Data from: Experimental rewilding enhances grassland functional composition and pollinator habitat use

1. Semi-natural grasslands are rich in biodiversity and thus important
habitats for conservation, yet subjected to rapid declines due to
agricultural intensification or abandonment. Promoting a more diverse
mammalian herbivore community, including large and megaherbivores, may
result in positive cascade effects for biodiversity and ecosystem
functioning. Therefore, reintroducing an ecologically functional
substitute of an extinct large herbivore could mitigate current
biodiversity declines and foster semi-natural grassland conservation. 2.
To test this hypothesis, we set up a 3-year rewilding experiment where 12
feral horses were introduced in three 10-hectare enclosure replicates
(four horses per enclosure). We used community-weighted mean plant
functional traits to elucidate plant community changes induced by grazing
through time. We additionally investigated the effects of the experimental
treatment on insect pollinated plants and on pollinator habitat use. 3.
The grassland community exerted a mixed tolerance/avoidance response to
grazing. This resulted in plant functional compositional changes which
favoured prostrate plant species with higher specific leaf area,
characteristic of ruderal communities. 4. Plant species richness was
higher in grazed compared to ungrazed areas. Butterfly and bumblebee
habitat use, as well as feeding and resting activities were also higher in
grazed areas. Moreover, the number of pollinators increased with plant
species richness. 5. Synthesis and applications. This study demonstrates
that to enhance the diversity of a given herbivore community with an
ecologically functional substitute of extinct wild horses can have
significant effects on the functional composition of grasslands, mitigate
plant species declines, and boost pollinator habitat use. Thus, rewilding
interventions with large herbivores may offset current biodiversity
declines by maintaining important functional links between plants and
pollinators in grassland ecosystems.