Whales to take refuge further south as sea temperatures rise
In the Canterbury region’s northern reaches, the town of Kaikōura is sustained by the sea – from its crowd-drawing whale watching tours to its famous seafood.
But new climate modelling shows warming seas could drive large whale species further south, making Kaikōura’s famous sperm whale population a less common sight.
The international study, published in the science journal Ecological Indicators and led by Massey and University of Canterbury researchers, used modelling to predict blue and sperm whale ranges by the year 2100, under different climate change scenarios.
It found many areas around New Zealand would become unsuitable for whales as global sea-surface temperatures continued to rise, and the giants of the deep would seek refuge further south, such as the subantarctic islands.
Research lead Katharina Peters said the team modelled three different scenarios: a worst-case 4.9C temperature increase by the end of the century; a moderate 2C to 3C increase; and a best-case under-2C increase.
‘‘Regardless of which of the climate change scenarios will be the reality, even the best-case scenario indicates notable changes in the distribution of suitable habitat for sperm and blue whales in New Zealand.’’
Co-author Karen Stockin, who leads the Cetacean Ecology Research Group at Massey University, said sperm whales in New Zealand were critical to tourism and local economies.
‘‘The whale watch industry off Kaikoura may be at potential risk due to fewer and less reliable sightings of sperm whales off that coastline in the future.
‘‘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.’’
Kaikōura mayor Craig Mackle said climate change was going to change everything for the community, ‘‘full stop’’.
‘‘Our sea life is more to us than just tourism. Whale watching in the scheme of things is a relatively new thing, but the sea life has supported us since [people have] been here.’’
Everything that lived in the sea was connected, from whales and dolphins to popular seafood such as kōura, he said. ‘‘You lose one, you lose a lot of things.’’
Larger whales were important ecosystem engineers, Stockin said. They helped to transfer nutrients from deep waters to the surface, and across regions as they migrated from feeding to calving areas. Their predicted future southward shift, driven by climate change, could potentially destabilise ecosystems in the northern part of New Zealand.
Co-author Dr Fre´de´rik Saltre´ said the study also highlighted habitats that could be suitable in the future for both blue and sperm whales, in the South Island and offshore islands. ‘‘Such areas have the potential to serve as climate [refuges] for both species. 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.’’
In the moderate and worst-case scenarios, the study showed sperm whales would generally be seen less often in most of the country’s coastal waters – with the modelling showing increases east towards the Chatham Islands and south, in the Auckland Island subantarctic area.
Blue whales could be seen more often around the South Island in those scenarios, although the study said there were currently no commercial blue whale watching operations in New Zealand.