Thomas C. Wanger
University of Göttingen
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Publication
Featured researches published by Thomas C. Wanger.
Proceedings of the National Academy of Sciences of the United States of America | 2011
Yann Clough; Jan Barkmann; Jana Juhrbandt; Michael Kessler; Thomas C. Wanger; Alam Anshary; Damayanti Buchori; Daniele Cicuzza; Kevin Darras; Dadang Dwi Putra; Stefan Erasmi; Ramadhanil Pitopang; Carsten Schmidt; Christian H. Schulze; Dominik Seidel; Ingolf Steffan-Dewenter; Kathrin Stenchly; Stefan Vidal; Maria Weist; Arno Wielgoss; Teja Tscharntke
Local and landscape-scale agricultural intensification is a major driver of global biodiversity loss. Controversially discussed solutions include wildlife-friendly farming or combining high-intensity farming with land-sparing for nature. Here, we integrate biodiversity and crop productivity data for smallholder cacao in Indonesia to exemplify for tropical agroforests that there is little relationship between yield and biodiversity under current management, opening substantial opportunities for wildlife-friendly management. Species richness of trees, fungi, invertebrates, and vertebrates did not decrease with yield. Moderate shade, adequate labor, and input level can be combined with a complex habitat structure to provide high biodiversity as well as high yields. Although livelihood impacts are held up as a major obstacle for wildlife-friendly farming in the tropics, our results suggest that in some situations, agroforests can be designed to optimize both biodiversity and crop production benefits without adding pressure to convert natural habitat to farmland.
Conservation Biology | 2010
Thomas C. Wanger; Djoko T. Iskandar; Iris Motzke; Barry W. Brook; Navjot S. Sodhi; Yann Clough; Teja Tscharntke
Little is known about the effects of anthropogenic land-use change on the amphibians and reptiles of the biodiverse tropical forests of Southeast Asia. We studied a land-use modification gradient stretching from primary forest, secondary forest, natural-shade cacao agroforest, planted-shade cacao agroforest to open areas in central Sulawesi, Indonesia. We determined species richness, abundance, turnover, and community composition in all habitat types and related these to environmental correlates, such as canopy heterogeneity and thickness of leaf litter. Amphibian species richness decreased systematically along the land-use modification gradient, but reptile richness and abundance peaked in natural-shade cacao agroforests. Species richness and abundance patterns across the disturbance gradient were best explained by canopy cover and leaf-litter thickness in amphibians and by canopy heterogeneity and cover in reptiles. Amphibians were more severely affected by forest disturbance in Sulawesi than reptiles. Heterogeneous canopy cover and thick leaf litter should be maintained in cacao plantations to facilitate the conservation value for both groups. For long-term and sustainable use of plantations, pruned shade trees should be permanently kept to allow rejuvenation of cacao and, thus, to prevent repeated forest encroachment.
Proceedings of the Royal Society B-Biological SciencesProceedings of the Royal Society B-Biological Sciences | 2011
Thomas C. Wanger; Arno Wielgoss; Iris Motzke; Yann Clough; Barry W. Brook; Navjot S. Sodhi; Teja Tscharntke
Interactions between native diversity and invasive species can be more complex than is currently understood. Invasive ant species often substantially reduce diversity in the native ants diversity that act as natural control agents for pest insects. In Indonesia (on the island of Sulawesi), the third largest cacao producer worldwide, we show that a predatory endemic toad (Ingerophrynus celebensis) controls invasive ant (Anoplolepis gracilipes) abundance, and positively affects native ant diversity. We call this the invasive-naivety effect (an opposite of enemy release), whereby alien species may not harbour anti-predatory defences against a novel native predator. A positive effect of the toads on native ants may facilitate their predation on insect vectors of cacao diseases. Hence, toads may increase crop yield, but further research is needed on this aspect. Ironically, amphibians are globally the most threatened vertebrate class and are strongly impacted by the conversion of rainforest to cacao plantations in Sulawesi. It is, therefore, crucial to manage cacao plantations to maintain these endemic toads, as they may provide critical ecosystem services, such as invasion resistance and preservation of native insect diversity.
