Gobabeb regularly hosts scientists from other institutions for extended periods. Some of these scientists work on topics that are not directly related to our current strategic research themes, e.g. on conservation genetics or social sciences, but their contribution to the Centre’s activities, output and training are nevertheless enormous. In this section we highlight the most recent and most active of these projects.
Shifting climate, Shifting lizards?
First results of a study on Namibian Lacertidae by Sebastian Kirchhof (Museum of Natural History Berlin/ Germany)
During the past decades the potential effects of rapid anthropogenic climate change on biodiversity, species distributions and species assemblages have been subject of heavy debate. A number of species throughout the world already show signs of measurable changes in their distributions and/or phenologies over the past decades. Examples of lizard species showed increased local extinction probability correlated with the magnitude of warming during the reproductive period by incorporating field (Tb) and preferred body temperatures (Tb preferred), maximum daily air temperatures (Tmax) and the cumulative hours of restricted activity (hr) due to thermal stress when the operative temperature (Te) exceeds Tb preferred.
The results of an ongoing study on Namibian species of Lacertidae show only minor range shifts during the past 100 years based on museum records and resurveys of known localities. The majority of species has extant populations even in areas which are affected the most by recent temperature raises. For a subset of the studied species, a long-term study has been launched at the Gobabeb Research & Training Centre, where Te, Tb, Tb preferred and Critical Thermal Maxima CTmax under consideration of Tmax will be recorded extensively for Meroles suborbitalis, M. cuneirostris, M. anchietae, Pedioplanis inornata, P. breviceps (and P. husabensis) until 2015. First results show dramatic microclimatic differences within the distribution ranges of the species resulting in different physiological adaptations to a wide range of different body temperatures up to just below the CTmax threshold. Based on these differences, predicted climatic changes in Namibia until 2080 will largely affect the future distribution of the Lacertidae species through reduction of areas of suitable environmental conditions.
Isotopes, Fog and Dust in the Namib
Many interesting research questions remain regarding the role and fate of fog in the Namib ecosystems. As an Environmental Sciences PhD student with the University of Virginia, I looked into some of these questions using stable isotope geochemistry of fog, aerosols, soil and vegetation. What percentage of deposited fog becomes viable for use in the ecosystem? How do marine and terrestrial aerosols affect fog occurrence and composition? What role does fog play in nutrient cycling? This work builds upon decades of fog research based at Gobabeb, and includes the first study of Welwitschia mirabilis stem and root water isotopic composition. The main finding of this work is that, with respect to isotopic composition, W. mirabilis stem and root water comes from the same source as trees growing in the Kuiseb River (Acacia erioloba, Faidherbia albida, Tamarisk usneoides). This common source appears to be heavy rainfall from the east and the resulting flood waters. The perennial shrubs and grasses growing on the dunes and gravel plains (Stipagrostis sabulicola, Trianthema hereroensis, Calicorema capitata, Zygophyllum stapffii, and Arthraerue leubnitziae) have a significantly different isotope composition that indicates substantial use of moisture originating from the nearby Atlantic Ocean and depositing as fog, dew or winter rainfall. This Atlantic source comprises approximately 20-60% of stem water for these species, some of which are endemic to the “fog zone” of the Namib.
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Keir Soderberg, PhD
S.S. Papadopulos & Associates, Inc.