By Stephen Beech
Polar bears are in better physical health than 25 years ago – despite sea ice losses, reveals new research.
The well-being of the iconic white mammals living around the Norwegian island of Svalbard has improved in the face of climate change, say scientists.
They found that the bears’ fat reserves have increased as sea ice levels decreased.
The findings, published in the journal Scientific Reports, differ from previous observations of polar bear population declines coinciding with sea ice loss across the Arctic.
Previous research has recorded temperature increases in the Barents Sea region surrounding Svalbard of up to two degrees Celsius per decade since 1980.
Following a 2004 census, the Barents Sea polar bear population numbered around 2,650 individuals and until recently appeared not to shrink in size, although the reasons for that have been unclear.
Dr. Jon Aars, senior scientist at the Norwegian Polar Institute, and his colleagues investigated the potential causes of the stability of the Svalbard populations.
The team used data from 1,188 body measurement records of 770 adult polar bears taken on Svalbard between 1992 and 2019.
They compared changes in the bears’ body composition index (BCI), an indicator of fat reserves and body condition, with the number of ice-free days in the Barents Sea region across the 27-year period.
The research team found that although the number of ice-free days increased by around 100 over the study period – at a rate of about four days per year – the mean BCI of the adult polar bears sampled increased following the year 2000.
Dr. Aars said: “This indicates that fat reserves increased as sea ice levels decreased.”
The researchers suggest that improvements in the body conditions of Svalbard polar bears could be attributed to the recovery of populations of land-based prey sources that were previously over-exploited by humans, such as reindeer and walrus.
They also believe that sea ice loss may lead to polar bear prey – such as ringed seals – concentrating across smaller areas of sea ice, and that trend may increase the efficiency of polar bear hunting.
Dr. Aars said: “Further reductions in sea ice may negatively affect the Svalbard populations by increasing the distances they need to travel to access hunting grounds, as this has already been observed in other polar bear populations.”
He added: “More research is needed to understand how different polar bear populations will adapt to a warming Arctic in the future.”
