Discussion of Estes et al. 2011 by Abelardo Colon Nieves, CIAM 6117, UPR Río Piedras

1. Trophic Downgrading of Planet Earth
Estes et al. 2011. Science. 333:301-306
Abelardo Colon Nieves
Coastal Environment
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2. Index
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Background
Keywords and concepts
Paper discussion
Conclusion
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3. James A. Estes
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Project:
Population Dynamics and Biology of the California Sea Otter at the Southern End of its Range
Education:
B.A. Zoology, University of Minnesota 1967
M.S. Zoology, Washington State University 1969
Ph.D. Biological Sciences/Statistics, University of Arizona 1974
Positions:
- 1984-present Supervisory Zoologist, GM-486/15, California Science Center, National Biological
Service, Santa Cruz, California
- 1978-pressent Adjunct Professor, Biological Sciences, University of California, Santa Cruz
- 1979-present Research Biologist, Institute for Marine Sciences, University of California, Santa
Cruz
- 1978-1981 Wildlife Biologist (Research), GS-486/12, Marine Mammal Section, National Fish
and Wildlife Laboratory, FWS, Santa Cruz, California
- 1977-1978 Wildlife Biologist (Research), GS-486/12, Marine Mammal Section, National Fish
and Wildlife Laboratory, FWS, Anchorage, Alaska
- 1974-1977 Wildlife Biologist (Research), GS-486/11, Marine Mammal Section, National Fish
and Wildlife Laboratory, FWS, Anchorage, Alaska
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4. Index
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Background
Keywords and concepts
Paper discussion
Conclusion
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5. Keywords and concepts
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6. Mass Extinction Events
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7. 6th massive extinction event (current):
Homo sappiens
loss of larger-bodied animals
in general
and of
apex consumers in particular
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8. Apex predator
Predators with few to no predators of their own,
residing at the top of their food chain. Apex consumers
species occupy the highest trophic level and have a
crucial role in maintaining the health of their
ecosystems.
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9. Marine Food Web/chain
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10. Think???
-Human intervention to nature, to what extend is
environmentally safe?
-Indirect and direct environmental implications in human
disturbed ecosystem…
-It is reversible? How long would it take to reach equilibrium?
-Global perspective…
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11. Index
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•
•
•
Background
Keywords and concepts
Paper discussion
Conclusion
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12. Trophic Downgrading of Planet Earth
• Tropic downgrading is defined as the studying
concept of consequences by removing large
apex consumers from nature.
• Link between loss of apex consumers and
effects disease, fire, carbon sequestration,
invasive species and biochemical dynamics in
earth’s soil, water and atmosphere.
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13. Ecological Theory
3 main ideas:
1) An ecosystem may be shaped by apex
Consumers. “trophic cascades,” broadly defined
as the propagation of impacts by consumers on
their prey downward through food webs.
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14. Ecological Theory
2) Alternative stable. Alternative stable states occur
when perturbations of sufficient magnitude and direction
push ecosystems from one basin of attraction to another.
Tipping points (also known as thresholds or breakpoints),
around which abrupt changes in ecosystem structure and
function occur, often characterize transitions between
alternative stable states. Ecosystem phase shifts can also
display hysteresis, a phenomenon in which the locations
of tipping points between states differ with the
directionality of change.
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15. Ecological Theory
3) Connectivity. Connectivity holds that ecosystems
are built around interaction webs within which
every species potentially can influence many other
species. These interactions, which include both
biological processes (predation, competition, and
mutualism) and physicochemical processes (the
nourishing or limiting influences of water,
temperature, and nutrients), link species together
at an array of spatial scales in a highly complex
network.
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16. These 3 main keys set the stage for the idea of trophic
downgrading.
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17. Apex consumer
absent
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present
Coral reef ecosystems
Uninhabited Jarvis Island (right, unfished) and
neighboring Kiritimati Island (left, with an active
reef fishery). Fishing alters the patterns of predation
and herbivory, leading to shifted benthic dynamics,
with the competitive advantage of reef-building
corals and coralline algae diminished in concert
with removal of large fish.
