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Unrealistic experiments mean that the real impact of nitrogen pollution on the environment is unknown – ScienceDaily

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

Human actions – primarily the 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 biased understanding of the effects of nitrogen pollution, which could hamper responses to global change.

Professor Dan Bebber, University of Exeter, writing in the journal Total environmental science, claims that scientific experiments were “unrealistic”. They often involve simulations of nitrogen deposition much higher than those encountered even in heavily polluted regions, in fact they are similar to mineral fertilizer applications in agriculture.

Professor Bebber said: “Despite decades of research, past experiences can tell us little about how the biosphere has responded to anthropogenic nitrogen deposition. A new approach is needed to improve our understanding of this important phenomenon. “

In most experiments, scientists used more than 100 kg N ha-1 Yes-1 to model the impact of nitrogen, while global average rates of land surface deposition are around 1 kg N ha-1 Yes-1 and only exceeds 10 kg N ha-1 Yes-1 in some regions, mainly in industrialized areas of Europe and Asia and in particular in forests. Many species are very sensitive to nitrogen and react very differently at these lower levels than at unrealistic experimental levels.

In his analysis, Prof. Bebber calls for future experiments to be designed to take into account the amount of nitrogen pollution found in different ecosystems and regions, and for researchers to monitor the impact of nitrogen pollution for longer periods to detect the 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 focus of global change research, through observational and experimental studies. However, there remains a large gap between global nitrogen deposition rates and the experimental treatments applied to simulate them.

“When the purpose of an experiment is to understand the effects of agricultural fertilizers, then high levels of nitrogen application rates are warranted. organisms and ecosystems at increased N availability can be subtle and nonlinear. “

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