Nitrogen is impoverishing Switzerland's butterfly diversity

This is reported by researchers at the University of Basel in the journal «Conservation Biology».

They examined the abundance and diversity of plants and butterflies across 383 sites in Switzerland. The result: the more nitrogen enters habitats through the air, the poorer in species and denser the vegetation, and the fewer butterflies.

This is because nitrogen fertilisation causes certain undemanding plant species to grow faster than others, which are then overgrown and shaded out. As a result, open, warm, and dry habitats become cooler, shadier, and more humid. «Some butterfly species depend on specific plant species as food during their caterpillar stage, or require a particular microclimate», said the lead author of the study, Tobias Roth of the University of Basel, in a press release from the institution.

A key role for the butterfly world

Alongside industrial agriculture, habitat fragmentation, and climate change, nitrogen deposition likely plays a key role in the occurrence of these colourful insects, according to the biodiversity researchers. Indeed, more than half of all butterfly species in Switzerland are considered threatened or potentially at risk.

To address the loss of diversity, they see one piece of the puzzle in landscape management as well as further technical improvements to reduce the amount of nitrogen entering habitats. Ultimately, however, they consider environmentally conscious consumer behaviour to be crucial — so that fewer vehicle emissions are released into the air and livestock farming can be reduced.

According to the Federal Office for the Environment (FOEN), two thirds of nitrogen inputs into sensitive ecosystems can be attributed to ammonia emissions from agriculture, while around one third comes from nitrogen oxides produced by combustion processes.