Ecological considerations in

developing marine ecosystem-based

management

Charles H. Peterson

University of North Carolina at Chapel Hill

Marine Science in Alaska: 2006 symposium

Outline of this presentationScientific consensus statement (2005) on marine EBM

• Pew Oceans Commission• U.S. Commission on Ocean Policy

Major stressors of ocean ecosystems

• Fishing, global warming, species introductions, eutrophication, pollution

Consequences of stress

Some approaches to solving the crisis in management

What is ecosystem-based management for the oceans?

Ecosystem-based management (EBM) is an integrated approach for management that considers the entire ecosystem. The goal of EBM is to keep an ecosystem in or restore it to a healthy, productive and resilient condition so that it can continue to provide the services humans want and need. EBM differs from current approaches that focus on a single species, sector, activity or concern.

Specifically, ecosystem-based management:

• Emphasizes the protection of ecosystem structure, functioning, and key processes;

• Is place-based, i.e., it considers a specific ecosystem and the range of activities affecting it;

• Explicitly accounts for the interconnectedness within systems, i.e., that many non-target species are integral components of the systems that produce the target species or key services;

• Acknowledges interconnectedness among systems, such as between land and sea; and

• Incorporates and integrates ecological, social, economic, and institutional perspectives, recognizing their interdependence.

Scientific consensus statement on marine EBM

Conceptual foundation• Essential to maintain functions and interactions

among strong key interacting species– Habitat engineers (kelps)

– Apex predators (killer whales, sea otters)

– Universal forage species (herring, capelin)

• Dynamics and complexity of ecosystems require a long-term perspective and management flexibility to unexpected, perhaps abrupt, change.

– Regime shifts (late 1970s in GOA)

– Progressive climate change

Scientific consensus statement

Conceptual foundation• Ecosystems can recover from many

disturbances but are not infinitely resilient– Preserving resilience key in management– Avoid passing thresholds of no return– Maintain biodiversity, redundancy

• Ecosystem services almost always undervalued– Unlike fish production, most ecosystem services not

appreciated or assigned value– Inattention places important valuable services at risk;

nutrient cycling, climate regulation, spiritual benefits, cultural heritage, disease and pest control

Major stressors of ocean ecosystems Fishing

• Extraction of target species• By-catch of fish, birds, mammals• Habitat destruction and degradation (deep

corals)

Global warming• Direct and indirect effects of temperature• Enhanced storminess• Modified precipitation, stratification, buoyancy-

driven transport, and circulation• Sea-level rise and direct and indirect coastal

habitat impacts • Changes in ice dynamics at high latitudes (polar

bears)

Major stressors of ocean ecosystems

Species introductions

Eutrophication• Most damaging in estuaries• Also evident in shallow ocean

margins

Atmospheric deposition of toxicants• DDT, DDE, PCBs, dioxins, heavy

metals• Concentrate in apex predators (Orcas,

albatrosses)

Major stressors of ocean ecosystems

Regional and local pollution• Oil spills and releases

• Storm-water inputs of PAHs, heavy metals and other toxicants into estuaries

• Land-use impacts (deforestation, dams, fire, development)

Consequences of stress Population-level consequences of fishing (direct effects)

• 50% of world’s fish stocks fully exploited and 22% over-exploited (Garcia & Newton 1997)

• Numerous examples of fishery collapses by over-exploitation (striped bass in US mid-Atlantic, western Atlantic cod, the great whales, etc)

• Particularly sensitive are stocks of great longevity and low reproductive rate (like deep-water fishes)

Consequences of stress Population-level consequences of fishing (direct effects) cont.

• Genetic impacts of selection for rapid maturation and early breeding, reducing genetic diversity and endangering resilience (Policansky 1993)

• Selective removal of larger consumers, at higher trophic levels (Pauly et al. 1998 “fishing down the food web”, Myers & Worms 2003)

Consequences of stress Ecosystem consequences of fishing (indirect effects)

• Fisheries pre-empt 8% of global and 24-35% of upwelling and shelf primary productivity (Pauly & Christensen 1995)

• Destruction of emergent biogenic habitats (coral reefs, oyster reefs, seagrass beds) on the seafloor is widespread via physical consequences of gear (dredges, trawls, dynamite) (Dayton et al. 1995)

− Consequent loss of habitat complexity− Loss of biodiversity− Loss of juvenile recruitment habitat

Consequences of stress Ecosystem consequences of fishing (indirect effects) cont.

