Long-term effects of rotational wetland mowing on breeding birds: evidence from a 30-year experiment

Abstract

Wetlands are amongst the richest, yet most threatened types of habitats on Earth. One major threat is the modification of water regime for human activities, which disrupts normal ecosystem equilibrium. In lacustrine wetlands, reduced flooding allows shrubs to take over, ultimately leading to a shift towards woody communities. To counter this, wetland managers have initiated a variety of measures, including mowing, burning, and pasturing. Because of the short time frames of previous studies on the subject, little is known on their potential negative side effects on the ecosystem. Here, we evaluate the long-term effect of mowing on breeding populations of the five most abundant species in our central European study area (the reed warbler Acrocephalus scirpaceus, the common reed bunting Emberiza schoeniclus, Savi's warbler Locustella luscinioides, the water rail Rallus aquaticus, and the bearded reedling Panurus biarmicus). This study, of an unprecedented time scale (30 years), shows that rotational mowing has no long-term detrimental effects on birds. However, optimal mowing regime for the birds might often be less frequent than what is usually applied. We recommend that mowing be spaced every 3 years at least, and ideally every 6 years or more. We discuss additional measures that could be implemented to complement mowing. Because of the widespread distribution of the target habitat and species, our study provides readily applicable information for wetland managers in Europe and worldwide.

Mowing may bring about vegetation change, but its effect is strongly modified by hydrological factors

“…It is sufficient to repeat this procedure every 4-5 years in the beginning of August when most of the plant species end their flowering and when the seeds have a chance to germinate in exposed areas. This mowing regime is also beneficial for the protection of birds (Antoniazza et al 2017).…”

The impact of climate change on flow conditions and wetland ecosystems in the Lower Biebrza River (Poland)

“…The disappearance of valley meadows that could be maintained by continuing periodic mowing ( Mioduszewski & Ślesicka, 2004 ) would also result in the loss of rare wetland birds such as Aquatic Warbler, Ruff, Great Snipe and Greater Spotted Eagle. However, it should be noted that although seasonal mowing is a positive management factor for the biodiversity of non-forested wetlands, analysis of the effects of rotational wetland mowing on breeding birds provided evidence for a positive effect on some wetland birds of significantly longer mowing intervals ( Antoniazza et al, 2018 ).…”

Peer Review #2 of "The impact of climate change on flow conditions and wetland ecosystems in the Lower Biebrza River (Poland) (v0.1)"

“…The disappearance of valley meadows that could be maintained by continuing periodic mowing (Mioduszewski, 2004) would also result in the loss of rare wetland birds such as Aquatic Warbler, Ruff, Great Snipe and Greater Spotted Eagle. However, it should be noted that although seasonal mowing is a positive management factor for the biodiversity of nonforested wetlands, analysis of the effects of rotational wetland mowing on breeding birds provided evidence for a positive effect on some wetland birds of significantly longer mowing intervals (Antoniazza et al, 2018). Grygoruk et al (2014) assume for the time horizon 2070-2100 a significant increase in precipitation in summer, a decrease in precipitation in autumn, winter and spring and a general increase in the average air temperature and on this basis, they present hypothetical scenarios of changes in flood condition and their ecological consequences in the Lower River Biebrza Basin.…”