Excess Nitrogen
Problem: Nitrogen is a limiting nutrient in most terrestrial ecosystems. As a result, inputs of nitrogen can have varying consequences in these ecosystems. Adding nitrogen to soils through fertilizers increases atmospheric concentrations of nitrogen. This nitrogen can be transported through the atmosphere and deposited by rainfall in natural ecosystems which have adapted over time. This excess nitrogen can alter the distribution and abundance of species in these ecosystems.
Experiment: A study was created, which observed nine different terrestrial ecosystems across the United States. Scientists added nitrogen fertilizer to some plots and left others unfertilized, which acted as control groups.
Results: The experiment allowed the scientists to find that by adding nitrogen reduced the number of species in a plot by up to 48%, because some species that could survive under low-nitrogen conditions could no longer compete against larger plants that thrived under high-nitrogen conditions. Similar studies have documented cases in which plant communities that have grown on low-nitrogen soils for millennia are now experiencing changes in their species composition.
Conclusion: An influx of nitrogen due to human activities has favored colonization by new species that are better adapted to soils with higher fertility. The observation that nutrients can have unintended effects on ecosystems highlights an important principle of environment science: in ecosystems containing species that have adapted to their environments over thousands of years, changes in conditions are likely to cause changes in biodiversity as well as in the movement of energy through, and the cycle of matter within, those ecosystems. Maintaining a healthy balance of nitrogen is key to a thriving, diverse ecosystem.
Experiment: A study was created, which observed nine different terrestrial ecosystems across the United States. Scientists added nitrogen fertilizer to some plots and left others unfertilized, which acted as control groups.
Results: The experiment allowed the scientists to find that by adding nitrogen reduced the number of species in a plot by up to 48%, because some species that could survive under low-nitrogen conditions could no longer compete against larger plants that thrived under high-nitrogen conditions. Similar studies have documented cases in which plant communities that have grown on low-nitrogen soils for millennia are now experiencing changes in their species composition.
Conclusion: An influx of nitrogen due to human activities has favored colonization by new species that are better adapted to soils with higher fertility. The observation that nutrients can have unintended effects on ecosystems highlights an important principle of environment science: in ecosystems containing species that have adapted to their environments over thousands of years, changes in conditions are likely to cause changes in biodiversity as well as in the movement of energy through, and the cycle of matter within, those ecosystems. Maintaining a healthy balance of nitrogen is key to a thriving, diverse ecosystem.