# Managing water control in Atlantic Coastal Wetland: Grasslands for grazing and amphibian conservation

Lilia Mzali, Vincent Boutifard, Daphné Durant

► To cite this version:

Lilia Mzali, Vincent Boutifard, Daphné Durant. Managing water control in Atlantic Coastal Wetland: Grasslands for grazing and amphibian conservation. 12th INTECOL WETLANDS CONFERENCE, International Association for Ecology, Jun 2025, Tartu (Estonie), Estonia. pp.15. hal-05168022

HAL Id: hal-05168022

https://hal.inrae.fr/hal-05168022v1

Submitted on 17 Jul 2025

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# Managing water control in Atlantic Coastal Wetland - Grasslands for grazing and amphibian conservation

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Mzali Lilia, Boutifard Vincent, Durant Daphné, INRAE, Experimental Unit of Saint-Laurent-de-la-Prée, France

July 1, 2025, Session 8, Tartu, ESTONIA,

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RÉPUBLIQUE
FRANÇAISE

Liberté
Égalité
Fraternité

INRAE

<figure><img src="image_4.png" /></figure>

RÉGION
Nouvelle-
Aquitaine

Nouvelle-Aquitaine

<figure><img src="image_5.png" /></figure>

tetrae

Transition en Territoires de l'Agriculture,
l'Alimentation et l'Environnement

<figure><img src="image_6.png" /></figure>

RÉPUBLIQUE
FRANÇAISE

Liberté
Égalité
Fraternité

eau
GRAND SUD-OUEST
AGENCE DE L'EAU ADOUR-GARONNE
# The case study: the marshes of the French Atlantic coast

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The INRAE experimental farm
in Saint-Laurent-de-la-Prée

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estuaire Charente

Dry marshes (freshwater)

* Contained

* Dense network of ditches

* Mixed crop-livestock farming

* Extensive suckler cattle farming

* Rich fauna specific to wetlands
# Water management in marshes

* "Man-made" marshes

* Controlling gate and pumps constitutes action levers on the water regimes in the ditches and on grassland.

* Flooding of clay marshes is linked to rainfall and overflow from ditches onto the grassland (gravitational transfers, slight variations in topography)

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<figure><img src="image_13.png" /><figcaption>Gate regulating water level</figcaption></figure>
# The research project of the Saint-Laurent-de-la-Prée experimental unit (UE SLP)

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Problem
posed

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## "Supporting the agroecological transition of marsh farms"

* Restoring **biodiversity**

* Supplying the local area with **organic plant and animal products**

* Adopting practices compatible with the **hydrological functions** of marshes

* Contributing to **climate** change mitigation

* Building a **sustainable farming** system
INRAO

How to act on water resources through the operation of gates to control water levels in the ditches and on fields with a dual purpose :

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Restoring **biodiversity** in marshes

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Maintaining **agricultural and food production capacity**

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Illustration on a field of the EU SLP "L2"

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# Knowledge acquired in Atlantic coastal marshes

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The plant composition on wetlands of the franch Atlantic coastal is explained by the water regimes and the salinity levels (Bouzillé et al, 2001). These regimes are linked to the microtopography.

<figure><img src="image_21.png" /><figcaption>Plant composition 2024 - Field "L2" EU INRAE SLP</figcaption></figure>

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Selon Kernéïs, 2025

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**Mesohygrophilic plant communities : up to 2 months with more than 10cm of water of flooding** (and from 2 to 10 cm of water in march.)

**Hygrophilic plant communities: between 2 and 8 months of flooding**
**with more than 10 cm** (and from 10 to 25 cm of water in march.)

Data acquired from 5
study sites
2024-2024
(TETRAE-MAVI Project)

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# Knowledge acquired in Atlantic coastal marshes

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The topographic depressions hosting mesohygrophilous and hygrophilous plant communities **provide a grazing resource with delayed production** (in terms of growth and phenology), which is grazed by the herd during **summer** when other forage resources are depleted.