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18. Cryptic Nature of Tropic Downgrading
• Not easy to prove under equilibrium conditions
but if it is perturbed, responses to the loss or
addition of species could take several years or
decades.
• Population of apex consumers have long been
reduced during time passes.
• Scale of tropic downgrading is too large in
comparison to empirical studies of species
interactions that have been done on small or
weakly motile species.
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19. Think???
• Tropic
downgrading
is happening
for real or
not?
• Tell me prove
of that.
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20. The widespread Occurrence of Tropic
Cascades
• Top-down forcing and trophic cascades often
have striking effects on the abundance and
species composition of autotrophs, leading to
regime shifts and alternative states of
ecosystems.
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21. Sea Otter
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22. Indirect effects of losing apex
consumers
• Disease: The establishment of no-take marine reserves in the Channel
Islands of southern California led to increases in the size and abundance of
spiny lobsters (Panulirus interruptus) and declines in population densities
of sea urchins, which are preyed on by the lobsters. The reduced urchin
densities thwarted the spread of disease among individual sea urchins,
which led to a lowered frequency of epidemics of sea urchin wasting
disease within the reserves.
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23. Marine disease
• In freshwater systems, the localized rise and
fall of human malaria is associated with the
impacts of predatory fishes on planktivores,
which are in turn important consumers of
mosquito larvae.
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24. Physical and chemical influences
•
Trophic cascades associated with the presence or absence of apex predatory fishes
in lakes can affect phytoplankton density, in turn affecting the rate of primary
production, the uptake rate of CO2, and the direction of carbon flux between lakes
and the atmosphere. Where apex predatory fishes are present in sufficient
numbers, they reduce the abundance of smaller planktivorous minnows, thus
releasing zooplankton from limitation by planktivores and increasing consumption
rates of phytoplankton by zooplankton. This trophic cascade causes lakes to switch
from net sinks for atmospheric CO2 when predatory fishes are absent to net
sources of atmospheric CO2 when these fishes are present.
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25. The whale industry example
• Industrial whaling during the 20th century transferred some
105 million tons of carbon from great whales to the
atmosphere, and even today whale feces return various
limiting nutrients from the aphotic to photic zones, thereby
directly enhancing primary productivity and its influence on
carbon flux and sequestration.
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26. Water: Salmon example
• In rivers, mass spawning by salmon suspends sediments, thus increasing
downstream sediment transport. This flushing of stream bed sediments
by the spawning fish and the increased circulation of freshwater through
the gravel interstices of the stream bed have positive feedbacks on salmon
populations by increasing oxygen for incubating eggs and fry and
decreasing the frequency with which bedmobilizing floods kill salmon in
these early life stages.
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27. Invasive species
• Invasive species. A common feature of many successful
invasive species is that they have left behind their natural
predators and freed themselves from top-down control.
Likewise, the loss of native predators leaves ecosystems more
vulnerable to invasion by nonnative species.
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28. Lion Fish sightings in Puerto Rico
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29. Index
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•
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Background
Keywords and concepts
Paper discussion
Conclusion
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30. Conclusion
• These examples support the conclusion that
disruptions of trophic cascades due to the
decline of predation constitute a threat to
biodiversity from within for which the best
management solution is likely the restoration
of effective predation regimes.
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31. A Paradigm Shift in Ecology
• Before: apex consumer seen as ecological passengers riding at
the top of the trophic pyramid but having little impact on the
structure below.
• After: Bottom-up forces are ubiquitous and fundamental, and
they are necessary to account for the responses of
ecosystems to perturbations, but they are not sufficient. Topdown forcing must be included in conceptual overviews if
there is to be any real hope of understanding and managing
the workings of nature.
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32. Think Coastal Environment…
• Paper discussion that can we link with this
review research?
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Ecological extinction and evolution in brave new ocean- Jackson 2008
The value of estuarine and coastal ecosystem services- Barbier et al. 2011 (services, goods and cultural
benefits…)
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33. Thank You
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