How the decline of ocean species threatens human well-being

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

2. But what “good” is biodiversity?

3. Impacts Benefits • Marine biodiversity • Genetic • Species • Ecosystem Linkage? • Marine ecosystem processes • Carbon & nutrient cycling • Primary and secondary productivity • Food and habitat provision • Processing of wastes Linkage? • Marine ecosystem services • Water quality control • Seafood production • Tourism and recreation • Ecosystem resilience Human society

4. 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.

5. Plant cover (%) Exp’t: Diversity increases productivity Plant species richness P1 P2 P3 P4 P5 P6 PLANTS PLANTS “Horizontal” biodiversity

6. 3 C1 TOP CARNIVORE O1 O2 OMNIVORES “Vertical” biodiversity 2 H2 H1 HERBIVORES 1 P1 P2 P3 P4 P5 P6 INEDIBLE PLANTS EDIBLE PLANTS “Horizontal” biodiversity Source: Duffy JE, et al. (2007) The functional role of biodiversity in ecosystems: incorporating trophic complexity. Ecology Letters 10: 522-538.

7. Trophic skew: Top consumers lost first in sea SF BAY INVASIONS Predators Consumers, Omnivores Herbivores, Detritivores Zooplanktivores, Zooplankton ~70% Invasions at intermediate levels GLOBAL & REGIONAL EXTINCTIONS Algae, Plants, Detritus ~70% extinctions at high levels Source: Byrnes JE, Reynolds PL, Stachowicz JJ (2007) Invasions and Extinctions Reshape Coastal Marine Food Webs. PLoS ONE 2: e295.

8. Consumers exert strong top-down control in sea Most marine production is grazed ~70% <20% Source: Cyr H, Pace ML (1993) Magnitude and patterns of herbivory in aquatic and terrestrial ecosystems. Nature 361: 148-150.

9. 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.

10. 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

11. 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

12. Diversity increases resource use and production N = 111 experiments BIOMASS PRODUCTION RESOURCE DEPLETION (1) Diversity increases biomass production and resource use C D H P (2) Patterns are similar across trophic levels (and habitats) Ln (mixture/average monoculture) Mean Max 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: 989-992.

13. 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

14. 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.

15. 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

16. Diversity & trophic transfer: the general pattern Prey (algal) & consumer diversity both increase consumer performance PRODUCER RICHNESS CONSUMER 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.

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

19. The real world: global fisheries FISHBASE.ORG

20. 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.

21. 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.

22. 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.

23. 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

25. The three R’s Reservation Restoration Reconciliation

26. Restoration: ocean health care seagrasses mangroves Oyster reefs Coral reefs

27. Reconciliation

28. 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.

29. 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.

30. 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.