Publication Details

Category Text Publication
Reference Category Qualification assignments
Document publication document
Title (Primary) Survival in changing environments - modeling the impact of climate change and land use on raptors in arid savanna
Author Wichmann, M.
Source Titel UFZ-Bericht
Year 2003
Department OESA
Volume 7/2003
Page To 105
Language englisch
UFZ inventory Leipzig - Reportsammlung, Bibliothek, 00032957, 03-0564 F/E
Abstract  The assessment of persistence time and extinction risk of populations has become a focus in recent research in ecology and nature conservation. Accordingly, in this thesis I developed a stochastic, individual-oriented model of the population dynamics of an arid area raptor, namely the tawny eagle (Aquila rapax) in the southern Kalahari arid savanna. I performed an extensive sensitivity analysis and found the model to be suitable to study the impacts of modified environments on the persistence of the tawny eagle population. I simulated various modifications in precipitation patterns (yielding prey availability) to the tawny eagle model population and found considerable influences on persistence time. Scenarios of climate change, in particular which were projected to be the most likely, led to dramatic increases in extinction risk. Even if average precipitation remains unaffected but variation among years increases I found the extinction risk to be severely augmented. Moreover, in this context this thesis presents a new way of relating breeding success of arid area raptors to annual precipitation that explicitly considers territory sizes. Furthermore, in a spatial model version, I found tree density and the pattern of tree distribution to also impact tawny eagle population persistence. Consequently, land use practices such as cattle farming and wood cutting that change these characteristics of the vegetation structure may potentially limit tawny eagle persistence and should be taken into account for nature conservation efforts. The impact of structural diversity on species diversity and the linkage between these two aspects of biodiversity are emphasized. However, the results of the model also led to new insights in theoretical population biology. I could show that our current knowledge of extinction risk in temporally stochastic environments does not hold for periodically fluctuating environments. Specifically, fluctuating environments with short periods lengths decrease the extinction risk over random environments - although other descriptive attributes of the time series remain constant. Furthermore, I present an alternative and broadly applicable method allowing the generation of time series that have strong auto-correlation with given variance. Applying this method and calculating the extinction risk in strongly auto-correlated environments led to results that deviate from what is known.On one hand, the results of this thesis document the implications for the conservation of tawny eagles and other raptors in arid savanna. In a more general context, these results offer future directions to guide ecological studies by considering climate change impacts on local populations and emphasizing the importance of structural diversity. On the other hand, my results contribute novel and exciting knowledge to the theory of population dynamics and extinction risk. New insights into both fields of ecological research found in this thesis will increase our understanding of population survival in changing environments.
Persistent UFZ Identifier
Wichmann, M. (2003):
Survival in changing environments - modeling the impact of climate change and land use on raptors in arid savanna
Dissertation, Universit├Ąt Potsdam
UFZ-Bericht 7/2003
UFZ Leipzig-Halle GmbH, Leipzig, 105 pp.