As a biologist I was very interested in the Poster Session “Biodiversity and ecosystem services”. Bernhard Freyer from BOKU Vienna (organisator of next year’s Tropentag) lead as the session chair and connected the different topics of the posters quite well. Interesting discussions developed subsequent to the presentations. Bernhard Freyer opens the discussion. The topics presented in that session dealt with the economy and ecology of tropical systems and their important ecosystem services. But in every presentation it became clear that biodiversity is very important to keep the system running. Matthias Schöller presents his poster. For example, Matthias Schöller from HU-Berlin presented his results on beetles in the tropical forests of the Kafa UNESCO biosphere reserve in Ethiopia. His research was funded by NABU and he got some quite interesting results. In another contribution it was up to Simon Shibru to show the impact of zebras, kudus, gazelles and other herbivores on the flora in Ethiopia’s Nach Sar National Park. He verified the well-known effect that herbivores support the spreading and growing of plant diaspores. The plants investigated were Dichrostachys cinerea, Acacia nilotica and Solanum incanum. Simon Shibru explaining his results. Furthermore, Kai Behn from Bonn referred to species richness investigations in Uganda’s wetlands and Lisa Stefanie Lautz to biodiversity in the "Nance" tree species in Yucatán. Posters of Kai Behn and Lisa Stefanie Lautz are described in separately blog entries. Interesting facts from this session: - At least 400 different beetle species have been detected in Kafa (Ethiopia) biosphere reserve, and there are even more expected. - Kafa is the natural home of the coffee plant Coffea arabica, which grows in the wild there. The natural pollinator of the coffee plant is still unknown, although several studies have been done - maybe it's an unknown species? - Fallow crop land in wetlands can have an important benefit for local populations after several month of wildlife growing. - Wild crop plant species that may be rare in nature can still be found in home gardens. - Intra-specific diversity is important to assure future food security. - Herbivores play an important role in dung diaspore dispersing.