasses to have less protein, and cause grazers to gain less weight in future. - Joseph Craine, Kansas State Univ.
He found that the average seven-year-old male bison in South Dakota weighed 856 kilograms (around 1,900 pounds), while counterparts in Oklahoma clocked in at 596 kg (1,300 lbs).The difference in mean annual temperature between the two ranges was 11° Celsius, and the two sets of values told an ominous story of change in a warming world – not just for wild bison, but also for domestic cattle.
The world is almost certain to warm by more than 2°C on average in this century, and the rise could be as great at 4°C.
Less protein
"We know that temperatures are going to go up," Craine said. "We also know that warmer grasslands have grasses with less protein, and we now know that warmer grasslands have smaller grazers. It all lines up to suggest that climate change will cause grasses to have less protein, and cause grazers to gain less weight in future."
As temperatures rise, precipitation is likely to fall, with consequences for plant growth. If the same reduction in weight gain applies to beef cattle as to bison, as researchers suspect, the finding is "a pretty clear indication" of bad news for food security and for the grazers.
There are around 500,000 bison in the United States – the species was all but extinguished during the 19th century – and more than 90 million cattle. Craine calculates that each 1°C rise in average temperatures could cost farmers $1 billion in profits, either through direct reduction in weight gains or in the costs of additional supplementary feeds.
The research is in line with other findings this year. Evidence from 55 million years ago – when the world warmed by 6°C – unearthed during the National Science Foundation's Bighorn Basin Coring Project in Wyoming indicated that animal size tended to dwindle with rising temperatures, almost certainly in response to changes in nutritional value.
The implication that mammals could dwarf and humans shrink towards hobbit-like stature under a changing climate was tragically confirmed by a study of body heights among children in north-east Brazil.
In response to near-starvation conditions, children brought up on a diet of rats, snakes and cacti reached an average adult size of only 1.35 meters, or 4.5 feet.
Tim Radford is an editor at Climate News Network, a journalism news service delivering news and commentary about climate change for free to media outlets worldwide.
The Daily Climate is an independent news service covering climate change, energy and the environment. Contact Douglas Fischer at dfischer [at] DailyClimate.org
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