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Denmark's Third National Communication on Climate Change

6 Vulnerability assessment, climate change impacts and adaption measures

6.1 Climate in the future

Future climate change as a consequence of man-made impacts through increased greenhouse effect, depletion of the ozone layer and aerosol emissions are evaluated by means of climate models. Climate models, which are based on the laws of physics and ascertained relationships, are mathematical descriptions of the components of the climate system: atmosphere, ice, ocean, and snow, land surfaces and the biosphere. The calculations are performed in a large computer system and the models are becoming increasingly complex.

6.2 Climate trend in Denmark

6.2.1 The latest developments

Denmark is situated on the west side of the European continent, between the mainland and the Scandinavian peninsular in a marine area and therefore has a coastal climate. DMI's statistics¹ show that the average mean temperature in the 1990s was slightly more than 8°C after having risen just under 1°C since 1870. The mean temperature is almost 16°C in the summer quarter and around 0.5°C in the winter quarter.

Average annual precipitation (measured values before precipitation adaptation) in the 1990s was about 735 mm and has thus risen by almost 100 mm since 1870. There are, however, significant regional differences. West and Southern Jutland have most precipitation (over 900 mm) and the Eastern islands less (slightly more than 500 mm).

The water level in Danish waters has generally risen in the last 100 years, but after adjustment for land movements, there has been no general rise in water level in Danish waters. However, since Denmark tilts, the water level in the southern part of the country is rising by about 1 mm per year. Unfortunately, the region in question has many low-lying, vulnerable areas.

6.2.2 Projected climate changes in Denmark

For several reasons, the basis for evaluating the impacts of the manmade increase in the greenhouse effect is uncertain. Serious problems are that the magnitude of future greenhouse gas emissions is uncertain and that the climate models are encumbered with uncertainty.

DMI/Denmark's Climate Center (in cooperation with, inter al., Max Planck Institut für Meteorologie in Hamburg) has carried out global and regional calculations for several scenarios for future emissions of greenhouse gases and aerosols - namely, IPCC's IS92a-Business-asUsual scenario and the new A2 and B2 scenarios from IPCC's special report - SRES-2000 - on emissions scenarios².

The calculations carried out do not directly provide scenarios for future changes in the water level around Denmark, but previous studies⁴ show that the rises in water level around Denmark would be slightly smaller than the average global rises because of vertical land movements. For example, it is estimated that an average global rise in water level of 0.5 m would lead to a rise of about 0.4 m around Denmark. These figures do not account for the regional impact on water level of changed ocean currents, flow, temperature, and wind conditions. The wind effect alone gives a rise of 3-5 cm⁵. IPCC estimates that the global water level would rise 0.1-0.9 m in the period up to 2100 in the SRES scenarios. In Danish impact and vulnerability studies, rises in water level of 0.25- 0.50 m are usually used.

6.2.3 Impacts and Denmark's possibilities for adaptation

Earlier evaluations

The impacts of possible climate changes in Denmark have been evaluated several times since 1988 and most recently with various aspects in the report: "Climate Change Research - Danish Contributions" edited by A.M.K. Jørgensen, J. Fenger and K. Halsnæs in a cooperative project between DMI, NERI and Risø and published by DMI in 2001, and have been treated in greater detail in the report "Danish adaptation to a changed climate" (J. Fenger and P. Frich), published by NERI in 2002.

The general conclusion has been that the direct impacts in moderate climate scenarios would be modest and could be countered by suitable ongoing adaptation. Danish studies of - and preparations for - impacts from climate changes have been very limited in their scope, and no action plans yet exist. However, the Danish Nature Council recommended in a report from 2000 (Vismandsrapport 2000) that preparedness be built up against the consequences of climate change for nature. It is suggested that the preparedness be based on technical reports and that relevant monitoring of nature follow it.

There have not as yet been any evaluations of secondary impacts for Denmark in the form of changed tourist destinations, environmental refugees, etc. or any evaluations of impacts from changed conditions in other countries on a little, open economy like Denmark. For an exportoriented industry like Danish agriculture, such secondary impacts could easily be more important than the primary impacts.