• Trophic consequences of loss of apex consumers

– Trophic cascades modify entire food web (Estes sea otter papers, Castilla Chilean “abalone” papers, Hay, Hughes, Steneck papers on coral overgrowth by algae)

– Removal of potentially stabilizing control on prey explosions, thereby challenging system resiliency to buffer future problems (Jackson et al. 2001, Scheffer et al. 2001)

clams

transient killer whale

sea otter

(now extinct)

Steller sea cow

harbor seal, Steller sea lion

sea urchin

kelps

bald eagle, piscivorous seabirds, larger fishes

herring and other fishes

Consequences of stress

Ecosystem consequences of fishing (indirect effects) cont.

• Trophic consequences of prey reductions– Heavy exploitation of forage fishes like

herring, sardines, anchovies can deprive seabirds and marine mammals of food

– Even loss of predatory fishes (Pollock fishing around Steller sea lion rookeries at rearing seasons) and sea mammals (depletion of whales influences prey selection by killer whales) may impact marine mammals at high trophic levels

Consequences of stress

Ecosystem consequences of fishing (indirect effects) cont.

• By-catch from non-selective fishing gear like trawls, gill nets, long lines

– Fish discards subsidize scavengers, favoring the largest, most aggressive with cascading consequences (large gulls enhanced by North Sea fish discards and their effects on other seabirds at nesting)

– Mortality of marine mammals (dolphins in tuna fishery) and seabirds (many examples)

Consequences of stress Direct and indirect effects of global warming (Peterson & Estes 2001)

• Range expansions and contractions (Barry) at varying rates creating novel species assemblages

• Tilting the ocean climate towards more frequent and durable El Nino conditions

• Enhancing water column stability inhibiting transport of nutrients to surface layers

• Modifying buoyancy-driven flows critical to much present ocean ecology

• Increasing off-shore wind transport and wind relaxation events critical for reproduction of key forage fishes in upwelling centers (Bakun effect)

• Sea-level rise at unprecedented rate, with indirect effects of coastal habitat loss from human defense of occupied coastlines

consumer interactioncompetitive interactionhabitatprovision

phytal crustaceans and

gastropods

black oystercatcher and other shorebirds

Nucella and other predatory

gastropods

balanoid barnacles

chthamaloid barnacles

mussels periwinkles and limpets

benthic microalgae

Ulva, Enteromorpha

and other ephemeral algae

Fucus and other

perennial algae

phytoplankton in water column

harlequin and other seaducks

Consequences of stress Direct and indirect effects of species introductions

• Many dramatic modifications of entire food web

• Changes in selection that can disrupt long-standing evolutionary relationships that may now stabilize ecosystem

Consequences of stress Direct and indirect effects of eutrophication

• Increased microalgal production (Paerl, Rabalais & Turner)

• Toxic blooms promoted (Burkholder)

• Bottom-water anoxia induced, creating dead zones

• Seagrass habitat destroyed through shading, toxicity of high nutrient concentrations, and sedimentation

• Food webs driven towards microbial loops rather than transferring energy to higher trophic levels (Baird et al. 2004)

Consequences of stress Ecological effects of atmospheric deposition of toxicants

• Concentrate in apex consumers, like killer whales and albatrosses with growing impacts on developmental anomalies and reproductive potential (Colburn, Matkin)

• Likely cascading influences on food web dynamics and resiliency after further population declines in these apex consumers

Consequences of stress Ecological consequences of localized pollution

• Oil spills and releases have their greatest impacts on marine mammals, seabirds, and sea turtles that make regular, necessary contact with the sea surface

• Shoreline habitats also affected by smothering and some toxicity

• Greatest long-term risk comes from sequestering oil in sediments where it can avoid normal degradation processes yet leak out over time (Peterson et al. 2003, Short)

• Storm-water transport from land into urbanized estuaries carries high risk of chronic exposures of sensitive reproductive stages of fish and invertebrates to toxic PAHs, other POPS, heavy metals, and sedimentation (Rice)

Some approaches to solving the crisis in management

• Initiate ecosystem-level planning– Include cumulative (interactive) impacts of human activities– Include vision of long-term environmental change

• Initiate zoning of the ocean in space and time– Comprehensive integration of regions– Include networks of fully protected marine reserves

• Incorporate adaptive management– Test hypotheses to learn (not just do something different if Plan A

fails)– Readjust based on new knowledge

• Establish and support long-term monitoring and research– Collect relevant ecological, social, economic data– Co-ordinate research and monitoring efforts