Prof Roman Turk already presented the negative impact of nitrogen levels emitted by large urban centres and the transportation sector as a major threat to wilderness back in 2014 during the European Wilderness academy Days in the HoheTauern Wilderness. New studies show that biodiversity is suffering under increased nitrogen deposition from agricultural practices. In the August edition of Biological Conservation, 12 articles explain how the use of fertilisers almost triples the amount of nitrogen in ecosystems in the Netherlands. Although the Dutch government tries to reduce the nitrogen deposition, the amount in the environment seems to be stable. Effects become more clear, now that more data is available. Nitrogen deposition changes the amount of accessible nitrogen in an ecosystem from a shortage to excessive factor.
Many species can handle nitrogen shortage, only a few benefit from excessive amounts. The latter species are able to quickly spread and soon dominate the ecosystem, destroying biodiversity.
Studies recorded the effects of excessive nitrogen on butterflies over the last 25 years. Scientists documented already three different effects, also showing the complexity of the ecosystem.
With increased nitrogen deposition, the plant vegetation changes. Grasses replace the herbaceous plants, which are essential for Alcon blue butterfly. It depends on the marsh gentian to lay its eggs.
The vegetation becomes more dense and rough. Caterpillars have difficulties to find a place to warm up in the sun, essential for their survival.
The nutritional values of the vegetation also change, and nitrogen is an indicator for caterpillars. Once caterpillars have consumed enough nitrogen, they will start the pupal phase. With the high nitrogen levels, caterpillars start the phase too early and without enough other nutrients.
In the Netherlands, 17 butterfly species are already on the IUCN Red list. More species continue to decline in population size. Further actions to reduce nitrogen deposition are thus absolutely necessary.
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