Climate change will drive blue and sperm whales in New Zealand southward, a study has found.
Sea surface temperature warming will be the main driver of their move southward, researchers from Massey University, University of Canterbury, Flinders University and University of Zurich say.
Their findings were recently published in journal Ecological Indicators.
The researchers looked at eight "environmental variables", which included depth, distance to shore and sea surface temperature, to predict habitat suitability out to 2100.
Blue whales mainly feed on krill found in cold coastal water or offshore upwelling systems.
Sperm whales, however, primarily feed on squid and prefer deep water.
The researchers looked at three climate change scenarios - a high, medium and minimal effort to curb greenhouse gas concentration - as part of their look at habitat suitability.
Under the worst-case scenario, a 61% and 42% loss and decrease of currently suitable habitat for sperm and blue whales respectively, mostly in the country's northern waters.
The researchers said large areas surrounding the South Island, including Kaikōura, will also see a decrease in habitat suitability.
Climate change could see southern and eastern offshore islands, such as Auckland, Campbell and Chatham, become more suitable for sperm whales, they said.
While habitat suitability fell for blue whales in the northeastern part of the South Taranaki Bight, it rose around the South Island and offshore islands.
One of the authors, Frédérik Saltré of Flinders University, said the areas have the potential to serve as climate "refugia" for the whales.
"Knowing about these areas early on provides an opportunity for their increased protection in the future, particularly when considering the placement of marine protected areas and the legislation of oil and gas exploration."
But the researchers aren't shy about what this could mean for New Zealand.
"Regardless of which of the climate change scenarios will be the reality for us, even the best-case scenario indicates there will be notable changes in the distribution of suitable habitat for sperm and blue whales in New Zealand," fellow author Katharina Peters of the University of Canterbury remarked.
Fellow author Karen Stockin from Massey University said the whale watch industry off Kaikōura may be at risk due to fewer and less reliable sightings of sperm whales.
"Such changes in sperm whale distribution would have socioeconomic impacts due to the direct and indirect reliance on the whale watching activities by the local economy."
Peters, Stockin and Saltré also said the shift of the whales southward will impact ecosystem functioning and potentially destabilise ecological processes in the northern part of the country.