Biodiversity is weakened by climate change

Climate change is on its way, and it cannot be avoided that nature will be dramatically affected. Several ecosystems will be thrown out of balance; vegetation and the tree line are moved to higher levels than before, and population changes in small rodents such as the lemur affect the populations of snowy owls and arctic foxes. Ocean currents cause the fish to change their spawning and migration patterns, which in turn affects the entire food web both in the sea and on land.

A historical retrospective
When the ice retreated in Norway 9-11,000 years ago and uncovered the seeds stored in the soil under the ice cover, many pioneer plant communities arose, which in turn became the basis for the further development of several ecosystems. The warmest period after the last ice age was 6–8,000 years ago, when the Jostedalsbreen (and all the other glaciers in Norway) had completely melted away. In this respect, the glaciers have been decisive for the design of the Norwegian landscape, through a cooperation of climatic, geological and biological processes. Colonizing plants also came by sea; soil was used as ballast in many cargo ships, and the soil was then dumped along the coast when the ships returned home with lumber and other goods from Norway. In this soil there were also seed and plant plants, of which 200 ballast plants have survived and become part of Norwegian flora.

Historically speaking, global warming and the colonization of new species is not a new phenomenon - what is new is the strength and extent to which climate change affects. The trend over the last 100 years has been somewhat uneven, but in the period from 1976 to the present day, global warming has been three times as fast as for the rest of the period. What significance does this have for our northern latitudes? In the long term, loss of biological diversity and environmental problems will be problems that affect globally – Norway included – and these processes and their underlying mechanisms are already well under way. But organisms, populations and ecological communities do not respond in a uniform manner to average global temperature increases. A clearer picture of reality only emerges when one takes a closer look at regional changes, and discovers an ecology that is clearly changing.

Changes in vegetation patterns
Increased rainfall and milder winters means that the tree line is in the process of moving both upwards and northwards, and some lichen species which constitute important winter grazing for reindeer are gradually being replaced by vascular plants. New doctoral research shows that such climate changes can result in significantly lower reindeer numbers and less reproduction, because the reindeer prepare for bad winters by building fat reserves rather than investing in raising calves. Reindeer is primarily important in meat production in northern regions, and the animal has a strong cultural significance. Several of our large predators have reindeer as prey, but as a species the reindeer is not currently threatened. In contrast, the lemur is a key species on the tundra and affects the entire system from vegetation to predators. When the winter conditions are right, the cavity under the snow cover is vital for the tree; here it can survive through the winter thanks to shelter from the elements, access to food plants and protection from predators. Changes in winter conditions will in all likelihood affect these rodent communities, which in turn will have ripple effects in the rest of the ecosystem. Proper loam years have not been observed since 1994, and it is already known that both arctic foxes, snowy owls and many other tundra predators stop breeding completely in years where there is little loam.

The effects of climate change on birds
The titmouse and black-and-white flycatcher are two songbird species that overlap in their distribution in Europe; they share the same forest habitat, exploit the same food resources and nest in the same types of nest holes and/or bird boxes. The breeding season of the two species also overlaps, but the titmouses consistently start earlier because they are resident birds and can begin the breeding period as soon as the local conditions are optimal. They can also take advantage of a good supply of food to produce a second litter in the same breeding season. Black-and-white flycatcher, on the other hand, is a migratory bird, and this species migrates from West Africa.

Research has shown that migratory species have a poorer ability than resident birds to adapt to climate change. As spring in Europe starts earlier and earlier in line with global warming, the latest arriving flycatchers run the risk of being completely out of step with the season and thereby failing to nest this year. These birds arrive at a time when the supply of insect larvae, which constitute the main food for the young birds, has long since passed its peak. This has meant that the population in some areas has decreased with 90% over the past 20 years. Competition for nest sites between titmouses and flycatchers may also become more acute due to climate change. Late-arriving birds find that the best nest sites have already been taken, and the rest of the area is very saturated with other birds. Many stragglers die trying to take over the nest site of a titmouse. Territory quality is so important to male flycatchers that they would rather take the chance of a risky hijack than choose an available nest site in a poorer habitat.