Water resources

Just as important as the quantity of groundwater is its quality, and here, the climate plays a role, albeit an indirect one. In Denmark, almost all fresh water is produced in potable water quality and from groundwater. Salt (NaC1) in the water is normally due to deposits in the subsoil. Only in a few areas does penetration of seawater play an important role such as small islands, e.g. Langeland and Samsø, and near low-lying coasts, e.g. along Køge Bay. With a rising sea level, salt penetration would increase and can be expected to reduce water recovery in slightly more places than is the case today.

Agriculture

The combined impacts are expected to benefit Danish agricultural productivity. Changes in cultivation practice can be implemented at short notice, and production is expected to increase with rising temperature and CO₂ concentration. There is at present a trend towards less cattle production and more pig and grain production. The projected climate changes could reinforce this trend because market constraints in the dairy sector would limit production and more land and grain would be available for pig production at competitive prices.

However, higher temperatures would increase the risk of pests and plant diseases resulting in an increased demand of pesticides. At the same time, increased production would require more fertilisers, which, together with more precipitation and higher winter temperatures, would increase the risk of nitrate leaching. Here, it might be necessary to change the environmental legislation to ensure a costeffective agricultural sector and protect water resources in a changed future climate.

Forestry

Danish forestry is characterised by a long duration of production determined by the rotation age of the trees, which is between 50 and 180 years. Long-term planning based on the most suitable species and genotypes in an optimal forest structure is therefore necessary.

Danish field and greenhouse studies have indicated that the projected climate change would promote tree growth, particularly for species with natural distribution having its northern limit in Southern Scandinavia. The only tree species expected to show decline is Norway Spruce, which has its natural distribution southwest of Denmark, but which has become the most common tree species in Denmark through planting. After the wind fall in December 1999 new planting of other species has become more widespread.

Forests are important carbon sinks, and reforestation, deforestation, and afforestation figure in the national CO₂ inventories. The planned doubling of forest land in Denmark during the next 100 years could sequester around 5% of the national emissions.

Natural ecosystems

Denmark is centrally situated in a natural vegetation area with temperate deciduous forests, and this will not change significantly. However, many species of fauna and flora have the limit of their dispersal in or around Denmark, and a northward shift could therefore be expected. Not all alien species are equally welcome, particularly in agriculture. The Colorado beetle has its northern limit just south of Denmark. The progress of the Iberian forest snail in recent years may be connected with a generally milder winter climate. The spread of new species is made diffinational cult by the fact that the landscape is very fragmented. This may mean a reduction in species diversity for a time but can be remedied by Denmark's intensive nature preservation and management of nature.

Freshwater ecosystems are sensitive to the quantity of water and can be burdened by reduced precipitation in the summertime. The effect may be intensified if increased leaching of nutrients occurs.

Coastal protection

The Danish coastline consists of raised beaches and wide foreshores in the northern part of the country and an archipelago to the south. The coastline is relatively long, about 7,400 km for an area of 42,000 km². 80% of a population of 5.33 million (1.1.2000) live in urban areas connected to the coast. The vulnerable areas are particularly raised seabed, marshlands, and reclaimed land, where 60-70,000 properties are situated.

Around 1,100 km of the coastline are protected by dikes and 700 km by other permanent installations. Increasing use is being made of soft solutions - particularly beach feeding. As yet, direct planning for rising water levels beyond the present secular rise is extremely modest and purely qualitative.

However, some thought has been given to the possible impact on coastal ecosystems, particularly salt marsh and dune areas. Here, the pattern of action will depend on the attitude to - and weighing up of - economic, sociological and biological interests and possibilities. The general strategy seems to be in the direction of preservation of a natural coastline - at the cost of agricultural land if necessary⁶.

Infrastructure

In connection with the construction of coastal infrastructure, including bridges, harbours, sewerage installations, etc. the general attitude has been "wait and see". Economic evaluations have been unofficial or lacking altogether.

