Water for forest & people in the Mediterranean Region: a challenging balance

The water cycle links ecosystems and human societies• Water: foundation for all biological life on Earth; equally fundamental for humans and nature • Basic link between biosphere and atmosphere

Med. Region: area with marked interactions between MaB

• Interactions & co-evolution between MaB over millenaries; over the last 150 years, contrasted evolutions in land use between the N & the S

• Water the main limiting factor for life; more constraints due to CC and demographic expansion • The need for water: Blue and Green, but what trade-off?

In a scarcity context, understanding the interactions water x forest x society is crucial

• Med. Region is mountainous, with forests located in upper part of watershed, acting as water tower, and influencing water resources and ecosystems (incl. aquatic) downstream

• A complex issue, characterized by “clichés” and commonly accepted opinions; «no one size fits all»

• Hydrological patterns specific to the Mediterranean call for specific approaches; soil and water are linked

• Balancing water between man and nature trough socio-eco-hydro-logical approach, based on integrated water/ecosystem/land/territories management: a necessity, but on which background?

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Provision• food• fresh water• wood & fibres• fuel

Cultural aspects• aesthetical• spiritual• education• recreation

Support functions • nutrients cycle • soil formation • primary production • functional biodiversity

Regulation• climate• erosion• peak flows & floods• water purification

Source : Millenium Ecosystem Assessment (2005)

Athens, 12/05/2009

Changing the paradigm of looking only at blue water

Considering water in all processes underlying the functioning of Forest (& adjacent Ecos. and the supply of goods and services 

Water-related ecosystem processes & services

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Climate change (temp. & rain) and water resources

Projection of changes in runoff by 2041-60 based on 12 modelsSource: IPCC, AR4, 2007

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The need for a collective scientific expert review• reconciling science’s findings and public perception

• assembling available knowledge scattered among disciplines (forestry, hydrology, soil science, climatology, ecology, economics)

• proposing ways to cope with future challenges

• EFIMED initiative – 40 authors

Yves Birot, Carlos Gracia and Marc Palahi (editors)

Outline

1.Green & blue water: what trade-offs?2.New approaches to assess the impact of land-use & forest management on water-related ecosystem services Supply of blue water to the Roman city of Nimes: the

Gard Aqueduct 2000 years BP - Photo: C. Birot

A glance at the book

Rainfall560 mm

Throughfall476 mm

Runoff 28 mm

AET 504 mm

Stemflow50 mm

Data from PRADES: Quercus ilex forest

Up to 90 per cent of rainfall goes back to the atmosphere!.

Water use in a Mediterranean forest

AET 504 mmRainfall 560 mm

Source: Gracia, 2011

1 g of C 500 g of H2O

A tree transpires 500 g H2O to fix 1 g of C

The tree respires and releases CO2 ; to fix 1 g of C (net) in tissues (wood, etc.), 1-1,5 l. H2O are needed

Source: Gracia,2011

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Can canopy manipulation increase water yield?

Study on 94 watersheds (Bosch, 1982)

Source : Lavabre 2000

Water foot print of wood (m3 of water/m3 of wood) depends on:

Tree species Water footprint

Tree species Water footprint

Quercus ilex 2,842 Pinus halepensis 2,073 Quercus suber 2,981 Pinus pinea 1,642 Castanea sativa 675 Pinus pinaster 698 Pinus radiata 332

a) Tree species

b) Management options

(P. sylvestris)

Source: Gracia, 2011

* *

It is crucial to understand the responses of forests not justin terms of C and biomass, but in terms of water

Blue water and green water are needed to sustain the benefits from the ecosystem services that we need

New approaches to assess the impact of land-use & forestmanagement on water-related ecosystem services

Source: Muys & Mavsar, 2011

Integrated water use

Integrated impact of land use & management on terrestrial and aquatic E.S. in a catchment is function of the actual E.Tr. Impact is minimal at the E.Tr. level of the potential natural vegetation and increases both sides reaching a maximum at complete soil denudation and at an increased transpiration level above the environmental water requirement of the aquatic ecosystem

Source: Maes et al, 2009

Tools for integrated water use

Improving the conservation of forest ecosystems as water providers, is possible through the payment by downstream users of clean water to upstream land users, and can allow internalizing what would otherwise be an externality

Source: Croitoru & Young, 2011

The artificial lake of La Môle in a fully forested watershed dominated by cork oak, supplying water to the tourist town of Saint-Tropez, Var, France. Photo by C. Birot.

The water company is paying annual fees to the local forestowners (public & private) for maintaining the fuel breaknetwork, and thus limiting the risk of wildfires, whoseimpact on dam siltation and water quality can be huge.

• The huge global flux of water vapour from terrestrial vegetation is a fundamental ecosystem service: Forests sustain the hydrological cycle through evapotranspiration, which cools climate through feedbacks with clouds and precipitation

• We should improve the understanding and modelling of the climatic responses –incl. precipitation patterns, to land cover change

• In the Med., forests are mostly water limited in summer period and energy limited in winter period

• Several factors influencing water use by tree plantations can be controlled by management

• Water footprint of forest products depends on tree species & growth conditions

Take home messages

• There is room to optimize the water oriented forest management

• In the Med., water and soil go together

• Integrating ecological, socio-economic and hydrological management is a key approach towards sustainability

• The Green water paradigm -in addition to the blue water paradigm-should receive increased attention, as green water flows sustain main ecosystem functions

• With regard to integration of water with other ecosystem services, a myriad of new tools for trade-off analysis and land management optimization has become available

Take home messages

Acknowledgements

a) For this presentationGiorgio MatteucciJerry VanclayJavier Martin VideCarlos GraciaBart MuysRobert Mavsar

b) For the book

The 40 authors

Thank you !

Book available in pdf (French and English) on www.efimed.efi.int