Wrapping up (2)

This is the penultimate post! (please, don't cheer too loudly). For the second half of the review (click here for the first part), I'm going to briefly consider some of the more tricky questions about the Arctic about the future. Of course, any answers are only based on past experience. It's impossible to tell what path environmental change in the Arctic will take, especially with the added complication of people who are even more unpredictable than the environment. So, here goes...

What is the likely impact of future human activity on aquatic and terrestrial arctic ecosystems?

It's only possible to extrapolate from what we know, meaning it's likely the changes seen in the past few decades are likely to continue. Also, natural systems exhibit lagged responses, especially when organisms take decades to grow. For example, shifts seen in aquatic ecosystems are very significant as they respond quickly to temperatures. Alterations to terrestrial vegetation, on the other hand, are slow, meaning the small changes evident in the past few years are probably responses to warming a few decades ago. Therefore, it's likely that aquatic communities will continue to shift with changing patterns of ice cover and benthic vegetation, woody (and perhaps even large vascular plants) will expand in extent, permafrost will melt and temperate organisms will begin to move north.

This is also a good point to bring up all the papers which I haven't had time to bring up, but indicate the potential for future changes in the Arctic as extrapolated from that seen in recent decades. In a great review article, Post et al. (2009) provided a short account of ecological responses to Climate Change in the Arctic. Changes with significant potential include range shifts (seen in moths), invasive species and phenology (see graph below).

Earlier flowering in Greenland (direct from Post et al., 2009)

Such movements in seasonality become problematic when there's a mismatch between producers and consumers. For example, a growing difference was observed between peak Caribou births and peak productivity of
the plants they consume by Post (2008). Patterns such as this are likely to increase in the future, and we're likely to become more aware of other such changes with future research. 

Of course, there are things which it's impossible to forecast, such as the possibility of oil prospecting in the Arctic, or development of tar sands in Canada. Or, positive warming feedback mechanisms could kick-in before anyone expects. In short, there's no way of telling, so it's wise to be cautious. 

Will changes in the Arctic have an effect on the global climate? 

Probably. It's generally accepted that falling sea-ice and snow cover throughout the Arctic will decrease albedo, meaning more warmth is absorbed that would normally be reflected. Arguably, melting permafrost has gained the most media attention in this area in recent years, especially when it was calculated that the tundra had become a source of carbon for the first time during the 1980s. When I looked into it though, I found that there are a number of developments which have slowed tundra carbon release down, such as the increased carbon uptake of vegetation through shifts in species assemblages. Therefore, I concluded that the potential for rapid runaway feedbacks because of permafrost melting were worrying, but probably overstated. The impact of carbon releases depends on the rate at which vegetation begin to use it, which is very difficult to predict.

Another possible but lesser-known feedback is through vegetation changes. Increase in ground cover or changes in dominant species alters both albedo on land, carbon cycling and GHG exchange. As a more interesting example, shrubs promote deeper layers of snow to settle, meaning soil beneath is insulated and therefore warmer, promoting nitrogen fixing microbial activity. Increased levels of nitrogen promotes further shrub growth, meaning expansion of shrubland could have positive feedbacks.

Despite all this, environmental mechanisms in the Arctic are relatively unknown as conditions for study are difficult, causing vast gaps in knowledge. Therefore, problems appear when it comes to modelling and forecasting impacts of climate change. However, it's pretty certain that any changes in the Arctic will affect the global climate, so we should be concerned about the relatively small (relative to what's expected in the future!) changes we're seeing at the moment. It's just a question of how quickly things will advance from here.

More on why we should be concerned in the next post!