Researchers from the Hebrew University have found that nitrogen pollution caused by human activities has a direct effect on the decline in the diversity of species in several hundred sites around the world, including Beit Guvrin: “Not enough efforts have been made in Israel to estimate the severity of the problem.”
Adding resources such as nitrogen, phosphorus and potassium to ecosystems is known to cause the extinction of plant species, but the reasons for this are controversial. While some studies have linked the phenomenon to an increase in the total mass of plants, which increases competition between species, others have attributed the extinction of species to the toxicity of excess nitrogen in the soil. A team of researchers from the Hebrew University found that nitrogen toxicity was the main cause of extinction, while an increase in mass had a marginal effect on species diversity.
The research was carried out as part of the graduate work of student Nir Bend and was conducted under the supervision of Prof. Ronen Kadmon of the Department of Ecology, Evolution and Behavior and Dr. Niv de Malach of the Institute of Plant Sciences and Genetics in Agriculture, in collaboration with Prof. Micha Mendel. PNAS. The team performed a super-analysis of data collected from 630 experiments, which examined the effect of adding resources on the variety of plant species at about 100 different sites around the world.. For example, the team examined the ecosystem in the Beit Guvrin area of Israel and found that The variety of species was tens of percent lower in plots where there was a high presence of nitrogen, compared to other plots.
Using advanced statistical methods, the researchers separated the direct effect of nitrogen from the indirect effect, which is associated with an increase in biomass as a result of nitrogen addition. The results showed that the direct effect of nitrogen was the main cause of the decline in species diversity and led to the extinction of 20% of species on average.
Nir Bend, the lead author of the study, argues “this study highlights the importance of global reduction in actions that cause an increase in nitrogen levels in ecosystems, in light of the devastating consequences of nitrogen pollution.” Regarding the situation in Israel, Band adds that while in Europe and the US a combination of monitoring and efforts to reduce nitrogen emissions has led to a reduction in pollution, in Israel there is no nitrogen deposition monitoring program, although experiments in Israel have shown that ecosystems are very sensitive to nitrogen additions.
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