The Marine Mammal Protection Act: What It Saved and What We Stand to Lose

In the early 1970s, public and scientific concerns grew over declining populations of marine mammals due to human activities such as whaling and fishing bycatch. Before its strong bipartisan enactment in 1972, an estimated six million dolphins were killed in fishing nets in the decade prior, tens of thousands of whales were killed a year by commercial whaling, and thousands of seal pups were clubbed to death for their fur, driven by commercial hunting and bounty programs.

Since the passing of the legislation, populations of humpback whales, Hawaiian monk seals, harbor porpoises, and many species of dolphins and small cetaceans have rebounded strongly, with not a single marine mammal going extinct in U.S. waters in over 50 years.

But a draft bill introduced to the House in July 2025 by Alaska Representative Nicholas Begich could undo the decades of protections for these critical species.

The Marine Mammal Protection Act was passed in response to a crisis already well underway, driven by decades of commercial exploitation and human activity. By the time the U.S. government signed it into law in 1972, the question was no longer whether populations were declining, but whether recovery through legislation was still possible at all.

North Pacific humpback whales were one of the many species caught in the decline.

Once abundant throughout the North Pacific, humpback whales were heavily hunted during the height of commercial whaling in the late 19th and early 20th centuries. Their long migrations and predictable behaviors made them easy targets, and industrial whaling reduced many populations at a pace far exceeding their natural capacity to recover. By the mid-20th century, North Pacific humpback populations had declined by more than 90 percent, leaving the species at the brink of extinction if whaling continued.

Humpbacks were not alone in this collapse. Their decline unfolded alongside widespread losses of dolphins, seals, and other whale species facing equal pressures from hunting, bycatch, and habitat disruption. Researchers warned that this continued exploitation could push several species past the point of recovery.

At the same time, public awareness was growing. Graphic documentation of commercial whaling, alongside emerging marine science, helped fuel a global “Save the Whales” movement throughout the 1960s and early 1970s. Public pressure mounted as citizens, scientists, and advocacy groups called for an end to the unchecked killing and oppression of marine mammals. That junction of scientific evidence and public concern reached policymakers, creating the momentum for overdue federal legislation.

That momentum would ultimately lead to the passage of the Marine Mammal Protection Act and, a year later, the Endangered Species Act.

When the Marine Mammal Protection Act became law, it marked an essential change in how marine mammals were treated under U.S. policy. For the first time, whales, dolphins, seals, and other marine mammals were granted comprehensive federal protection, recognizing their ecological importance and vulnerability rather than viewing them primarily as commercial resources.

The MMPA made it illegal to “take” marine mammals in U.S. waters or by U.S. citizens, defining “take” to include killing, hunting, capturing, or harassing animals. By taking a broad definition approach, the Act safeguarded survival dependent not only on ending direct hunting but also on reducing disturbance, injury, and accidental harm, factors that affect slow-reproducing species such as large whales.

The MMPA also enacted a proactive, rather than reactive, approach to marine mammal protection. Rather than allowing human activities to proceed until serious harm was proven, the law set strict limits on what impacts were permitted in the first place. Industries and agencies were required to assess and reduce their effects on marine mammals (shifting responsibility away from declining species and onto human activity).

Beyond legal protections, the law authorized federal funding for marine mammal research, long-term population monitoring, and ecosystem studies through the creation of the Marine Mammal Commission to provide independent scientific oversight and policy guidance. It also laid the foundation for coordinated stranding and health response programs, improving the nation’s ability to respond to entanglements, ship strikes, disease outbreaks, and mass mortality events.

Over time, these protections contributed to measurable recovery across multiple species. North Pacific humpback whales, once reduced by more than 90 percent in some regions, began a slow but sustained rebound. By the early 21st century, several distinct populations showed significant increases, with overall numbers rising into the tens of thousands across the North Pacific. Similar trends were observed in other marine mammals, including gray whales, harbor seals, and certain dolphin populations, though recovery varied widely by species and region.

