Climate change impact on nature
Del artikel Print

Climate change impact on nature

Climate change will affect Danish natural habitats and the species composition of plants and animals.  Rising water levels and more precipitation could cause flooding and  other impacts on coastal habitats, for example. Nature restoration and the further protection of nature from society will help preserve Denmark's natural habitats.

We are already seeing that Danish nature is being affected by climate change. This may be expected to continue in step with changing climatic patterns. Some of the changes in ecosystem composition will be irreversible. Habitats, ecosystems and species are affected differently by climate factors, and we can generally foresee three types of climate impacts likely to be the most influential on Danish nature:

1) Increased biological production in some ecosystems, as a result of higher temperatures and longer growing seasons;

2) Increased nutrient load and thus increased overgrowth and oxygen depletion in Danish waters as a result of increased precipitation and altered precipitation patterns; and

3) Increased erosion and flooding of low-lying coasts, tidal areas and river valleys as a result of sea-level rise, increased precipitation and altered precipitation patterns.

These effects will generally mean that a number of habitat types will become fragile and some species will be at higher risk of disappearing, because they have no possibility for moving to other areas or time to adapt. Ecosystems may become less resilient, and thus more vulnerable, and irreversible changes might occur. The challenge of reaching established goals for nature and water quality could therefore grow even further and require additional effort.

Options for climate change mitigation and adaptation in Danish nature management
Mitigation of and adaptation to the effects of climate change should preferably be through nature management, and by integrating nature and environment management as part of the solution in all sectors.

A number of nature management efforts of significance for climate change mitigation and adaptation are already underway and should enjoy continued priority.

Habitat types
A number of Danish natural habitat types will be affected by climate change due to increased sea levels, altered precipitation patterns or increased biological production.

Coastal areas
The Danish coastline stretches about 7,300km. In many places, the expected rise in water levels will force back the existing coastline.

Coasts with a small tidal range are likely to be most affected by the higher water levels. Coastal habitats are important breeding and resting grounds for many waterbirds. Many species of waders and terns which migrate to and from their breeding grounds in Scandinavia, northern parts of Russia and in Greenland are likely to have to cope with changes to their habitats in Denmark.

Furthermore, rising sea levels will reduce the existence of shallow waters, in e.g. fjords and inlets. Such areas are among the most biologically productive and are home to large populations of fish, shellfish and aquatic birds. Similarly, they are important growing sites for fry.

It is possible to preserve many of the natural assets of the coastline, even in the face of sea level rises of 0.5m to 1m or more over a number of years. More specifically, adaptation to sea level rises can be achieved by establishing compensatory habitats. In other words, by carrying out various construction works, it is possible to re-establish or conserve the habitat types under threat. A number of nature restoration projects have already been implemented in Danish coastal areas and these projects have succeeded in creating good conditions for plants and animals, as well as beautiful natural areas for people to enjoy.

River valleys
In the long run, climate change may bring up to 40% more rain to Denmark in winter, which means that Danish rivers and watercourses must be able to hold large volumes of rain during winter periods in the future.

In earlier times, it was quite common that the meadows along Danish rivers were flooded for shorter or longer periods during winter. However, a great number of these rivers have been embanked and straightened in connection with land drainage and cultivation projects. Future more powerful storms could therefore lead to inadvertent flooding further down the river, where the runoff of water could be blocked by the build up of sea water against the coast. Re-establishing opportunities for natural flooding in river valleys creates a buffer against harmful flooding.

Peat bogs
Peat bogs are very efficient carbon storages, and according to the United Nations Environment Programme (UNEP), on a global scale, peat bogs for example contain twice the amount of carbon as all the forests of the world combined.  Nature restoration of peat bogs and other wetlands can help reduce climate change, especially in the long run. Drainage or burning of peat bogs entails the release of large quantities of carbon to the atmosphere, which contributes to the greenhouse effect. The carbon is released from peat bogs through decomposition and respiration. On the other hand, the greenhouse gas methane is often released when former bogs are restored. According to UNEP's assessment, the destruction of peat bogs on a global scale releases carbon to the atmosphere corresponding to about 10% of emissions from burning fossil fuels.

In the long run, however, it is likely that fewer greenhouse gases will be released when draining is ceased and the soil once more becomes wet and peat starts to form. Throughout the past 20 years, restoration of several large bogs have been initiated in Denmark. However, the importance of preserving and enhancing the value of peat bogs as carbon stores has not been in focus until recently, and this new focus may help justify more targeted restoration of these areas.

Plant and animal species
Climate change will influence Danish plant species directly and indirectly through impacts on suitable habitats.

Species with a northern distribution may settle in Denmark, while species with southern distribution may settle down. For instance, the two orchid species small white orchid and yellow marsh saxifrage, which grow near springs, are among the species likely to disappear completely when a warmer climate in Denmark becomes a reality. On the other hand, species such as bay laurel, sweet chestnut, spreading bellflower and great burnet could be among the new species to colonise Denmark. A widespread species such as the wood anemone could extend its range northward.

Furthermore, species growing in Denmark will have altered conditions, e.g. leafing and flowering happens earlier today than  20-30 years ago.

Birds react quickly to climate change, and changes in bird populations, which may partly be attributed to a milder climate, have already been observed in Denmark. It is possible that a great number of breeding-bird species, e.g. the ruff and the thrush nightingale, will disappear. However, it is expected that about the same number of new breeding bird species will come to Denmark from southern regions. These could include the little egret, the great egret and the common nightingale.

Especially coastal birds will be vulnerable to the climate in future, as they depend on the coast, which in some places will be exposed to flooding.

Fish populations have previously been very affected by changes in the climate, and it is expected they will be affected in future as well. In particular, warmer sea temperatures, changes in the salinity of seawater in the Baltic Sea, and changes to the food basis will influence the composition of fish species. Several fish species are currently entering Danish waters from the Bay of Biscay, such as sardines, anchovies, red mullet, thick-lipped grey mullet, European seabass, gilthead seabream, swordfish and European John Dory (St. Peter's fish). On the other hand, a commercially valuable species such as the cod may become more vulnerable, especially in the Baltic Sea.