Sea life relocating fast in response to climate change

Many fish and plankton are relocating towards the North and South poles at an astonishing rate of hundreds of kilometres per decade in response to climate change, a new study has found. That is shaking up ecosystems and forcing the fishing industry to adjust.

The changes are far more dramatic than those seen on land, where species have been creeping nearer the poles at just six kilometres per decade, reported an international team of scientists led by University of Queensland biologist Elvira Poloczanska in Nature Climate Change this week.

"I think we were surprised at how much faster things were moving," said Mary O'Connor, a University of British Columbia researcher who co-authored the study.

Bony fish (a group that includes most fish, except for sharks and rays) are moving an average of 277 kilometres per decade, zooplankton at 142 kilometres per decade and phytoplankton at a whopping 470 kilometres per decade. Less mobile species moved more slowly, but on average, marine species moved 72 kilometres per decade.

In some cases, the movements are bringing together species that have never had contact before.

For example, Antarctic waters were traditionally free of predators with jaws capable of crushing their prey.

"Now that it's warming, those predators including sharks and big crabs are expanding into Antarctica, and they're eating things that evolved without crushing predators," O'Connor said. "It's probably going to lead to extinctions of prey."

Goodbye salmon, hello tuna?

In other cases, changes require some adaptation by humans.

For example, climate change is bringing warmer-water species such as tuna within reach of the Canadian border, while having a negative impact on B.C. populations of Pacific salmon.

"There are certainly trade-offs," O'Connor said. "We might like to have some tuna every now and then, but we certainly will miss our salmon."

The study also found that warmer spring temperatures are prompting some species to breed earlier and earlier each year — about 11 days earlier per decade in the case of fish and zooplankton. Meanwhile, phytoplankton, which are a major food source for baby fish and zooplankton, are influenced more by the amount of sunlight and less by the temperature. They have started blooming just six days earlier per decade, leading to a worrying mismatch between the hatching of zooplankton and baby fish and the availability of their food.

O'Connor said that problem has already been documented, and has affected ocean productivity in some places such as northern Europe.

It has been known for about 15 years that the ranges of plants and animals on land have been changing in response to climate change, but no comparable study had been done for marine life.

Change not random

In order to conduct their study, Poloczanska and her team analyzed 208 studies of 857 species that had been monitored for 19 to 343 years. They looked at the changes in range over time, and determined whether the changes were random or consistent with climate change. In 80 per cent of the cases, the movements were consistent with climate change.

"In general, the ranges are getting a little bit bigger, and they're doing so by expanding towards the pole where it's cooler," O'Connor said. "And they're retreating from the areas that are too hot…. It's quite unlikely that it's just random change."

O'Connor said one thing she noticed while taking part in the study was that there was very little data from Canada compared to other places, where governments have been keeping tabs on oceans in order to manage land use, development, resource extraction, and marine resources such as fisheries.

She thinks Canada needs to do a better job in order to manage its oceans at a time when things appear to be changing quickly.

"We're seeing signals of climate change in the ocean," she said. "And it should influence how we interact with the ocean."