Rare plants are displaced by more common species

Scientists estimate that globally two out of five plant species are threatened with extinction. Despite this clear trend, there is still much debate over whether species richness is also declining locally. This phenomenon is referred to as the “biodiversity conservation paradox.”

An international team of scientists led by iDiv has now taken a closer look at the displacement of rare plants by analyzing a shift in species composition across three habitats. Plant species were examined in mountain summits, woodland understories, and meadows and pastures. 

The results show that widely distributed plants which prefer nutrient rich soils are becoming more common, while plants with small ranges requiring low nutrient soils are in decline. 

Across the mountain habitats, species numbers are still increasing. However, according to study first author Dr. Ingmar Staude, this may not always be the case. He said that in the long term, species displacement may be expected here too.

The plant species composition analysis was derived from research at 141 study areas spread across 19 countries. The data goes back as far as the 1940s. 

The researchers found that the major culprit of species displacement is an increase in soil nutrients such as nitrogen, which is associated with agriculture. Combustion and an increase in soil temperatures are also contributing factors. These additional factors cause the phenomena to be far outside of normal agricultural areas. 

“We are witnessing these dynamics unfolding in near-natural habitats, places we’d expect to provide safe havens for specialized species and those of high conservation value,” said Dr. Ingmar. “This suggests that the Anthropocene is not stopping at the doors of the few remaining wild areas that we consider protected.”

“The results of the study are not just be seen as an ‘early warning signal,’ said study co-author Professor Harold Pauli. “Particularly concerning is that the species change has proceeded in the same direction across strongly differing ecosystems. We, therefore, expect that we are dealing here with a pervasive, large-scale phenomenon.”

Overall, the research highlights the issue of intense agriculture driving local extinction of rare plants. Unfortunately, this problem will only get worse with a growing population that will demand even more agriculture. 

The study is published in the journal Ecology Letters.

—By Zach Fitzner, Earth.com Staff Writer