Trophic Downgrading of Planet Earth Sofia Olivero Lora November 29, 2012 Estes et al. 2011
Jun 14, 2015
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!