Transcript Ecological function Ecological function

Understanding the impacts of extinction:
the next step for biodiversity research
Andrew Gonzalez
Canada Research Chair
Department of Biology
Key Message
“Changes in biodiversity due to human activities were more rapid in
the past 50 years than at any time in human history, and the drivers
of change…show no evidence of declining over time, or are
increasing in intensity.”
Extinction rates are 100-1000
times higher than the
background rate
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MES: Biodiversity Synthesis
• BD loss has happened, is
ongoing.
• BD matters for ecosystem
functioning.
• In ~15 yrs of BD research
we have learnt a great deal.
• A deeper understanding of
of BD loss is required--more
science.
• Conflicting human and
ecological needs.
• High uncertainty
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Key Issue for future biodiversity research
“A mismatch exists between the dynamics of
changes in natural systems and human
responses to those changes.” pg21 MABS
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Functional Effects of Biodiversity Loss
Characteristics:
1. Ignorance of mechanism
2. Potential catastrophic costs
3. Relatively modest benefits
4. Low subjective probability
5. Internal experience of costs
6. External transfer of benefits
7. Collective risk
8. Latency (lagged effects)
9. Irreversibility
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Is Biodiversity Loss a Component of Global
Change?
Hypothesis: Does diversity loss affect ecosystem
function?
Anthropogenic
Disturbance
Ecosystem
Function
?
Extinction
Ecosystem
Function
?
Diversity
gradients
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Articulating the Hypothesis
Simple 'models' proposed (circa 1993) for the relation
between diversity and ecosystem function
"Complementarity"
"Redundancy"
Ecological
function
Ecological
function
diversity
diversity
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Experimental Evidence
Cedar Creek, Minnesota
Experiments have been performed at small spatial and
temporal scales and assume way the ‘dynamics’ of
extinction.
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Getting Real
Hypothesis: Extinctions are a consequence of
disturbance and can amplify the effects of disturbance.
Anthropogenic
Disturbance
Ecosystem
Ecosystem
Function
Function
?
Extinction
Diversity
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Biodiversity Loss: why response mismatches?
Characteristics:
1. Ignorance of mechanism
2. Potential catastrophic costs
3. Relatively modest benefits
4. Low subjective probability
5. Internal experience of costs
6. External transfer of benefits
7. Collective risk
8. Latency (lagged effects)
9. Irreversibility
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Example of a response mismatch:
“Extinction debts”
“Extinction debt”: the difference between the initial and
final levels of diversity attained long after the initial
disturbance.
Extinction is a highly nonlinear process (perhaps
cascading) with inherent response delays.
Current experimental protocols based on “random
species assembly” do not mimic extinction.
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Studying the lagged effects of extinction: habitat
loss
A complementary ‘dynamic’ approach:
• Allows the study of the extinction process
50cm
20cm²
50cm
200cm²
Control
Fragments
Replicated experimental landscapes of natural (micro) ecosystems
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An Example of an Extinction ‘Debt’
Secondary biomass
Species richness (# spp)
27
<40%
22
17
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Secondary biomass (mg)
Species richness
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7
6
5
4
3
2
1
0
2
0
2
4
6
8
10
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<68%
8
0
2
4
6
8
10
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Time after fragmentation
Controls
Fragments
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“A mismatch exists between the dynamics of
changes in natural systems and human
responses to those changes.” pg21 MABS
Characteristics:
1. Ignorance of mechanism
2. Potential catastrophic costs
3. Relatively modest benefits
4. Low subjective probability
5. Internal experience of costs
6. External transfer of benefits
7. Collective risk
8. Latency (lagged effects)
9. Irreversibility
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Conclusions
• Significant progress in biodiversity research to date,
but still only a poor understanding of the functional
effects of extinction.
• It is imperative that we study the dynamics of extinction
within the context of anthropogenic disturbance: this is
possible but new approaches are required.
• Without this knowledge it will be difficult to mitigate
the functional consequences of future extinctions so
clearly articulated in the Millenium Assessment.
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