1. Biodiversity and functioning of floodplain forests

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

2 Riparian forests retain sediments and water, they function as nutrient filters Sanchez-Perez et al. 1991, Acta Oecologica As furnishers of organic matter (coarse woody debris) to the river Lassettre et al. 2007, Earth Surf. Process. Landforms 2

3 Early stages of succession stabilize stream banks Willow growth, five year after silt deposit,upper Rhine valley The major forest communities in Europe Data recorded from phytosociological studies (1965 to 2006) encompass 177 communities, secondly grouped in 6 main habitats types. Schnitzler et al. 2007, Biological Conservation 3

4 Oak-elm-ash hardwoods: elevated terraces Willow-poplars: close to the river Frequent and severe floods 4

5 White poplars: elevated terraces Bush willows: islands, river banks 5

6 White poplar Willow Poplar Bush willow Ash-alder: edges of the river plain Root hair against anoxia 6

7 Marsh alders: old channels Species richness in woody plants and vines in floodplain forests of Europe 7

8 Similar communities occur in rivers of the United States Wisconsin Species richness in floodplain forests of North America (Schnitzler et al. 2005,Biod. Cons.) 8

9 Hardwood communities : the «temperate jungle» of Europe Complexity of the canopy architecture, Upper Rhine valley Hardwoods of the Danube, Rhone and Rhine forests : complex architecture Walter,

10 Plant richness in forests of the upper sectors of The Rhine, the Rhône, the Danube RIVER total SR % woody % vines % exotics Rhône ,5 6,7 8,7 Danube ,2 3,2 2,4 Rhine ,1 Schnitzler et al. 2007, Biological conservation Rapid growth and gigantism for woody plants Quercus robur, Danube valley Ulmus minor, Rhine valley 10

11 In understoreys Malus sylvestris Crataegus monogyna Hedera helix, upper Rhine 11

12 Clematis vitalba, upper Rhine Vitis vinifera ssp silvestris Turkey, Kocegi lake Danube delta 12

13 In hardwoods, densities of birds are higher than in adjacent upland oak forests Sylvia atricapilla Turdus philomelos Parus major Coccothraustes coccothraustes Parus palustris Dendrocopos major Oriolus oriolus Streptopelia turtur Rhine forests Upland oak forests Dronneau 2007, Alauda 2. Biodiversity threats Deforestation Heavy hydraulic works Excessive logging Plantations 13

14 Landscapes have deeply changed in 150 years Romantic view of the upper Rhine, 1830 Monastery The same view in 2006 Monastery 14

15 Evolution of the Rhône landscapes in 150 years The Rhone, 19th century 2006 Main impacts: loss and degradation of floodplain habitats Physical destruction of forests: 95 % (Tockner Stanford 2002, Environment Conservation); 88 % (Research programme FLOBAR2 2003) Lossof wetlandareas (66%, de Waal et al, 1995) Contamination with pollutants 15

16 Impacts of hydraulic works: loss of habitats and plant species (example of the low Rhône) Species richness Cèze Durance Rhône Durance Ouvèze Cèze Delta Rhône Ouvèze Cèze Rhône Cèze Durance Ouvèze Rhône Durance Ouvèze Durance Cèze Ouvèze Salici Populetum Populetum albae Querco- Ulmetum Alno-Fraxinetum oxycarpae Alnetum incanae Saponario- Salicetum Schnitzler Carbiener, Forêts méditerranéennes, 2006 Loss of species depending on river dynamics Vitis vinifera ssp silvestris Thalictrum aquilegifolium Equisetum hiemale Alnus incana 16

17 The oak (Quercus robur) is highly sensitive to artificial changes in groundwater levels Upper Rhine valley, France Prypiat valley, Belarus Invasion of exotics: 49 species (2.7%) in floodplain forests of Europe, including 13 invasive species 17

18 3. The last well-preserved forested landscapes of Europe The Danube in Austria, Romania, Croatia: the best preserved floodplain forests of Europe 18

19 Some forests along tributaries are also well preserved The Moselle river, Rhine basin The Ain river, Rhône basin The Tagliamento river Pô basin What has been done? Many concrete actions for restoring partially the free course of the river, for re-establishing the connexions between the river and the terrestrial ecosystems Legal protections (Ramsar, Unesco, National Park, natural reserve, Natura 2000 ) 19

20 The Danube is the best protected river of Europe (Ramsar, Unesco Man and biosphere, National Park) Ha Danube Pô Rhône Rhin What would be ideal for forests? Natural reconquest of the potential forest zones 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?) 20

21 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 21

22 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» 22

23 In the natural reserve (180 ha), many hygrophilic trees are dying and opportunistic species, previously eliminated by floods, have invaded the understoreys Invasion of Acer pseudoplatanus Solidago gigantea in forest gaps 23

24 The Erstein reserve: some propositions of Eco-gardening transplantation of endangered species Artificial recreation of pools To struggle against alien plants 24

25 30 ha of newly formed forest (50 yrs), growing spontaneously after destruction of the previous forest Building of the Great Canal (Ottmarsheim), upper Rhine 25

26 Re-creation of old channels (upper Rhine valley) This portion of ancient floodplain is now protected Salty pools Artificial meadows Spontaneous dry forests What can we do with such altered landscapes? 26

27 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 27

28 3) The remnant dry forests will be let to a free development What is considered as valuable for «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. 28

29 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 ecological justifications 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. 29

30 Thank you for your attention 30