As a Population of Alaskan Belugas Slowly Vanishes, Researchers Search for Answers

Study documents acoustic footprint of human activities in the Cook Inlet waters, finds sound levels often exceed harassment limits set by NOAA.

This is part-one in a multi-part series on Alaska’s endangered Cook Inlet beluga whales.

Light penetrates just a few feet into the slate-gray water of Alaska's Cook Inlet. Further down, suspended glacial silt creates a cold, opaque space where vision is little help to a foraging predator. To nab halibut and flounder from the muddy bottom, to chase salmon through shallows and river mouths, one needs to rely on other senses.

photo of belugas
Alaska's Cook Inlet is home to a geographically and genetically isolated population of beluga whales. The population is listed as endangered under the US Endangered Species Act. Photo courtesy of NOAA.

Cook Inlet's belugas have inhabited their small world — a shallow, 230-mile long gash in Alaska's mountainous south-central coast — for thousands of years, isolated geographically and genetically from other Alaskan belugas. Hunting by echolocation and using signature calls to find and identify one another, sound has let them prosper in their dark environment.

Humans have been eavesdropping on the belugas' sonic world. Between 2008 and 2013, the Cook Inlet Beluga Acoustics team — which is composed of federal, state, and university scientists — created the most complete hydrophone recording of their habitat to date. Their primary goal was to learn more about where belugas forage, but with the same dataset they also listened for the noise of another species: their own.

The resulting study, published in late 2018, looked at 14 months of recordings (spanning all of a year, though not continuously) from seven locations with heavy overlap between beluga and human activity. It found human-caused (anthropogenic) sound in every recorded day — from ship traffic, jet and propeller aircraft, oil and gas extraction, dredging, pile driving, and motor boats, much of it potentially able to drown out beluga echolocation and signature calls. Sound levels often topped the harassment limits that the National Oceanic and Atmospheric Administration created to protect the endangered belugas — but in a way that escapes NOAA's controls on harassment.

Cook Inlet’s industrialization over the past several decades has created this matrix of anthropogenic noise. In 1979, the first population estimate of Cook Inlet belugas put their number at 1,293. Their habitat that year was in the midst of economic transformation. Alaska's first oil had been discovered twenty years before, just east of Cook Inlet. Through the '60s, exploratory drilling and seismic surveys — which use the echoes of underwater airgun blasts to map below the seafloor — discovered three oilfields in the inlet itself. By 1979, the Cook Inlet belugas shared their environment with 14 oil and gas platforms served by a network of underwater pipelines. Between 1960 and 1980, Cook Inlet's shoreline city of Anchorage almost tripled its population, while some smaller towns in the area doubled theirs. By 1995, about 60 percent of Alaskans would live in the Cook Inlet watershed. Between that year and 1998, Cook Inlet's belugas would decline by 47 percent.

Around this time, beluga researchers reached two conclusions. First, unregulated hunting was sending the Cook Inlet beluga population toward extinction. Second, genetic analysis showed that other belugas may have separated from their Cook Inlet brethren around the end of the last Ice Age, and would probably not repopulate the area any time soon. The disappearance of belugas from Cook Inlet was likely, and would likely be permanent.

Responding to these findings, Alaska Native groups voluntarily restricted their beluga hunts in 1999 and ended them in 2005. (By then, hunting was restricted to subsistence and culturally based hunts by Native Americans, who were exempted from the bans imposed by 1972’s Marine Mammal Protection Act). A sustainable hunt could resume when the population rebounded — a matter of time, scientists and hunters assumed, if everyone stopped taking belugas from the breeding pool.

In fact, ending the hunts slowed but didn't stop the trend. The beluga population has continued declining by about 1.3 percent every year since. NOAA presently estimates there are fewer than 350 Cook Inlet belugas. When the agency listed the whales as endangered in 2008, the conservation focus shifted from hunting to habitat integrity. In 2011, NOAA protected 3,016 acres of Cook Inlet water as critical habitat — yet the population trend remains fixed. The Cook Inlet Beluga Acoustics team is now one of several trying to decipher the tangles of cause and effect still preventing the belugas from rebounding.

