The Detroit River is a 51-kilometer (32-mile) strait connecting Lake St. Clair to the north with Lake Erie to the south, forming part of the international border between the United States and Canada. Despite its modest length, this waterway carries roughly a fifth of the surface freshwater in North America through one of the continent’s most heavily industrialized corridors. It is simultaneously a shipping superhighway, a recovering ecological treasure, and a case study in what happens when two nations try to share and restore a single body of water after more than a century of abuse.
How Shipping Reshaped the River
Before Europeans arrived, the Detroit River was a braided, shallow waterway dotted with islands and gravel shoals. Indigenous communities, including those who call the corridor Aamjiwnaan, used the river for fishing, transportation, and trade for thousands of years. The modern river looks almost nothing like that earlier version. Beginning in the late 1800s, the U.S. Army Corps of Engineers and Canadian counterparts embarked on massive dredging campaigns to accommodate increasingly large commercial vessels. According to a U.S. Geological Survey report, large-scale dredging, disposal of dredge spoils, and construction of water-level compensating works greatly altered channel morphology and flow dynamics, disrupting ecological function and fishery productivity while influencing Great Lakes water levels.1U.S. Geological Survey. Construction of shipping channels in the Detroit River: History and environmental consequences
The practical effect was dramatic. Natural gravel beds that once served as spawning grounds for sturgeon, walleye, and whitefish were blasted or buried. Islands were removed or reshaped to straighten shipping lanes. Dredge spoils dumped in open water smothered habitat along the river’s bottom. What remained was a deeper, faster, more uniform channel ideal for freighters but hostile to the biological communities that had thrived in the shallows. Much of the restoration work happening today is an attempt to undo, or at least compensate for, that century of engineering.
The Pollution Legacy
The Detroit River runs between two cities built on heavy industry: Detroit, Michigan, and Windsor, Ontario. Steel mills, chemical plants, automobile factories, oil refineries, and municipal wastewater plants all discharged waste into the river for decades. By the mid-twentieth century, the river was one of the most polluted waterways in North America. In 1985, both the U.S. and Canadian governments designated it a Great Lakes “Area of Concern,” a label reserved for the most degraded sites in the basin.
Among the most persistent contaminants are polychlorinated biphenyls, commonly known as PCBs. These synthetic chemicals were used widely in electrical equipment and industrial processes before being banned in the late 1970s, but they break down extremely slowly in the environment. Research using food web bioaccumulation models found that PCB concentrations in Detroit River sediment and water exhibit high spatial variation, and that previously contained areas of high contamination may have spread to adjacent food webs as fish move through the corridor.2PubMed. Use of a Food Web Bioaccumulation Model to Uncover Spatially Integrated Polychlorinated Biphenyl Exposures in Detroit River Sport Fish In other words, contamination that was once localized near industrial outfalls has been carried by fish into broader stretches of the river.
The problem is not just about how much PCB is in the sediment but also about how it moves through the food chain. A study of lower trophic level fish species in the Detroit River found that individual variability in PCB concentrations depended on both the chemical properties of specific PCB types and on the feeding habits of different fish species. Benthic feeding specialists, which eat from the river bottom, showed lower variance in contamination than generalist feeders, which accumulated different levels depending on where and how they foraged.3Environmental Toxicology and Chemistry. Ecological factors contributing to variability of persistent organic pollutant bioaccumulation within forage fish communities of the Detroit River, Ontario, Canada Further modeling work confirmed that PCB uptake in aquatic organisms is significantly affected by the degree of chemical imbalance between sediments and overlying water, meaning that disturbing contaminated sediment through dredging or natural currents can reintroduce PCBs into the food web.4Integrated Environmental Assessment and Management. Characterizing polychlorinated biphenyl exposure pathways from sediment and water in aquatic life using a food web bioaccumulation model
For people who fish the Detroit River, this is not abstract science. State and provincial agencies issue fish consumption advisories for species like walleye, carp, and channel catfish caught in the river. The advisories vary by species, size, and location, but they remain in place precisely because PCBs and other legacy pollutants persist in sediment that will take decades, and possibly longer, to fully remediate.
Sewage and Microbial Contamination
Industrial chemicals are only part of the story. The river also suffers from microbial pollution linked to aging urban sewer systems. Many older cities along the Great Lakes connecting channels were built with combined sewer systems that carry both stormwater and household sewage in the same pipes. During heavy rains, these systems overflow and discharge untreated sewage directly into the waterway. A study of microbiological pollution across the upper Great Lakes connecting channels found poor water quality along a long stretch of the Detroit River near Windsor, Ontario, where 25 combined sewer overflows were identified. By contrast, the Sault Ste. Marie connecting channel, which has no combined sewer overflows, showed excellent water quality.5Water Science and Technology. Microbiological pollution in the Canadian Upper Great Lakes Connecting Channels
Both Detroit and Windsor have invested heavily in sewer infrastructure upgrades in recent decades, including retention basins designed to capture overflow during storms. Progress has been real, but combined sewer overflows still occur during extreme rainfall events. Climate projections for the Great Lakes region suggest more intense storms in the coming decades, which could increase the frequency of these overflows and set back gains in water quality.
