Climate Impacts: Field of Action Biological Diversity

colourful flowering summer meadowClick to enlarge
Changes in climate can have negative consequences for many species and ecosystems.
Source: patzita/photocase.com

Climate change leads to a shift in climate zones and vegetation phases. This changes the habitats of plants and animals, sometimes profoundly. Biodiversity is also both directly and indirectly threatened by climate change.

Table of Contents

 

Effects of climate change on plants and animals

Changes in temperature, altered precipitation and extreme weather events influence the living conditions of plants and animals.

Thus, in Germany, on average, it has become approximately 1.6 degrees warmer over the last 139 years. As a consequence, the number of cold and very cold days decreased and the number of warm and very warm days increased. This results in changes and shifts in vegetation phases as a whole. The phenological spring already begins today, on average, around two weeks earlier than some decades ago. The phenological autumn lasts longer while the phenological winter has shortened from an average of 120 days per year to only 102 days.

If these important basic conditions change, many animals and plants change their behavior and their characteristics:

  • periodically recurring growth and development processes of plants and animals adapt to the new conditions,
  • food relationships shift,
  • animals display new behavioral patterns,
  • shift in the reproductive cycles of animals and plants,
  • animals and plants settle in new distribution areas and habitats,
  • native species are increasingly in competition with newly immigrated species.

Such changes in the living conditions and behavior of animals and plants can have profound effects on complex biotopes, habitats and ecosystems.

 

Consequences for species and populations

If the climate changes, it also influences the composition of biocoenoses and the habitats of species. Against this background, temperature and precipitation trends have a significant impact on biodiversity.

Species that have a very narrow tolerance range with regard to their requirements for living conditions may decline in number and distribution or even become extinct. These species can only poorly adapt as it is hardly possible for them to move to new habitats. Also, species that are less mobile cannot reach new, suitable habitats. In the course of climate change, habitats for species that love the cold and moisture are becoming scarcer in Germany. However, conditions are improving for warmth-loving species, which will become more widespread.

The increase in temperature and the prolonged vegetation period allows the spread of new species that form new communities or influence the composition of existing communities. This can increase the number of species in a biotope. However, the spread of new, so-called invasive species, which are very competitive, can also displace native flora and fauna and thus lead to a shift or even loss of biodiversity.

The climate sensitivity of a species depends on many other factors, including biotope connectivity, area size, current population situation and reproduction rate.

Climate change also threatens biodiversity. An analysis of 500 selected indigenous animal species commissioned by the Federal Agency for Nature Conservation, showed that climate change poses a high risk for 63 species, with butterflies, molluscs (e.g. snails) and beetles most affected.

In addition to direct impacts, climate change also has indirect effects on biodiversity. Triggers are adaptations in land use, for example in agriculture and forestry, or measures to protect the population and infrastructure, such as modified water management. The implementation of climate protection measures, such as the expansion of renewable energies or the insulation of buildings, also influences the occurrence of species and the quality of habitats. However, in most cases, it is difficult to demonstrate the extent to which these developments influence biodiversity since numerous other factors besides climate change usually have an additional impact.

 

Consequences for biotopes, habitats and ecosystems

Biotopes and ecosystems live on the interrelation of different plant and animal species. A modified species composition, as well as changes in the characteristics and behavior of individual species, endanger this complex interaction. Since, for example, shifts in life cycles do not occur in the same way for all species, interdependent species (e.g. predator-prey, flower-pollinator dependencies) can be decoupled in time and space.

An example of such a spatial decoupling is the caterpillars of many butterfly species, which require the leaves of special tree species as food. This interrelation is lost due to the progressively divergent distribution of animals and plants as a result of climate change.

Temporal decoupling of food chains can be observed in the example of migratory birds. Some species do not find enough larvae as food when they return in spring, because the insects have already developed.
It has been proven that fish begin their spawning earlier. The flowering times of plants also shift, so that they no longer match the life cycle of the insects pollinating them.

Even changes in individual species and small variances of just a few days can throw an ecosystem out of balance and seriously disrupt food chains.

The beginning of the phenological spring, summer and autumn has shifted forward on average during the last 70 years. The winter has become significantly shorter, and early autumn significantly longer. These changes are an expression of the ability of plants to adapt to a changing climate, but they can also have more far-reaching consequences for biodiversity and even endanger animal and plant species.

Die Grafik zeigt eine phänologische Uhr. Konzentrisch sind drei Zeiträume 1951 bis 1980 und 1981 bis 2010 und 1988 bis 2017 abgetragen. Dargestellt sind die Veränderung der folgenden zehn durch Wildpflanzen repräsentierten Leitphasen.
BD-I-1: Phänologische Veränderungen bei Wildpflanzenarten

Die Grafik zeigt eine phänologische Uhr. Konzentrisch sind drei Zeiträume 1951 bis 1980 und 1981 bis 2010 und 1988 bis 2017 abgetragen. Dargestellt sind die Veränderung der folgenden zehn durch Wildpflanzen repräsentierten Leitphasen; im Folgenden werden die Zahlenwerte der drei Zeiträume jeweils gelesen: Stieleiche (Beginn des Blattfalls) Winter: 143, 135 und 133 Tage, Huflattich (Beginn der Blüte) für den Vorfrühling: 14, 14 und 13 Tage, Buschwindröschen (Beginn der Blüte) für den Erstfrühling: 31, 31 und 31 Tage, Stieleiche (Beginn der Blattentfaltung) für den Vollfrühling: 30, 28 und 28 Tage, Schwarzer Holunder (Beginn der Blüte) für den Frühsommer: 20, 22 und 23 Tage, Sommerlinde (Beginn der Blüte) für den Hochsommer: 49, 43 und 44 Tage, Eberesche (Entwicklung erster reifer Früchte) für den Spätsommer: 21, 24 und 23 Tage, Schwarzer Holunder (Entwicklung erster reifer Früchte) für den Frühherbst: 29, 39 und 43 Tage, Hängebirke (Beginn der Blattverfärbung) für dem Vollherbst: 20, 22 und 22 Tage, Rotbuche (Beginn des Blattfalls) für den Spätherbst: 7,7 und 7 Tage.

Source: DWD (Phänologisches-Beobachtungsnetz)

Various ecosystems are differently sensitive to climate change. Dry habitats such as dunes, dry grasslands and heathlands are considered relatively resistant because they are not very sensitive to water shortages. On the other hand, moors, swamps, spring areas and wet grassland are particularly sensitive to water shortages. This applies increasingly to forests as well. Further information can also be found in the fields of action Soil and Forestry.

Habitats near and in the water are also highly endangered since warming and a negative climatic water balance (evaporation exceeds the water supply by precipitation) lead to more frequent low waters. This increases the risk of dehydration or eutrophication, that is an excessive input of nutrients into the water body and the accompanied lack of oxygen, especially for smaller standing waters. More information can also be found in the field of action Water, Floods and Coastal Protection.