However, in connection with the planning of the new metropolitan district "Ørestad" on the partially reclaimed land on the island of Amager near Copenhagen, a rise in water level of around 0.5 m was taken into account for the stairs leading down to Metro stations.

Higher temperatures and lower salinity in Danish waters would affect the survival, growth, and reproduction of the present fish population. It would also result in a longer growth season for plankton and thus favour species that directly live from plankton. This could include sardines⁷.

Energy consumption

Denmark has a reasonably cool climate now and no tradition for air conditioning (although many new cars are now fitted with an airconditioning system). Less need for heating would therefore presumably mean lower energy consumption.

Health and well-being

In the next 100 years the projected climate change would hardly give Denmark a climate that differs significantly from today's climate in, for example, Northern France. Direct health impacts in the form of a higher risk of heat stroke or a reduced risk of colds can therefore not be expected.

On the other hand, a number of indirect impacts can be predicted. A considerably larger amount of pollen and a several weeks' earlier start to the pollen season have already been observed. This could be the reason for the increase in allergy cases. In addition, vector-borne diseases could occur with invasion by, for example, malarial mosquitoes.

Infection via refugees (possibly environmental refugees) and immigrants would increase the risk not only of "southern" diseases, but also of diseases that are at present under control in Denmark - e.g. tuberculosis.

A warmer climate could also increase the risk of photochemical air pollution, which, in Denmark, is mainly due to long transport from Central Europe and elsewhere.

Greenhouse gas emissions

A changed climate could in many cases mean changes in greenhouse gas emissions and thus a feedback effect on the climate system. Possible sources affected, besides energy production and forestry, are different forms of agricultural activities, including livestock (methane) and use of manure (nitrous oxide). The consequences of going over to organic farming have been discussed, although without any clear conclusions.

6.3 Climate changes in Greenland

Greenland has an arctic climate. 82% of the land is covered by the up to 3km-thick ice cap, while the icefree land areas are limited to a coastal strip up to some hundred kilometres wide. However, furthest south, the climate is sub-Arctic with a mean temperature of more than 10°C in the warmest month, while the climate in the rest of Greenland can be divided into a low-Arctic zone and a high Arctic zone. The low-Arctic zone, which extends northward to Melville Bay on the west coast and to Scoresbysund on the east coast, is characterised by relatively mild winters with a lot of snow and periods of thaw and summers with a mean temperature of 5-10°C in the warmest month and frequent rain. This description applies particularly to the maritime coastal zone, while, inland, Southwest Greenland has a winter climate that is more like high-Arctic.

The high-Arctic region, which covers the entire northern and northeastern part of Greenland, has a continental climate with very cold winters (more than 50 degrees of frost occur in North Greenland), in which the temperature rarely rises above zero from September to May, and in which winter precipitation is limited. Parts of North Greenland have a desertlike climate with only about 25 mm precipitation per year, or about 1% of the precipitation at the southern point of Greenland. The continental climate in high-Arctic Greenland is due to field ice, which often constitutes a several-hundredkilometre wide belt of tightly packed polar ice that drifts down along the east coast and so to speak "extends" the land out to sea. The climate in highArctic Greenland is therefore greatly influenced by precisely the amount of field ice.

A description is given in the following two sections of what could or would happen on land and in the marine environment as a consequence of the expected climate changes. The description is based exclusively on general evaluations⁹ with the present extremely limited knowledge concerning factors determining the welfare of the species and ecosystems in question¹⁰.

6.3.1 Impacts and adaptations in terrestrial ecosystems

The very big differences between the climate in the low-Arctic and high Arctic parts of Greenland are reflected in marked differences in the natural conditions in the two parts. Low Arctic Southeast and West Greenland are characterised by luxuriant vegetation with bushes and often thick plant cover. In winter the snow often lies deep and soft from November to some time in May. Unlike this, in Northeast and North Greenland, the plant cover is usually only a few centimetres high, and increasingly large areas are entirely without vegetation as one moves northward. This is because of the poor snow cover, with many areas blown free of snow for most of the winter, while the rest is covered by often tightly packed snow that does not disappear until the end of June or the beginning of July.