Signs of Ecological Recovery
The Detroit River’s story is not just one of degradation. Since the 1970s, when landmark water quality legislation was enacted on both sides of the border, the river has shown substantial biological recovery. Long-term monitoring has documented increasing populations of bald eagles, peregrine falcons, lake sturgeon, lake whitefish, walleye, and burrowing mayflies in the Detroit River and western Lake Erie.6PubMed. Long-term ecosystem monitoring and assessment of the Detroit River and Western Lake Erie The return of burrowing mayflies is particularly telling because these insects spend most of their lives as larvae burrowed into river-bottom sediment. Their presence indicates that oxygen levels and sediment quality have improved enough to support species that are highly sensitive to pollution.
Bald eagles nesting along the Detroit River corridor were unthinkable a generation ago. The birds were nearly eliminated from the lower Great Lakes by DDT and other organochlorine pesticides that caused eggshell thinning. Their return to the river reflects both the ban on DDT and the broader improvement in water and prey-fish quality. Lake sturgeon, another species that disappeared from much of the river during the industrial era, have also begun recolonizing stretches where they had not been seen in decades.
Rebuilding Habitat
Recovery does not happen passively when a river has been physically reshaped as thoroughly as the Detroit River has. Agencies on both sides of the border have undertaken an ambitious program of habitat restoration. By 2018, the effort had produced 14 habitat restoration projects on both the Canadian and U.S. sides of the river, 53 soft shoreline engineering projects in the watershed, nine fish spawning reefs in the river, Common Tern habitat at four locations, and numerous wetland and green infrastructure projects.7Taylor & Francis Online. Habitat rehabilitation in the Detroit River Area of Concern
The spawning reefs deserve particular attention. When the natural gravel beds were destroyed by dredging, fish like walleye and lake sturgeon lost the hard substrate they need to deposit and fertilize eggs. Researchers and agencies have constructed artificial reefs by placing clean rock and gravel on the river bottom in areas with suitable water flow. Monitoring of these reefs has confirmed that fish are using them. In spring 2004, researchers collected 136 fish eggs from near the head of the Detroit River using egg mats placed on the bottom. All eleven larvae that hatched were identified as walleye, constituting the first credible scientific evidence that walleye spawn in the Detroit River.8Journal of Great Lakes Research. First Evidence of Egg Deposition by Walleye (Sander vitreus) in the Detroit River The researchers noted that the existence of a river-spawning walleye stock could add resilience to walleye populations that spawn and are harvested in adjacent lakes.
Soft shoreline engineering is another key strategy. Traditional hardened shorelines made of steel sheet piling and concrete are excellent at protecting property but terrible for aquatic life. Soft engineering replaces those hard edges with sloped banks, native vegetation, and submerged structures that provide shelter for fish, insects, and birds. Dozens of these projects along the Detroit River corridor have created small pockets of habitat where the shoreline had previously offered none.
A Crossroads for Migratory Birds
The Detroit River corridor sits at the intersection of two major North American bird migration flyways, the Atlantic and Mississippi. That geographic accident makes the river and its surrounding wetlands extraordinarily important for birds. Surveys have documented over 300,000 diving ducks, 75,000 shorebirds, and hundreds of thousands of land birds and fall raptors using the area to rest, nest, and feed along the shoreline habitats, islands, and marshes. More than 30 species of waterfowl, 23 species of raptors, 31 species of shorebirds, and 160 species of songbirds are found along or migrate through this corridor.9ScienceDirect. Habitat management lessons from the environs of the Detroit River International Wildlife Refuge
In 2001, the U.S. Congress established the Detroit River International Wildlife Refuge, the only international wildlife refuge in North America. It encompasses islands, coastal wetlands, marshes, and shoals along the lower Detroit River and the western shore of Lake Erie. The refuge exists in large part because the river’s remaining natural areas provide irreplaceable stopover habitat for migratory species. Lose those patches of marsh and shoreline, and hundreds of thousands of birds lose a refueling station on journeys that stretch thousands of miles.
Humbug Marsh and the Last Natural Shoreline
One jewel within the refuge is Humbug Marsh, a 166-hectare wetland that represents the last kilometer of natural shoreline on the U.S. mainland of the Detroit River. It is Michigan’s only “Wetland of International Importance” designated under the 1971 Ramsar Convention, a global treaty protecting the most ecologically significant wetlands on Earth.10Sustainability. Transformation of an Industrial Brownfield into an Ecological Buffer for Michigan’s Only Ramsar Wetland of International Importance That a single kilometer of natural riverbank warrants international protection says a great deal about how thoroughly the rest of the shoreline was industrialized.
The land adjacent to Humbug Marsh was formerly an industrial brownfield. It has since been remediated and converted into an ecological buffer, illustrating a model that other Great Lakes communities are beginning to replicate: transforming abandoned industrial sites not just into parks or housing but into functional habitat that supports the biological communities the river needs to recover. Humbug Marsh harbors species found nowhere else along the U.S. mainland stretch of the river, including rare plants and nesting birds that depend on undeveloped coastal wetland.
