European mad cow outbreak fuelled surge in Canadian birds through 'butterfly effect'Postmedia News: In a study described as a 'striking illustration' of the long-distance links between a global trade disruption and impacts in the natural world, two Canadian scientists have connected the dots between the emergence of mad cow disease in Europe in the mid-1980s and a subsequent series of population spikes among grassland birds in southern Saskatchewan, Alberta and Ontario.
The rare example of successfully tracking a 'butterfly effect' linkage between seeming disparate phenomena, carried out by researchers from Trent University in Peterborough, Ont., showed how 18 of 20 bird species in North America appeared to benefit from the 1985 outbreak of BSE -- bovine spongiform encephalopathy -- after it destroyed cattle herds in Britain. [The study is published in the Proceedings of The National Academy of Sciences.]...
First, the scientists describe how the appearance of the bovine brain-wasting disease prompted cattle culls and beef export bans across Europe. This, in turn, led to increased beef exports from Canada and the U.S., thus shrinking herd sizes in North America and reducing the need for hay to feed cows. Reduced hay harvesting, then, meant a greater availability of grassland habitat for such birds as the sage wren, grasshopper sparrow and Eastern meadowlark, each of which thrived form greater nesting opportunities in fields that were uncharacteristically left uncut.
The researchers determined that the time lag between the closing of European beef exports and the population explosions among grassland bird species was about three years.
