Transcript pete_peterson

Marine Science in Alaska: 2006 symposium
Ecological
considerations in
developing marine
ecosystem-based
management
Charles H. Peterson
University of North Carolina at Chapel Hill
Outline of this presentation
Scientific 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:
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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
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Extraction of target species
By-catch of fish, birds, mammals
Habitat destruction and degradation (deep
corals)
Global warming
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Direct and indirect effects of temperature
Enhanced storminess
Modified precipitation, stratification, buoyancydriven 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
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Most damaging in estuaries
Also evident in shallow ocean margins
Atmospheric deposition of toxicants
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DDT, DDE, PCBs, dioxins, heavy
metals
Concentrate in apex predators (Orcas,
albatrosses)
Major stressors of ocean ecosystems
Regional and local pollution
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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)
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50% of world’s fish stocks fully exploited and 22%
over-exploited (Garcia & Newton 1997)
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Numerous examples of fishery collapses by overexploitation (striped bass in US mid-Atlantic,
western Atlantic cod, the great whales, etc)
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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.
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Genetic impacts of selection for rapid maturation
and early breeding, reducing genetic diversity and
endangering resilience (Policansky 1993)
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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)
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Fisheries pre-empt 8% of global and 24-35% of
upwelling and shelf primary productivity (Pauly &
Christensen 1995)
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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.
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Trophic consequences of loss of
apex consumers
transient
killer
whale
– Trophic cascades modify entire (now extinct)
food web (Estes sea otter
Steller
sea
sea cow
papers, Castilla Chilean
harbor seal,
otter
Steller sea lion
“abalone” papers, Hay, Hughes,
bald eagle, piscivorous
clams
Steneck papers on coral
seabirds, larger fishes
sea
overgrowth by algae)
urchin
– Removal of potentially
herring and
stabilizing control on prey
other fishes
explosions, thereby challenging
kelps
system resiliency to buffer
future problems (Jackson et al.
2001, Scheffer et al. 2001)
Consequences of stress
Ecosystem consequences of fishing
(indirect effects) cont.
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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.
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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)
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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
Consequences of stress
Direct and indirect effects of species introductions
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Many dramatic modifications of entire food web
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Changes in selection that can disrupt long-standing
evolutionary relationships that may now stabilize
ecosystem
black oystercatcher
and other shorebirds
harlequin and
other seaducks
Nucella and
other predatory
gastropods
balanoid
barnacles
phytoplankton
in water
column
chthamaloid
barnacles
Fucus and
other
perennial
algae
mussels
phytal
crustaceans and
gastropods
Ulva,
Enteromorpha
and other
ephemeral algae
consumer
interaction
competitive
interaction
habitat
provision
periwinkles
and limpets
benthic
microalgae
Consequences of stress
Direct and indirect effects of eutrophication
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Increased microalgal production (Paerl, Rabalais &
Turner)
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Toxic blooms promoted (Burkholder)
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Bottom-water anoxia induced, creating dead zones
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Seagrass habitat destroyed through shading, toxicity
of high nutrient concentrations, and sedimentation
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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
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Concentrate in apex consumers,
like killer whales and albatrosses
with growing impacts on
developmental anomalies and
reproductive potential (Colburn,
Matkin)
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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
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Oil spills and releases have their greatest impacts on marine
mammals, seabirds, and sea turtles that make regular, necessary
contact with the sea surface
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Shoreline habitats also affected by smothering and some
toxicity
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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)
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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