Dramatic Comebacks & Current Scope of Biodiversity

Thanks to landmark protections like the Marine Mammal Protection Act (1972) and the Endangered Species Act (1973), many of California’s marine mammals have staged impressive recoveries over the past 50 years. Species such as California sea lions, northern elephant seals, harbor seals, whales, dolphins, porpoises, and southern sea otters are now more abundant. The state’s nutrient-rich upwelling systems support this high diversity—over 40 marine mammal species use its coastal waters.

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Emerging Threats & Population Declines

Despite these gains, problems are mounting:

• Gray whales: Their population, which had grown to ~27,000 by 2016, has sharply declined to around 12,950. Major causes include loss of prey via Arctic ice melt, reduced under-ice algae, and cascading effects that reduce reproduction and nutrition.
• Strandings & mortality: Between 2019–2025 over 1,200 gray whales stranded along the U.S. West Coast—far higher than historical norms. Most deaths are linked to starvation.
• Sea lions & other mammals are suffering from harmful algal blooms (HABs), toxins like domoic acid, disease outbreaks (e.g. leptospirosis), and cancer associated with legacy pollutants like DDT.
• Southern sea otters, though greatly recovered from near-extinction, haven’t expanded beyond certain areas. Predation (especially from increased great white shark encounters) and opposition to reintroduction limit their range growth.

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Policy & Regulatory Pressure

Even as ecological pressures mount, regulatory protections are under threat:

• Proposed amendments to the Marine Mammal Protection Act could weaken “incidental take” rules, which currently help prevent harm from activities like shipping, fishing gear entanglement, or industrial disturbance.
• A bill introduced in Congress (H.R.1897) seeks to redefine “harm” in the Endangered Species Act in a way that might allow habitat destruction.
• Cuts in funding and scaling back of scientific monitoring (for example, NOAA’s California Current Ecosystem Program) are reducing capacity to track threats and species health.

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A Narrow Window for Action

The article argues that the combination of environmental change, new threats, and weakened regulatory guardrails could reverse much of California’s marine mammal conservation successes. Without vigilant policy protections, continued scientific monitoring, reduced pollution, and climate adaptation efforts, many of these species remain vulnerable. Experts warn that the ocean is changing in real time and that mammal populations are already pushed to the edge.

Read the full article on Monga Bay.