Researchers say grass-rich ecosystems are most vulnerable to the negative effects of rising atmospheric nitrogen. Photo by CU-Boulder

BOULDER, Colo., March 28 (UPI) -- Many studies have looked at the relationship between plant life and CO2, and many have looked at methane, but few have explored the relationship between nitrogen and vegetation.

New research out of the University of Colorado suggests rising nitrogen levels in the atmosphere are diminishing plant diversity.


Nitrogen is a natural fertilizer. Its presence in the soil is key to plant growth. However, previous studies have shown too much nitrogen can have negative effects on plant communities, specifically a loss of biodiversity.

In measuring nitrogen levels at 15,000 forest, woodland, brush and grassland sites, researchers at Colorado determined that nearly a quarter of all ecosystems are experiencing unhealthy levels of nitrogen.

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Nitrogen emissions have tripled over the last 100 years as a result of industrial and agricultural growth.

The latest research, published in the journal PNAS, suggests grasslands are most vulnerable to the negative impacts of rising nitrogen levels, while groundcover species in forests are most resilient.

Researchers say they need to do more research to measure how the effects of rising nitrogen levels might ripple up and down the food chain -- and throughout a dynamic ecosystem.

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"The numerous plant species that live in an ecosystem are a bit like rivets on an airplane," lead study author Samuel Simkin, a post-doctoral research associate at Colorado's Institute of Arctic and Alpine Research, said in a news release. "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."

"Plant species diversity acts as an ecological buffer against events such as drought," added co-author William Bowman, an ecology professor at Colorado. "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."