In spite of Alaska's unspoiled “Last Frontier” image, Cook Inlet is an urban and industrial body of water. Its oilfields are responsible for heating, fueling, and powering most of south central Alaska. Anchorage, the state's largest population center with 294,000 people, sits on its shore. To its north is Elmendorf Air Force Base, where fighter and transport jets regularly take off over the water on training flights. Anchorage International Airport, among the busiest air cargo hubs in the world, also has a flight path over the water. About half the food, products, and other cargo entering Alaska travel up Cook Inlet to land in Anchorage at the Port of Alaska. The fine silt that pours through Cook Inlet from its glacier-fed source rivers fills up this essential harbor so quickly that the Army Corps of Engineers has had to dredge it out every summer since 1958, scooping out up to 1.8 million cubic yards of silt and dumping it in the middle of the nearby strait. All of this is noisy.

When a car drives down your street with rattling suspension, thumping stereo, and no muffler, you and your neighbors might feel harassed by noise. In the Cook Inlet, the aquatic equivalents of this loud car are the dredging, pile-driving, and seismic exploration for offshore oil and gas reservoirs. Those companies and government entities making the noise get permission to work in Cook Inlet from NOAA by filing for Incidental Harassment Authorizations. These authorizations allow them to make more than 125 decibels of noise — the level at which NOAA defines noise as harassment of marine mammals — if the agency determines it would not affect too many whales. The permits sometimes require trained observers to watch for whales near the work site, halting the job if any are spotted. Anchorage’s harbor dredging, for instance, stops if belugas are seen within 50 meters.

The effectiveness of the permitting system is debatable — in one month of recording at one location in the inlet, hydrophones picked up two instances of unpermitted noise harassment, and the new paper recommends better enforcement of harassment rules. But even when rules are perfectly enforced, the existing system still lets noise “exceed behavioral harassment levels on a daily basis in a significant portion of the critical habitat,” the acoustic researchers wrote. Incidental Harassment Permits aim to keep too many loud cars from cruising too often through the belugas' neighborhood. But if individually quieter cars pass through, there are no rules to control them collectively — even if they reach highway traffic density and together are as loud or louder than the mufferless rattletrap.

About 63 percent of the anthropogenic noise in the recent recordings came from commercial shipping. To a beluga, a ship's passage may be comparable to dimming the lights. Acoustic researchers in St. Lawrence Estuary, an area on the Canadian Atlantic coast where belugas also share space with freight traffic, estimated that the loudest ship noise could shrink the range of beluga communication and echolocation by 85 percent. In Cook Inlet, the recorded ship noise was generally louder than in the St. Lawrence. A single ship isn’t loud enough to need a harassment permit from NOAA, but the totality of ship traffic often inundated areas near shipping lanes with harassing levels of noise.

Ship and beluga calls (audio):

Though ships made the longest and most frequent noises, jets made the loudest. Penetrating the water, their sound can also mask beluga calls.

Researchers are less sure about the noise of oil and gas extraction. Recordings from the shore of Trading Bay — which has five oil platforms connected by underwater pipelines to an onshore tank farm — contained machinery noise but was little analyzed in the new study because most of it couldn't be identified. “The acoustic footprint of this industry in Cook Inlet has been barely described,” the researchers note.

photo of beluga research
A member of Cook Inlet Beluga Acoustics team deploys an acoustic recorder. Photo courtesy of NOAA.

The location of noise is as important as volume and frequency. Anthropogenic noise was in only 11 percent of the recordings researchers examined, but what they heard was concentrated in pockets of human activity. The waters around Anchorage represent the loudest such pocket, and for the belugas it happens to be in exactly the wrong spot.

Cook Inlet becomes shallower in its northern reaches, spreading vein-like into a sprawling watershed. The upper inlet is richly featured with mudflats, sandbars, streams, and river deltas, which in summer fill with salmon, whitefish, eulachon, and pollock. Belugas ranged widely over the inlet's coastline during their peak, but for the past 30 years they've favored the upper inlet to feed, breed, and molt in the summer. In particular, large numbers move into Knik Arm, a branch of Cook Inlet that splits from the main trunk near Anchorage. Native hunters told interviewers that belugas will spend the summer following the tides in and out of Knik Arm, where researchers speculate that tidal flats offer easy fish-hunting in their channels, as well as sandy shallows where belugas can rub off old skin during their summer molt.

At its entrance, Knik Arm bottlenecks into a shallow, two-and-a-half-mile strait. Anchorage and Elmendorf Air Force base sit on the east side of the strait, with Port MacKenzie — a much smaller port that lacks regularly scheduled dockings and doesn't require dredging — on the west. Belugas traveling this passage to rich feeding ground are funneled through a concentration of anthropogenic noise. If they pass during Anchorage's port dredging, or while piles are being driven for the port's ongoing renovation, there may be no space to avoid harassment levels of noise. A recording station on the west side of Knik Arm recorded harassment noise levels coming from dredging and pile driving at the port on the east. Researchers calculated that the area in which belugas would likely experience noise harassment reaches slightly beyond the Knik Arm mouth's west shore.

