Invasive carp threaten the Great Lakes − and reveal a surprising twist in national politics

In his second term, President Donald Trump has not taken many actions that draw near-universal praise from across the political spectrum. But there is at least one of these political anomalies, and it illustrates the broad appeal of environmental protection and conservation projects – particularly when it concerns an ecosystem of vital importance to millions of Americans.

In May 2025, Trump issued a presidential memorandum supporting the construction of a physical barrier that is key to keeping invasive carp out of the Great Lakes. These fish have made their way up the Mississippi River system and could have dire ecological consequences if they enter the Great Lakes.

It was not a given that Trump would back this project, which had long been supported by environmental and conservation organizations. But two very different strategies from two Democratic governors – both potential presidential candidates in 2028 – reflected the importance of the Great Lakes to America.

As a water policy and politics scholar focused on the Great Lakes, I see this development not only as an environmental and conservation milestone, but also a potential pathway for more political unity in the U.S.

A feared invasion

Perhaps nothing alarms Great Lakes ecologists more than the potential for invasive carp from Asia to establish a breeding population in the Great Lakes. These fish were intentionally introduced in the U.S. Southeast by private fish farm and wastewater treatment operators as a means to control algae in aquaculture and sewage treatment ponds. Sometime in the 1990s, the fish escaped from those ponds and moved rapidly up the Mississippi River system, including into the Illinois River, which connects to the Great Lakes.

Sometimes said to “breed like mosquitoes and eat like hogs,” these fish can consume up to 40% of their body weight each day, outcompeting many native species and literally sucking up other species and food sources.

Studies of Lake Erie, for example, predict that if the carp enter and thrive, they could make up approximately one-third of the fish biomass of the entire lake within 20 years, replacing popular sportfishing species such as walleye and other ecologically and economically important species.

Invasive carp are generally not eaten in the U.S. and are not desirable for sportfishing. In fact, silver carp have a propensity to jump up to 10 feet out of the water when startled by a boat motor. That can make parts of the Illinois River, which is packed with the invasive fish, almost impossible to fish or even maneuver a boat.

The Brandon Road Lock and Dam solution

Originally, the Great Lakes and the Mississippi River were not connected to each other. But in 1900, the city of Chicago connected them to avoid sending its sewage into Lake Michigan, from which the city draws its drinking water.

The most complete way to block the carp from invading the Great Lakes would be to undo that connection – but that would recreate sewage and flooding issues for Chicago, or require other expensive infrastructure upgrades. The more practical, short-term alternative is to modify the historic Brandon Road Lock and Dam in Joliet, Illinois, by adding several obstacles that together would block the carp from swimming farther upriver toward the Great Lakes.

The barrier, estimated to cost US$1.15 billion, was authorized by Congress in 2020 and 2022 after many years of intense planning and negotiations. For the first phase of construction, the project received $226 million in federal money from the Bipartisan Infrastructure Law to complement $114 million in state funding – $64 million from Michigan and $50 million from Illinois.

On the first day of Trump’s second term, however, he paused a wide swath of federal funding, including funding from the Bipartisan Infrastructure Law. And that’s when two different political strategies emerged.

Pritzker vs. Whitmer vs. Trump

Illinois, a state that has voted for the Democratic candidate in every presidential election since 1992, has the most financially at stake in the Brandon Road project because the project requires the state to acquire land and operate the barrier. When Trump issued his order, Illinois Gov. JB Pritzker, a Democrat, postponed the purchase of a key piece of land, blaming the “Trump Administration’s lack of clarity and commitment” to the project. Pritzker essentially dared Trump to be the reason for the collapse of the Great Lakes ecosystem and fisheries.

Another Democrat, Gov. Gretchen Whitmer of Michigan, a swing state with the most at stake economically and ecologically if these carp species enter the Great Lakes, took a very different approach. She went to the White House to talk with Trump about invasive carp and other issues. She defended her nonconfrontational approach to critics, though she also hid her face from cameras when Trump surprised her with an Oval Office press conference. When Trump visited Michigan, she stood beside him as they praised each other.

When Trump released the federal funding in early May, Pritzker kept up his adversarial language, saying he was “glad that the Trump administration heard our calls … and decided to finally meet their obligation.” Whitmer stayed more conciliatory, calling the funding decision a “huge win that will protect our Great Lakes and secure our economy.” She said she was “grateful to the president for his commitment.”

Why unity on carp?

Whether coordinated or not, the net result of Pritzker’s and Whitmer’s actions drew praise from both sides of the aisle but was little noticed nationally.

Trump’s support for the project was a rare moment of political unity and an extremely unusual example of leading Democrats being on the same page as Trump. I attribute this surprising outcome to two key factors.

First, the Great Lakes region holds disproportionate power in presidential elections. Michigan, Wisconsin and Pennsylvania have backed the eventual winner in every presidential race for the past 20 years. This swing state power has been used by advocates and state political leaders to drive funding for Great Lakes protection for many years.

Second, Great Lakes are the uniting force in the region. According to polling from the International Joint Commission, the binational body charged with overseeing waterways that cross the U.S.-Canada border, there is “nearly unanimous support (96%) for the importance of government investment in Great Lakes protections” from residents of the region.

There aren’t any other issues with such high voter resonance, so politicians want to be sure Great Lakes voters are happy. For example, Vice President JD Vance has been particularly vocal about the Great Lakes. And Great Lakes restoration funding was one of the few things in the presidential budget that Democrats and Republicans agreed on.

Both Pritzker and Whitmer likely had state-based and national motivations in mind and big aspirations at stake.

Their combined effort has put the project back on track: As of May 12, 2025, Pritzker authorized Illinois to sign the land-purchase agreement he had paused back in February.

And perhaps the governors have identified a new area for unity in a divided United States: Conservation and environmental issues have broad public support, particularly when they involve iconic natural resources, shared values and popular outdoor pursuits such as fishing and boating. Even when political strategies diverge, the results can bring bipartisan satisfaction.