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Data acquired from 5 study sites
2024-2024
(TETRAE-MAVI Project)

## Nutritional value of different plant communities on wet grasslands in early summer

Source - 5 Atlantic marsh sites June 2024 - Mavi Project

Water regimes
and flora

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April
**mesophilic**
**hygrophilic**

May
**mesophilic**
**hygrophilic**

June
**Study of the behavior of cows in pastures, according to the season and location in depressions or on "bumps"**
(Mialhe, 2021, Kernéïs et al, 2022)

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# Knowledge acquired in Atlantic coastal marshes

**Amphibians** are distributed among different wetlands according to their reproductive cycle, diet and survival strategy ((Cayuela et al., 2012; Morand & Joly, 1995; Wellborn et al., 1996; Werner et al., 2007). They breed in **temporary watering holes** with dense and varied vegetation (Vági et al., 2013)

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Amphibian distribution within the depression of the test field

Data acquired from 5 study sites
2024-2024
(TETRAE-MAVI Project)

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These three populations are positively associated with topographic depressions connected to the ditches (GLM analysis- p-value < 0.05)

Water regimes and amphibians

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Pelodytes punctatus

Pelophylax sp.

Hyla meridionalis

Amphibian populations present on 5 sites in the Atlantic coastal marshes between February and June 2024-2025

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# Formulating objectives of water management on test field
## Deriving management guidelines through simulation

An adaptive
management
approach with a
results-based logic
adapted from Durant,
2025

1

Promote a habitat to accommodate amphibians (target 5 common parsley frog- pelodytes punctuatus) by maintaining flooded depressions on field.

2

Maintaining heterogeneity of water conditions to preserve the range of plant biodiversity

3

Maintaining grass quality and growth for pasture by promoting a resource available in summer (to limit the need to bring hay to cows in summer)

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**Simulation model** (based on Digital Surface Model)
**Flooded area and depth for the target water level of 2m80NGF**

Field "L2" - EU INRAE SLP

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### Conversion of objectives into the targeted wetland habitat on the field area

**Objective** = water level from **10 to 25 cm** from January to June on at least 20% of the field

( approximately 50% mesophilous; 20% mesohygrophilous and 30% hygrophilous

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### Conversion of the desired wetland habitat into water level management guidelines
by using a simulation based on Digital Surface Model

**Management level between 2.80 m NGF and 2.85 mNGF from December to March**

NGF = French Vertical Datum
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## 2- Monitoring water level regulation

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Respect water levels in the ditch
(2,85 and 2.80 from december to march)

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1- Practical management =
opening/closing gate
## 3. Conversion into field flooding
with simulation model

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## 2- Monitoring water level regulation

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## 1- Practical management =
opening/closing gate
## 4-Target

Food, economic, biodiversity

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## 3. Conversion into field flooding
with simulation model

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## 2- Monitoring water level regulation

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1- Practical management =
opening/closing gate
A management tool for our constantly evolving system

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* Annual learning based on results/ gaps, consultation of the EU collective (multidisciplinary):

* Field campaign to validate simulation

* Acquisition of additional knowledge on the relationships between water regime, flora, and fauna

* Adaptation of practices, technical adjustments/revision of targets (re-design)

Adapted from Ferrané et al, 2020

Taking into account other factors in the analysis: weather, invasive species, field management, ...
Thank you for your attention

Mzali Lilia, Boutifard Vincent, Durant Daphné, INRAE,
Experimental Unit of Saint-Laurent-de-la-Prée, France

July 1, 2025, Session 8, Tartu, ESTONIA,

lilia.mzali@inrae.fr

<figure><img src="image_50.png" /></figure>

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RÉPUBLIQUE
FRANÇAISE

Liberté
Égalité
Fraternité

INRAE

<figure><img src="image_52.png" /></figure>

RÉGION
Nouvelle-
Aquitaine

<figure><img src="image_53.png" /></figure>

Nouvelle-Aquitaine

tetrae

Transition en Territoires de l'Agriculture,
l'Alimentation et l'Environnement

<figure><img src="image_54.png" /></figure>

RÉPUBLIQUE
FRANÇAISE

Liberté
Égalité
Fraternité

eau
GRAND SUD-OUEST
AGENCE DE L'EAU ADOUR-GARONNE