The Arctic fauna and flora, which, compared with the situation in more southern climate zones, are poor in species, are adapted to the extreme climatic conditions. Some plants, invertebrates, and mammals depend on stable snow cover to protect them from the cold. However, many other species are dependent on the snow disappearing early - or being blown away altogether in winter. The distribution, duration, and thickness of the snow cover are therefore just as important factors as the temperature in the general conditions of life for many plants and animals in Greenland.

The importance of the snow cover

As a consequence of earlier snow melting in low-Arctic Greenland, higher summer temperatures and more summer precipitation, a long growth season can be expected and thus a more extensive and vigorous plant cover. Immigration of species from the south can be envisaged, but would be impeded by barriers in the form of the waters and competition from already established species. Conversely, species with a more northerly dispersal could disappear from southern areas.

In high-Arctic Greenland, more ample precipitation in both summer and winter, together with slightly higher summer temperatures, would presumably mean increased growth and more extensive plant cover, and it can be envisaged that large parts of this zone would change character in the direction of low-Arctic conditions. However, the increased snow cover would delay melting, which would impede plant growth and delay plant reproduction or make it completely impossible. There would be a risk of more northerly species, such as sabine ranunculus, disappearing altogether.

The increased UV-B radiation as a consequence of the depletion of the ozone layer, which is expected to continue for a couple of decades, would presumably cause problems in Arctic plants that are adapted to low UV-B radiation. The extent to which the plants would be able to adapt to the greater radiation is not known.

Increased microbial activity and thicker active strata (the part of the earth that dries up on top of the permafrost) would also release more greenhouse gases, but in the case of carbon dioxide, this would be counteracted by a bigger uptake in the plants as a result of the increased growth. Owing to Greenland's very hilly landscape, there are not the very large layers of peat that are so widespread in parts of Siberia and Canada. For this reason, Greenland's contribution to the feared release of enormous quantities of carbon dioxide from such peat layers would presumably be modest.

Mammals

A great deal of Greenland's fauna would presumably also benefit from a milder climate and consequently more luxurious and widespread plant growth, although there are important exceptions. Many of the species in high-Arctic Greenland are dependent on the low-precipitation continental climate. This applies, for example, to the musk ox, where thicker snow cover and more frequent periods of thaw in winter (with the formation of ice crusts in the snow) could make it difficult for the animals to forage. Examples of this are already known with the present climatic conditions, and reindeer died out for the same reason in the whole of high-Arctic Greenland during a snowy period more than 100 years ago. The artificially established population of musk oxen in Southwest Greenland are hardly likely to suffer similar problems. On the contrary, both reindeer and musk oxen might thrive even better in the continental low-Arctic region.

Another "risk group" is the high Arctic waders, which are the dominant bird group in Greenland. Nine out of ten of Greenland's 11 species of wader are only found in - or have their main dispersal in the high-Arctic part. They are totally dependent on the sparse vegetation. Later melting of snow would also impede their reproduction since they are entirely dependent on early snow melting both in order to procure sufficient food, mainly in the form of early active arthropods and in order to be able to lay eggs on such large snowfree areas that the foxes cannot find all the nests. On top of this there is the prospect of the large wading areas that these birds make outside the breeding time in temperate and tropical climate zones being permanently flooded as a consequence of the expected rise in sea level.

Immigration of new animal species

Many insects and other arthropods could spread northwards, and new species, particularly of mobile insects and birds, could immigrate from the south, but they would undoubtedly come from regions where they are already common and would thus from a global point of view be unable to replace any loss of highArctic species, which would be definitive.

Humans

Seen from the point of view of local society, the changes mentioned in the terrestrial ecosystems would be of limited practical importance and perhaps even an advantage in the form of more plant growth, more reindeer and musk oxen and perhaps better possibilities for farming in South Greenland. The increased thawing of the permafrost could bring problems in areas where houses and other structures are founded in the permafrost, but since the vast majority of structures in Greenland stand on solid rock, the problem would only be a local one. Increased melting of the ice cap would provide more water - for hydropower for example - but this resource is not generally a constraint today. The cost of heating in winter would be reduced and there would be generally fewer problems in connection with hard frost.