Ecological Research | 2009
Thomas C. Wanger; Iris Motzke; Samuel Furrer; Barry W. Brook; Bernd Gruber
Rapid and reliable estimation of population size is needed for the efficient monitoring of animal populations of conservation concern. Unfortunately, technical advances in this area have not been paralleled in uptake in conservation, which may be due to difficulties in implementation or the lack of general guidelines for application. Here we tested five different methods used to estimate population size [capture–mark–recapture (CMR), finite-mixture models, model averaging of finite-mixture models, accumulation curve methods (ACM), and the line transect method (LT)] using extensive capture–recapture data of the giant day gecko (Gekkonidae, Phelsuma madagascariensis grandis, Gray 1870) at the Masoala rainforest exhibit, Zurich Zoo. When the complete data were analyzed [30 sessions (and 27 sessions for the LT)], all methods except the LT produced similar estimates of population size. The simple ACM gave a small coefficient of variation (CV), but did not cover the most likely value of population size at moderate sampling effort. Nevertheless, the ACM was the only method that showed a reasonable convergence when subsets of data were used. CMR and Pledger models included the reference value in their confidence intervals (CI) after 25 and 30 sessions, respectively. Although model averaging did slightly improve the estimate, the CV was still high for the full dataset. Our method of using subsets of data to test the robustness of estimates is simple to apply and could be adopted more widely in such analyzes to evaluate sensitivity to method of evaluation. In conclusion, simple accumulation methods showed similar efficiency to more complex statistical models, and are likely to be sufficiently precise for most conservation monitoring purposes.
Clough, Y; Abrahamczyk, S; Adams, M O; et al; Cicuzza, D; Kessler, M (2010). Biodiversity patterns and trophic interactions in human-dominated tropical landscapes in Sulawesi (Indonesia): plants, arthropods and vertebrates. In: Tscharntke, T; et al. Tropical rainforests and agroforests under global change. Berlin: Springer, 15-71. | 2010
Yann Clough; Stefan Abrahamczyk; Marc-Oliver Adams; Alam Anshary; Nunik Sri Ariyanti; Lydia Betz; Damayanti Buchori; Daniele Cicuzza; Kevin Darras; Dadang Dwi Putra; Brigitte Fiala; S. Robbert Gradstein; Michael Kessler; Alexandra-Maria Klein; Ramadhanil Pitopang; Bandung Sahari; Christoph Scherber; Christian H. Schulze; Shahabuddin; Simone G. Sporn; Kathrin Stenchly; Sri S. Tjitrosoedirdjo; Thomas C. Wanger; Maria Weist; Arno Wielgoss; Teja Tscharntke
The need to capture primary production in order to sustain and improve economic livelihoods has lead to increasing conversion of natural habitat and intensification of agricultural practices in many parts of the world including most tropical regions. Understanding how these processes affect ecosystems and their functioning, in particular in the high-diversity ecosystems of the tropics, has become a key issue in ecological research. In this chapter, our focus is on the agriculture-forest landscapes of Central Sulawesi, Indonesia, an island widely known for its endemic yet still poorly known flora and fauna. The rise of the region to one of the largest cacao producing areas in the world is at the core of recent land-use change and intensification processes. Covering plants (trees, rattan palms, herbs, bryophytes) and several invertebrate (ants, dung beetles, cacao insect herbivores, fruit-feeding butterflies, parasitic Hymenoptera, spiders) and vertebrate groups (amphibians, birds, murids, reptiles), we give an in-depth overview of the determinants of biodiversity in cacao landscapes, including both management and landscape-scale variables into our analyses. Results show that shaded agroforests host a rich community of species. By adopting a large-scale study design we showed that proximity of natural forest is a key predictor for species richness of plants, invertebrates and vertebrates alike. Endemics and forest specialists benefit most from indigenous shade tree cover and proximity to natural forest. Importantly, several functionally important groups such as insectivorous and seed-dispersing birds benefit from tall shade trees, shade tree diversity and proximity to forest edge, while parasitoid diversity is greatest close to natural forests. Available data on the effects of landuse change in cacao landscape of Central Sulawesi is increasing. Change in landscape configuration and management practices are being clearly reflected in the composition of species communities, with likely impacts on ecosystem services such as pest control and pollination. More knowledge is needed especially in terms of species interactions and ecosystem functioning, but also on how existing knowledge can contribute to effective conservation in human-dominated landscapes outside protected areas.
