PhD Thesis

Climate change impacts on habitats and biodiversity: From environmental envelope modelling to nature conservation strategies

Torsten Bittner (02/2009-09/2011)

Support: Carl Beierkuhnlein, Michael Hauhs, Bettina Engelbrecht, Heike Feldhaar

The present dissertation thesis depicts various aspects of impacts on the environment due to expected climate change, reveals new scientific and methodological approaches and formulates policy options for nature conservation. Climate change will pose entirely new challenges for nature conservation. A literature study of 852 publications (between 2003 and 2010) illuminates this topic, examines driving research forces as well as focal points and shows recent research gaps. Here could be shown that changes in species distribution, diverse consequences for habitats, changing communities as well as biotic interactions and general aspects of diversity are the major challenges. Therefore, further developments of nature conservation strategies are needed. However, these aspects also offer new perspectives, options for preservation and development of biodiversity. The potential climatic modifications can alter deeply the distribution of animals and plants. Range changes due to recent climate change already exist and are traceable for many animal and plant groups. In the near future, further distribution changes are expected. In order to quantify such changes, environmental envelope modelling can be used. In addition to individual species, changes in distribution of more complex units are also conceivable. The present work mainly focuses on habitat types listed in the Annex I of the European Habitats Directive. To reveal the potential range changes of habitat types, two principally different modelling approaches have been developed. An indirect approach modelling the distribution of a habitat type using the distribution of its characteristic plant species and a direct approach, using the distribution of the habitat type itself. These two approaches were tested by modelling five grassland habitat types. Looking at the modelled results all habitats are projected to lose between 22% and 93% of their range in the ‘no dispersal’ scenario. In the ‘unrestricted dispersal’ scenario almost all habitats gain suitable climate space between 5% and 100% of their current range. Both approaches produce reasonable results. However, modelling an extensive set of habitat types using the indirect approach is currently not possible, because of the required but actually lacking amount of plant distribution data. Therefore, the direct approach is an appropriate instrument for modelling habitat types. Here, all 127 widespread terrestrial habitat types defined in the Annex I of the Habitats Directive were modelled and, resulting from this, a map of terrestrial habitat type diversity was calculated. Several habitat types are projected to lose many of their actually suitable areas, in particular bogs (up to a median of 43%), rocky habitats (up to a median of 49.5%), grassland (up to a median of 50.5%) and in part forests (up to a median of 48%). Due to their developmental time or rather due to their special abiotic requirements, bogs and rocky habitats even lose under the assumption of a full dispersal scenario. However, most heath and grassland habitats are also projected to lose in the full dispersal scenario. A couple of habitats, in particular scrublands and in part forests, are projected to win appropriate areas and some are remarkably stable. Pooling all modelled results together, terrestrial habitat type diversity is shifting partly to mountain regions and the atlantic biogeographical region is projected to decrease in habitat type diversity. According to the Habitats Directive habitat types listed in Annex I are protected in ‘sites of community interest’ aiming to maintain or restore them at a favourable conservation status. Due to the projected changes a static nature conservation concept could face problems which particularly concern the coherence of the protected area network. This could lead to a loss of protective goods in spite of protected areas. To illustrate the potential problems and difficulties emerging with respect to spatial coherence of habitat types between protected areas, an analysis of spatial coherence under future conditions for a variety of habitat types in Germany was conducted. Here, a combination of environmental envelope modelling and graph theory is presented to assess the coherence of nature conservation networks. The possible incapacity of species to reach all climatically suitable areas is currently debated. Therefore, spatial scales are not only crucial for the coherence of protected areas but also for the question if future projected suitable areas could be colonized. Biological restrictions such as ecology and morphology are limiting the dispersal capacity of most species. Moreover, dispersal movements of species are only infrequently possible in our highly fragmented landscape. To answer this raising question, Odonata listed in the Habitats Directive with known dispersal distances were contemplated. The species Coenagrion ornatum, Coenagrion mercuriale and Ophiogomphus cecilia are projected to lose range (up to -68%) when incorporating specific dispersal distances, while they are projected to extend their range (up to +23%) in the unrestricted dispersal scenario. Furthermore, suitable climatic conditions tend to decline for Leucorrhinia albifrons and Leucorrhina caudalis (up to -73%), whereas Leucorrhinia pectoralis is projected to gain distribution area (up to +37%) assuming either species-specific or unrestricted dispersal. Therefore, integration of realistic dispersal distances yielded new insights regarding the interpretation of environmental envelope model results. None of the considered species reached all projected climatically suitable areas. The nature conservation measure of translocation is an at least 100 years old methodology with pros and cons. The importance and application of the methodology under current and projected changes will gain new dimensions. First anthropogenic translocations of insects in a climate change context have already been effected. In this thesis, the emerging problems and opportunities of this species preservation strategy are presented. Further, a new question about the ‘focal unit’ is pointed out as well as the problem of genetic variability and the aspect of pre-adopted subspecies. Moreover, a selective assisted colonisation not by moving species but ecotypes is referred. The present thesis is not an exhaustive discussion of nature conservation in climate change. However, some relevant topics are highlighted and reveal new perspectives. This thesis improves the current state of research, demonstrates innovative approaches, provides ideas and creates new scientific links.