After decades of slow recovery, the Marine Mammal Protection Act is often cited as a conservation success. Yet, even as its benefits continue to emerge, new legislative proposals could weaken the very protections that made this progress possible.

In recent years, proposals have emerged in Congress to revise key provisions of the MMPA under the banner of “modernization”. The most prominent of these efforts comes from Rep. Nick Begich (R-AK), who introduced in July 2025 a discussion draft that would modify how harm and harassment are defined, adjust permitting timelines, and narrow the circumstances under which activities must be limited to protect marine mammals. Supporters argue that these changes would reduce regulatory burdens on industries such as fishing, shipping, and energy development and bring the law more in line with current economic and technological realities.

Begich’s proposal has not advanced in isolation. It has been taken up within broader hearings and discussions led by the Natural Resources Committee and its subcommittee on Water, Wildlife, and Fisheries, where several Republican lawmakers have expressed interest in revisiting long-standing wildlife protections. While not all members have endorsed specific amendments, the committee process itself signals growing momentum among some lawmakers to reconsider the scope and enforcement of the MMPA.

At the same time, opposition has been vocal. Democratic lawmakers, conservation scientists, and tribal and environmental organizations have warned that weakening the MMPA’s precautionary standards could have far-reaching consequences for marine mammals that are still vulnerable to ship strikes, entanglement, noise pollution, and habitat disruption. Critics argue that shifting the law away from population recovery and toward minimal survival would undermine the very framework that allowed species like humpback whales to rebound in the first place.

This debate is unfolding within a broader federal policy environment that has increasingly emphasized reducing environmental regulatory requirements. While President Donald Trump has not publicly endorsed specific changes to the MMPA, his administration has supported rollbacks and reinterpretations of related conservation laws, including the Endangered Species Act. That stance has shaped the political context in which proposals to weaken the MMPA are now being considered, even without direct executive involvement.

These proposals raise fundamental questions about the future of marine mammal protection in the United States. The safeguards established under the Marine Mammal Protection Act did not simply enable recovery; they continue to play a critical role in maintaining and supporting healthy, growing populations. For species like humpback whales, whose survival depends on long-term, proactive management, weakening those protections reintroduces pressures the law was designed to prevent. As lawmakers consider changes to the Act, public understanding and engagement will be essential in shaping what marine mammal conservation looks like moving forward.

The Marine Mammal Protection Act was shaped by public concern, scientific evidence, and sustained civic engagement, and its continued strength depends on those same forces today. As discussions around proposed changes to the law move forward, public awareness and participation remain an essential part of the policy process.

Calling or emailing your elected representative is one of the most direct ways to voice your concern. Congressional offices track constituent input, and even brief messages help signal where public priorities lie.

Here is a short script you can share:

Following how the MMPA is discussed in Congress, particularly within committees that oversee wildlife and marine policy, is crucial for public understanding and action. Legislative hearings, discussion drafts, and proposed amendments often shape the direction of a law long before a formal vote occurs. Staying informed helps ensure that decisions affecting marine mammals are made transparently and with public input.

Supporting organizations that conduct marine mammal research, respond to strandings, and advocate for science-based policy is another meaningful way to contribute. These groups provide the data, expertise, and on-the-ground insight that inform effective conservation and bridge the gap between science and policy.

Finally, sharing accurate, credible information matters. Marine mammal protection is often discussed in abstract terms, but its impacts are ongoing and measurable. Helping others understand how laws like the MMPA function, and why they remain essential, keeps conservation grounded in evidence rather than rhetoric.

The future of marine mammal protection will be shaped by decisions made now. Staying informed, engaged, and willing to speak up is one way to help ensure that decades of progress continue forward.

The Marine Mammal Protection Act shows what’s possible when strong protections are put in place and defended. The Endangered Species Act, passed just one year later, carries a similar legacy and is now facing similar threats. Next month, we’ll be diving into the Endangered Species Act and what’s at stake if those protections are weakened.

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Thumbnail: New Zealand Fur Seal Pup, courtesy of William Morris (@wanderwithbill)