Walleye, Sturgeon, and How Fish Use the Corridor
The Detroit River is not just a place where fish live. It is a corridor they pass through. Because the river connects Lake St. Clair and Lake Huron to the north with Lake Erie to the south, it serves as a migration route for species moving between the two lake systems. Researchers have used acoustic telemetry tags to track walleye movements through the Huron-Erie Corridor, which includes the St. Clair River, Lake St. Clair, and the Detroit River. The results were somewhat surprising: very few walleye tagged in either the Tittabawassee River (a Lake Huron tributary) or the Maumee River (a Lake Erie tributary) made the full passage between the two lakes. Most walleye from Lake Huron that entered the corridor were detected only in the St. Clair River and never made it as far south as the Detroit River. Of those that did reach the Detroit River, only one was detected in Lake Erie, and it returned to Lake Huron within a month. Similarly, half of the Lake Erie walleye that entered the corridor from the south did not move upstream beyond the Detroit River.11Journal of Great Lakes Research. Telemetry reveals limited exchange of walleye between Lake Erie and Lake Huron: Movement of two populations through the Huron-Erie Corridor
This matters for fishery management. If walleye from Lake Erie and walleye from Lake Huron function as largely separate populations with limited mixing, they need to be managed independently. Overharvesting the Lake Erie stock cannot be offset by immigration from Lake Huron, because the fish mostly stay in their own lake system. The Detroit River, despite being physically open, acts as more of a boundary than a highway for walleye. Understanding this has practical consequences for setting catch limits and protecting spawning habitat in each system.
Invasive Species in the Corridor
The same connectivity that makes the Detroit River ecologically important also makes it a conduit for invasive species. The Great Lakes have been invaded by more than 180 non-native species, many of which entered through ballast water from ocean-going ships. Among the most transformative are the zebra mussel and quagga mussel, both native to the Ponto-Caspian region. These filter-feeding mussels colonize hard and soft substrates throughout the Great Lakes and have fundamentally altered ecosystem function. Their effects include increased water clarity from their high filtration rates, selective rejection of colonial cyanobacteria in their waste, alteration of nutrient ratios in the water, and the fouling of native mussel species that cannot compete for space on the same surfaces.12Canadian Journal of Fisheries and Aquatic Sciences. Dispersal and emerging ecological impacts of Ponto-Caspian species in the Laurentian Great Lakes
The Detroit River is particularly vulnerable because of the sheer volume of commercial shipping that passes through it. The river handles more tonnage annually than almost any other inland waterway on the continent, and each vessel is a potential vector for moving organisms from one lake to another. The round goby, another Ponto-Caspian invader, has established dense populations throughout the river and competes with native bottom-dwelling fish for food and spawning sites. On the other hand, round gobies have become an important food source for recovering predator populations like walleye and smallmouth bass, an ironic twist in which one invasive species helps prop up the recovery of native species that managers are working hard to restore.
The invasive species that looms largest over the corridor is the Asian carp complex, particularly bighead and silver carp. These large, voracious filter feeders have colonized the Mississippi River basin and are advancing toward the Great Lakes. If they establish breeding populations in the lakes, they could outcompete native planktivores and disrupt the food web from the bottom up. The Detroit River’s role as a connecting channel means that any carp reaching Lake Erie would have a direct pathway toward Lake Huron and beyond.
Two Countries, One River
Managing the Detroit River requires cooperation between two countries, multiple states and provinces, Indigenous nations, and dozens of local governments. The overarching framework for this cooperation is the Great Lakes Water Quality Agreement, originally signed in 1972 and most recently updated in 2012. The International Joint Commission, an independent agency established by the Boundary Waters Treaty of 1909, guides Canada and the United States on how to settle disputes involving their transboundary river basins, and the 2012 agreement serves as a case study of how this body responds to complex basin-wide challenges.13Water Science Policy. Intergovernmental River Basin Management: The Role of the International Joint Commission in the Great Lakes Basin between the United States and Canada
At a more local scale, the St. Clair-Detroit River System Initiative, established in 2004, brings together U.S. federal and state agencies, Canadian federal and provincial agencies, and a First Nation, Bkejwanong-Walpole Island, to address regional needs across the connecting waters.14Journal of Great Lakes Research. Critical intersections of flow: Connecting waters among the Laurentian Great Lakes This partnership has been described as a role model for the kind of multi-partner, multi-nation approach that complex waterways demand. It reflects the reality that the Detroit River does not belong to any single jurisdiction. Pollution released in Michigan travels past Ontario. Fish spawning on a Canadian reef may be caught by American anglers. Invasive species do not stop at the border. Effective governance has to be as borderless as the water itself.
Progress toward delisting the Detroit River as an Area of Concern has been slow but measurable. Several of the original “beneficial use impairments” identified in the 1980s, ranging from degraded fish populations to restrictions on dredging, have been addressed or are close to being removed. The river is not clean yet, and the pace of restoration frustrates people who have spent careers working on it. But the trajectory is unmistakably upward, and the combination of habitat construction, pollution controls, and cross-border cooperation has produced results that would have seemed impossible when the river was at its worst.