Discussion on the trophic downgrading of Planet Earth by Sofia Olivero Lora.

1. Trophic Downgrading of
Planet Earth
Sofia Olivero Lora
November 29, 2012
Estes et al. 2011

2. Mass extinction events
(http://evolution.berkeley.edu)

3. (http://evolution.berkeley.edu)

4. 6th mass extinction
• Early to middle stages
• Differences
– Homo sapiens
– Loos larger-bodied animals in general, apex
consumers in particular
• Global occurrence

5. Apex consumers
• Global and perpetual
• Effects on processes
– Carbon sequestration, invasive species,
biogeochemical exchanges, etc.
• Removal-trophic downgrading

6. Trophic cascade
http://pubs.usgs.gov/fs/2010/3099/

7. http://www.ucc.ie/staff/memmers/Lough%20Hyne.htm

8. 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

9. 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

10. Connectivity
• Ecosystems are built around interaction webs
• Every species can potentially influence many
others
• Interactions
– Biological processes
– Physicochemical processes
– Highly complex network

11. Ecological Society of America
http://phys.org/news/2012-10-scientists-greenbelts-wildlife-sanctuaries.html

12. Trophic Downgrading
• Not widely appreciated, difficult to observe
• Need for perturbation, to be perceived
• Time scales
– When noticed, too late
• Space scales

13. • 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

14. • 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

15. • Kelp increase
enhances
abundance of
kelp forest fish
• Increases
organic carbon-
+growth rate of
mussels
• Gulls (gaviotas)
– Fish-
invertebrates
• Fish, mammals,
birds

18. 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

19. Discussion
• What about other anthropogenic threats?
• Do present conservation strategies
contemplate this new paradigm?

20. Surrogate species?
Species used to represent other species or
aspects of the environment to obtain a
conservation objective. (Caro, 2010)
Indicator
Umbrella
Keystone
Flagship

21. Thanks for your attention!