40
Les conséquences écologiques de l’érosion de la biodiversité Par : Michel Loreau Professeur, Département de biologie, Université McGill Chaire de recherche du Canada en écologie théorique BIENVENUE

Aucun titre de diapositive - Partenariat Innovation Forêt decembre... · Les conséquences écologiques . de l’érosion de la biodiversité. Par : Michel Loreau. Professeur, Département

  • Upload
    others

  • View
    1

  • Download
    0

Embed Size (px)

Citation preview

Les conséquences écologiques de l’érosion de la biodiversité

Par :Michel LoreauProfesseur, Département de biologie, Université

McGillChaire de recherche du Canada en écologie théorique

BIENVENUE

Michel LoreauDepartment of Biology, McGill University, Montreal

E-mail: [email protected]

The ecological consequences of biodiversity loss

Heading for a global biodiversity crisis

Heading for a global biodiversity crisis

Proximate drivers of biodiversity loss

Loreau, The Challenges of Biodiversity Science (2010)

• The world population increased by a factor of 2.4 between 1950 and 2000

• Average per capita affluence increased by a factor of 2.8 in the same period

• As a result, the gross world product increased sevenfold

The ultimate cause of biodiversity loss: Human environmental impact

Why does biodiversity matter?

Biodiversity, ecosystem functioning,

and human wellbeing

Importance of “vertical” diversityRemoval of sea otters

Population explosion of sea urchins

Overgrazing of kelp

Extinction of other species living in kelp

Increased wave action, coastal erosion and storm damage

Evolution of chemical defences in kelp

Sea otter

Sea urchin

Kelp

But what is the ecological significance of “horizontal”

diversity?

Neutral theory Functional redundancy

Niche theory Functional

complementarity

Diversity

Prod

uctiv

ity

Diversity

Prod

uctiv

ity

Separation between community ecology (biodiversity) and ecosystem ecology (ecosystem functioning, management)

Cedar Creek biodiversity experiment

BIODEPTH biodiversity experiment

Species diversity increases plant biomass production in grasslands

Hector et al., Science 286: 1123–1127 (1999)

Abo

vegr

ound

bio

mas

s (g

/m2 )

Species richness

Tilman et al., Science 294: 843–845 (2001)

A general form of biodiversity– ecosystem functioning relationships?

Cardinale et al., Nature 443: 989–992 (2006)

Loreau et al., Science 294: 804–808 (2001)

The controversy over mechanisms

ΔY = S.ΔRY .M + S.cov(ΔRY, M)

Loreau & Hector, Nature 412: 72–76 (2001)

Net effect = Complementarity effect + Selection effect

Partitioning selection and complementarity in biodiversity experiments

Net effect = Increase in yield above that expected from monoculturesComplementarity effect: Due to improved average performanceSelection effect: Due to dominance by most productive species

Species richness

Biodiversity effects on plant biomass production in BIODEPTH

Loreau & Hector, Nature 412: 72–76 (2001)

Species richness

Selection effect (g1/2/m) Complementarity effect (g1/2/m)

Selection effect (g/m2)

Biodiversity effects on plant biomass production: A meta-analysis

Cardinale et al., PNAS 104: 18123–18128 (2007)

Complementarity effect (g/m2)

The results of biodiversity experiments support niche theory

Neutral theory Functional redundancy

Niche theory Functional

complementarity

Diversity

Prod

uctiv

ity

Diversity

Prod

uctiv

ityNo net biodiversity effectNo complementarity effectNo selection effect

Positive net biodiversity effectPositive complementarity effectVariable selection effect

Biodiversity and ecosystem stability: The insurance hypothesis

Yachi & Loreau, PNAS 96: 1463–1468 (1999)

Based on Tilman et al., Nature 441: 629–632 (2006)Hector et al., Ecology 441: 629–632 (2010)

Species diversity stabilises plant biomass production in grasslands

Species richness Species richness

CV

tota

l bio

mas

s (x

100)

CV

tota

l bio

mas

s

The whole is the sum of its parts, but it obeys different rulesHector et al., Ecology 441: 629–632 (2010)

Population vs. ecosystem stability in grassland plants

Species richness

CV

biom

ass

(x10

0)

Biodiversity as insurance: Mechanisms

1.

