The evil quartet
If we know what causes biodiversity
loss, we should also know the solutions
Jared Diamond
Dave Dawson February 2011
THE EVIL QUARTET
In the 80s Diamond investigated
recent extinctions
and found that their agents of
decline, where known, could be
classed under four headings:
1. Overkill.
2. Habitat destruction and
fragmentation.
3. Impact of introduced species.
4. Chains of extinction.
From Caughley (1994)
The evil sextet
•
•
•
•
•
•
If we know what causes biodiversity loss, we
should also know the solutions
Over-exploitation
Invasive alien species
Loss and degradation of habitat
Pollution and intensive management
Climate change
Us
Dave Dawson February 2011
1
Jack Sepkoski
Prof. Norman
MacLeod Natural
History Museum
1
2
3
4
5
David Raup
Stages in geological time
McLeod (2003)
The evil quartet
If we know what causes biodiversity
loss, we should also know the solutions
• Over-exploitation
McLeod 2003
Dave Dawson February 2011
2
Prehistoric overkill
• Rapid extinction of
megafauna shortly
after arrival of people
Paul Martin
•People in small
numbers, but they
were
•Sophisticated, group
hunters
•with advanced tools
Martin (1989)
3
Millennium Ecosystem Assessment
World fisheries
Vitousek et al. (1997a)
The tragedy of the commons
The evil quartet
If we know what causes biodiversity loss,
we should also know the solutions
•Over-exploitation
• Invasive alien species
Garratt Hardin 1968
Dave Dawson February 2011
4
Grass flora of New Zealand
46
157
226
31
Endemic
Indigenous
Naturalised
Transient
Edgar & Connor (2000)
Steven Gaines
Dove Sax
5
Plant species on well-studied islands
The increase of alien species over time
Plant species on islands
Sax & Gaines (2008)
Sax &
Gaines
(2008)
Species invasions and extinction: The future
of native biodiversity on islands
• Predation by exotic species has caused
the extinction of many native animal
species on islands, whereas competition
from exotic plants has caused few native
plant extinctions
• But, could there be a surplus of species,
and so an extinction debt of island plants?
• Probably not, at least not yet
Sax & Gaines (2008)
6
Mainland invasive non-native species
• Most non-native species don’t
harm native biodiversity (Didham et
al. 2005, Hamilton 2011, but see Vitoųsek
et al. 1997, Burton et al. 2010)
• And concern here is rather with the
cost to the GB economy (estimated
to be 1.7 billion (Williams et al. 2010),
and
• So this is a real issue, but perhaps
not a very significant one for our
local biodiversity?
The evil quartet
Number of
amphibian and
reptile species,
log scale
If we know what causes biodiversity loss, we
should also know the solutions
•Over-exploitation
•Invasive alien species
Island size, log scale
West Indies.
• Loss and degradation of habitat
The number of species, S,
relates to the area of the
island, A
Darlington (1957)
D = cAz
Preston (1962)
Dave Dawson February 2011
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MacArthur & Wilson
(1967) The theory of
island biogeography
E.O. Wilson, studied ants on New Guinea islands
New Guinea satellite islands
Land bridge islands
(connected to New Guinea
10,000 years ago)
Carry an “extinction
debt”
Oceanic islands
in equilibrium
Jared Diamond
Diamond (1975)
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New Guinea satellite islands
Diamond (1975)
•Bigger better
Fraction of
near island
number, log
scale
•Single large better than several
small
•Close spacing better
•Grouping better
•Better linked with corridors = B
Diamond (1975)
•Better compact than thin
1980
Lenore Fahrig
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Habitat
Habitat
Habitat fragmentation (Fahrig 2003)
Matrix
Habitat fragmentation (Fahrig 2003)
Habitat
Matrix
Dominance of each process, areas
and numbers
Landscape multicollinearity
1
Perforation
0.9
0.7
Fragmentati
on
Shrinkage
0.6
Attrition
0.8
0.5
Patch size
0.4
0.3
Core
0.2
Isolation
0.1
# of patches
0
0
Habitat fragmentation (Fahrig 2003)
