Multi-year water level drawdown and wildlife grazing drive wetland vegetation succession

Kerstin Bouma; Gabriela Carrasco Oliva; Mats I. Douma; Perry Cornelissen; Mennobart R. van Eerden; Ralph J.M. Temmink; Bart A. Nolet; Elisabeth S. Bakker

doi:10.1016/j.ecoleng.2025.107819

Multi-year water level drawdown and wildlife grazing drive wetland vegetation succession

Kerstin Bouma^* (Corresponding author), Gabriela Carrasco Oliva, Mats I. Douma, Perry Cornelissen, Mennobart R. van Eerden, Ralph J.M. Temmink, Bart A. Nolet, Elisabeth S. Bakker

^*Corresponding author for this work

Research output: Contribution to journal/periodical › Article › Scientific › peer-review

Abstract

In wetlands, multi-annual water level drawdowns and herbivory can induce cyclic vegetation succession. While water level drawdowns can be used in wetland management to increase the area of reed vegetation, an important habitat for wetland birds, herbivory may interfere with this process. Here, we studied the combined effects of a human-induced water level drawdown, i.e. the intentional temporarily and large scale lowering of the water level, and herbivores on wetland vegetation development.In the Oostvaardersplassen wetland, we used satellite imagery to assess vegetation development with and without water level drawdown and with and without red deer presence (introduced in 1992). An herbivore exclosure experiment (2022–2024) across an elevational gradient tested the effect of grazing on vegetation development during a drawdown.Satellite imagery showed an expansion of reed cover by 560 ha in the period without red deer (1987–1991) and by 420 ha with red deer (2020–2024), only in the area with drawdowns. The exclosure experiment highlighted an interaction between herbivory and water depth: The presence of red deer at drier locations had minor effects on reed expansion, whereas reed expansion was strongly inhibited at wet locations with presence of geese.Our findings provide large-scale quantitative evidence of the interaction between a water level drawdown and herbivory on the restoration of reed-dominated wetlands. We show the effectiveness of a water level drawdown, when dry conditions can be maintained for several consecutive years, as a restoration tool to promote reed development and the potential to steer the impact of herbivores during restoration.

Original language	English
Article number	107819
Journal	Ecological Engineering
Volume	222
Early online date	01 Oct 2025
DOIs	https://doi.org/10.1016/j.ecoleng.2025.107819
Publication status	Published - Jan 2026

Keywords

Geese
Grazing
Phragmites australis
Red deer
Vegetation development
Water level drawdown
Wetland

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10.1016/j.ecoleng.2025.107819Licence: CC BY

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@article{9e7a79c0961d432d9bdbf916f0f49f8c,

title = "Multi-year water level drawdown and wildlife grazing drive wetland vegetation succession",

abstract = "In wetlands, multi-annual water level drawdowns and herbivory can induce cyclic vegetation succession. While water level drawdowns can be used in wetland management to increase the area of reed vegetation, an important habitat for wetland birds, herbivory may interfere with this process. Here, we studied the combined effects of a human-induced water level drawdown, i.e. the intentional temporarily and large scale lowering of the water level, and herbivores on wetland vegetation development.In the Oostvaardersplassen wetland, we used satellite imagery to assess vegetation development with and without water level drawdown and with and without red deer presence (introduced in 1992). An herbivore exclosure experiment (2022–2024) across an elevational gradient tested the effect of grazing on vegetation development during a drawdown.Satellite imagery showed an expansion of reed cover by 560 ha in the period without red deer (1987–1991) and by 420 ha with red deer (2020–2024), only in the area with drawdowns. The exclosure experiment highlighted an interaction between herbivory and water depth: The presence of red deer at drier locations had minor effects on reed expansion, whereas reed expansion was strongly inhibited at wet locations with presence of geese.Our findings provide large-scale quantitative evidence of the interaction between a water level drawdown and herbivory on the restoration of reed-dominated wetlands. We show the effectiveness of a water level drawdown, when dry conditions can be maintained for several consecutive years, as a restoration tool to promote reed development and the potential to steer the impact of herbivores during restoration.",

keywords = "Geese, Grazing, Phragmites australis, Red deer, Vegetation development, Water level drawdown, Wetland",

