Transcript Response Diversity

Response Diversity
Monika Gorzelak
October 20th 2014
“Nature is not fragile . . . what is fragile are the
ecosystems services on which humans depend”.
(Levin 1999)
Ecosystem resilience
Amount of disturbance a system can take
without changing states
o Ability to reorganize, renew after disturbance
o capacity to self-organize
o Learning and adaptation
Response diversity
Definition
• Diversity of responses to environmental
change among species that contribute to the
same ecosystem function
• Diversity within functional groups is important
to the adaptive capacity of ecosystems; not
just species richness
Role of Biological Diversity in
Ecosystem Resilience
Functional diversity Ecologically redundant (eg. Both
fungi and bacteria are decomposers)
Species diversity eg. Many species of decomposer
fungi (may have a range of decomposing
ability...example: may differ in optimal temperature)
Response diversity
Response diversity
• How to best illustrate this??
Examples
Bother?
Disturbance
Natural
• pulse disturbance
Human
• Chronic disturbance
• Compounded
perturbations
Response diversity
• Is not species richness
Response Diversity
Example: seed dispersal in tropical forests
• Western Polynesia after cyclone
• Frugivore species disperse tree seeds
• Frugivore flying foxes, the dominante P. tonaganus and D. pacifica
declined by 90% whereas P. samoensis declined by only 10%. P.
samoensis, previously subdominant, was able to maintain function
(seed dispersal)
Response Diversity
Example: plants in rangelands
(Walker et al. 1999)
• Rank abundance with fill depicting different function
• Dominant species are functionally different
• Grazed grass replaced with functional equivalent
Response Diversity
Example: freshwater detritovores
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Stoneflies are sensitive to organic pollution
Crustaceans are sensitive to acidification
Both break down leaf litter
Species richness did not affect leaf breakdown
rate, but species identity did.
Response Diversity
Example: coral reef grazers
• Coral reef is made of framework-builders,
primary producers, herbivores, predators
• Herbivores eat algae which blooms in their
absence. Algae eventually kills reef
• Sea urchins graze, but are not
resilient to disease, get wiped out,
algae takes over, dead reef
• Sea urchins are not functional
Response diversity across scales
• Palm seed dispersal across a range of scales
– Small rodents 5m (maintains patch of palms)
– Tapiers 2km (establishes new palm patches)
• With disturbance such as hurricane, some
patches may be wiped out, but others will
remain to re-populate
Response diversity across scales
Example: coral reef
Response Diversity
Other examples?
• Can we describe the pine beetle outbreak
using this concept?
• Other examples?
• How do we manage ecosystems with response
diversity in mind?
Response diversity across scales
Coral reef
• reduced competition between species that
feed at different scales (frequency and
distance)
• All contribute to the same ecosystem
function: eating the algae and preventing a
bloom, which would precipitate coral
bleaching and death
Managing response diversity
• Reduce human homogenization of landscapes
• Avoid elimination of functional groups (ex.
predators)
• Consider response diversity to maintain
ecosystem buffering capacity, in order to
maintain the ecosystem services we rely on
• Testable
Managing response diversity
• More barley cultivars in Finland is not better
because they all have similar drought
tolerance.
Quantifying response diversity
construct diversity index (similarity
index) and validate with real data.
Determine how far are we from
resilience
(Kahiluoto et al. 2014)
Response diversity in Forests
• What is the goal? Productivity? Resistance to
pest outbreaks (pine beetle)?
• What are the critical factors?
• How do we estimate the impact?
• Can we model responses, validate models?