20
40
60
80
100
Percentage of Habitat Lost
Correlated effects of Habitat loss, after Forman (1997) & Fahrig (2003)
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An apparent effect of patch size on biodiversity
could actually be an effect of:
•
•
•
•
•
•
•
the total amount of habitat left in the landscape (Fahrig 2003)
isolation from other patches (Diamond 1975)
a change in edge to core ratio of patches (Ewers & Didham 2007)
extinction debt (Diamond 1975)
historical factors (e.g. time since fragmentation, differing invasive
aliens)
a coincidental correlation with some other cause (Didham et al. 2005)
“habitat heterogeneity” within the landscape and a selective loss of this:
Báldi (2008), Boakes et al. (2010)……
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Studies are needed at the landscape,
not the patch level
• “Habitat patches” are never homogeneous
• Work is needed at a scale appropriate to the
movement of the species
• To distinguish the effects of habitat loss and
fragmentation
• To take proper account of the matrix
• Difficult to study, as replicate landscapes are
needed
Meg Game
George Peterken
McGarigal & Cushman (2002), Fahrig (2003), Ewers & Didham (2005), Kupfer et al.(2006)
Incidence of Dog's mercury in recent woods with distance
from older woods (Game & Peterken 1981)
Woodland herbs in central Lincolnshire (after Game & Peterken
1984)
160
140
Number of species
Percentage with Dog's mercury
(95% confidence limits)
100
50
5ha
15ha
120
100
40ha
70ha
150ha
250ha
350ha
600ha
80
60
40
20
0
0
1
< 0.2
0.2 - 0.4 0.4 - 0.8 0.8 - 1.6 1.6 - 3.2 3.2 - 6.4
10
100
Number of ancient woods (log scale)
Distance from source (Km, log scale)
Increasing fragmentation
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100%
80% forest cover
Proportion
of
landscape
blocks with
Hazel
Dormice
Incidence of Hazel
Dormouse in 41
landscape blocks
in central Italy
Mortelliti et al. (2011)
Under 10% forest cover
Alessio Mortelliti
0%
Increasing amount of hedgerows (length in a 4x4 km landscape block)
Dr Raphael Didham
Dr Robert Ewers
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5% of the species preferred
the grassland matrix
Beetle
population
abundance
Beetle species’
responses to the
edge between
temperate
rainforest (left) and
grassland matrix
(right).
45% showed little
or no edge effect.
Distance from edge
between forest (left) and
grassland matrix right
(logarithmic scale)
Beetle species’
responses to the
edge between
temperate
rainforest (left) and
grassland matrix
(right).
Beetle
population
abundance
Distance from edge
between forest (left) and
grassland matrix right
(logarithmic scale)
Ewers & Didham 2008
12% of the species were affected
1000m, or more, into the forest!
38% of the species were affected
up to 50m into the forest
Beetle species’
responses to the
edge between
temperate
rainforest (left) and
grassland matrix
(right).
Ewers & Didham 2008
Edge effects reducing
and fragmenting the
core
Beetle
population
abundance
Distance (m) from edge
between forest (left) and
grassland matrix right
(logarithmic scale)
Ewers & Didham 2008
Ewers & Didham (2007)
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Extinction debt
Extinction debt
Kakamega Forest, Kenya
Brooks et al. (1999)
Kakamega Forest, Kenya
Brooks et al. (1999)
Extinction debt is difficult both to study and to apply
• An initial equilibrium is assumed: Whittaker et al. (2005)
• We assume the slopes of the two species-area curves (z)
and often ignore the matrix: Whittaker et al. (2005), Wright & MullerLandau (2006), Ladle (2009), Smith (2010) but see Koh & Ghazoul (2010)
•
•
•
•
•
•
It’s difficult to obtain comparable species lists (Ladle 2009)
The timing of fragmentation is not firm
We should study replicate landscapes, not patches
What of other taxa (e.g. beetles)?
And of other habitats and geographic areas?
How much confidence have we here, let alone
extrapolation to other (e.g. northern temperate) regions?
