Rising atmospheric nitrogen could be a serious problem for plants, according to a new study. Scientists have found that this type of pollution threatens plant diversity at nearly one-quarter of sites across a widespread portion of the U.S.
Nitrogen plays a huge role when it comes to biological processes. It also makes up a key part of fertilizers that farmers use for their crops. However, it's possible to over-fertilize plants with too much nitrogen; more specifically, there's been a huge upswing in the global emissions of nitrogen to the atmosphere, and this has caused a decrease in plant species richness.
"The numerous plant species that live in an ecosystems are a bit like rivets on an airplane," said Samuel Simkin, lead author of the new study. "You might be able to lose a few without issue, but losing too many can be disastrous. It's hard to determine where that tipping point is."
How much has nitrogen played a role in this decrease in species richness? In order to find out, the researchers looked at more than 15,000 forest, woodland, shrubland and grassland sites. At these sites, the researchers measured the threshold at which nitrogen inputs became harmful to plants while also taking other environmental factors into account. They found that in 24 percent of the sites, nitrogen was at or above the levels at which there is a loss in plant species.
"Plant species diversity acts as an ecological buffer against events such as drought," said William Bowman, co-author of the new study. "If we see a reduction in plant species in some ecosystems as a result of atmospheric nitrogen, that might lead to unintended consequences and affect communities adversely."
The findings show that when it comes to nitrogen, there may simply be too much in the environment. This, in turn, may have wide-ranging implications for future air quality standards and biodiversity conservation efforts.
More specifically, new standards need to be put into place in order to limit some of the nitrogen entering the environment. If current rates continue, then it's likely that we will lose species richness over time.
The findings were published in the March 2016 issue of the journal Proceedings of the National Academy of Sciences.
