Ocean Toastiness Sending Fish Fleeing for the Poles
Some like it hot. But generally, marine species don't, as they have evolved over eons in relatively stable water temperatures (or at least slowly changing temperatures that don't differ that much from year-to-year).
Human-driven climate change, however, has warmed ocean surface temperatures around the world, and it's having a big impact on marine life.
A review of thousands of observations of marine life over the last half-century shows that as the climate warms, the oceans' animals and plant life have shifted their ranges significantly, stretching much further north than before. Like snowbirds who flock to warmer climes in the winter, these animals and plants chase the range of temperature where they can survive, and have moved northward as temperatures toward the poles increase, research shows.
At the same time, animals and plants are more active earlier in the spring and later in the fall, according to a study published recently in the journal Nature Climate Change.
This change in range is hardly insignificant—we're talking enormous. The average bony fish (a group that includes basically all animals you think of when you think of "fish") has moved its range 500 to 1,000 miles to the north over the last 40 years, said Ben Halpern, a researcher at the University of California at Santa Barbara.
The range of phytoplankton, types of tiny plant-like cells that form the basis of the food web, has shifted the most, moving 1,000 miles on average to the north in a span of 40 years. "That's a huge distance," Halpern said. "That means that things that eat them—essentially everything—have to move with them."
The front-line or leading edge of all marine species distributions is "moving toward the poles at an average of 72 kilometers (about 45 miles) per decade—considerably faster than terrestrial species, which are moving poleward at an average of six kilometers (about four miles) per decade," said study author Elvira Poloczanska, a research scientist with Australia's national science agency, the Commonwealth Scientific and Industrial Research Organisation (CSIRO), in a statement.
This may be because water can hold more heat than air, so effects on marine species are more severe. The nature of marine life is also different; many species passively travel long distances on ocean currents early in their life cycle and can more easily shift their ranges, Halpern said. Interestingly, although the oceans have absorbed more than 80 percent of the heat added to the climate, surface waters have warmed three times slower than air temperatures over land, the study found.
This shift has likely already caused some species to die out. Ultimately, it's hard to know what will happen, although it's likely that "many species will go extinct," Halpern said. Certainly, many animals and plants "have to deal with new species and areas at a pace that they've never had to experience," he said.
In some areas, changes in fish distribution have hurt fishermen and put them out of work, Halpern said.
When animals mature earlier or faster, it can throw the food web off—over millennia, cycles of animal development have come to correspond with peaks in food abundance, and changes can leave animals and their environments out of sync, Halpern said.
The research forms part of the Fifth Assessment Report of the United Nations Intergovernmental Panel for Climate Change (IPCC), which will be completed next year and provide a comprehensive update on the scientific and socio-economic aspects of climate change.