Grazing animals are improving biodiversity by increasing the amount of light available for plants at ground level.

The research, published in Nature, is by an international team of scientists led by the University of Minnesota and including Lancaster University.

Understanding the interplay among fertilisers, herbivores and plant growth is critical to our capacity to feed a growing human population and protect threatened species and ecosystems.

Scientists at 40 sites on six continents set up research plots with and without added fertilizer and with and without fences to keep out the local herbivores such as deer, kangaroos, sheep or zebras.

One of the sites is in Lancashire where the researcher was Dr Carly Stevens, of Lancaster University’s Lancaster Environment Centre, who said: “This experiment demonstrates how grazing shapes our grassland ecosystems and provides benefits to biodiversity.  By carefully managing grazing in grasslands habitats hopefully we can offset at least some of the damage that can be done by fertilisers”. 

The scientists measured the amount of plant material grown, light reaching the ground, and number of species of plants growing in the plots.

When the researchers compared data across the 40 study sites, they found that fertilizing reduced the number of plant species in the plots as species less able to tolerate a lack of light were overshadowed by fast-growing neighbours.

On both fertilized and unfertilized plots, where removal of vegetation by herbivores increased the amount of light that struck the ground, plant species diversity increased.

These results held true whether the grassland was in Minnesota, Argentina or China, and whether the herbivores involved were rabbits, sheep, elephants or something else.

The findings add a key piece to the puzzle of how human impacts affect prairies, savannas, alpine meadows and other grasslands.

The study was made possible due to the formation of the Nutrient Network, also known as NutNet. This is a collaborative international experiment as a resource to understand how grasslands around the world respond to a changing environment.