When dealing with complex scientific issues that involve high levels of uncertainty, good science requires multiple working hypotheses to account for alternative explanations. Unfortunately, NOAA’s **2015 Arctic Report Card** failed to follow this principle when assessing the status of the **Pacific walrus**. Instead, NOAA promoted a single, unproven hypothesis: that a reduction in sea ice is harmful to walruses by denying them access to foraging habitats. This approach not only oversimplifies a complex issue but also ignores growing evidence that suggests the walrus population may be benefiting from changes in sea ice. NOAA’s failure to communicate the full scope of uncertainties and possible alternative hypotheses has led to a misleading narrative. Contrary to the agency’s claims, **indicators of a growing walrus population**—such as an increase in the number of calves per cow and improved calf survival—suggest that Pacific walruses are thriving, not suffering, under current conditions. ### The Flawed Hypothesis: Sea Ice Decline as a Threat to Walruses NOAA’s 2015 Arctic Report Card argues that the decline in Arctic sea ice is reducing the **carrying capacity** of walrus habitats by making foraging more difficult. The report assumes that less sea ice leaves walruses stranded on land haulouts far from their food sources, causing nutritional stress and potentially threatening the species’ survival. While this may sound plausible, it hinges on an untested assumption—that sea ice loss is inherently harmful to walrus populations. The evidence, however, suggests a different story. In the **Pacific**, historical records compiled by walrus expert **Fay (1982, 1989)** show that walrus populations increased in conjunction with greater use of land-based haulouts, indicating that the shift from ice to land has been a natural part of walrus behavior for centuries. Walruses have long adapted to using land when sea ice is unavailable, and the current shift toward more frequent land use may actually reflect a growing population rather than a declining one. Similarly, in the **Barents Sea’s Svalbard Archipelago**, where sea ice has declined more dramatically than in many other parts of the Arctic, walrus populations have **boomed**. Recent research by **Kovacs (2014)** documented an **exponential population increase**, with a **48% growth** between 2006 and 2012. This surge in population coincides with the walruses’ increased use of land haulouts, further calling into question NOAA’s claim that less sea ice automatically means a lower carrying capacity for the species. ### An Alternative Hypothesis: Less Sea Ice, More Foraging Habitat Rather than assuming that sea ice loss is detrimental to walruses, the evidence supports an alternative hypothesis: that a **reduction in sea ice** actually **expands the foraging habitat** available to walruses. As sea ice retreats, previously inaccessible areas of the continental shelf become open for exploration, allowing walruses to access **bountiful food sources** that were once under thick ice cover. This would increase the overall **carrying capacity** of the region, not reduce it. To assess whether the carrying capacity of walrus habitats has truly declined, we need to consider four key factors: 1. **Population Pressure on Prey**: Carrying capacity will decline if the walrus population becomes so large that it depletes its prey base, creating competition for dwindling food sources. However, there is no current evidence of overpopulation or a collapse of prey species that would suggest nutritional stress among walruses. 2. **Marine Productivity**: Carrying capacity will decline if there is a significant reduction in marine productivity, meaning less food is available in the ecosystem. While some areas of the Arctic may experience localized declines in productivity, the expansion of **open water** and the upwelling of nutrients associated with sea ice retreat can enhance productivity in other regions, creating more foraging opportunities for walruses. 3. **Extent of Foraging Habitat**: Carrying capacity will decline if the area of potential foraging habitat shrinks. On the contrary, as sea ice retreats, the **areal extent of foraging habitat** on the continental shelf has expanded, giving walruses access to new regions rich in benthic prey. 4. **Access to Foraging Habitat**: Carrying capacity will decline if walruses’ access to foraging habitats is reduced. Far from being trapped on land, walruses have shown remarkable adaptability in using both land and ice as haulout locations, and their access to foraging grounds appears to have improved as new areas open up. ### Evidence Supporting Increased Carrying Capacity NOAA’s assertion that the overall carrying capacity of walrus habitat is “almost certainly declining” due to sea ice loss does not hold up against the growing body of evidence suggesting that walrus populations are increasing and thriving. Several key studies provide evidence that walrus populations are adapting well to their changing environment: - **Historical Data**: Fay’s studies on the **Pacific walrus** document that walrus populations grew alongside an increased use of land-based haulouts, undermining the idea that land haulouts are inherently dangerous for the species. Walruses have been using both sea ice and land as resting platforms for centuries, and their ability to switch between the two suggests flexibility rather than vulnerability. - **Svalbard Archipelago**: The **Barents Sea** population’s 48% increase over six years, coinciding with a shift to land haulouts due to sea ice retreat, directly contradicts the assumption that declining sea ice reduces walrus habitat. If sea ice loss was indeed harmful, we would expect to see population declines rather than explosive growth in this region. - **Increased Calf Survival**: In the Pacific, the rising number of **calves per cow** and improved **calf survival rates** are both indicators of a **growing, healthy walrus population**. These positive population trends undermine NOAA’s assertion that declining sea ice is leading to a reduction in the region’s carrying capacity. ### Conclusion: NOAA’s Misleading Narrative By focusing on an unproven hypothesis that links sea ice decline with decreased walrus survival, NOAA’s 2015 Arctic Report Card has misled the public about the true state of the **Pacific walrus population**. Instead of presenting a balanced view that considers the full range of scientific evidence, NOAA downplays indicators of a growing walrus population and overstates the impact of sea ice loss. The available evidence suggests that the **carrying capacity** of walrus habitats has likely increased, not decreased, as sea ice retreats and opens up new foraging areas. Walruses are not only surviving in these changing conditions; they appear to be thriving, as shown by rising population numbers and increased calf survival rates. To ensure the public is well-informed and policies are based on sound science, it is essential that organizations like NOAA recognize the uncertainties involved in complex ecological systems and offer a full range of hypotheses when presenting their findings. The resilience of walruses in the face of changing ice conditions is a testament to the adaptability of nature, and it deserves to be understood and appreciated in its full context.