Climate change inevitable
There is now clear evidence that the global climate is changing and that current trends will continue for many years. This has for example been documented in the Assessment Reports from the Intergovernmental Panel on Climate Change (IPCC) and in the 2004 Arctic Climate Impact Assessment (ACIA) commissioned by the Arctic Council. The changes are a response to earlier greenhouse gas emissions, and we must therefore combine adaptation to climate with finding ways of cutting emissions now and in the future.
According to scenarios for climate change in Norway, we can expect the annual mean temperature to rise by 2.3–4.6 degrees by 2100. The growing season is also expected to become 1–2 months longer in most lowland areas and 2–4 months longer in most high-mountain areas. In much of the country, the growing season is already 2–3 weeks longer than it was in the 1980s.
Changes already apparent in Norway
Many changes have already been observed in Norway as temperatures rise on land, in freshwater and in the sea. Migratory birds are arriving earlier in spring; for example, pink-footed geese are now moving northwards about two weeks earlier than in the 1990s.
Other observations show that animals are reaching sexual maturity more quickly; production and reproduction rates are higher; trees are coming into leaf earlier; salmonids leaving rivers for the sea are younger; and the spawning areas used by fish in the sea are changing. Some habitat types are also at risk. Palsa mires are being lost as the permafrost thaws. These are peat bogs dotted with hummocks with a core of ice, and are globally threatened.
According to regional and local climate scenarios developed for Norway, future climate change is expected to result in change in all habitat types. The precise effects will be determined by complex ecological interactions, and by the combination of climate change and other factors such as overgrowing of open habitats, construction and development, and pollution.
Northerly shifts in species distribution
Climate change is expected to result in changes in species composition in Norwegian ecosystems. Rising temperatures will enable species from further south to expand into areas where the climate was previously too cold for them. For example, several new bat species are likely to become established in Norway.
On the other hand, there will be less suitable habitat for species that are adapted to a cold climate. Species that are already near the edge of their distribution range will be particularly vulnerable and may not be able to survive in Norway. The total number of species in Norway may well increase, but overall biodiversity may nevertheless decrease if distinctive habitat types are lost.
Other species will be able to expand in Norway as conditions become more favourable. For instance, a milder climate and less snow in the lowlands will probably allow roe deer and certain bird species to spread to new areas.
Alien species may find a foothold
A milder climate will also make conditions more suitable for a number of alien species, making it easier for them to survive, spread and become established in Norway. Worldwide, invasive alien species are considered to be the second most important threat to biodiversity, behind land-use change. Steps to prevent the spread of invasive alien species will therefore be vital as the Norwegian climate changes.
With a milder climate and longer growing season, the volume of standing wood in Norwegian forests is expected to increase more rapidly. The total area of forest is also expected to rise, and there will be a larger proportion of tree species that prefer a warmer climate.
Trees may become more vulnerable to insect and fungal pests as the mean temperature rises and rainfall and snowfall patterns change. An increase in the abundance of certain types of mosses and lichens has already been observed in Norwegian forests, and is explained by the temperature rise and lengthening of the growing season that has already taken place.
Threat to salmon and trout stocks
A number of the freshwater ecosystems in Norway are naturally species-poor and are found hardly anywhere else in the world. Many of these are likely to change in character as the climate warms. A rise in biological production and changes in the species composition of the plankton are expected in response to higher water temperatures and more runoff from agricultural areas. These changes will affect whole food chains in rivers and lakes and may lead to eutrophication and excessive plant growth.
Species that prefer warmer water may spread at the expense of cold-water species. The Arctic char is highly adapted to low water temperatures and may find conditions particularly difficult. In addition, climate change may allow various fish species, including salmon, to spread to more northerly areas that were previously unsuitable because the water was too cold.
Warmer and more acid seas
A warmer climate is likely to have major impacts on Norway’s seas. As the sea temperature rises, some species will expand northwards and others will move in from further south.
Researchers are already seeing signs of change in plankton distribution. This will have repercussions for many other species as their food supplies are affected. For example, the survival rates of fish larvae may be altered, which could have serious impacts on many fish species, and indirectly on fish-eating seabirds. In the long term, there is also a risk that ocean current patterns will change. The impacts of this are unkown.
