Marine Heatwave Devastates Alaska’s Common Murre Population

The common murre population in Alaska has faced a catastrophic decline due to an extreme marine heatwave linked to climate change. This event, which unfolded between 2014 and 2016, resulted in the loss of nearly four million seabirds, representing about half of the global murre population. Researchers from the United States Fish and Wildlife Service and partners documented this unprecedented wildlife mortality event, marking it as the largest in modern history.

Impact of Climate Change on Marine Ecosystems

Climate change has led to rising ocean temperatures. These changes can result in severe and lasting impacts on marine ecosystems. The heatwave in Alaska caused alterations in the availability of forage fish, crucial for the survival of seabirds like the common murre. The study indicates that such temperature increases could lead to permanent changes in marine habitats.

Population Decline of Common Murres

Before the heatwave, Alaska had an estimated eight million common murres. This number represented about 25% of the global population. The study monitored 13 colonies and found a staggering decline of 52-78% in murre numbers during the heatwave. Approximately 1.28 million murres died in the monitored colonies alone, with an extrapolated total loss of four million across all known colonies.

Breeding and Foraging Behaviour

Common murres are adept divers, capable of reaching depths of 200 metres to forage for small fish and krill. They primarily breed in the Gulf of Alaska and the Eastern Bering Sea. The study revealed that about 80% of the murre population bred in these regions. The decline in forage fish availability led to mass starvation, which contributed to the population drop.

Broader Ecological Consequences

The effects of the heatwave extended beyond common murres. Other species, such as Pacific cod and humpback whales, also faced population declines. Pacific cod numbers fell by nearly 80%, leading to fishery closures. Humpback whales saw a 20% decrease in their population, attributed to reduced food availability. These changes indicate a broader ecological imbalance that may have long-term consequences.

Absence of Recovery

Seven years post-heatwave, many of the common murres have not returned to their colonies. Although some birds that skipped breeding during the heatwave have reappeared, number remain absent. The lack of recovery raises concerns about the future of this species and the health of marine ecosystems in Alaska.

Research Findings and Future Implications

The study concluded that the sudden decline in forage fish quality and quantity was a primary factor in the mass mortality of common murres. The findings suggest that the decline of such a widespread top predator could signify a new ecological threshold in response to global warming. This event marks the urgent need for understanding and addressing the impacts of climate change on marine wildlife.

Questions for UPSC:

1. Critically discuss the long-term ecological impacts of marine heatwaves on seabird populations.
2. Analyse the relationship between climate change and the decline of fish populations in marine ecosystems.
3. Examine the consequences of reduced biodiversity on marine food webs and predator-prey dynamics.
4. Estimate the potential economic impacts of declining marine species on local fishing industries and communities.

Answer Hints:

1. Critically discuss the long-term ecological impacts of marine heatwaves on seabird populations.

1. Marine heatwaves cause mortality events, as seen with the common murre population decline of nearly four million birds.
2. Long-term impacts include shifts in breeding patterns and potential changes in habitat suitability for seabirds.
3. Alterations in prey availability due to heatwaves can lead to mass starvation and reduced reproductive success.
4. Persistent ecological imbalances may result in the loss of top predator species, affecting overall ecosystem health.
5. The absence of recovery in seabird populations indicates potential permanent changes in marine ecosystems.

2. Analyse the relationship between climate change and the decline of fish populations in marine ecosystems.

1. Climate change leads to rising ocean temperatures, which disrupt fish reproduction and survival rates.
2. Marine heatwaves can cause drastic declines in fish populations, as evidenced by a nearly 80% drop in Pacific cod numbers.
3. Changes in ocean temperature affect the distribution and abundance of forage fish, crucial for seabird and marine predator survival.
4. Reduced fish populations can trigger fishery closures, impacting local economies and food security.
5. Overall, climate change creates a feedback loop that exacerbates the decline of marine species and ecosystems.

3. Examine the consequences of reduced biodiversity on marine food webs and predator-prey dynamics.

1. Reduced biodiversity can destabilize marine food webs, leading to imbalances in predator-prey relationships.
2. Declines in top predators, such as common murres, can result in overpopulation of prey species, disrupting ecosystem dynamics.
3. Loss of species diversity reduces ecosystem resilience, making it harder for marine environments to recover from disturbances.
4. Alterations in species composition can lead to shifts in nutrient cycling and energy flow within marine ecosystems.
5. Overall, decreased biodiversity threatens the health and sustainability of marine ecosystems, impacting all trophic levels.

4. Estimate the potential economic impacts of declining marine species on local fishing industries and communities.

1. Declining fish populations can lead to reduced catches, directly impacting local fishing industries and livelihoods.
2. Fishery closures, like those seen with Pacific cod, can result in job losses and economic downturns in coastal communities.
3. Decreased availability of seafood can lead to higher prices and reduced food security for local populations.
4. Long-term declines in marine species may deter tourism, further exacerbating economic challenges in coastal regions.
5. Overall, the economic impacts of declining marine species can ripple through communities, affecting multiple sectors and livelihoods.