1 Biodiversity of surface water, floodplains and groundwater October 29/30, 2008 Bonn, Germany BIODIVERSITY THREATS IN FLOODPLAINS FORESTS OF EUROPE WHAT CAN WE DO ? Annik SCHNITZLER L.I.E.B.E. University Paul Verlaine, CNRS 7146, 57070 Metz, France. 1. Biodiversity and functioning of floodplain forests
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BIODIVERSITY THREATS IN FLOODPLAINS … · L.I.E.B.E. University Paul Verlaine, CNRS 7146, 57070 Metz, France. 1. Biodiversity and functioning of floodplain forests. 2 Riparian forests
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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
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.