Scenario analysis using the framework
Despite the uncertainty about the likelihood of the scenarios studied and how they may combine, they reveal only three types of impacts on economically important fisheries: (1) an increase in targeted fish stocks, (2) an increase in crab stocks associated with a decrease in fish stocks, and (3) a decrease in crab and fish stocks. In the scenarios where most wild species would decrease, aquaculture may become an alternative for livelihood and food production. However, food originating from substantially decreasing fish stocks may become more expensive and growing conditions for the cultivated species in a new environment with warmer and potentially more acidic water may not be optimal (Troell et al.
2017).
Examining jointly both scenarios of focus reveals that competition from red king crabs with associated increased predation pressure on capelin larvae could further reinforce a decreasing trend in fish stocks from a shift in
Calanus species (Mikkelsen
2013). Such predation occurs already and is likely to increase unless negative impacts on crab survival, for example from ocean acidification, outweigh the advantage of increased water temperature for crab expansion. Simultaneously, activities like transportation, tourism and resource extraction will generate more pollution in Arctic waters (Nordam et al.
2017) and atmosphere (Law et al.
2017). Differences in physiology (Scott et al.
2000) between
Calanus species may generate different responses to the expected increased water pollution, an aspect that Ellingsen et al. (
2008) do not account for in their simulations.
The economic implications for fishermen would depend on the size of the decrease in fish stock, whether invasive species like crabs could be profitably fished, whether change in zooplankton also affect these species, and whether alternative activities are available to fishermen, in case fishing becomes unprofitable. The overall effect on fish stocks and fisheries depends on the size of these changes in relation to large natural variations in the Arctic seascape. Fisheries are exposed to substantial price variations that may impact the sector more than the large, but expected, variations in the ecosystem (Eide
2008,
2017; Troell et al.
2017).
Most impact assessment studies (e.g. ACIA
2004) showing increases in fish stocks account only for the
direct impacts from global warming on fisheries, through changes in water temperatures and other oceanographic changes. Analysing the
indirect impacts, using the
IEBM framework, reveals that climate change could put synchronised pressure on different parts of the system, which all separately lead to potential downward trends in fish stocks. Hence, extremely low fish stocks relative to natural variation could become a more frequent reality if the extremes of all these different trends happen to align.
Moreover, spin-offs from climate change impacts in other parts of the world will likely affect economic and governance systems in the Arctic. For example decreasing fish stocks in the rest of the world combined with collapse of agricultural activities in some regions (IPCC
2014) is likely to increase demand for Arctic fish stocks, leading to price increase and thus incentives to fish more.
Having identified these important links qualitatively, through expert knowledge elicitation, the next steps would be to quantify the impacts of each scenario on all parts of the system. The information provided in our framework could facilitate such an exercise by highlighting non-obvious dynamic social, economic and ecological links that need to be included.
A thorough quantification exercise requires substantial baseline data and data on how much changes in stocks of zooplankton, pollutants, invasive species, among others, are likely to alter the system. This is costly and time consuming. The IEBM framework helps in separating destabilising dynamics (positive feedbacks) from dynamics that stabilise the system (negative feedbacks), thus identifying potentially risky situations, like when multiple, seemingly independent, processes reinforce each other and risk to move the system towards a new trajectory. For example, a decrease in Calanus, due to pollution, could coincide with substantial crab invasion, while ocean acidification remains at a manageable level for the crabs, potentially leading to fish stock collapses. The framework could also provide guidance on how to prioritise which additional information should be collected, in particular, which variables to monitor regularly.
Pathological dynamics in climate change scenarios
Examination of Fig.
1 in the
IEBM framework reveals that the
long fuse big bang dynamics, leading to a shift in primary production studied in scenario 1, could change food chain interactions in the Arctic marine food webs (Corten
2000; Søreide et al.
2008), triggering another
PD called
unforeseen processes (Peterson et al.
2017). Changes in food webs and ecosystem composition, in response to geophysical changes associated with climate change, are uncertain, but could have substantial impacts on the stocks of commercial fish species. The difficulty of anticipating such changes makes an appropriate social response challenging.
In scenario 1, dynamics during the regime shift may become too rapid to control through governance or management, creating a process of
rapid social–
ecological evolution (Fig.
3b; Peterson et al.
2017). The main difficulty is to address the speed of social–ecological innovation, and improve the rate and ability of social–ecological system to adapt to rapid change. For example, if
Calanus finmarchicus becomes rapidly the dominant zooplankton in the Arctic, and this change triggers a substantial drop in the main commercial fish stocks, the economic activities linked to these fish stocks and the institutions that regulate them may not be able to react quickly enough to the ecological change, leading to inappropriate management.
All three PDs mentioned exhibit missing or delayed feedbacks between social impacts and governance. They all possess problematic links between human actions, ecological impacts and social impacts because these are either lagged, too rapid or unexpected.
In contrast, scenario 2 reveals common dilemma dynamic, which happens when the incentives shaping agents’ behaviours do not align with the collective consequences of their actions. Key features are substantial mobility or spatial diffusion of the resource and expectations about other people’s behaviour. This scenario could also trigger unforeseen processes.
Peterson et al. (
2017) identified two potential solutions common to
long fuse big bang,
unforeseen processes and
rapid evolution. These are
monitoring and
reduced pressure on the environment.
Monitoring is also a potential solution to
common dilemmas. The Arctic Council has emphasised the need to better monitor the Arctic through its working group “Arctic Monitoring and Assessment Programme”.
Monitoring by collecting information about complex ecosystem dynamics would improve understanding of the problematic links present in all four
PDs. Such understanding could reveal early warning signs of impending change, and provide incentives for more prosocial behaviour. The
IEBM could help prioritise among possible monitoring activities.
In contrast,
reduced pressure on the environment is a precautionary approach to management that would decrease the risk of operating in poorly understood, underexplored environments. Precaution has been previously advocated when managing systems with endogenous risks of abrupt changes affecting system dynamics (Polasky et al.
2011b).
Scientific research and strengthening institutional linkages are common solutions to rapid evolution and unforeseen processes. Scientific research would help understand the complex food chain processes involved in a shift between Calanus species and thus maybe identify potential interventions, while strengthening institutional linkages would improve the likelihood to be able to observe and address unusual change in species interactions in a coherent way. Strengthening institutional linkages could also help address common dilemmas.