One effect of the rising concentration of CO2 in the atmosphere is that the oceans are becoming more acidic. They absorb about one quarter of all anthropogenic emissions, and over the past 100 years the pH of seawater has dropped by about 0.1 pH units. Acidification will continue and may have serious impacts on all animals with calcareous skeletons or shells, for example corals.
Pressure on mountain areas
As the temperature rises, species distribution will shift upwards as well as northwards. Observations show that a number of plant species have expanded upwards in the Norwegian mountains since the 1930s, and the treeline is also expected to shift upwards.
This is likely to put pressure on species that already occupy mountain habitats. In the longer term, it is expected to threaten the survival of species that are strongly associated with alpine and arctic ecosystems, because of a combination of habitat loss and competition from new species.
For example, Arctic fox are dependent on tundra and high-mountain habitats. They are also facing increasing competition from red foxes, which are expanding upwards. In addition, Arctic foxes feed mainly on small rodents and will be affected by changes to their population cycles resulting from climate change.
Milder and wetter winters may have serious impacts on wild reindeer. Ice formation on winter grazing areas is likely to be more frequent, and areas of suitable habitat will shrink as the treeline shifts upwards.
More rapid loss of open landscapes
Mechanisation and the introduction of intensive farming resulted in drastic changes in the agricultural sector during the twentieth century. Large areas of pasture and meadow are no longer actively managed, and are gradually being invaded by scrub and woodland. Climate change is reinforcing this tendency.
In many parts of Norway, the character of traditional agricultural landscapes has already changed considerably as they become overgrown. This is a threat to the high biodiversity often associated with these habitat types. For example, many areas of coastal heathland, which were once valued as pasture, are being lost to scrub and woodland. Pasture and hay meadows at many mountain summer farms have also been abandoned and are therefore threatened.
Climate change appears to be speeding up these processes even further in some parts of Norway. In North Norway, scrub and woodland are spreading more slowly, but the changes are nevertheless marked. As the growing season lengthens and biological production increases with climate change, open habitats will change even more quickly.
We know relatively little about the impacts of climate change on species associated with cultural landscapes. There may be various indirect effects : for example, a longer growing season may make it possible to cultivate crops on areas of traditional hay meadow or pasture in the mountains that currently support high biodiversity. A warmer climate may also make it possible for farmers to take a third cut from grassland or to cultivate corn at higher altitudes than today.
Major changes in the Arctic
In general, climate change is expected to have greater impacts on species and ecosystems in the Arctic than further south. In 2010, the NorACIA project (Norway’s follow-up of the Arctic Climate Impact Assessment) published a report describing how far-reaching the changes may be in the Norwegian part of the Arctic, in other words the Svalbard archipelago and parts of North Norway.
The extent of the sea ice is shrinking, which is a threat to a wide variety of ice-dependent species – from seals and polar bears to seabirds and ice algae. Ocean acidification is projected to be particularly marked in northern waters, partly because the water is colder and can absorb more CO2 than further south. Rising sea temperatures will result in shifts in the distribution of plankton species, and perhaps in food shortages for many Arctic fish species.
No more skiing?
Climate change will also have major consequences for outdoor recreation. Snow cover will not last as long, and opportunities for skiing will be much more restricted, especially in the lowlands. This will add to the pressure to develop ski centres, trails and other facilities in the mountains. Svalbard and other Arctic areas are also expected to become increasingly attractive destinations and will be under more pressure as well.
In the lowlands, climate change will result in restrictions on public access. Cultivated fields and farmland are open to walkers and skiers in winter, but only when the ground is frozen or snow-covered.
With a milder climate, vegetation will grow faster and scrub and woodland will encroach on open areas, which is likely to hinder access to paths and block viewpoints. As a result, many areas may become less attractive for outdoor recreation and tourism. Higher precipitation is likely to make paths and vegetation more vulnerable to erosion and landslides.
The bathing and boating season will probably be longer in Southern and Eastern Norway, where the scenarios predict dryer and warmer summers. However, there may also be periods of drought and greater pressure to allow building along undeveloped stretches of coastline.
Hunting and fishing legislation may need to be amended as the distribution of various species shifts or the timing of the breeding season changes. And as new species become established in Norway, some may be classified as game species that can be hunted.