Cruise Ships Cause Murrelets to Demur: Management and Tourism in Glacier Bay

Visitors aboard a cruise ship visit Margerie Glacier in Glacier Bay National Park (Source: National Park Service).

When the U.S. National Park Service was established by the Organic Act of 1916, just over 100 years ago, it was given two mandates: to protect the natural resources in its parks, while also allowing for enjoyment of those resources. Sometimes, these mandates conflict. In a May 2017 paper in PLOS One, Timothy Marcella and his co-authors describe one such case. The paper shows that cruise ship traffic in Alaska’s Glacier Bay National Park and Preserve disturbs two rare seabird species, Kittlitz’s and marbled murrelets.

Glacier Bay National Park and Preserve, a 3.3 million acre region of water and land in Southeast Alaska’s Inside Passage, is characterized by vast tidewater glaciers and the landscape created as they recede, a succession from bare rock to mature spruce and hemlock forests. The Park provides crucial habitat for Kittlitz’s murrelets, which nest on the ground in deglaciated terrain, drawn to tidewater glaciers and the marine invertebrates and fish that live in glacial outflow. Up to 37 percent of the global population of Kittlitz’s murrelets visits Glacier Bay in the spring and summer, and as much as 95 percent breeds in Alaska, as the authors indicate. Closely related to Kittlitz’s murrelets, marbled murrelets nest in old-growth forests, crucial habitat preserved by the Park.

Wildlife observers poised on the bows of cruise ships found that, in areas of the cruise track dominated by Kittlitz’s murrelets, 61 percent of all murrelets approached within 850 meters by a cruise ship showed signs of disturbance. For a seabird, this means changing from a “loafing” behavior like sleeping, preening or swimming, to either taking flight or diving. In areas of the park where marbled murrelets were more prevalent, the effect was even greater— 71 percent of birds dove or flew away.

A Kittlitz’s murrelet flies over Kachemak Bay, Alaska (Source: Alan Shmierer/Creative Commons).

However, Scott Gende, project lead and co-author of the PLOS One paper, believes these diving and flushing behaviors aren’t necessarily harmful. Speaking from Juneau, where he and his team prepared for a cruise to study disturbance in harbor seal pups, Gende pointed out that long-term monitoring of both species suggests that their populations within Glacier Bay are stable. “If the murrelets are living on the energetic margin (having only sufficient resources for survival, and no more), one more dive could make a difference— disturbance events could equate to a population effect. If we assume that the stable numbers of murrelets over the years is reflective of their ability to forage and breed successfully in Glacier Bay, it’s not likely that the disturbance events are so egregious that it’s causing the murrelets to have lower reproductive success or survival rates,” Gende told GlacierHub.

If the murrelets’ populations are healthy, is disturbing them inherently a problem? Gende doesn’t think so. “Parks are for people,” he quipped, and noted it is far easier to measure impact to a natural resource, like seabirds, than to measure the positive effect of people on the ship experiencing that resource.

“People are moved by Glacier Bay, seeing wildlife— bears on the beach, whales, the scenic wilderness. That can have a profound impact on their experience of national parks,” he said. Positive experiences in national parks are important not just to individuals, but to the protection and longevity of the national park system itself, which relies on public and congressional support. “Over the years I’ve been doing this research,” Gende reflected, “I’ve talked to hundreds of people, and I’m convinced the experience they have pays dividends to recognizing values of having national parks and these protected areas in general.”

In addition, the cruise ship presence in Glacier Bay directly creates an opportunity for wildlife biologists to collect information difficult to gather in many other parts of the United States. The data for this murrelet study was collected by observers who boarded cruise ships for the day, a valuable and rare method of studying marine wildlife.

A marbled murrelet displays what the PLOS One study termed “loafing behavior” (Source: U.S. Fish and Wildlife Service/Creative Commons).

The trick is to create policy that balances conservation and tourism, says Gende: “It boils down to value-based decisions, because it is a trade-off. Some would say only kayakers should be allowed in Glacier Bay, some would say more cruise ships should be let in. There’s a suite of values in people. The park service has done a great job balancing that range and minimizing impacts while maximizing conservation.”

The lessons of murrelet management extend to the entire national park system. All visitors, whether in Yellowstone or Denali, will impact resources, says Gende. “Even on a well-worn trail, you step on a plant, or create disturbance to soil, water or wildlife. The goal is to mitigate disturbance while providing a visitation experience,” he added.

In Glacier Bay, the Park Service’s mandates of conservation and visitation seem to be mutually supportive. Perhaps, in a time when public protection of wild lands is under debate, the reciprocally beneficial nature of these mandates can benefit other parks, too.

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1 Comment

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David Evansreply
June 12 at 11:06 PM

1. Thank you for covering one of the most uncovered near threatened species that relies on the glacial habitat: Kittlitz’s murrelet

2. Thank you for writing about both opinions on the impact from cruise ships

Refreshing!

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