Experimental rewilding enhances grassland functional composition and pollinator habitat use

Abstract

Semi‐natural grasslands are rich in biodiversity and thus important habitats for conservation, yet they are experiencing rapid declines due to agricultural intensification and 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. 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 also investigated the effects of this experimental treatment on insect pollinated plants and on pollinator habitat use. 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. 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. Synthesis and applications. This study demonstrates that, to enhance the diversity of a given herbivore community with ecological replacements of extinct wild horses can have significant effects on the functional composition of grasslands. It can also mitigate plant species declines, in particular bee‐dependent plants, and boost pollinator habitat use. Novel management alternatives are urgently needed to reverse the negative effect of land abandonment in European agricultural landscapes. Thus, rewilding interventions with large mammalian herbivores may offset current biodiversity declines by maintaining important functional links between plants and pollinators in grassland ecosystems.

The differences between rewilding and restoring an ecologically degraded landscape

“…In all cases, the system is continually self‐organizing as the environment changes, and the functional composition of the system is a higher consideration than the taxonomy of its operating components (e.g. Garrido et al, ).…”

Restoring a butterfly hot spot by large ungulates refaunation: The case of the Milovice military training range, Czech Republic

“…Hennig et al 2017, Cromsigt et al 2018b, Zielke et al 2019, the immediate effects of year-round wild ungulates presence included reduction of tall coarse grasses, slowing down scrub growth due to browsing and bark peeling, reduction of grass blooming by feeding on grass in orescences, and exposing barren ground around tracks and wallows. As in experiments with feral horses (Garrido et al 2019), some richly blooming forbs, including species that rarely bloomed in the years preceding the refaunation (unpublished data), became notably more abundant. The differences in butter y assemblages composition between refaunated and neglected plots became apparent only after statistical control for the effect of years and to monitored plots position.…”

“…The current rewilding/ refaunation /naturalistic grazing movements (Seddon et al 2014;Merckx and Pereira 2015;Svenning et al 2016;Cromsigt et al 2018;Garrido et al 2019) strive to reverse the transformation of ecosystems that started in the late Pleistocene and culminated with recent land use intensi cation (Dirzo et al 2014;Jirku and Dostal 2015;Henning et al 2017;Pedersen et al 2019). Although insect conservationists have long advocated habitat management by ungulate grazing (e.g., Öckinger et al 2006;Cizek et al 2013;Slancarova et al 2014), relatively few megafauna refaunation projects have focused primarily on insect conservation or are systematically monitored for impacts on insects (van Klink et al 2018).…”

“…Each refaunation project develops within speci c sociocultural constraints, rarely allowing for proper replications (cf. Root-Bernstein et al 2018; but see Garrido et al 2019). There is an urgent need to study refaunation effects on invertebrates, both as encouragement for others and as feedback for the wider conservation community (Jepson 2016;van Klink et al 2018).…”

Green Assets of Equines in the European Context of the Ecological Transition of Agriculture

“…However, there is a decrease in permanent grasslands in Europe [15], while pastures are known to have different positive impacts: they are seen as pleasant and aesthetic [16] and provide multifunctional goods [15] that produce agricultural commodities and maintain biodiversity, soil, and water quality, even in suburban areas [17], in addition to meeting the needs of herbivorous productions. Animal grazing presents three general consequences: (1) it maintains a certain level of vegetal biomass [18] with the control of invasive species (through the intake of plants [19] and trampling [19]); (2) it has effects on plant metabolism (defence, resistance, and avoidance) [19]; and (3) it enables the creation of ecological niches [20].…”