Unrealistic experiments mean true impact of nitrogen pollution on the environment is unknown

Date:
August 25, 2021
Source:
University of Exeter
Summary:
Unrealistic and flawed scientific experiments mean the true impact
of nitrogen pollution on the environment is unknownremains poorly
understood, a new study warns.



FULL STORY ========================================================================== Unrealistic scientific experiments mean the true impact of nitrogen
pollution on the environment remains poorly understood, a new study warns.


========================================================================== Human actions -- mostly burning of biomass and fossil fuels -- have dramatically altered the global nitrogen cycle, affecting natural habitats
and contributing to acid rain.

The study warns that many decades of experimental work have left us with
a skewed understanding of the effects of nitrogen pollution, and this
could hamper responses to global change.

Professor Dan Bebber, from the University of Exeter, writing in the
journal Science of the Total Environment, says scientific experiments have
been "unrealistic." They often involve simulations of nitrogen deposition
far higher than those experienced even in heavily polluted regions, in
fact they are similar to mineral fertilizer applications in agriculture.

Professor Bebber said: "Despite decades of research, past experiments can
tell us little about how the biosphere has responded to anthropogenic
nitrogen deposition. A new approach is required to improve our
understanding of this important phenomenon." In most experiments
scientists have used more than 100 kg N ha-1 y-1 to model the impact of nitrogen, while global average land surface deposition rates are around
1 kg N ha-1 y-1 and only exceed 10 kg N ha-1 y-1 in certain regions,
primarily in industrialized areas of Europe and Asia and particularly in forests. Many species are highly sensitive to nitrogen, and react very differently to these lower levels than to unrealistic experimental levels.

In his analysis, Professor Bebber calls for future experiments to be
designed to take into account how much nitrogen pollution is found in
different ecosystems and regions, and for researchers to monitor the
impact of nitrogen pollution for longer periods to detect cumulative
effects. Research should also examine the relationship between the concentration of nitrogen released and the environmental response.

Professor Bebber said: "Understanding the impacts of anthropogenic
nitrogen has been a major goal of global change research, through
observational and experimental studies. However, there remains a wide
gulf between global nitrogen deposition rates, and the experimental
treatments applied to simulate them.

"Where the purpose of an experiment is to understand the effects
of agricultural fertilizers, then high levels of N application
rates are justified. Researchers employing more realistic nitrogen
treatments have questioned the validity of rates far exceeding
current or predicted N deposition levels. The responses of organisms
and ecosystems to enhanced N availability can be subtle and non-linear." ========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Daniel P. Bebber. The gap between atmospheric nitrogen deposition
experiments and reality. Science of The Total Environment, 2021;
801: 149774 DOI: 10.1016/j.scitotenv.2021.149774 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210825113633.htm

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