The possible loss of biodiversity, for example in the form of bird species in the high Arctic, would mean a loss of experiential quality, not only there but also in the birds' resting and wintering grounds. There would thus be a risk of most of the high-Arctic zone disappearing together with the special fauna and flora that are adapted to precisely this zone. Most of the continental high-Arctic areas are in North and North-east Greenland and on the northern Canadian islands.

6.3.2 Impacts and adaptations in marine ecosystems

In North-east Greenland the expected climate change would result in the thickness of the ice halving in the fjords and a doubling of the icefree period. As a result, about 60% more light would penetrate down in the water column, which would stimulate the production of both plankton algae and bottom-living algae. However, the increased precipitation (snow) would impair the light conditions in the ice in early spring and probably have an adverse effect on the production of sea-ice algae and the animals that benefit from the early production. All in all, however, production would increase.

Algae, water copepods, mussels, and walruses

An increased fresh water supply as a consequence of increased precipitation and melting of the ice cap in the inner parts of the fjords would increase the water exchange in the fjords and bring more nutritious water in from the open sea and thus contribute still further to increased primary production. The increased production would have a powerful effect in the top levels of the food chain. Today, water copepods (crustaceans that live on algae) are limited by food, and stimulation of plankton production would immediately mean increased grazing and growth of copepods. Sedimentation of the copepods' faeces would therefore increase, thereby increasing the quantity of food for bottom-living animals. This would, for example, increase growth in mussels, which are today very limited by food.

The increased mussel growth would benefit walruses. Rising winter temperatures would mean that the ice did not reach the same thickness as today and would therefore break up more easily in spring and that the walruses could seek food on the mussel banks for longer periods.

The polar bear, on the other hand, is facing an uncertain future in East Greenland. If the ice disappeared it would reduce the bears' hunting grounds and they would probably follow the ice northwards. Seals, which are attached to the ice, would presumably become concentrated in smaller areas with ice and would therefore be more easily accessible to the bears, but in the longer term, the number of bears would decrease. In addition, the polar bear is not good at hunting seals in water. The ice conditions on the west coast of Greenland would probably not change as much as on the east coast, and the polar bears off the west coast would therefore be less affected by the climatic changes than those off the east coast.

Fish

Rising surface temperatures would also have a major effect on the composition of fish in the highArctic zone. In the case of rock trout, reproduction ceases when the temperature rises above 5°C because the enzymes in the egg sacs denature when the temperature is just a little over 5°C. As a result, the eggs rot in the body and the fish dies. At the same time, a number of Arctic fish species would be more exposed to parasites and bacterial and fungal attack, and their immune defence system would be reduced with rising temperatures.

For many of Greenland's fish species, the seas off Greenland limit their dispersal, for example, cod, Norway haddock, striped catfish, halibut and herring, which have their northern limit there. Conversely, too high sea temperatures set a southern limit for the dispersal of Arctic species, such as polar cod, and Arctic roc. Therefore, relatively small variations in the temperature of the sea could result in considerable fluctuations in the dispersal of many fish species. The trend in cod fishing largely follows the average sea temperature. In the last 30 years, cod and a number of other boreal fish species have largely disappeared as a consequence of a generally colder climate in South and West Greenland. Today, more cold-adapted populations of prawn, crab, and halibut constitute the main commercial fishing resources in Greenland.

A change in sea currents and a rise in temperature as a consequence of the climate changes would probably improve the conditions of life for cod and some other commercially exploited fish species in these areas. However, a larger cod population would have an adverse effect on the prawn population due to predation. It can therefore be envisaged that there would be a change in the fishing resources from dominance by prawns today to dominance by cod towards the end of this century.

Crabs, copepods, and sea birds

There are no crabs in areas with temperatures below 0.5ºC, which characterises large areas off East Greenland. The temperature rises in the future would perhaps mean that crabs would migrate into the area and thus distinctly change the composition of bottom-living animals.