Journal of Applied Ecology | 2015
Iris Motzke; Teja Tscharntke; Thomas C. Wanger; Alexandra-Maria Klein
Summary Pollination can be an essential but often neglected ecosystem service to mitigate crop yield gaps. Pollination services are usually studied in isolation, and their relative role and possible interactions with other factors, such as major management practices, is little understood. We tested how pollination (insect vs. wind- and self-pollination) interacts with weed control, fertilization and insect herbivore control and how these factors as well as flower-visiting bees influence fruit set and yield of cucumber Cucumis sativus L. in 13 traditional Indonesian home gardens. Although insect pollination, fertilization and weed control additively increased crop yield, fertilization and weed control alone could not compensate for pollination loss. Pollination individually accounted for 75% of the yield and was, hence, the most important driver of yield. In contrast, herbivore control through insecticides at commonly applied levels did not increase yield. Yield strongly increased with higher number of flower-visiting bee individuals, while the number of bee individuals in turn was not influenced by weed control, fertilization or herbivore control, but increased with higher number of cucumber flowers. Synthesis and applications. Although multiple management practices influence yield, they cannot compensate yield gaps from pollinator loss in cucumber smallholder production in Indonesia. Our results also show that the widespread use of insecticides without considering the impacts on pest reduction is uneconomical. Here, reducing insecticides caused no income loss and, at the same time, reduces potential risks to important pollinators, which needs to be acknowledged by policy-driven regulations for pesticide application in tropical agroecosystems. Our results stress the importance of enhancing bee populations to facilitate pollination services. Bee management practices, such as sustaining additional food resources for pollinators, need to be established.
Research and Reports in Biodiversity Studies | 2013
Lochran W. Traill; Thomas C. Wanger; Siobhan C. de Little; Barry W. Brook
Steps toward conserving biodiversity should start at understanding the components across spatial scales and a determination of the drivers of these. Here we determine additive species diversity for arid South Australia, based on over 50 years of survey data. Elevation and soil data were sourced through the Australian Government, and climate data from the WorldClim database. Alternative hypotheses relating the effect of climatic and environmental parameters to diversity were tested using generalized linear models and ranked according to information-theoretic statistics. Total species richness for the region was 1824, similar to all arid regions. α-diversity values were low, relative to the contributions made by β-diversity toward total γ-diversity, similar to additive diversity indices for nonarid biomes. There was a lack of statistical support for our hypothesis that regional spatial variation in arid region diversity can be explained by climate topography. Arid South Australian species diversity appears to be largely driven by environmental parameters at the localized scale – beyond the resolution of available survey data. Heterogeneity in habitat, provided by mountainous regions, likely contributes toward the high β-diversity values. Our research is the first application of the additive (not multiplicative) approach toward understanding diversity within arid Australia.
Nature Ecology and Evolution | 2017
Thomas C. Wanger; Lochran W. Traill; Rosie Cooney; Jonathan R. Rhodes; Teja Tscharntke
Adaptive certification is the best remaining option for the trophy hunting industry in Africa to demonstrate sustainable and ethical hunting practices that benefit local communities and wildlife conservation.
Science | 2013
Lucas A. Garibaldi; Ingolf Steffan-Dewenter; Rachael Winfree; Marcelo A. Aizen; Riccardo Bommarco; Saul A. Cunningham; Claire Kremen; Luísa G. Carvalheiro; Lawrence D. Harder; Ohad Afik; Ignasi Bartomeus; Faye Benjamin; Virginie Boreux; Daniel P. Cariveau; Natacha P. Chacoff; Jan H. Dudenhöffer; Breno Magalhães Freitas; Jaboury Ghazoul; Sarah S. Greenleaf; Juliana Hipólito; Andrea Holzschuh; Brad G. Howlett; Rufus Isaacs; Steven K. Javorek; Christina M. Kennedy; Kristin M. Krewenka; Smitha Krishnan; Yael Mandelik; Margaret M. Mayfield; Iris Motzke
Biological Conservation | 2012
Teja Tscharntke; Yann Clough; Thomas C. Wanger; Louise E. Jackson; Iris Motzke; Ivette Perfecto; John Vandermeer; Anthony Whitbread