An international study has linked nitrogen pollution to westward shifts in the distribution of European forest plants.

The study, published in Science, was led by Ghent University and co-authored by Dr Michael Perring, an adjunct senior lecturer from The University of Western Australia’s Institute of Agriculture.

Researchers analysed the shift in the distribution area of 266 forest plant species across Europe over several decades, with the first measurements taken in 1933 at some of the locations.

The study found many species were moving towards the west, which was unexpected as it was previously thought that rising temperatures were pushing many species towards cooler, northern areas.

“We found that 39 per cent of the plant species shifted westward, while only 15 per cent of the species shifted northward,” Dr Perring said.

“This finding reshapes our understanding of how environmental factors, and in particular nitrogen pollution, influence biodiversity.”

High levels of nitrogen deposition from atmospheric pollution allowed a rapid spread of nitrogen-tolerating plant species, mainly from Eastern Europe.

“The establishment of highly competitive species in areas with high nitrogen deposition rates often comes at the expense of the more specialised plant species,” Dr Perring said.

The results highlight that future biodiversity patterns are driven by complex interactions among multiple environmental changes, and not due to the exclusive effects of climate change alone.

“Understanding these complex interactions is critical for land managers and policymakers to protect biodiversity and ecosystem functioning,” he said.