Download - Estes et al. 2011 paper discussion
Trophic Downgrading of Planet Earth
Sofia Olivero Lora
November 29, 2012
Estes et al. 2011
Mass extinction events
(http://evolution.berkeley.edu)
(http://evolution.berkeley.edu)
6th mass extinction
• Early to middle stages
• Differences
– Homo sapiens
– Loos larger-bodied animals in general, apex consumers in particular
• Global occurrence
Apex consumers
• Global and perpetual
• Effects on processes
– Carbon sequestration, invasive species, biogeochemical exchanges, etc.
• Removal-trophic downgrading
Trophic cascade
http://pubs.usgs.gov/fs/2010/3099/
http://www.ucc.ie/staff/memmers/Lough%20Hyne.htm
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
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
Connectivity
• Ecosystems are built around interaction webs
• Every species can potentially influence many others
• Interactions – Biological processes
– Physicochemical processes
– Highly complex network
Ecological Society of America http://phys.org/news/2012-10-scientists-greenbelts-wildlife-sanctuaries.html
Trophic Downgrading
• Not widely appreciated, difficult to observe
• Need for perturbation, to be perceived
• Time scales – When noticed, too late
• Space scales
• 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
• 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
• Kelp increase enhances abundance of kelp forest fish
• Increases organic carbon- +growth rate of mussels
• Gulls (gaviotas) – Fish-
invertebrates
• Fish, mammals, birds
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
Discussion
• What about other anthropogenic threats?
• Do present conservation strategies contemplate this new paradigm?
Surrogate species?
Species used to represent other species or aspects of the environment to obtain a
conservation objective. (Caro, 2010)
Indicator
Umbrella
Keystone
Flagship
Thanks for your attention!