Nitrogen deposition has negative effects on Swiss butterflies ( https://conbio.onlinelibrary.wiley.com/doi/abs/10.1111/cobi.13744?s=09). Why has Nitrogen deposition become such an important threat for butterflies? 1/

N-deposition (mainly due to high local ammonia emissions from intensive livestock farming) reaches dozens of kms from the source to deep into even te biggest nature reserves ( https://www.clo.nl/indicatoren/nl0189-stikstofdepositie). 2/

It acts as a fertilizer increasing the growth rate of plants that can deal with a high N-load, as grasses. This changes the vegetation, succession speeds up and low vegetation and open soil is soon covered by tall grasses. 3/

In combination with climate change this leads to microclimatic cooling creating unsuitable conditions, esp. for larval and egg hibernators ( https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-2486.2006.01202.x) as this Glanville Fritillary (Melitaea cinxia). 4/

Ndep in host plants increases the mortality of common Lepidoptera species ( https://pubmed.ncbi.nlm.nih.gov/30288608/ ), e.g. with the Sooty Copper (Lycaena tityrus). This is probably caused by a shift in the N:P ratio in the foodplants ( https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2435.12707). 5/

This imbalance by overabundance of Nitrogen has a big effect on the nutritional quality of foodplants and its subsequent effects on consumers ( https://edepot.wur.nl/530421 ). Butterflies are more affected by this, a full metamorphosis means a high need of aminoacids. 6/

Ndep also leads to acidification and a decline in the availability of other nutrients and elements ( https://research.wur.nl/en/publications/continuous-and-cumulative-acidification-and-n-deposition-induce-p). 7/

For a more detailed overview of all pathways for the effects of increased nitrogen deposition on fauna see
https://www.natuurkennis.nl/Uploaded_files/Publicaties/nijssen-etal-2017.0b6d7c.pdf 8/

We developed a nitrogen index to track changes in butterfly species assemblages under nitrogen deposition ( https://research.wur.nl/en/publications/a-nitrogen-index-to-track-changes-in-butterfly-species-assemblage). 9/

Removing N from nature reserves is almost impossible as that also removes P and other elements. However N is quickly replenished leaving the area in a worse state as before (N:P ratio get furter unbalanced). 10/

The only solution is to reduce the Nitrogen emission at the source. This however, is still a step too far for part of the society ( https://www.nu.nl/binnenland/6062744/boze-boeren-zorgen-met-trekkers-voor-10-kilometer-file-op-a2.html). 11/end