NOAA's 2016 Cook Inlet Beluga Recovery Plan lists “cumulative effects of multiple stressors” as one of its highest priorities and includes seven action items calling for research into how threats such as noise, chemical pollution, and predation by killer whales interact. None, however, focus specifically on overlapping noise sources. Noise is also a top priority in itself, but although the six noise-related action items mention cumulative noise as a consideration for a monitoring plan, the document says nothing explicitly prioritizing limits on it.

NOAA's national officials are also grappling with this problem. The laws under which the agency protects whales — 1972's Marine Mammal Protection Act and 1973's Endangered Species Act — charge it with preventing extinctions, promoting recovery, and ensuring that marine mammals remain functioning parts of their ecosystems. Under these broad mandates, NOAA has managed noise on a case-by-case basis, but its Ocean Noise Strategy Roadmap — a document examining the issue — states that such piecemeal actions “don't address aggregate or cumulative effects very well.” Controlling the collective consequences of actions that are individually within bounds is not easy in the context of laws meant to prevent individual-focused harms such as “takes” and “harassment” by specific entities.

Aside from these general problems, the mouth of Knik Arm has a more particular regulatory obstacle: it's excluded from Cook Inlet's protected beluga habitat. Because the Port of Alaska supplies Elmendorf Air Force Base and the co-located Fort Richardson, NOAA decided in 2011 that subjecting its maintenance to the delays of permitting and monitoring could impede military operations, and so excluded it from the beluga's critical habitat zone, where noise that results in belugas abandoning the area is prohibited. Work in the area still requires harassment permits, however, which are given under the Marine Mammal Protection Act, while the critical habitat was created under the Endangered Species Act. The excluded area is less than 1 percent of the Inlet’s critical beluga habitat, but it is both the most sonicly disturbed area researchers have recorded and an unavoidable passage into a feeding ground. The recent paper recommends that NOAA reconsider the exclusion zone. NOAA spokesperson Julie Speegle wrote in an email that her agency “is not contemplating any changes to the critical habitat at this time.”

Looking for possible near-term actions to deal with cumulative noise, researchers turned 1,400 miles south, where ship traffic around Seattle, Vancouver, and other ports in the Salish Sea is making life hard for orcas. The story of the area's southern resident orcas is similar to Cook Inlet's belugas. Killing and capture halved their population by the 1960s. Though they had a small, temporary rebound when these activities were prohibited in the ‘90s, the orcas have since declined to 75 individuals and produced only one surviving calf since 2015 — despite having been declared endangered in 2005.

In 2017, the Enhancing Cetacean Habitat and Observation (ECHO) program — a group of government and industry representatives led by Vancouver's Fraser Port Authority — declared voluntary speed limits for vessels traveling Haro Strait, an approach channel to the Port of Vancouver. Slowing down to the recommended 11 knots greatly reduced noise — hydrophones monitoring the strait during a trial period found that large vessels had dropped their sound intensity by 44 percent.

Commercial jet (audio):

“An initiative similar to the ECHO program in Cook Inlet could help in evaluating possible ways to mitigate negative effects by shipping noise, but it is very likely that lack of recovery of Cook Inlet belugas is related to a combination of effects, not just noise,” Speegle wrote. Port of Alaska representatives did not respond to questions for this article.

Noise is relatively easy to measure and analyze, but the belugas' response to it isn't. Noise and behavior may not relate in ways we'd expect — jets taking off over the water produce intense noise, but it usually lasts ten to fifteen seconds and belugas might acclimate to it. Small motorboats, on the other hand, are relatively quiet and infrequent, but researchers speculate belugas may have a much stronger reaction to them. Long-lived and intelligent, many alive today likely remember being chased down by motorboats when hunting was common.

Cook Inlet is noisy and belugas are declining, but correlation is not causation. Future studies of beluga behavior will ask how strongly noise has contributed to the decline and in what ways it has done so. Has human noise has driven belugas away from feeding grounds? Has it damaged their hearing? Research is underway, Speegle wrote in an email, but it's “very challenging work, as we need to have a very good understanding of the baseline behaviors in order to identify deviations from it by noise.”

This work won’t be easy, particularly given the strong currents and silty waters in the Cook Inlet. But let's hope the science is sound, and the response swift.

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