Great plant diversity often found in smaller areas


Although it sounds strange, it’s true: the steppes of Eastern Europe are home to a similar number of plant species as the regions of the Amazon rainforest. This is only seen when species are counted in small sampling areas rather than over hectares of land. An international research team led by Martin Luther University Halle-Wittenberg (MLU) and the German Center for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig has now demonstrated how much plant diversity estimates change when the sampling area varies from a few square meters to hectares. Their findings have been published in the journal “Nature Communications” and could be used in new, more appropriate nature conservation strategies.

Mohamed Zakaria Hatim, PhD candidate at Wageningen University and Research, and part of the research team explain that the project took around two and a half years to complete. “We analyzed a dataset of approximately 170,000 vegetation plot records from all climate zones on Earth. The data included information on all plant species found at a location and the coordinates of the respective area under study. The data was extracted from the globally unique vegetation database “sPlot”, which is located at the German Center for Integrative Biodiversity Research (iDiv).

Small areas can have relatively high biodiversity

“Most studies of global biodiversity are conducted at a relatively large scale, such as a state or province. We wanted to find out how much the results differ when smaller areas are examined,” says Professor Helge Bruelheide from Martin Luther University (MLU) Halle-Wittenberg. The team used artificial intelligence to study, among other things, the relationship between the number of plant species and the size of the area studied.

The richest vascular plant community ever recorded on Earth at 10 m2 grain size, 115 species. It is a semi-natural meso-xeric grassland near Cluj-Napoca, Transylvania, Romania (Photo: J. Dengler)

Their investigation showed that there are regions on Earth where focusing on large study areas only provides a limited understanding of the distribution of biodiversity: sometimes small areas can have relatively high biodiversity, for example in the steppes of Eastern Europe, in Siberia and in the Alpine countries of Europe. At fine spatial scales, the large difference in biodiversity between the tropics, such as the Amazon, and temperate climatic zones almost disappears.

Diversity varies greatly in the African tropics

The same applies to the African tropics, which were previously considered an exception in the tropical plant world. “The tropics have always been among the most biodiverse areas in the world. We wondered why this shouldn’t also apply to West Africa,” says Dr. Francesco Maria Sabatini, who led the study at MLU and is now an assistant professor at the University of Bologna. In fact, the distribution of plant species varies widely across the African tropics, says Sabatini. These species are distributed over very large distances, so they are not always recorded when a small sample area is examined. “To correctly recognize the great biodiversity in West Africa, many small areas are needed,” adds Sabatini.

The study also shows that the spatial scale at which other highly biodiverse areas are examined, such as the Cerrado savannah region of Brazil or parts of Southeast Asia, is irrelevant. These results are also important for species protection. “Ecosystems with high biodiversity spread over a wide area cannot be protected by the traditional patchwork of nature reserves. In contrast, ecosystems that have high biodiversity in a small area could well benefit from several separate protected areas,” concludes Bruelheide.

The study was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation).

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