Butterflies at risk due to excess nitrogen: Study

It was discovered by researchers at the University of Basel that nitrogen present in agriculture, vehicle emissions, and industry gets deposited in the soil by the air, negatively impacting the butterflies as a result. According to the authors of a recent study in Conservation Biology, the findings suggest that unintentional fertilisation contributes to the low diversity of butterflies in Switzerland.

Switzerland has about 55% of butterfly species on the verge of extinction, and over a third are possibly facing extinction. The usual approach to discovering the cause of an issue is to search for agriculture, pesticide use, and climate change. A research team from the University of Basel, led by Professor Valentin Amrhein, has, however, examined another influencing factor: nitrogen deposition from agriculture and industry and traffic-emitted nitrogen found in soils via the air.

Research that had been previously completed found that too much nitrogen causes more dense vegetation, but because of a smaller variety of plant species, it was well known.

Nitrogen encourages the growth of species with smaller growth requirements, such as low-maintenance plants, while displacing more specialised species. We wanted to see whether a nitrogen surplus would also indirectly affect the diversity of butterflies by altering the vegetation, so we conducted this study, according to Dr. Tobias Roth, one of the study’s lead authors.

They combed through data from Biodiversity Monitoring Switzerland, which includes information on the abundance and distribution of plants and butterflies on 383 plots in Switzerland, to understand more about the diversity and distribution of plants and butterflies in Switzerland. As can be seen, the results were obvious: the more nitrogen was introduced to the air above the study areas, the fewer butterfly species could be found.

For some butterfly species, plant species are necessary as food, or as part of the habitat, according to Roth. Overfertilization causes plant growth to be more intense, which subsequently creates open, warm, and dry places to become cooler, shadier, and damper due to an increase in plant growth.

The rise in the amount of nitrogen in the environment results in an increase in the number of butterfly species, such as species that prefer open and dry habitats. Because these species are rare and endangered, they provided the clearest result. Roth states that nitrogen from the air is almost certainly involved in the reasons why these species are endangered.

The existing literature on butterfly diversity tends to focus on habitat quality or climate in explaining species presence or absence. The research team performed a literature review and found that plant diversity and vegetation density have thus far been ignored.

When discussing nitrogen enrichment, we believe it may have an unknown impact on butterflies, according to Amrhein. Nitrogen appears to have a similar impact on butterfly diversity as global warming. The researchers do not believe that they have found a simple approach to resolving the problem, but they do think that new technology has the potential to help. Roth says, “Over time, the slurry was applied to farmland, for example, and windborne transfer of some of this took place to other locations.” Today, he claims that the use of drag hoses has increased over the years, and that they are now often used to apply the slurry directly to the soil. Reducing nitrogen input to locations where it is not wanted results in this.

Additionally, buffer zones and landscape management that is adapted to the environment can help mitigate the impact on sensitive habitats. This is good for a variety of plant life, and beneficial to butterflies. It is claimed that there is no way around environmentally-friendly consumer behaviour, such as reduced vehicle emissions and reduced livestock farming, when it comes to reducing unwanted nitrogen input. Ammonia emissions from livestock farming today account for two-thirds of nitrogen input into sensitive ecosystems in Switzerland.

source: ANI

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