The biodiversity of ecosystems worldwide has changed greatly under the influence of humans. A research team including Prof. Dr Manuel Steinbauer from the University of Bayreuth has studied these processes using birds on ocean islands as an example. The study published in „Science Advances“ shows that the number of alien species that become newly established is often higher than the number of species that have become extinct under anthropogenic influences. However, the immigrant species cannot fully replace the diverse ecological functions of extinct species. The loss of native species therefore causes a long-term unification of ecosystems and their functions.