The icterine warbler is one of the species affected by climate change.
Source: Photograph: © Ron Knight | Wikimedia Commons/CC BY 2.0
2019 Monitoring Report on the German Strategy for Adaptation to Climate Change
Climate change entails changes in species communities. In respect of 88 breeding bird species occurring in Germany the relative frequencies have shifted between 1990 and 2016 in favour of hermophilic species or, putting it another way, shifted to the detriment of psychrophilic species. At present it is not sufficiently clear what further impacts this will have on biodiversity. The trend reversal indicated suggests the cause to have been a number of severe winters between 2009 and 2013 which had an effect independent of the long-term climatic trend.
Birds are comparatively sensitive to changes in their environment. This means that the composition of bird communities can change strongly as a function of environmental impacts. As a rule, such changes are the result of various impact factors combined. As a rule, there is no single cause for a change in species communities and the decline or loss of individual species. There is however evidence from scientific research which indicates that, in addition to changes in land use, climate-related changes can play a crucial role.
Breeding birds require species-specific temperatures at breeding time. These are lower, for instance, in respect of whinchat, thrush nightingale and icterine warbler than for stonechat, nightingale and melodious warbler. If, as a result of climate change, temperatures during the breeding season increase in terms of the long-term mean, onditions will become more favourable for thermophilic species which will then become more frequent compared to other bird species. Vice versa psychrophilic species will decline compared to other bird species.
In the period between 1990 and 2016, such a development has been observed in 88 bird species breeding in Germany. As indicated by the temperature index for frequently occurring breeding bird species, the relative frequencies of the breeding birds observed have shifted in this period in favour of thermophilic species or, putting it another way, shifted to the detriment of psychrophilic species. From 1994 onwards the sliding 5-year average of the temperature index first shows an increase taking place until approximately 2010, but afterwards the development remained more or less the same. However, the development from 2010 onwards can be attributed to effects of weather patterns which had an impact regardless of the long-term climatic trend. In the years 2009/10 to 2012/13 there were several consecutive hard winters with adverse impacts on the numbers of many breeding birds. As part of ecological change processes, the occurrence of extraordinarily cold winters is of major importance even at a time of progressive climatic warming.
For the purpose of calculating the temperature index, a species-specific temperature requirement value is allocated to each of the 88 bird species occurring in their European distribution area, based on the average temperature for the reference period 1961 to 1990. These species-specific temperature requirement values – weighted according to the relative frequency of the species in any particular year – are included in calculating the index. The greater the rise in the temperature index of frequently occurring breeding bird species, the stronger the shift in the relative frequencies among thermophilic species and consequently, the stronger the influence of temperature rise on the group of birds under observation. The index values shown refer to Germany nationwide. This proves that it is not possible to make any statements on a changed composition of regional breeding bird communities.
Other groups of species such as butterflies or vascular plants can also be used as indicators for long-term temperature changes related to climate change. In this context species shifts become most obvious in ecologically marginal regions such as mountain ranges. For instance, Europe-wide studies of vegetation in the peak areas of mountain ranges above the treeline show that the composition of species communities of vascular plants in those areas is changing. This is where thermophilic species from areas at lower altitude form colonies. Likewise, in rivers, lakes and seas, changes are taking place regarding the composition of species communities.
Apart from shifts in the frequency of species within existing species communities, climate change also leads to the immigration and distribution of species which have not occurred in our climes before. These developments take place in respect of both, plants and animals. Examples for this are the melodious warbler which emanates from south-western Europe and became a German breeding bird in 1980 extending its range ever since, or the praying mantis which came from the Mediterranean to Germany in the 1990s and is gradually spreading ever more northwards.
FW-I-1: Tree species composition in designated forest nature reserves - case study
FI-I-1: Distribution of thermophilic marine species
FI-I-2: Occurrence of thermophilic species in inland waters - case study
Buffering and minimising the impacts of climate change on biodiversity in Germany (e.g. shifts in vegetation zones, changes in bird migration behaviour, threats to psychrophilic species) (NBS, ch. B 3.2)
The UBA’s motto, For our environment (“Für Mensch und Umwelt”), sums up our mission pretty well, we feel. In this video we give an insight into our work.
