Writing in 1916, conservationist John Muir noted that “there is not a ‘fragment’ in all nature, for every relative fragment of one thing is a full harmonious unit in itself.” A century later, in the Pacific Northwest, land managers, tribal leaders, environmental stewards, lawmakers and business interests are locked in a fight over which harmonious units and relative fragments can be rearranged to satisfy all parties.

But while they grapple over the details of regulations and policy changes, and the various perceived and demonstrated economic effects any such legislation may have, whales continue to miscarry at an unprecedented rate.

In the salty waters off the coast of Seattle, the region’s orca population is spontaneously miscarrying the majority of its pregnancies, according to a recent study by researchers at the University of Washington, published in PLoS One. By studying the feces of orcas through the use of detection dogs, the researchers tracked the whales’ hormones over time. Their findings were stark: 69 percent of all detectable orca pregnancies ended with miscarriage; 33 percent of those pregnancies failed in the late stages of gestation or immediate postpartum.

While the temperature of the ocean, boating and commercial shipping are often looked to as identifiable reasons for orca stress, one of the most important places to look for answers may actually be on land, where the human footprint has choked off the primary food source of the Southern Resident killer whale population – the Chinook salmon.

The Center for Whale Research, which has been surveying Puget Sound killer whales for decades, reports that Chinook make up about 80 percent of the average orca’s diet; each whale must consume between 18 and 25 salmon per day just to retain its energy levels. To feed the entire population of Southern Resident killer whales, the Puget Sound and surrounding waterways must provide at least 1,500 salmon per day.

But since the Pacific Salmon Commission began tracking salmon in 1984, it has noted a 60 percent reduction in the population of Chinook. The commission estimated that under half a million were left in the Salish Sea in 2010 – less than a year’s supply of fish for the orca.

While researchers have known for years that the reduction in supply has a direct effect on the area’s killer whale population, the University of Washington study sheds light on a new, previously underdiagnosed problem: It appears that lower numbers of salmon put undue burden on pregnant whales, who need even more of the high-fat, high-protein fish to feed both themselves and their growing babies.

“Low availability of Chinook salmon appears to be an important stressor among these fish-eating whales as well as a significant cause of late pregnancy failure, including unobserved perinatal loss,” the University of Washington researchers note.

Researchers have already noted a decline in orca population – a survey in 2012 found that the Puget Sound pods had posted some of their lowest numbers since the 1970s. Still, the high incidence of miscarriage came as a surprise, largely because observers were unaware the whales had been pregnant at all.

Based on the data collected, researchers concluded that underfed orcas don’t produce the hormones they need to keep themselves and their babies healthy; when the salmon runs arrive late or don’t arrive at all, it’s often too late to carry a calf to term. And the feeding season needs to be both consistent and lengthy, because orcas are typically pregnant for 17 months or more.

But salmon aren’t dying off in a vacuum; human behavior – including construction, housing, pollution and various industries – is causing the decline.

Massive growth of the Seattle Metropolitan Region – close to 300 new residents per day have moved to the city in the last year alone – is a major contributor to the decline in both orca and salmon populations. Runoff from roads can seriously affect the survival of fish in streams, deforestation increases the temperature of the water and new development can change the patterns of currents and disturb the nests that salmon rely on to shelter their eggs. Recreation has also led to destruction of habitats – everyone moves to Seattle to go hiking, after all.

There’s still a lot of cleanup to do from earlier days, too; Kirt Hughes, the Department of Fish and Wildlife’s statewide salmon and steelhead fishery manager, explains that many chemicals that are dangerous to orcas and are banned in construction are “still making their way into the waterways.” They’re in the vegetation, the rocks, even in the fish that are passed up through the food chain.

The problems for salmon begin much further upstream than Seattle, though. About 470 miles away, in the upper Snake River Basin on the border between Oregon and Idaho, dams at Hells Canyon have, for decades, been keeping salmon from their natural migration patterns.

Part of a larger damming project in the late 1950s and early ’60s, the Hells Canyon dams were initially built to help create inland waterways for shipping and trade. Parts of the Midwest – Idaho, Montana, Nevada and beyond – needed quicker, more reliable access to the ports in cities like Seattle and Portland to trade and import timber, grain, textiles and other bulk commodities.

In the age of interstates and air cargo, that feature has largely been rendered obsolete. The dams generate a modest amount of power for the surrounding areas, which is generally touted as the reason for keeping them in place. However, amid Idaho’s solar boom – which promises to generate more efficient, less detrimental power in larger volumes – the dams are even less necessary, conservationists argue, particularly when their impact on salmon and orcas is so profound.

“We do have one single situation where we have a lethal corridor created by four dams,” says longtime Sierra Club organizer Bill Arthur. “If we removed these four dams … it would go a huge distance in addressing the fundamental problem of restoring Snake River salmon runs.”

There has been substantial resistance from lawmakers to getting rid of the dams. Much of the argument for keeping the dams centers on the hydropower they create and the economic driver that they’re perceived to be. But Hughes says that salmon and whales are a much more powerful moneymaker for the state.

Though orca observers and environmental activists agree that dams are lethal for salmon, the role of dams in salmon die-off and, as a result, orca health, remains up for debate in some circles. Opponents of dam removal argue that the salmon population was plummeting before the dams were put in place, and that other factors – like tribal behavior and conservation efforts – are truly to blame. Even many residents of the area surrounding the Snake River would prefer to see the dams stay in place, if only because they believe that salmon protections go too far and represent government overreach.

Regardless of how most Northwest residents view salmon protections and regulations, they generally do agree that salmon are good and necessary for the state. In addition to helping reduce the number of orca miscarriages, elevating and sustaining the salmon population could also increase the number of fishing licenses the state grants, in turn bolstering revenue and increasing lucrative commercial and tourism dollars that could be used for future conservation efforts.

Back down the river on the shores of Seattle, local environmentalists and municipalities alike are looking for new ways to protect both the salmon and the whales. The $3 billion transit expansion that voters passed last year was expressly messaged as a way to reduce groundwater pollution, and King County Metro, the region’s transit authority, launched advertisements promising that “salmon love this bus.” Seattle Public Utilities’ “Salmon Friendly” program is designed to protect local waterways – and residents are encouraged to stencil their local storm drain with a reminder that wastewater affects fish. Hearing the call to reduce crowding on the mountains, the county has also rolled out new public transit options for hikers.

But it’s an uphill battle. In addition to combating the decades-long decline, area conservationists are also dealing with unforced errors, like a massive failure at a local waste management plant earlier this year that sent untreated sewage straight into Puget Sound, continue to happen. And a National Oceanic and Atmospheric Administration report released in 2016 found that local salmon were riddled with chemicals and pharmaceuticals – proof that, despite the best efforts of local governments and activists, there are a lot of seemingly unrelated social issues affecting fish and whales. Opioid addiction is bad for groundwater. Poverty is bad for groundwater. Gridlock is bad for groundwater.

There are numerous campaigns and nonprofits working to clean up the waterways and reduce the myriad issues that cause declines in both salmon and orcas, but it’s difficult to reduce a footprint that’s also readymade. As long as people keep moving to Seattle for the beauty of it – for the hiking, the boating and, yes, even the fishing – there will continue to be both up- and downstream effects on the region’s fauna, particularly those that rely on natural resources.

The views expressed in this article belong to the author and do not necessarily reflect the editorial policy of Oceans Deeply.

This story originally appeared as “Why do Most Orca Pregnancies End in Miscarriage? Look Upstream” on Pacific Standard.  Subscribe to the magazine in print and follow Pacific Standard on Twitter to support journalism in the public interest.