University of Bayreuth, Press Release No 009/2024 - 24 January 2024
Lost Diversity: The Evolution of Plant Life Over 5,000 Years
The influence of humans is causing originally diverse ecosystems around the world to to become increasingly similar. Scientists in an international research collaboration have uncovered this phenomenon, with their findings recently published in the journal Nature Ecology & Evolution.
Jagoba Malumbres Olarte.
"So the world is becoming more alike," says geoecologist Prof. Dr. Manuel Steinbauer from the University of Bayreuth. " We demonstrate this phenomenon using Pacific islands, where the arrival of humans has led to a convergence in plant compositions among different islands. Over time, the islands become more similar, resulting in an overall decrease in biodiversity." According to the researchers, the main drivers of this trend are human activities such as the alteration of ecosystems, the introduction of non-native plant and animal species and the resulting extinction or disappearance of native plant species.
Archives of the past
However, little is known about when floristic homogenization began or what floristic similarity patterns existed before humans. The study investigates vegetation trends over the last 5,000 years in the tropical, subtropical, and warm-temperate South Pacific. To do this, the scientists utilized information about plant pollen obtained from cores in lake sediments or bogs at 15 locations on 13 islands. " The pollen has accumulated over millennia, allowing us to precisely trace changes in vegetation today," explains Steinbauer, adding: " The pollen is identified using a microscope and assigned to different plant species. What makes the study special is that we can trace human arrival on the islands using this data. While humans have been influencing nature on the mainland for much longer, they arrived on most oceanic islands at a point in time that we can reach with the pollen archives of the sediment cores."
In a previous work, the research team demonstrated that human arrival on previously untouched islands led to comprehensive changes in plant life (Link). For the new article now published in Nature Ecology & Evolution, scientists compared the species composition of different islands. "This is even more complex, as we must ensure that the identification of pollen and the preparation of sediment cores on different islands are comparable." The data shows that the vegetation of the islands became increasingly uniform with the arrival of humans. It also shows that higher-altitude locations, which are less affected by human intervention, tend to have less altered plant compositions and remain more diverse. "While declining biodiversity is often referred to as a contemporary problem, we found a much earlier trend that was obviously caused by human colonization of the islands and its consequences," summarizes Dr. Anna Walentowitz from the Department of Biogeography, who was involved in the work.
Strandberg, N.A., Steinbauer, M.J., Walentowitz, A. et al.: "Floristic homogenization of South Pacific islands commenced with human arrival" in Nat Ecol Evol (2024). DOI: https://doi.org/10.1038/s41559-023-02306-3
Related papers of the working group:
- Humans are accelerating biodiversity change: https://idw-online.de/en/news767859
- Global study shows increasing spread of non-native plants on islands since one thousand years: https://www.uni-bayreuth.de/press-releases/Invasive-Plants
- Human caused bird extinction: https://www.uni-bayreuth.de/en/press-release/human-caused-bird-extinction