There were only 73 reported polar bear attacks on humans between 1870 and 2014, according to a study published this month in Wildlife Society Bulletin. But 20% of those attacks happened in just the last five years of the study, and Alaska Dispatch News reports researchers have found a correlation between the dramatic increase in polar bear attacks and the decline in Arctic sea ice.

From 1960 to 2009, there were an average of 9.4 polar bear attacks per decade; there were 15 from 2010 to 2014 alone. Signs point to the increase in polar bear attacks being tied to a lack of sea ice, from which polar bears typically hunt for seals.

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Arctic ice hit a record summer low in 2012 and is still just above that level. Nearly 90% of attacks happened between July and December when ice is at its lowest, and nearly two-thirds of attacks were committed by polar bears in bad condition, the Canadian Press reports.

Researchers found polar bears didn't often attack humans unless they were starving. Biologist Geoff York says there's "just cause for concern." He says with warmer temperatures and less ice, more polar bears are venturing onto dry land for food just as more people are visiting the Arctic, creating a "perfect storm." (Video of a polar bear petting a dog went viral; then came the bad news.)

This article originally appeared on Newser: As Sea Ice Dwindles, Polar Bear Attacks Rise