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Biodiversity of surface water,floodplains and groundwater

October 29/30, 2008Bonn, Germany

BIODIVERSITY THREATS IN FLOODPLAINSFORESTS OF EUROPEWHAT CAN WE DO ?

Annik SCHNITZLERL.I.E.B.E. University Paul Verlaine,

CNRS 7146,57070 Metz, France.

1. Biodiversity and functioningof floodplain forests

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Riparian forests retainsediments and water,

they function as nutrient filters

Sanchez-Perez et al. 1991, Acta Oecologica

As furnishers of organic matter (coarsewoody debris) to the river

Lassettre et al. 2007, Earth Surf. Process. Landforms

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Early stages of succession stabilizestream banks

Willow growth, five year after silt deposit,upper Rhine valley

The major forest communitiesin Europe

Data recorded from phytosociologicalstudies (1965 to 2006) encompass177 communities, secondly groupedin 6 main habitats types.

Schnitzler et al. 2007, Biological Conservation

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Oak-elm-ashhardwoods:

elevated terraces

Willow-poplars: close to the river

Frequent and severe floods

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White poplars: elevated terraces

Bush willows: islands, river banks

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Bush willow

White poplar

Willow Poplar

Ash-alder: edges of the river plain

Root hair against anoxia

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Marsh alders: old channels

Species richness in woody plants and vines in floodplain forests of Europe

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Similar communities occur in riversof the United States

Wisconsin

Species richness in floodplain forestsof North America (Schnitzler et al.

2005,Biod. Cons.)

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Hardwoodcommunities :

the « temperatejungle » of

Europe

Complexity of the canopy architecture,

Upper Rhine valley

Hardwoods of the Danube, Rhone and Rhine forests : complex architecture

Walter, 1979

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Schnitzler et al. 2007, Biological conservation

4,1546120Rhine2,43,226,2122Danube8,76,729,5149Rhône

% exotics% vines% woodytotal SRRIVER

Plant richness in forests of the upper sectors of The Rhine, the Rhône, the Danube

Rapid growth and gigantism for woody plants

Quercus robur, Danube valley Ulmus minor, Rhine valley

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Malus sylvestris Crataegus monogyna

In understoreys

Hedera helix, upper Rhine

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Clematis vitalba, upper Rhine

Vitis vinifera ssp silvestris

Turkey, Kocegi lakeDanube delta

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In hardwoods, densities of birds are higher than in adjacent upland oak forests

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Rhine forests

Upland oak forests

Dronneau 2007, Alauda

2. Biodiversity threats

DeforestationHeavy hydraulic works

Excessive loggingPlantations

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Landscapes have deeply changed in 150 years

Romantic view of the upper Rhine, 1830

Monastery

The same view in 2006

Monastery

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Evolution of the Rhône landscapes in 150 years

The Rhone, 19th century2006

Main impacts: loss and degradation of floodplain

habitats• Physical destruction of forests:• 95 % (Tockner § Stanford 2002, Environment

Conservation); 88 % (Research programme FLOBAR2 2003)

• Loss of wetland areas • (66%, de Waal et al, 1995)

• Contamination with pollutants

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Impacts of hydraulic works:loss of habitats and plant species

(example of the low Rhône)

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SaliciPopuletum

Populetum albae Querco-Ulmetum

Alno-Fraxinetumoxycarpae

Alnetumincanae

Saponario-Salicetum

Species richness

Schnitzler § Carbiener, Forêts méditerranéennes, 2006

Loss of species depending on river dynamics

Vitis vinifera ssp silvestris

Equisetum hiemale Alnus incana

Thalictrum aquilegifolium

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The oak (Quercus robur) is highlysensitive to artificial changes in

groundwater levels

Upper Rhine valley, FrancePrypiat valley, Belarus

Invasion of exotics:49 species (2.7%) in floodplain forests of

Europe, including 13 invasive species

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• 3. The last well-preservedforested landscapes of Europe

The Danube in Austria, Romania, Croatia: the best preservedfloodplain forests of Europe

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Some forests along tributariesare also well preserved

The Ain river, Rhône basin

The Tagliamento riverPô basin

The Moselle river, Rhine basin

What has been done ?

• Many concrete actions for restoringpartially the free course of the river, for re-establishing the connexions between the river and the terrestrialecosystems

• Legal protections (Ramsar, Unesco, National Park, natural reserve, Natura2000…)

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0

200 000

400 000

600 000

800 000

1 000 000

1 200 000

Danube Pô Rhône Rhin

Ha

The Danube is the best protected river of Europe (Ramsar, Unesco Man and biosphere, National Park)

What would be ideal for forests ?

• Natural reconquest of the potential forestzones even in sites where the flood pulse was not restored

• Strict protection of all these forests(remnants and newly formed forests), i.e. no agriculture, forestry (hunting ?)

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These rules are easy when the flood pulse has been preserved,

and land uses have changed

The Moselle valley in 1950 The same in 2007

Spontaneity of forest growth on the long term has permitted woody

debris to accumulate in the river

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But what can we do when the flood pulse has been deeply altered ?

• The case of the upper Rhine valley, France

Re-inundations through the concept of the « polder »

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In the natural reserve (180 ha), manyhygrophilic trees are dying…

… and opportunistic species, previously eliminated by floods, have

invaded the understoreys

Solidago gigantea in forest gapsInvasion of Acer pseudoplatanus

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The Erstein reserve: some propositions of“Eco-gardening”

transplantation of endangered speciesArtificial recreation of pools

To struggle against alien plants

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30 ha of newly formed forest (50 yrs), growingspontaneously after destruction of the previous

forest

Building of the Great Canal (Ottmarsheim), upper Rhine

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Re-creation of old channels(upper Rhine valley)

What can we do with such alteredlandscapes ?

This portion of ancient floodplain is now protected

Saltypools

Artificialmeadows

Spontaneous

dry forests

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• 1) The creation of an artificial wetland, from

the salty pools, for migratory birds

2) The widening of the open landscapes

By destruction of the dry spontaneous forest

By pasture

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3) The remnant dry forests will belet to a free development

What is considered as valuablefor « biodiversity managers » ??

• Only the sites actively managed• (artificial pools, pastures)

• The dry forests let to spontaneity are not considered as valuable for biodiversity, even if they correspond to natural successions.

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The naturalness concept• Whatever the level of preservation,

ancient floodplain forests must be totally protected, and let to natural forest dynamics, even if flood pulses cannot be restored.

• Schnitzler et al. 2008, J. Agricultural and Environmental Ethics

Ethical and ecologicaljustifications

• These current successions are different from former forests because of heavy human heritages

• They give future generations an interesting reference point for the profound changes that have taken place in our current landscape.

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Thank you for your attention