Climate change is causing profound changes in the Southern Ocean and could threaten the future of some species there, according to a study published in July 2019 in the Annual Review of Marine Sciences. The Southern Ocean is home to abundant wildlife and provides critical functions for life on Earth, for example by absorbing significant amounts of greenhouse gases.
In one example of the impacts caused by climate change, the study found that the range of Antarctic krill, a crustacean that underpins the region’s marine food web, has shifted more than 400 kilometers south since the 1970s—a move that could threaten the species that depend on krill.
The expert assessment suggests that Sub-Antarctic islands such as South Georgia and the South Sandwich Islands (SGSSI) are particularly vulnerable because of the abundance of range-restricted and endemic species living there—animals that cannot move to a more suitable home when their habitat becomes inhospitable.
The work concludes that a network of marine protected areas (MPAs) in the Southern Ocean surrounding Antarctica would be an effective, immediate way of protecting the biodiversity in this region and could help the ecosystems build resilience against the changing climate over time. As one of the top priority regions for protection in the Southern Ocean, the biodiverse SGSSI, which is home to a quarter of the world’s penguins, should be fully protected now to help ensure that the impacts of climate change in this sensitive area are, at the very least, not worsened by human activities such as fishing.
To learn more about one of the most comprehensive studies of climate change effects on these types of remote marine environments, The Pew Charitable Trusts interviewed the study’s lead author, Alex Rogers, professor of conservation biology at the University of Oxford. This interview has been edited for clarity and length.
Q: What are the key findings of this study?
A: The main findings are:
- That some elements of the Antarctic biota are likely to suffer negative consequences from climate change, especially ice-dependent species like some of the seals, and small-range endemic coastal and shallow-water species, such as those found in Sub-Antarctic islands like South Georgia. These include species like the orange notothen, Trematomus vicarious, only found to date in Cumberland and Stromness bays, and a few other sites around South Georgia. Other species, such as gentoo penguins, may increase their abundance and geographic range because of climate change—but overall, the impact is likely to be negative in terms of the health of the Southern Ocean ecosystem.
- The effects of climate change in the Antarctic are highly region-specific.
- The changing climate in the Southern Ocean is likely to increase access to some goods and services for humans (e.g. tourism, expanded fishing grounds, and mineral resources, although exploration of the last is banned under the Antarctic Treaty). However, at the same time we are seeing a loss of endemic biodiversity. The Antarctic therefore represents a challenging management scenario where rising pressure to exploit resources is combined with climate impacts that in turn may accelerate the loss of biodiversity. As such it is crucial that human activities that affect biodiversity remain actively managed into the future.
- The Southern Ocean is still difficult to model, and there is a need for increased oceanographic and biological observations.
Q: What surprised you about your findings?
A: The separation of endemic biodiversity from ecosystem function, was quite surprising. It is assumed that biodiversity is positively correlated with ecosystem function. In this case, though, the overwhelming influence of changes to the physical environment, especially reduced duration and area of ice are driving change, which actually results in increased productivity, such as nutrient upwelling. Even though this appears to be a benefit, it is, in fact, a redistribution of these nutrients, and as a result some Antarctic fauna may decline or become wiped out as their living conditions change. These animals may be replaced by others, perhaps even species moving from lower latitudes, fundamentally changing Southern Ocean ecosystems.
Q: Which species do you think will be most affected by climate change in the South Atlantic and Southern Ocean?
A: Ice-dependent species, such as seals living on pack ice, Adélie penguins, and perhaps minke whales. Also, low-range endemic species, such as the fish, the orange notothen, and a range of invertebrates including molluscs, ascidians, and crustaceans from some of the Sub-Antarctic islands, are especially vulnerable to changes in physical conditions and to displacement by species expanding their distribution southward. There may also be interactions between different human activities, such as fishing or tourism, and the negative impacts of climate change on the ecosystem, which could accelerate the decline of these species.
Q: What can be done to help conserve this environment?
A: First, researchers, like me, need to know more. The lack of information on the physical environment and of biodiversity in the Antarctic hampers our understanding of change in the system, especially since we have no baselines for many biological communities. With better data we can monitor change in Antarctic marine ecosystems more effectively, which will allow management decisions to be made that reduce the impact on species vulnerable to climate change.
Q: What specific measures could be applied to South Georgia and the South Sandwich Islands (SGSSI)?
A: South Georgia and the South Sandwich Islands are special as they host large populations of marine predators and have an unusually high number of endemic species—those that have not been recorded elsewhere. We know these islands are in the forefront of climate change impacts with the majority of glaciers in retreat on South Georgia and changes in the relative abundance of some penguin species around SGSSI. Because there is a high proportion of species that have their southernmost or northernmost range at these islands, the islands are ideal for monitoring the effects of climate change on species distribution. Some believe the combination of climate change and industrial fishing are having negative impacts on Antarctic krill. Therefore, I believe that the waters of SGSSI should be designated as no-take marine protected areas, with other activities such as tourism carefully managed to prevent further direct impacts. In fact, the islands are so special given their unique geology and spectacular wildlife populations, I believe they should be afforded UNESCO World Heritage status.
Q: What research are you undertaking next in this region?
A: I am currently outlining the research program related to climate change for REV Ocean, a nonprofit ocean conservation foundation. Because of the importance of the Southern Ocean in uptake of CO2, it will be one of the major geographic targets for our research. This will focus on how the Southern Ocean is changing with climate change, especially where this may have positive or negative feedbacks to uptake, and hence to atmospheric CO2. It will also focus on how climate change is impacting the biota of the Antarctic, and what management strategies may best mitigate the effects of climate change and other human impacts. The mesopelagic zone [roughly 200 to 1,000 meters (660 to 3,300 feet) in depth], which may become a target for fishing but which is also potentially extremely important in the global carbon cycle, will also be a focus for research.