Nutrients, isolation and lack of grazing limit plant diversity in restored wetlands
Baumane,M., L. Baastrup-Spohr, K. Sand-Jensen, I. Goldberg, K.T. Martinsen and H.H. Bruun . 2025.
Abstract
1. Agricultural intensification has led to the loss of most natural wetlands from
human-dominated landscapes but, in recent decades, wetland restoration has
gained traction worldwide. Restoration of suitable habitat conditions is hampered
by nutrient residues from decades of high-input farming, by continued input of
nutrients from surrounding farmland and by incomplete restoration of natural
hydrology.
2. We assessed the effect of wetland restoration and disturbance (grazing) on vas-
cular plant and bryophyte diversity in restored wetlands in Denmark at plot and
landscape scales.
3. Compared to near-natural wetlands, we found a lower species richness and com-
munity uniqueness in restored wetlands, but we also found that grazing had a
positive effect on vascular plant richness in restored wetlands. The size of the
local species pool, presence of near-natural habitat prior to restoration and near-
natural restored hydrology all had positive effects on plant diversity, whereas
high soil iron and nitrogen had negative effects.
4. Synthesis and applications: Restoration of plant diversity in wetlands is challeng-
ing, but our results point to potential remedies: plan restoration areas near colo-
nisation sources of the target biota, restore hydrology to near-natural conditions,
discontinue nutrient loads from surrounding arable land and restore near-natural
grazing regimes. Bryophytes may be particularly useful as indicators for success-
ful restoration of wetlands
Key Words
agricultural landscape, biodiversity, bryophytes, grazing, hydrology, nutrient residue, species pool
