Global Database Reveals Humans are Biggest Driver of Plant Homogenization

Researchers at Harvard University have compiled a dataset of over 200,000 plant species worldwide to illustrate the extent to which species extinctions and non-native invasive plants reorganize plant communities in the Anthropocene, the current geological age dominated by human activity.

Led by Barnabas H. Daru, a former postdoctoral fellow at the Harvard University Herbaria and in the Department of Organismic and Evolutionary Biology, the project began several years ago with mapping North American biomes. Daru expanded it to include the biomes of Australia, South Africa, Europe, and China. The study examined how plant landscapes and communities change, especially after the bridging of the eastern and western hemispheres 500 years ago.

Daru noted that extinction and the naturalization of non-native species cause biotic homogenization or the gradual replacement of native species by locally spreading non-native species. This leads to species reduction and evolutionary differences and cal also have negative impacts on key ecosystem functions.

The study showed that regardless of the extinction scenario, the strongest contributor to biotic homogenizations resulted from non-native plants naturalized by humans. These changes occurred over a short evolutionary span of approximately 500 years and were facilitated – intentionally or unintentionally – by humans moving organisms around the landscape. Daru developed the GreenMaps database from globalized Herbaria collections. The global map helped in closing the knowledge gap in global distributions of plant occurrence records by generating predicted distributions for more than 200,000 species worldwide.

For more details, read the article in Harvard University's Department of Organismic & Evolutionary Biology.