author = "Kerstin Bouma and Oliva, {Gabriela Carrasco} and Douma, {Mats I.} and Perry Cornelissen and {van Eerden}, {Mennobart R.} and Temmink, {Ralph J.M.} and Nolet, {Bart A.} and Bakker, {Elisabeth S.}",

note = "Publisher Copyright: {\textcopyright} 2025 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/",

year = "2026",

month = jan,

doi = "10.1016/j.ecoleng.2025.107819",

language = "English",

volume = "222",

journal = "Ecological Engineering",

issn = "0925-8574",

publisher = "Elsevier B.V.",

}

TY - JOUR

T1 - Multi-year water level drawdown and wildlife grazing drive wetland vegetation succession

AU - Bouma, Kerstin

AU - Oliva, Gabriela Carrasco

AU - Douma, Mats I.

AU - Cornelissen, Perry

AU - van Eerden, Mennobart R.

AU - Temmink, Ralph J.M.

AU - Nolet, Bart A.

AU - Bakker, Elisabeth S.

PY - 2026/1

Y1 - 2026/1

N2 - In wetlands, multi-annual water level drawdowns and herbivory can induce cyclic vegetation succession. While water level drawdowns can be used in wetland management to increase the area of reed vegetation, an important habitat for wetland birds, herbivory may interfere with this process. Here, we studied the combined effects of a human-induced water level drawdown, i.e. the intentional temporarily and large scale lowering of the water level, and herbivores on wetland vegetation development.In the Oostvaardersplassen wetland, we used satellite imagery to assess vegetation development with and without water level drawdown and with and without red deer presence (introduced in 1992). An herbivore exclosure experiment (2022–2024) across an elevational gradient tested the effect of grazing on vegetation development during a drawdown.Satellite imagery showed an expansion of reed cover by 560 ha in the period without red deer (1987–1991) and by 420 ha with red deer (2020–2024), only in the area with drawdowns. The exclosure experiment highlighted an interaction between herbivory and water depth: The presence of red deer at drier locations had minor effects on reed expansion, whereas reed expansion was strongly inhibited at wet locations with presence of geese.Our findings provide large-scale quantitative evidence of the interaction between a water level drawdown and herbivory on the restoration of reed-dominated wetlands. We show the effectiveness of a water level drawdown, when dry conditions can be maintained for several consecutive years, as a restoration tool to promote reed development and the potential to steer the impact of herbivores during restoration.

AB - In wetlands, multi-annual water level drawdowns and herbivory can induce cyclic vegetation succession. While water level drawdowns can be used in wetland management to increase the area of reed vegetation, an important habitat for wetland birds, herbivory may interfere with this process. Here, we studied the combined effects of a human-induced water level drawdown, i.e. the intentional temporarily and large scale lowering of the water level, and herbivores on wetland vegetation development.In the Oostvaardersplassen wetland, we used satellite imagery to assess vegetation development with and without water level drawdown and with and without red deer presence (introduced in 1992). An herbivore exclosure experiment (2022–2024) across an elevational gradient tested the effect of grazing on vegetation development during a drawdown.Satellite imagery showed an expansion of reed cover by 560 ha in the period without red deer (1987–1991) and by 420 ha with red deer (2020–2024), only in the area with drawdowns. The exclosure experiment highlighted an interaction between herbivory and water depth: The presence of red deer at drier locations had minor effects on reed expansion, whereas reed expansion was strongly inhibited at wet locations with presence of geese.Our findings provide large-scale quantitative evidence of the interaction between a water level drawdown and herbivory on the restoration of reed-dominated wetlands. We show the effectiveness of a water level drawdown, when dry conditions can be maintained for several consecutive years, as a restoration tool to promote reed development and the potential to steer the impact of herbivores during restoration.

KW - Geese

KW - Grazing

KW - Phragmites australis

KW - Red deer

KW - Vegetation development

KW - Water level drawdown

KW - Wetland

U2 - 10.1016/j.ecoleng.2025.107819

DO - 10.1016/j.ecoleng.2025.107819

M3 - Article

AN - SCOPUS:105018038351

SN - 0925-8574

VL - 222

JO - Ecological Engineering

JF - Ecological Engineering

M1 - 107819

ER -

Multi-year water level drawdown and wildlife grazing drive wetland vegetation succession

Abstract

Keywords

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