How the decline of ocean species

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How the decline of ocean species threatens human
well-being
Emmett Duffy Virginia Institute of Marine
Science The College of William and Mary
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But what good is biodiversity?
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Human society
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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.
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P1
P6
P5
P4
P3
P2
PLANTS
PLANTS
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P1
P6
P5
P4
P3
P2
EDIBLE PLANTS
INEDIBLE PLANTS
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Trophic skew Top consumers lost first in sea
SF BAY INVASIONS
GLOBAL REGIONAL EXTINCTIONS
Source Byrnes JE, Reynolds PL, Stachowicz JJ
(2007) Invasions and Extinctions Reshape Coastal
Marine Food Webs. PLoS ONE 2 e295.
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Consumers exert strong top-down control in sea
Most marine production is grazed
Source Cyr H, Pace ML (1993) Magnitude and
patterns of herbivory in aquatic and terrestrial
ecosystems. Nature 361 148-150.
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Consumer loss ripples through food web
Healthy scallop fisheries depend on top predators
Great sharks
Elasmobranch mesopredators
Scallops
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.
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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
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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
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Diversity increases resource use and production
N 111 experiments
BIOMASS PRODUCTION
RESOURCE DEPLETION
(1) Diversity increases biomass production and
resource use
Ln (mixture/average monoculture)
Mean
Mean
Max
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.
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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
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Diversity top-down control the general pattern
Diversity confers resistance to grazing in
aquatic algae
N 172 experiments
Log (grazed/control)
Source Hillebrand H, Cardinale BJ (2004)
Consumer effects decline with prey diversity.
Ecology Letters 7 192-201.
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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
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Diversity trophic transfer the general pattern
CONSUMER RICHNESS
PRODUCER RICHNESS
Ln (mixture/average monoculture)
N 32 experiments
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.
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But do experiments scale up to the real world?
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The real world global fisheries
FISHBASE.ORG
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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.
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Mechanism? Redundancy and stability inn fisheries
Diversity provides functional redundancy, i.e.,
insurance
Source Chavez et al. (2003) Science 299
217-221.
Source Myers RA, Worm B (2003) Nature 423
280-283.
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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.
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Concluding thoughts
Marine biodiversity has horizontal and vertical
dimensions Top-down control is strong in
sea predator loss ripples through food web Real
world evidence is generally concordant with
experiments Large fishes often maintain
desirable ecosystem states Restoration of marine
biodiversity recovers ecosystem services
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The three Rs
Reservation
Restoration
Reconciliation
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Restoration ocean health care
seagrasses
mangroves
Oyster reefs
Coral reefs
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Reconciliation
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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.
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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.
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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.