Seabirds that nest along the Norwegian coast are also affected by climate change. The puffin has only one young a year, and the survival of the young depends entirely on the availability of year-old small herring (mussa) that drift past Røst. A study that has been ongoing for more than 20 years documents that in the years when the blooms of phytoplankton occur in early spring, this has a negative impact on the feeding and rearing conditions for the herring larvae, which in turn affects the food supply for the puffins. This year (2009), the puffin was unable to obtain enough food for itself and its young out in the open sea, and none of this year's young survived the season. You have to go back to 2006 to find the last year when the grove produced young on Røst. An adaptation to this is that the puffin can live to a very old age, 25-30 years, but the poor supply of nutrients has been greater and more prolonged than is known from the "old days". Strong northerly winds may also have led to the herring wanting to spawn further out to sea. The puffin is now on the national red list of species in Norway with the status "Vulnerable". Seabirds that obtain their nutrition from the sea surface, such as the tern, are known to be even more sensitive to changes in nutrient availability than diving seabirds. Krykkje are monitored annually on Runde, Sklinna, Røst Hjelmsøy and Hornøy, as well as on Bjørnøya and Spitsbergen, and since monitoring began in 1980, a significant decline in the population has been recorded, which is presumably linked to poor access to food. Krykkje is also on the national red list with the status "Vulnerable".

The effects of climate change on fish
As the climatic variations between Iceland and the Azores (NAO) move towards warmer times, survival among cod in the Barents Sea decreases. The cod larvae are already at the upper tolerance limit of their temperature regime, and recruitment of the year classes is consequently poor in warm years. At the same time, overfishing the full-grown cod causes reproduction to fail at both ends. Global warming and an ocean temperature that is 1.5 degrees warmer than the long-term average mean that the cod does not spawn where it previously had its core areas, but moves north with the increase in temperature. It is to be expected that cod will largely disappear into the Russian sector of the Barents Sea, both in search of new spawning grounds, but also for the important feeding fish capelin, which also moves north. How does escaped farmed cod affect the remaining recruitment? Farmed cod has adapted to a life in the cage and rapid growth. These characteristics are largely genetically determined and will therefore have a negative effect on the coastal cod. The coastal cod is genetically programmed to survive in its natural environment, and because farmed cod escape and reproduce, the coastal cod fry will have a lower survival rate. The coastal cod is already on the red list, and now the best possible survival rate for the fry is of crucial importance to keep the species.

The consequences of climate change on Svalbard
By analyzing DNA from more than 8,000 plants of 18 different species, it has been shown that colonization of Svalbard has occurred repeatedly from several different source areas. The results indicate that it has been much more difficult for the plants to establish themselves and survive on Svalbard than to spread their seeds there - the data show that the better adapted a species is to the current climate, the more times it has established itself on Svalbard. This means that, despite the long dispersal distance, the colonization of Svalbard will probably increase in line with global warming, and that southern species will not have problems colonizing other areas in the Arctic either. The 18 largest glaciers in Norway are located on Svalbard, including the largest glacier in Europe, Austfonna in Nordaustlandet. Life on land and partly in the coastal sea areas on Svalbard is well protected, and a full 65 % of the land area on the archipelago is a protected area. Svalbard still has a lot of pure nature, but we gradually find many traces of dangerous pollution that is transported here from other parts of the world. Not only is the archipelago affected by pollution, but climate change is also felt to be greater here. Temperatures are rising and rainfall is increasing at all the measuring stations on Svalbard, and the temperature is rising faster here than in the rest of Norway. The Norwegian Polar Institute reports that there is soot in both the air and snow on Svalbard, and this can lead to increased snowmelt. As you know, soot is colored black and, like other dark objects, absorbs more solar energy and heat than light objects. This can cause the glaciers to melt faster via a catalytic effect than they would without this source of pollution.