Asynchrony of species environmental responses

(= temporal complementarity)

2.

Increase in total biomass

(due to functional complementarity)

Loreau, From Populations to Ecosystems (2010)

in theory

Biodiversity as insurance: Mechanisms in the Cedar Creek experiment

Log Synchrony of environmental 

responses

Log Total biomass

Log CV

 of total biomass

r2

= 0.27 (P

< 10−9)

r2

= 0.44 (P

< 10−15)

de Mazancourt et al., unpublished results

Inorganic nutrientdepletion zone

L1

PlantP1

qR

kL1kσ1 R

Inorganic nutrient poolR

I

kLSkσS R

…cL1P1 L1 P1

HerbivoreH1

cP1H1 P1 H1

CarnivoreC1

cH1C1 H1 C1

PlantPS

cLSPS LS PS

HerbivoreHS

CarnivoreCS

cPSHS PS HS

cHSCS HS CS

Inorganic nutrientdepletion zone

LS

cPSH1 PS H1

cHSC1 HS C1

cP1HS P1 HS

cH1CS H1 CS

mPS PS λPS mPS PS

mHS HS λHS mHS HS

mCS CS λCS mCS CS

mP1 P1

mH1 H1

mC1 C1

λP1 mP1 P1

λH1 mH1 H1

λC1 mC1 C1

Complex BEF relationships in food webs

Loreau, From Populations to Ecosystems (2010)

Complex BEF relationships in food webs

Species richness

Tot

al b

iom

ass

H1

P1

HS−1

PS−1

HS

PS

H1

P1

HS−1

PS−1

HS

PS

Herbivores

Plants

Both plant diversity and

herbivore diversity vary

Herbivore diversity alone

varies

Loreau, From Populations to Ecosystems (2010)

Biodiversity and ecosystem multifunctionality in BIODEPTH

Hector & Bagchi, Nature 448: 188–190 (2007)

Biodiversity and ecosystem multifunctionality in grasslands

Isbell et al., unpublished results

Biodiversity and ecosystem multifunctionality in grasslands

Isbell et al., unpublished results

From ecosystem functioning to ecosystem services

Plant species diversity increases forage yield in grasslands

Sanderson et al., Crop Sci. 44: 1132–1144 (2004)Bullock et al., Ecol. Lett. 4: 185–189 (2001)

Forage yield increases in species-rich mixtures as compared with the species-poor mixtures recommended by the UK Ministry across several sites in southern England

Forage yield increases with the number of productive species in Utah

Recommended mixture

Vilà

et al., Ecol. Lett. 10: 241–250 (2007)

⇒ Impact on carbon storage?

Biodiversity increases wood production in Mediterranean forests

Plant species diversity as a reservoir of adaptation to environmental changes

Reich et al., Nature 410: 809–812 (2001)

Genetic diversity increases rice resistance to blast disease

“Disease-susceptible rice varieties planted in mixtures had 89% greater yield and blast was 94% less severe than when they were grown in monoculture. The experiment was so successful that fungicidal spray was no longer applied by the end of the two-year programme.”

Zhu et al., Nature 406: 718–722 (2000)

International Center for Integrated Mountain Development (Nepal)

Loss of insect pollinators compensated by human labour in Himalaya

Conclusions

Biodiversity loss has significant impacts on ecosystem functioning, in particular:

Horizontal diversity enhances resource use and biomass production through functional complementarity between species

Horizontal diversity stabilises ecosystem properties through a combination of temporal and functional complementarity between species

Conclusions

The ecological consequences of biodiversity loss have been vastly underestimated because of the traditional focus on small scales, single trophic levels, and single ecosystem processes

Interactions between multiple trophic levels tend to generate complex biodiversity effects; they are potentially

a major source of surprises and uncertainty

Most grassland plant species play a significant role in ecosystem functioning when variability across space, time, functions, and environmental drivers is taken into account

Conclusions

Biodiversity loss is likely to strongly affect the provision of ecosystem services and is, therefore, a serious threat to human wellbeing and sustainable development

http://www.int-res.com/book-

series/excellence-in-ecology-

books/ee17/Princeton University Press (2010)

If you want to know more…