If you have any question about the power of human activity to influence the environment, look no further than the North Atlantic right whale.

The massive and slow-moving species prized for its abundance of oil was just about fished into oblivion until whaling was outlawed. Accidental run-ins with other fishing vessels and their gear also caused problems, until a concerted effort starting a couple of decades ago helped grow the number of North Atlantic right whales from about 300 to around 500 today.

Now the species is in trouble once again, and officials in Canada and the United States are working together to find out just what is going on. Undoubtedly, it will have something to do with us.

Thirteen right whales have been found dead in the past year, 10 off Canada, in the Gulf of St. Lawrence, and three off Massachusetts. That’s more than three times the expected number.

As a result, the National Oceanic and Atmospheric Administration has issued an Unusual Mortality Event notice, which it does when there is a “significant die-off of any marine mammal population” that “demands immediate response.”

Some of the whales, which can grow to nearly 50 feet long and weigh 72 tons, were clearly hit by ships, while others had become entangled in fishing gear. But that doesn’t necessarily explain the sudden surge in deaths. After all, shipping and fishing have always existed in those areas.

So if the ships aren’t new, then maybe the whales are.

The number of right whales in the Gulf of St. Lawrence has been increasing since 2014. At the same time, the number has dwindled in the Gulf of Maine and Bay of Fundy.

One theory has the warming in those latter areas – the Gulf of Maine is warming faster than all but one region on Earth – has altered the timing, growth and movement of zooplankton, the food source for right whales. It could be that there is insufficient food where the whales used to eat – and where humans were used to having them – so they moved into new areas where they are not expected to be, and are thus in danger.

Just as with lobster, shrimp and countless other species, it seems climate change is altering the lives of right whales.

Answers are necessary to save the right whale, which was struggling “even before we had all the dead whales this summer,” a researcher with the New England Aquarium told the Portland Press Herald.

Canada has already imposed emergency restrictions on shipping and fishing in the Gulf of St. Lawrence, similar to those imposed in 2002, when shipping lanes in the Bay of Fundy were changed to save right whales, cutting way down on collisions.

Now NOAA is working with Fisheries and Oceans Canada to review the deaths. They’ll collect data on each death, then issue a report that could lead to policy changes in order to protect right whales.

If that means modifying fishing gear or changing how ships conduct business, it should be easy to pull off – those kinds of adjustments have been made before.

But if it is rapidly warming seas – caused by carbon emissions – then it will be more difficult to change course, and right whales will become yet another casualty of climate change.