by , 02 October 2010
One of the emerging themes of my course in rapid environmental change is how humans have accelerated natural processes to a pace never seen before in earth’s history. For instance, climate change has in the past occurred at scales of tens of thousands of years or longer, but man-made climate change in happening at the pace of decades or centuries.
Less well-known is the effect we can have on the speed of evolution. Human-driven environmental pressures can force species to adapt at speeds rarely seen in the past. For instance, the extreme scale and intensity of fishing in the past fifty years has caused rapid evolution in fish. When we catch and eat all the big fish in in a population, we make it evolutionarily advantageous for fish to lay eggs when they are younger and smaller. During the collapse of the North Atlantic cod fishery in the late ’80s and early ’90s, it took just a decade for the average of maturity to drop from six years to five.
This cod story is documented in a 2004 paper by Olsen et. al. in Nature. While the phenomenon had been observed before, their team used a novel technique to tease the evolutionary signal out from other trends in the cod population. More interesting to me, though, is that they were able to detect the change using old data not originally collected for this purpose. They found that the accelerating pace of evolution was evident as far back as 1985, just as the collapse of the cod fishery was getting underway.
This suggests that one might be able to monitor species for evolutionary changes as a warning of extreme environmental pressures. The authors themselves warn that evolutionary changes should not be misinterpreted as signs of imminent collapse, but surely when human impacts become the driving factor behind evolution, something is amiss. We may be able to catch ourselves before we permanently alter a population for the worse.
Olsen, E., Heino, M., Lilly, G., Morgan, M., Brattey, J., Ernande, B., & Dieckmann, U. (2004). Maturation trends indicative of rapid evolution preceded the collapse of northern cod Nature, 428 (6986), 932-935 DOI: 10.1038/nature02430