Does Fertilizer Destabilize Grasslands? Study

A recent study shows that fertilizer could be a bad thing for the world's grasslands.

According to background information from the study, additional nitrogen found in the compounds could increase the amount of grass that is grown. However, this crowds other better admitted animals, for the exception of the small number of species that thrive from the compounds. This results in wilder swings in the amount of available forage.

"More nitrogen means more production, but it's less stable," said Johannes M.H. Knops, a University of Nebraska-Lincoln biologist and one of the paper's international co-authors, via a press release."There are more good years and more bad years. Not all years are going to be good and the bad years are going to be worse."

For this sthree-year study, researchers monitored real-world grasslands at 41 locations on five continents. The sites included such places as tallgrass praries in the United States, grasslands in China, pastures in Switzerland and savanna in Tanzania.

The study found common trends among grasslands around the world, courtesy of the release:

• Natural -- unfertilized -- grasslands with a variety of grass species have more stability because of species "asynchrony," which means that different species thrive at different times so that the grassland produces more consistently over time. This finding was consistent with the findings of previous, single-site studies as well as previous biodiversity experiments conducted in Europe.
• Fertilized plots saw declines in the numbers of species compared to unfertilized control plots. The plots averaged from 4.4 species to 32.3 species per square meter and declined by an average of 1.3 species per site.
• Fertilization reduced species asynchrony and increased the variation in production levels over time compared to control plots. This weakened the benefits of species diversity seen in the un-manipulated plots.

Researchers further discuss concerns regarding elevated levels of mineral nitrogen in the environment. According to Knops, fertilizer overuse could increase the detrimental effects of drought on grasslands, such as the drought that devastated cattle herds in Texas and Oklahoma from 2011 to 2013. Researchers also believe that it could increase the risk of erosion, through reduction of bland cover and water filtration.

"In the past you didn't see a collaborative effort at a really large scale like this in biology or in ecology," he said, via the release.

More information regarding the study can be found via the journal Nature.