At the migration’s peak in late April, Flemming counts around 120,000 to 150,000 western sandpipers in a day. “It’s quite busy when you’re trying to count them. You’ve got to move fast,” says Mark Drever, a research scientist with Environment and Climate Change Canada who is also involved in the surveys. “One day, you come back to do your count, and they are not here anymore. I always wish them well in these long flights and tell them ‘Good luck, little buddies.’”

By mid-May, the sandpipers have all left to their next major stopover, the Stikine River estuary in southwest Alaska, more than 850 kilometres away. Roberts Bank is one of the best and last major stopover spots on the Pacific Flyway because, on the way north, there aren’t many large estuaries. A study of radio-tagged western sandpipers showed that, on average, it took 7.7 days for the birds
to travel 3,250 kilometres between San Francisco Bay — one of their major stopover sites — and the Copper River delta in Alaska, the last stop before the breeding grounds. One bird flew the distance in less than 42 hours, or about 1,850 kilometres per day. 

Even though mudflats are one of Earth’s oldest and largest coastal ecosystems, few have studied them, largely because they are difficult to work in. “Mud is almost unknowable. If it was a rocky shore, we could walk out there, pick up mussels and dig clams. But here we have something that is deep and complex,” Elner explains. “It’s like being an explorer: you are finding life in a wasteland.”

Following Elner as he effortlessly navigates the mud with his hip boots feels worthy of an Olympic discipline. The terrain is uneven, unpredictable, deceptive, hard in some spots and soft in others, always challenging. Meanwhile, Elner displays a sense of excitement unabated in the last 30 years. “Here, we are surrounded by 70,000 western sandpipers. You are joining these birds in this intense migration. You are stepping into their universe,” he says. “It’s powerful. It is a natural drug. That thrill never leaves you.”

The sandpipers are so dependent on the biofilm at Roberts Bank that it accounts for 45 to 59 per cent of the mass in their diet and half their daily energy budget. Without it, many birds would not make it to their final destination, as the nutrients cannot be obtained from any other available food. “It’s the magic carpet that enables them to fly,” says Elner.

Since the first observations of biofilm grazing by western sandpipers, it’s been found that biofilm feeds at least 21 other species of shorebirds at estuarine stopover sites. Perhaps more importantly, the story of western sandpipers at Roberts Bank has shed a new light on the ecological value of a largely misunderstood ecosystem.

Compared with more charismatic habitat types like eelgrass or salt-marsh, western science generally sees intertidal mud as a purposeless wasteland. Globally, mudflat ecosystems decreased 16 per cent in certain areas between 1984 and 2016, largely due to degradation from coastal development, pollution and disturbances from marine traffic.

Meanwhile, a study of 28 shorebird species in North America revealed that between 1980 and 2019, more than half of the surveyed species lost more than half of their populations. Jim Johnson, a biologist who studies migratory shorebird species in Alaska’s breeding grounds, says habitat loss is a driving force in shorebird declines. “The most devastating part of these declines is what’s happening in the non-breeding areas where these birds are migrating and wintering.” 

Linking the global loss of critical mudflats and the demise of migrating shorebirds is a logical connection to make, and possibly a sign of wider issues to come. “Birds are great harbingers of what’s happening in systems,” Elner says. At Roberts Bank, the fatty acids produced in mudflats are also important to invertebrates, salmon and the endangered southern resident orcas that depend on them and, ultimately, human health. “The birds have told us this, and if they had not been there, no one would have figured out that biofilm production is critical.”

It’s therefore ironic that as scientists are learning about the global importance of mudflats, the site where it all began is now threatened by the port development. Proponents of the project, however, downplay adverse effects — and point to the huge economic potential of the development. Alex Munro, senior communications advisor, issues management and media relations at the Vancouver Fraser Port Authority, said in a written statement to Canadian Geographic that the project will deliver critical capacity and resilience to support Canada’s trade needs. He said it will create tens of thousands of supply chain jobs, support an estimated $100 billion in Canadian trade per year, and deliver hundreds of millions of dollars in tax revenues and billions of dollars in Canadian GDP during operation. At a time when Canada’s economy is struggling, many see the benefits as enticing — especially when, according to Munro’s statement, the project is advancing “in a way that protects the environment,” and is “not expected to have adverse effects on biofilm and western sandpipers.” 

But not everybody agrees. A coalition of environmental groups in British Columbia has filed an application for a judicial review in the Federal Court, challenging the federal government’s decision to approve the Roberts Bank Terminal 2 Project and arguing it is contrary to the Species at Risk Act.

And, in a review of the project, Environment and Climate Change Canada found that in addition to the direct loss of mudflats, the impacts on biofilm would be permanent, irreversible and unmitigable, with species-level consequences for western sandpipers. There would also be no way to recreate the rich biofilm habitat. 

This is because the invisible processes at work in the mudflats of Roberts Bank are influenced by complex physical and chemical interactions. Spring is a time of rapid change over the mudflats, with more sunlight, rising temperatures and lowest tides that occur during daylight hours. Photosynthetic activity increases and diatoms grow rapidly. At the same time, the Fraser River’s pulse of fresh water from the snowmelt-fuelled spring freshet changes the salinity of the mud, causing a stress response

in the diatoms that stimulate them to produce omega-3 fatty acids, the birds’ superfood. The freshwater “shocks the diatoms,” Elner says. The magic in this delicate natural cycle is this is all perfectly timed with the arrival of the western sandpipers on their spring migration.