Nitrogen pollution - which finds its way into our air and water from various sources, including fertilizers, agriculture, smokestacks and car tailpipes - is a real threat to endangered species in the United States. However, there are solutions as well.
That's according to a new study led by researchers from University of California Santa Cruz, which looked at this chemical element's effect on biodiversity across the country.
"Nitrogen pollution is a prevalent atmospheric and biogeochemical global change driver, with growing effects on terrestrial, aquatic, and coastal ecosystems," the researchers wrote in their report.
"It starts in the air and water," study co-author Erika Zavaleta, of UC Santa Cruz, said. "On land, nitrogen pollution ultimately ends up in the soil. It's essentially fertilizers coming out of air and water," from smokestacks and auto tailpipes.
In their work, the research team looked at 1,400 species with Endangered Species Act listings. They found that 78 of those are battling known threats caused by excess nitrogen. The element can have a wide range of impacts on a spectrum that includes direct toxicity, lowered oxygen from over-fertilization, and encouragement of invasive species that take over the usual range of local populations or consume their food sources.
In order to look at a local area in California, the researchers examined grasslands on serpentine rock outcroppings in certain fault areas of southern Santa Clara County and the East Bay. These are areas that have "rare and endemic plant and animal species you can't find any other place in the world," Zavaleta said.
There, the team was able to examine how nitrogen has left a residual impact over 150 years in an area with rare plants used by a threatened butterfly, the Edith's Bay checkerspot. At the same time, they said that the element's pollution is diffuse and a bit hard to track, because it has so many different sources. "It's a policy challenge and a conservation challenge," Zavaleta said.
Nitrogen pollution's sources have steadily grown over those 150 years, with regulations not keeping pace. The sources include fertilizers, an emphasis on crops that store nitrogen (beans, peas, acacia, carob, others) and the burning of fossil fuels.
The key is to change regulations to combat these problems, say the study authors. In that case, efforts to mitigate nitrogen's effects on endangered species may be fruitful - because nitrogen pollution "can be more readily addressed within the boundaries of a single nation, region, or watershed," the researchers said.
The study was published online in the journal BioScience.
Follow Catherine Arnold on Twitter at @TreesWhales.
