The effects of global warming are felt earlier in Arctic regions than elsewhere in the world. Now research shows that Arctic marine food webs can adapt to climate change — but the study authors warn that this impression of resilience may be false in the long term.
As climate change advances, many people have their eyes on the Arctic region. The Arctic is warming two to three times faster than the global average, requiring us to understand and mitigate the effects of climate change there earlier than elsewhere in the world. During this unprecedented change, the well-being of the ecosystems and people of the polar regions depends on Arctic resilience: the ability of the Arctic to cope with the change and adapt to it without losing the essential identity and function of the region. Writing in Nature Climate Change, Gary Griffith and colleagues1 report that Arctic marine communities are able to adapt to considerable environmental change, suggesting resilience to climate change impacts.
Estimating the resilience of entire ecological communities to climate change is difficult. Arctic food webs are generally dominated by relatively few key species, which together with highly variable climatic conditions makes them prone to environmentally driven fluctuations with cascading effects through entire ecosystems2. These food webs have shown substantial resilience to natural environmental variability2, but the climate change that is reshaping the Arctic now is happening faster than ever before. Climate change influences marine communities by altering species composition and relative abundances, potentially changing the food web structure considerably3. In combination with environmental drivers, these changes can decrease the community resilience to the extent where a food web abruptly shifts to a new state, characterized by different species interactions, community function and benefits to people. Such regime shifts are commonly hard to reverse. As climate change increases the likelihood of regime shifts in the oceans4, there is an urgent need to understand the resilience of the Arctic marine food web.
As the Arctic is the ‘ground zero’ for climate change effects, an Arctic glacial fjord called Kongsfjorden (Svalbard) provides a primary location for studying the impact of environmental change on Arctic marine ecosystems. Kongsfjorden is already experiencing ocean warming, decreasing sea ice and increased arrival of Atlantic species5. The responses of its food web to these ongoing changes can indicate the resilience of wider Arctic marine communities to future climate change5. Using food web data from both inside and outside Kongsfjorden, Griffith and colleagues apply statistical network modelling to investigate which core ecological processes (for example omnivory or generalism) give rise to observed food web structures6. Applying this method to annual food webs reveals shifts in food web function. A resilient food web is able to maintain its core ecological processes over time, despite changing conditions; a regime shift is indicated by a significant change in the core functioning, such as a shift to fewer ecological processes6.
Surprisingly, Griffith and colleagues detected that despite environmental and biological changes, the Kongsfjorden food web has maintained its core ecological processes for the past decade (2004–2016). That the food web has a capacity to adapt to greatly changing conditions suggests that Arctic marine food webs can withstand climate change effects without loss of core function. Although community-wide regime shifts were not detected, the results show that Kongsfjorden has experienced times of lower and higher resilience during the past 12 years, corresponding with the influx of unusually large volumes of warmer Atlantic water and continuing input of highly predated Atlantic species to the fjord, respectively. At present, Kongsfjorden shows signs of recovery from a period of lower resilience.
The concept of resilience is contextual, and indicators of resilience must therefore be interpreted carefully. The authors note that although the results demonstrate adaptive capacity, several factors will determine whether this detected positive trend in resilience can continue. For instance, many Arctic species cannot move further northward to avoid warming conditions, but within fjords, marine species can take refuge in the colder parts of a fjord. However, as warming continues, these cold refuges will shrink and set their marine communities up for a persistent collapse. Furthermore, to some species, changes in feeding interactions may mean a shift to less energy-rich prey. If the energy received from prey decreases, many species will experience a decline in body condition. With these examples, Griffith and colleagues warn that the detected resilience of Arctic food webs could be short-lived.
This work1 provides another piece of the puzzle in the quest to understand Arctic resilience to climate change3,7. By providing a warning that the detected food web resilience may be eroded by other Arctic changes, the results emphasize that complexity of the Arctic makes it challenging to forecast change. To a large part, the resilience of the Arctic as a region will depend on how climate effects and adaptations at different scales interact and affect each other: species, ecological communities, physical environment, local societies and global human community. At best, more adaptive Arctic systems can strengthen the resilience of less adaptive parts of the region. For example, local people can take additional pressure off species that are highly affected by climate change with rotational switching of resource use, if supported by regional and global policies8. On the other hand, climate responses may form reinforcing feedbacks that decrease the overall Arctic resilience: environmental degradation (such as weak sea ice) can reduce the ability of young people to learn local skills for living sustainably in the Arctic environment, or to perceive the need for climate mitigation8.
Understanding Arctic resilience to climate change requires multiple perspectives and research methods. Incorporating the findings of Griffith and colleagues1 into the wider literature, and continuing to investigate changes in Arctic marine food webs2,3,4, will provide much-needed lessons in how to strengthen Arctic resilience and, in so doing, strengthen planetary resilience to climate change7,9.
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Yletyinen, J. Arctic climate resilience. Nat. Clim. Chang. 9, 805–806 (2019). https://doi.org/10.1038/s41558-019-0616-4