How the decline of ocean species How the decline of ocean species threatens human well-beingthreatens human well-being

How the decline of ocean species How the decline of ocean species threatens human well-beingthreatens human well-being

Emmett DuffyEmmett DuffyVirginia Institute of Marine ScienceVirginia Institute of Marine ScienceThe College of William and MaryThe College of William and Mary

Emmett DuffyEmmett DuffyVirginia Institute of Marine ScienceVirginia Institute of Marine ScienceThe College of William and MaryThe College of William and Mary

But what “good” is biodiversity?

Human society

Marine ecosystem services• Water quality control• Seafood production• Tourism and recreation• Ecosystem resilience

Linkage?

Marine biodiversity• Genetic• Species• Ecosystem

Impacts

Linkage?

Marine ecosystem processes• Carbon & nutrient cycling• Primary and secondary productivity• Food and habitat provision• Processing of wastes

Benefits

Theory: Biodiversity should increase productivity

More species use greater fraction of resources, thus produce more

Source: Tilman D (2000) Causes, consequences and ethics of biodiversity. Nature 405: 208-211.

P1 P6P5P4P3P2

““Horizontal” biodiversity Horizontal” biodiversity

PLANTS PLANTS

Plant species richness

Pla

nt c

over

(%

)

Exp’t: Diversity increases productivity

11

““Vertical”Vertical”biodiversity biodiversity

C1

O1 O2

H2H1

33

22

TOP CARNIVORE

HERBIVORES

OMNIVORES

Source: Duffy JE, et al. (2007) The functional role of biodiversity in ecosystems: incorporating trophic complexity. Ecology Letters 10: 522-538.

P1 P6P5P4P3P2

““Horizontal” biodiversity Horizontal” biodiversity

EDIBLE PLANTS INEDIBLE PLANTS

Predators

Consumers, Omnivores

Herbivores, DetritivoresZooplanktivores, Zooplankton

Algae, Plants, Detritus

Source: Byrnes JE, Reynolds PL, Stachowicz JJ (2007) Invasions and Extinctions Reshape Coastal Marine Food Webs. PLoS ONE 2: e295.

~70% extinctions

at high levels

~70% extinctions

at high levels

~70% Invasions at intermediate

levels

~70% Invasions at intermediate

levels

Trophic skew: Top consumers lost first in sea

SF BAY INVASIONS

GLOBAL & REGIONALEXTINCTIONS

Consumers exert strong top-down control in sea

Source: Cyr H, Pace ML (1993) Magnitude and patterns of herbivory in aquatic and terrestrial ecosystems. Nature 361: 148-150.

Most marine production is grazed

~70%

<20%

Gre

at

sh

ark

sE

las

mo

bra

nc

hm

es

op

red

ato

rsS

ca

llo

ps

Consumer loss ripples through food web

Source: Myers RA, Baum JK, Shepherd TD, Powers SP, Peterson CH (2007) Cascading effects of the loss of apex predatory sharks from a coastal ocean. Science 315: 1846-1850.

Healthy scallop fisheries depend on top predators

How does 2-D Biodiversity affect ecosystems?

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

How does 2-D Biodiversity affect ecosystems?

Diversity increases resource use and production

BIOMASSPRODUCTION

RESOURCEDEPLETION

(1) Diversity increases biomass production and resource use

(2) Patterns are similar across trophic levels (and habitats)

PH

DC

Mean MeanMax Max

Source: Cardinale BJ, Srivastava DS, Duffy JE, Wright JP, Downing AL, et al. (2006) Effects of biodiversity on the functioning of trophic groups and ecosystems. Nature 443: 989-992.

N = 111 experiments

Ln

(m

ixtu

re/a

vera

ge

mo

no

cult

ure

)

How does 2-D Biodiversity affect ecosystems?

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

Diversity & top-down control: the general pattern

Source: Hillebrand H, Cardinale BJ (2004) Consumer effects decline with prey diversity. Ecology Letters 7: 192-201.

Lo

g (

gra

zed

/co

ntr

ol)

Diversity confers resistance to grazing in aquatic algae

N = 172 experiments

How does 2-D Biodiversity affect ecosystems?

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

1. Diversity increases production and resource use

2. Diversity increases stability: resistance to top-down control

3. Diversity enhances trophic transfer

• All types of habitats

• singly sp. vs mixture

Source: Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, et al. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790.

Diversity & trophic transfer: the general pattern

N = 32 experiments

Prey (algal) & consumer diversity both increase consumer performance

Ln

(m

ixtu

re/a

vera

ge

mo

no

cult

ure

)

CONSUMER RICHNESS

PRODUCER RICHNESS

But do experiments “scale up” to the real world?But do experiments “scale up” to the real world?

The real world: global fisheries

FISHBASE.ORG

The real world: Resilience in global fisheries

Production & stability of fisheries increase with diversity

Source: Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, et al. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790.

Mechanism? Redundancy and stability inn fisheries

Source: Myers RA, Worm B (2003) Nature 423: 280-283.

Source: Chavez et al. (2003) Science 299: 217-221.

Diversity provides functional redundancy, i.e., “insurance”

One (of several) solutions: Marine Protected Areas

Source: Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, et al. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790.

Marine biodiversity has horizontal and vertical dimensionsMarine biodiversity has horizontal and vertical dimensionsTop-down control is strong in seaTop-down control is strong in seapredator loss ripples through food webpredator loss ripples through food web

Real world evidence is generally concordant with experimentsReal world evidence is generally concordant with experiments

Large fishes often maintain desirable ecosystem statesLarge fishes often maintain desirable ecosystem states

Restoration of marine biodiversity recovers ecosystem servicesRestoration of marine biodiversity recovers ecosystem services

Marine biodiversity has horizontal and vertical dimensionsMarine biodiversity has horizontal and vertical dimensionsTop-down control is strong in seaTop-down control is strong in seapredator loss ripples through food webpredator loss ripples through food web

Real world evidence is generally concordant with experimentsReal world evidence is generally concordant with experiments

Large fishes often maintain desirable ecosystem statesLarge fishes often maintain desirable ecosystem states

Restoration of marine biodiversity recovers ecosystem servicesRestoration of marine biodiversity recovers ecosystem services

Concluding thoughts

The three R’s

Reservation

Restoration

Reconciliation

Restoration: ocean health care

mangrovesmangroves

Coral reefsCoral reefs

seagrassesseagrasses

Oyster reefsOyster reefs

Reconciliation

Loss of diversity

Source: Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, et al. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790.

Loss of services

Source: Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, et al. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790.

Increased risks

Source: Worm B, Barbier EB, Beaumont N, Duffy JE, Folke C, et al. (2006) Impacts of biodiversity loss on ocean ecosystem services. Science 314: 787-790.