As discussed in other chapters of this report, several aspects of the impact that human activities have on the ecosystem are clearly manifested and visible or will likely become so in the near future (see chapters General background description of the ecosystem - Ecosystem interactions - Human impact; Current and expected state of the ecosystem - Human activities /impact and Current and expected state of the ecosystem - Conclusions about state of the ecosystem). Other aspects may become visible longer time into the future, and this is the topic of the present chapter.
The issues focused here are broad impact on the ecosystem from climate change (Current and expected state of the ecosystem - Some aspects of possible long-term future changes in the ecosystem - Future climate change and its effects on the ecosystem and human activities) and ocean acidification (Current and expected state of the ecosystem - Some aspects of possible long-term future changes in the ecosystem - Possible effects of ocean acidification), fishery induced evolution in maturation in Northeast Atlantic cod (Current and expected state of the ecosystem - Some aspects of possible long-term future changes in the ecosystem - Evolutionary effect of fishing on maturity in cod) and changes in pollution caused by climate change (Current and expected state of the ecosystem - Some aspects of possible long-term future changes in the ecosystem - Effects of climate change on pollution). It should be underlined that this is not a complete list of potentially important long term changes. Putting up such a list would be a major undertaking that would go beyond the scope of this report. For example, fisheries may have long term effects on the ecosystem beyond what is discussed here and risk of accidental discharges from ship traffic and oil and gas activities may change considerably with increases in these activities. In addition, it should be acknowledged that our knowledge about future impact is limited. For example, until recently, ocean acidification was rarely considered an important factor, yet today it is considered a driver that may have profound effects on marine ecosystems.
As is known from previous reports (e.g. Loeng 2008), climate change may have considerable impact on the Barents Sea ecosystem. Some of these effects may already be visible in the ecosystem (see chapter Current and expected state of the ecosystem - Conclusions about state of the ecosystem). Effects may be large also from ocean acidification, but the uncertainty associated with this is much larger than for climate change effects. Fishery induced evolution may be responsible for a decreasing trend in onset of reproduction of cod that has been observed for several decades. If the trend is indeed an evolutionary response, it may continue and affect the reproductive potential in the cod stock and the role of cod as an important predator in the ecosystem. Climate change may cause increased input of pollution to the Barents Sea, and some signs of this may already be visible.
