How the decline of ocean species threatens human well-being How the decline of ocean species threatens human well-being Emmett Duffy Virginia Institute of Marine Science The College of William and Mary Emmett Duffy Virginia Institute of Marine Science The 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:

P1P6P5P4P3P2 “Horizontal” biodiversity PLANTS Plant species richness Plant cover (%) Exp’t: Diversity increases productivity

1 “Vertical”biodiversity C1 O1O2 H2 H1 3 2 TOP CARNIVORE HERBIVORES OMNIVORES Source: Duffy JE, et al. (2007) The functional role of biodiversity in ecosystems: incorporating trophic complexity. Ecology Letters 10: P1P6P5P4P3P2 “Horizontal” biodiversity EDIBLE PLANTS INEDIBLE PLANTS

Predators Consumers, Omnivores Herbivores, Detritivores Zooplanktivores, 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 & REGIONAL EXTINCTIONS

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: Most marine production is grazed ~70% <20%

Great sharks Elasmobranch mesopredators Scallops 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: 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 BIOMASS PRODUCTION RESOURCE DEPLETION (1) Diversity increases biomass production and resource use (2) Patterns are similar across trophic levels (and habitats) P H D C Mean 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: N = 111 experiments Ln (mixture/average monoculture)

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: Log (grazed/control) 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: Diversity & trophic transfer: the general pattern N = 32 experiments Prey (algal) & consumer diversity both increase consumer performance Ln (mixture/average monoculture) CONSUMER RICHNESS PRODUCER RICHNESS

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:

Mechanism? Redundancy and stability inn fisheries Source: Myers RA, Worm B (2003) Nature 423: Source: Chavez et al. (2003) Science 299: 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:

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 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 Concluding thoughts

The three R’s R eservation R estoration R econciliation

Restoration: ocean health care mangroves Coral reefs seagrasses Oyster 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:

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:

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: