Estes et al. 2011 paper discussion
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Transcript of Estes et al. 2011 paper discussion
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Trophic Downgrading of Planet Earth
Sofia Olivero Lora
November 29, 2012
Estes et al. 2011
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Mass extinction events
(http://evolution.berkeley.edu)
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(http://evolution.berkeley.edu)
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6th mass extinction
• Early to middle stages
• Differences
– Homo sapiens
– Loos larger-bodied animals in general, apex consumers in particular
• Global occurrence
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Apex consumers
• Global and perpetual
• Effects on processes
– Carbon sequestration, invasive species, biogeochemical exchanges, etc.
• Removal-trophic downgrading
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Trophic cascade
http://pubs.usgs.gov/fs/2010/3099/
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http://www.ucc.ie/staff/memmers/Lough%20Hyne.htm
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Alternative stable states
• Sets of unique biotic and abiotic conditions
• Basins of attraction – Set of individual conditions lead to long-time behavior
– Collection of all possible initial conditions of a dynamical state
• ASS- perturbations push ecosystem from one basin to another
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Alternative stable states
• Tipping points
– Phase shifts – abrupt changes in ecosystem structure and function.
• Hysteresis
– Multiple states persist under equal environmental conditions
– Example: Tropical cloud forests
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Connectivity
• Ecosystems are built around interaction webs
• Every species can potentially influence many others
• Interactions – Biological processes
– Physicochemical processes
– Highly complex network
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Ecological Society of America http://phys.org/news/2012-10-scientists-greenbelts-wildlife-sanctuaries.html
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Trophic Downgrading
• Not widely appreciated, difficult to observe
• Need for perturbation, to be perceived
• Time scales – When noticed, too late
• Space scales
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• Sea Otter (nutria) – Population collapse – -herbivorous sea urchins – +kelp abundance
• Seastar – Prevents dominance mussels
(mejillon)
• Bass (robalo) – Reduce phytoplankton – Eats zooplanktivorous
• Large reef fish – Fisheries (left)
• Bass – Eats minnows – Promotes benthic algae
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• Artic fox (zorro) – Eat seabirds – Reduces nutrients inputs
from sea to land
• Jaguar – Herbivore guild – Reduction plant
recruitment and survival
• Wolf – Elk (alce) browsing
• Wildebeest (gorgon) – Rinderpest (virus) – Increase biomass-fire
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• Kelp increase enhances abundance of kelp forest fish
• Increases organic carbon- +growth rate of mussels
• Gulls (gaviotas) – Fish-
invertebrates
• Fish, mammals, birds
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Discussion
• Management solution: restoration of apex consumers.
• Ecological surprises
– Pandemics, loss valuable sp., shifts ecosystem states, loss ES
– Altered top-down regimes
– Apex loss or introduction of exotics
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Discussion
• What about other anthropogenic threats?
• Do present conservation strategies contemplate this new paradigm?
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Surrogate species?
Species used to represent other species or aspects of the environment to obtain a
conservation objective. (Caro, 2010)
Indicator
Umbrella
Keystone
Flagship
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Thanks for your attention!