Another marked change that could happen is a change in currents, so that North Atlantic sea water containing a smaller species of copepod (Calanus finmarchicus) could penetrate areas that are today dominated by polar water with larger and longer-living species of copepod (C. Glacialis and C. hyperborus).

If C. finmarchicus ousted the larger species it would have very serious consequences for little auks, which breed in their millions in the Thule area and around Scoresbysund, and which are specialised in foraging along the edges of ice with high concentrations of food animals. The little auk lives almost exclusively from the large species of copepod and could not get enough energy out of the little copepod. Polar guillemots, among other sea birds, would perhaps have more difficulty in West Greenland, but the populations there have already been reduced to some few per cent of the natural population by hunting, so the climate would undoubtedly be of secondary importance. Conversely, the Atlantic guillemot would be able to immigrate in large numbers in South-west Greenland, just as a number of other sea bird species would benefit from the increased marine production and the reduced ice cover.

Whales

Whales, which are associated with sea ice, such as the narwhale, the white whale, and the Greenland whale, would have reduced living areas in the winter months, while new areas would become available to them in the summer months. However, the reduced drift ice would mean reduced areas with concentrated food along the edges of the ice in the same way as for the little auk. In winter, the whales would get increased competition for food from other marine mammals. Other species of whale that use the Arctic and north boreal waters in summer would be able to use more northern areas.

Our knowledge about the way the ecosystems function is constantly improving, but in the case of such large changes in such a short space of time, we as yet know too little to make precise predictions. One of the biggest uncertainties in connection with the marine environment in South Greenland is the extent to which the sea currents and thus sea temperatures follow changes in air temperature. The balance between the part of the seawater in Southwest Greenland that comes from the cold East Greenland Current and the part that comes from the warm North Atlantic drift (a branch of the Gulf Stream, which bends westward, south around Iceland), and the cold water masses in Baffin Bay and Davis Strait, thus totally determine the ecological conditions off Southwest Greenland, where most of Greenland's population live.

Humans

For Greenland society, a warmer climate would probably mean increased fishing in the form of more cod, Norway haddock and other species, but fewer prawns. The possibilities for hunting ring seals and polar bears would probably be reduced, while the occurrence of several other game animals would depend more on the pressure of hunting itself. Communication conditions would be much better because the period of open water would be longer, making it easier for boats to call at many towns and villages. There would be far less field ice, but on the other hand, a reduced possibility of using the ice to get from place to place.

Retraction of glaciers and the ice cap, together with less "Arctic wilderness" could adversely affect the tourist industry, but the improved communication - including a longer summer season - could have a beneficial effect.

6.4 Climate changes on the Faroe Islands

Only minor changes in terrestrial ecosystems are expected. The isolation of the Faroe Islands in the Atlantic Ocean may have the consequence that climate-induced changes in plant and animal life will be unbalanced. Thus, the rate of possible species loss from terrestrial ecosystems may not be counterbalanced by a similar immigration rate, resulting in reduced species diversity.

The greatest changes are expected at sea, although the uncertainty is also greatest here as long as the fate of the North Atlantic Current has not been clarified. Warmer deep water could result in a redistribution of pelagic and benthic communities.

Impacts on plankton would be similar to those mentioned for Greenland. Fish species that settle in shallow waters in the early spring such as flatfish, lumpfish, and species with pelagic drifting eggs and larvae would have a high risk of UV-B induced damage.

Effects on marine mammals and sea birds are expected mainly to concern spatial shifts in areas of food production and primary productivity (changes in upwelling sites), nesting and rearing sites, and increases in diseases and oceanic biotoxin production (from both temperature increase and current changes).

The reappearance of cod seems highly dependent on what happens to sea currents. That there have been three to four times as many storms as normal in recent years has contributed to the disappearance of the cod by blowing the fry towards waters too cold for their survival. A reduction in water arriving from the south would worsen the present lack of the fry's favourite food.