Colonization by alien species
A warmer climate makes it easier for foreign species to settle in Norway. 40 out of 65 alien species assessed in a new report are expected to get better conditions if the climate changes. 18 of them are already in Norway, while 22 are knocking on our door. The harlequin ladybird spreads easily by flight and can displace 8 of our native ladybird species that are already on the red list. Marhund spread to Norway in 1983, but is not yet properly established in this country. One of the reasons why the raccoon is not wanted in Norwegian nature is the danger that it will spread parasites and disease, including a tapeworm that is dangerous to humans. Another is that this predator is an omnivore that will be able to do great damage to ground-nesting bird populations. Crayfish does not have much in common with the raccoon, except that it is undesirable. Crayfish plague is a small parasite that can live on signal crayfish without causing much damage, but in the highly threatened Norwegian crayfish, noble crayfish, it leads to acute illness and death. Releasing signal crayfish is prohibited in Norway, but it has been introduced illegally in some lakes in Eastern Norway. If signal crayfish are allowed to spread, and climate change is as expected, we risk a crayfish plague as far north as Nordland.

Well-established ecosystems are at risk of radical change, and both old and new species can then gain access to previously inaccessible areas. Floor moss and lichen already occur in increased quantities in large parts of the country, probably due to a changed climate with longer and wetter growing seasons. So-called colonizing species can make it easier for other species to enter, and the prevailing competitive conditions that keep plant communities in balance can change radically; common species become uncommon, while uncommon species become dominant. As always in an evolutionary race, it is generally the organisms that reproduce slowly that have the biggest problems: a low generational turnover means that the organisms take a long time to develop adaptations to the rapid climate changes. The evolutionary race is therefore very uneven, with some clear losers.

So far, this article has not considered human-induced climate change of another kind, but it should not be neglected either: with a warmer climate, the conditions are right for both agriculture and human settlement to intensify. An increase in industrial agriculture will be necessary to keep pace with population growth, but this can lead to more pests and diseases, which in turn means that more chemicals are used against insects and weeds. It is already known that flying taxa such as insects and birds are particularly important bioindicators in ecological risk analyzes because they can spread easily. In some already existing ecosystems, bats fulfill the role of both pollinating birds and insects, as well as fruit-eating mammals when it comes to seed and pollen dispersal. Can one imagine future ecosystems where animals such as bats spread far north and displace local populations of insect-eating birds? Such a consideration is speculative at best, as previous studies have shown that bats accumulate environmental toxins to a far greater extent than birds. Pesticides such as DDT bind to fat, and in the hibernation phase can lead to acute poisoning in bats which, like other hibernating mammals, eat away at their fat reserves. So even if the conditions are favorable for increased colonization, an increase in the levels of environmental toxins will decimate biological diversity. The trends are already evident in the polar regions, where the largest predators accumulate toxins in living tissue, and where the concentration of toxins increases up the food chain.

It is difficult to conclude how climate change will affect Norway; we are witnessing a dynamic development that has not stopped yet. Well-established ecosystems, which have taken tens of thousands of years to form and shape, will not be able to last as we know them today. Norwegian symbol species and Norwegian key species are in danger of disappearing, and which will take their place is only the subject of educated guesses at this point. What is certain is that we will not be untouched.


Ahola et al.: "Climate change can alter competitive relationships between resident and migratory birds", Journal of Animal Ecology, 2007

Both et al.: "Climate change and population declines in a long-distance migratory bird", Nature Letters vol. 441, 2006

Bårdsen: "Risk sensitive reproductive strategies: the effect of environmental unpredictability", doctoral thesis 2009

Durant et al.: "Ocean climate prior to breeding affects the duration of the nestling period in the Atlantic puffin", Biology Letters vol. 2, 2006

Jones et al.: "Carpe noctem: the importance of bats as bioindicators", Endangered Species Research, vol. 8. 2009

Kausrud et al.: "Linking climate change to lemming cycles", Nature Letters vol. 456, 2008

NINA's report no. 439, The national monitoring program for seabirds.

Turunen et al.: "Does climate change influence the availability and quality of reindeer forage plants?" Polar Biology, vol 32, 2009.

Walther et al.: "Ecological responses to recent climate change". Nature, vol 416, 2002.

World Meteorological Organization (WMO) Statement on the Status of the Global Climate in 2002, WMO Press Release No. 684, Geneva.

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