Fish catches will decline as climate change pushes them poleward, study finds
Climate change will see a greatly reduced number of fish species that could be realistically harvested for food, according to a study at Rutgers University in New Jersey, USA.
It found that as temperatures warm, predator-prey interactions will prevent species from keeping up with the conditions where they could thrive.
Not only will large species and commercially important fisheries shift out of their historical ranges as climate warms, but they will likely not be as abundant even in their new geographic ranges. For instance, a cod fisherman in the Atlantic might still find fish 200 years from now but in significantly lower numbers.
“What that suggests from a fisheries perspective is that while the species we fish today will be there tomorrow, they will not be there in the same abundance. In such a context, overfishing becomes easier because the population growth rates are low,” said study co-author Malin Pinsky. “Warming coupled with food-web dynamics will be like putting marine biodiversity in a blender.”
The new study looked at “trophic interactions”, the process of one species being nourished at the expense of another, and other food-web dynamics to determine how climate change will affect where different species cohabit in the future.
Using computer models, the researchers determined that predator-prey interactions cause many species, especially large predators, to shift their geographical range more slowly than the speed of climate change.
“The model suggests that over the next 200 years of warming, species are going to continually reshuffle and be in the process of shifting their ranges,” said lead author E.W. Tekwa.
“Even after 200 years, marine species will still be lagging behind temperature shifts, and this is particularly true for those at the top of the food web.”
As the climate warms, it is expected that millions of species will shift towards the poles to escape soaring temperatures.
The researchers developed a “spatially explicit food-web model” that included parameters such as metabolism, body size and optimal temperature ranges. By accounting for climate change, their model revealed that dynamic trophic interactions hamper species’ ability to react quickly to warming temperatures.
They also found that larger-bodied top predators stay longer than smaller prey in historical habitats, in part because of the arrival of new food sources to their pre-warming ranges.
“These dynamics will not only be in one place but globally,” Pinsky said. “That does not bode well for marine life, and this is not an effect that has been widely recognised.”
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