Action required: Climate change impact on ocean giants
Sir David Attenborough’s latest film, Ocean, is a compelling paean to the seas and their myriad wildlife. Inspired by this, two UN Scientific Councillors working for the Convention on the Conservation of Migratory Species of Wild Animals (CMS) make a plea for supporting whales, dolphins and porpoises. Their work is included in a UN Climate Change Expert Workshop Report published this week.
Mark P Simmonds and Des Thompson
We live in a time of great change with growing concerns about the effects of climate change on wildlife. Whilst concerns have tended to focus on terrestrial systems, the effects in the marine environment are every bit as real and damaging to marine ecosystems. These include warming of surface waters, altered ocean currents and deoxygenation.
Marine species have long been predicted to respond to changes by shifts in their geographical location. Moving poleward is increasingly reported. A recent systematic review of the literature reported changes in beluga whale (Delphinapterus leucas) distributions in the Arctic and a significant increase in the sightings of humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus) and common minke whales (Balaenoptera acutorostrata) in the sub-Arctic. Additionally it showed sperm whales (Physeter macrocephalus) and orcas (Orcinus orca) becoming more frequently encountered in Arctic waters. Outside of the Arctic, there is also published evidence of distributional shifts in fin whales and Bryde’s whales (Balaenoptera edeni) towards the poles.
Coming closer to home, research in the North East Atlantic has indicated northward shifts of cetacean species concurrent with shifting prey and/or increasing sea surface temperature (SST). This includes fin whales off Norway and blue whales (Balaenoptera musculus) and potentially minke whales off Iceland. The strandings records of cetaceans in the British Isles have recently been interrogated to see if they show changes too. Modelling indicates an increase in the proportion of stranded warm water adapted species over time across the UK. Another recent study shows a likely northward shift of minke whales.
Such shifts may facilitate the survival of the population concerned, but they may create new risks. For example, disease transmission through contact with different species, and new wildlife-human conflicts when populations come into contact with human activities that they did not previously encounter.
Vulnerabilities to climate change
Highly migratory baleen whales may be especially vulnerable to climate change because of their dependence on finding dependable blooms of planktonic animals in the polar regions in the spring. If these blooms fail or happen in their absence there would be implications for their nutritional status, health and ability to reproduce. They are also likely to be dependent on certain specific conditions elsewhere during their annual migrations. The complexity of these dynamic interactions remains difficult to study. As one researcher recently put it, ‘the vast spatio temporal scale(s) of ocean climate change, occurring across entire ocean basins and over decades, creates significant challenges for understanding and predicting impacts on baleen whales, whose biological imperatives of feeding, breeding and migration operate on more constrained seasonal and regional schedules’.
The International Whaling Commission (IWC) has been considering the implications of climate change for the 93 or so known species of cetaceans since the 1990a, and members of its working group on climate change recently reported into a workshop on this topic convened by the Convention for the Conservation of Migratory Species (CMS) on climate change held earlier this year in Edinburgh.
The three most immediately vulnerable big whale populations are likely to be:
- North Atlantic Right whales – because they are highly sensitive to climate change due to their small population and dependence on prey which are sensitive to temperature changes.
- Sub-Arctic Bowhead whales – Bowhead whales face prey shortages, and they, belugas and other ice-dependent species are vulnerable to ice retreat and loss of critical habitat.
- Gray whales – increased mortality in this species has been linked to poor body condition resulting from reduced prey availability.
Concerns were also highlighted for riverine species and populations, such as the boto or pink river dolphin, Inia geoffrensis, as changes in their environment may be swift, acute and deadly, including the drying up and fractionation of their habitat.
Generally, the consequences for cetaceans of climate change are predicted to be directly negative on their feeding and breeding areas. In addition, increased interactions with human activities, such as fishing, shipping and marine mining resulting from changes in distribution of both cetacean populations and human activities, are expected to be negative. For example, the retreat of the Arctic ice is allowing industrial activities and fishing activities in areas where they were previously rare or unknown.
How can we manage these new risks?
What are the best responses to try to address these new risks, given that the effects of climate change simply cannot be turned off?
At a local level, responses are typically focused on strategies that increase species or ecosystem resilience. For example, this might include reducing non‐climate stressors, such as fishing leading to bycatch and whaling or other cetacean hunting. Historically, the biggest threat to whales was commercial whaling, and whilst Japan, Iceland and Norway continue to take whales for profit, other threats are now of equal or even greater consequence for some populations, including entanglement in fishing gear, vessel strike, exposure to noise (e.g. from seismic exploration), toxins, pollutants and exposure to novel pathogens.
More rapid and dynamic implementation of marine mammal conservation actions is required to address unexpected climate change‐induced impacts in a timely fashion. It may even be possible to develop ‘climate‐ready spatial protection’ measures that adapt to moving distributions of krill and other prey and their whale predators. Viv Tulloch, an acclaimed expert in this field, calls for the development of ‘dynamic models of species’ potential range shifts that incorporate population and dispersal processes as well as ecological processes ‘in order to better assess climatic change impacts upon species’ relative extinction risks, and to develop conservation management strategies which can adapt to climate change.
Some key points emerging from the Edinburgh workshop
A number of key points for conservation of cetaceans were highlighted in the report of the Edinburgh CMS workshop:
- Climate change operates at large spatial and temporal scales, making it difficult to align research and conservation efforts accordingly. We need to match scientific processes with conservation actions to ensure effective management.
- Climate change operates at different scales impacting numerous jurisdictions, with few cetacean species’ distributions limited to only one international jurisdiction. This creates significant management challenges, particularly for Marine Protected Areas (MPAs), which may be too small and based only on current distributions. Many conservation actions remain too small-scale to encompass the full range of a species’ movements
- Research should prioritise long-term studies to capture climate change trends over time. Alongside temporal research expansion, spatially expanded conservation efforts are needed.
- Climate change studies should incorporate physiological changes in cetaceans to enhance predictive models. A more integrated approach should combine multiple data sources to ensure detailed and accurate assessments using process-based models.
- While spatial protection for large whales can be useful it must be adaptable to shifting distributions, be dynamic, and be capable of integrating transnational considerations.
Clearly, MPAs alone are insufficient. A more comprehensive strategy addressing multiple threats – including pollution reduction, bycatch mitigation, and habitat degradation amelioration – is necessary. IWC Conservation Management Plans are an example of a flexible management tool that can provide a framework for multiple states to work together on addressing threats to shared cetacean populations, as part of a resilience-based approach.
A final thought
Sir David Attenborough’s latest film, Ocean, is truly inspiring. Clearly, we need to transform the emerging science into policies and practices which make real differences. The science on climate change risks to whales and other cetaceans points to the clear need for increased surveillance, monitoring and conservation action. These top of the food chain migratory animals are beacons of hope or portents of despair – we need to ensure the former wins out.
