For the first time in its history, Science Café will be held in English. Our two guests, prof. Petr Pyšek and prof. Dave Richardson will present the global problem of plant invasions, which threaten not only natural ecosystems but also human well-being. PETR PYŠEK: SOME THINGS WERE BETTER LOST THAN FOUND: PLANT INVASIONS IN THE CURRENT WORLD Biological invasions are a global consequence of an increasingly connected world and the rise in human population size. The number of species introduced outside their native distribution range where they successfully naturalized is rapidly increasing, currently exceeding 4% of the world flora. Many naturalized species become invasive, spread rapidly and cause significant harm by disrupting natural habitats, reducing the number of native species, increasing the risk of native species extinction, and altering how ecosystems work by changing nutrient levels and water regime. The talk will demonstrate how we understand the historical processes of human-caused plant exchange between continents and mechanisms that determine the current spread of plants beyond their original ranges. DAVE M. RICHARDSON: SOUTH AFRICA: DONOR OF SOME NOTABLE PLANT INVADERS TO THE WORLD, BUT WORLD CAPITAL OF INVASIVE TREES & SHRUBS South Africa is home to more than 22 000 native seed plants. The local environment has acted as a “factory” for the evolution of species that are well equipped to become invasive when transferred to other parts of the world. Over 1000 South African native plant species are “naturalised” outside their native range and 80 species are invasive. Two groups then are especially successful as invasive species: grasses and geophytes. South Africa has also received invasive plants from many taxonomic groups and from many regions of the world, but the country’s invasive flora is dominated by alien tree species (a third of the 759 known naturalized species are trees). South Africa has been called “the world capital of tree invasions”. The talk explores the history of introductions of alien trees, and the spectacular success of some species. * Akce je zdarma, jsme ale malá neziskovka a bez podpory fanoušků, kteří se chtějí díky Science Café dozvídat něco nového, se neobejdeme. Budeme vděční za vaši podporu na www.darujme.cz/projekt/1202966 * Záznamy předcházejících Science Café si můžete pustit na www.slideslive.com/sciencecafe nebo na @sciencecafe * Hlavními partnery jsou společnosti LMC a MSD, partnery jsou Nakladatelství Academia, VESMÍR, SlidesLive, LukyLab a HybCity. * Akci pořádáme ve spolupráci s Czexpats in Science www.darujme.cz/projekt/1202966 Hudba znělky: Funky Element – Bensound.com www.sciencecafe.cz