• A persuasive case for some species (Marsh fritilliary, Bulman et
al. 2007)
• We should be cautious over simple predictions of future
extinctions
World biodiversity “Hotspots”
Myers (1988)
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Combined
Priority afforded
by schemes that
focus on:
A (Red), where
most has been
lost or
The evil quartet
If we know what causes biodiversity loss, we
should also know the solutions
•Over-exploitation
•Invasive alien species
•Loss and degradation of habitat
B (Green), where
most remains,
and so which are
vulnerable in
future
• Pollution and intensive management
Dave Dawson February 2011
Fritz Haber
Paul Müller
Published 1962, DDT banned in US 1972
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Peregrine Falcon eggshell thinning
and organochlorine pesticide use
Ratcliffe (1970)
Eggshell
thickness
The second silent spring? Krebs et al. 1999
Year
Anon 2010, see also Gregory et al. (2004)
What is needed in the agricultural matrix?
•
•
•
•
“Extensification”
“Agri-environment” enhancements?
Organic farming?
Most agree that the solutions need to be
focussed on individual farms, but
• Don’t forget the habitat patches, and
• Big re-wilding schemes?
The second silent spring (Krebs et al. 1999).
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The evil quartet
If we know what causes biodiversity loss, we
should also know the solutions
•Over-exploitation
•Invasive alien species
•Loss and degradation of habitat
•Pollution and intensive management
• Climate change
(2007)
Dave Dawson February 2011
Climate change and habitat loss
Climate change and habitat loss
Climate envelope
Species’ distribution
Climate envelope
Species’ distribution
Lost habitat
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Climate change and habitat loss
Climate change and habitat loss
Climate envelope
Species’ distribution
Lost habitat
Climate envelope
Species’ distribution
Lost habitat
R.J. Whittaker et al. (2005)
Whittaker et al. (2005)
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Diamond (1975)
•Bigger better
•Single large better than several
small
•Close spacing better
•Grouping better
•Better linked with corridors = B
Jared Diamond
What should the principles be?
1.
2.
3.
•
•
•
First, increase the total area of high quality habitats
Go for high environmental heterogeneity
Control other threats from human activity
Where it’s readily accommodated, also go for some big
reserves, and only then for….
connectivity, mainly from improvements to the matrix
Realise that fragmentation per se has little to do with it
•Better compact than thin
Are extinctions the sole concern?
• We expect many more extinctions as a result of our
impact on the environment
• But mainly on islands and other little-modified
ecosystems (e.g. the Amazon, Kakamega)
• GB has lost only some 12 species of higher plants in
the last 200 years, and all but one of these survives
on the continent (Kevin Walker in prep.)
• The values of common species have been ignored
(Gaston & Fuller 2008)
• Is it because of this that we have enthusiastically
embraced “ecosystem services”?
After Harrison & Bruna (1999), Dawson (2006), Laurance (2008) & Hodgeson et al. (2009)
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Millennium Ecosystem Assessment Biodiversity Synthesis
The evil quartet
•If we know what causes biodiversity
loss, we should also know the solutions
•Over-exploitation
•Invasive alien species
•Pollution and intensive management
•Loss and degradation of habitat
•Climate change
• Us
See also Diaz et al. (2006)
1978
Dave Dawson February 2011
Dr Paul Ehrlich
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May 2010
Lord (Robert) May of Oxford, President
of the Royal Society 2000-2005
Government Chief Scientific adviser
1995-2000
Ecological footprint and biocapacity
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Intergovernmental Platform on Biodiversity and
Ecosystem Services (IPBES)
May recommends
• Educate women and afford women control over
their lives
• Decarbonize energy supplies
• Produce more food, whilst preserving habitats
and species
• Realise that ritual, authority and faith will trump
the evidence and so can prevent a sensible
response
Announced December 2010. To be set up this
year
– Will mirror the IPCC
May 2010
Mark Van Vugt
The challenge is to
find ways to maintain
cooperation in the
common good even
without the
mechanism of
competition and
conflict with other
groups.
We need social norms
that meet this
challenge and find
leaders to take us
down that path.
Simon Levin (2010)
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Averting the Tragedy of the Commons
Using Social Psychological Science to Protect the Environment
Mark Van Vugt
Four necessary components:
• Information
• Identity
• Institutions
• Incentives
Edward O. Wilson
Biophilia: “…the
connections that human
beings subconsciously
seek with the rest of life.” E.O
Wilson, Biophilia Harvard University Press 1984.
He proposed the possibility
that the deep affiliations
humans have with nature are
rooted in our biology.
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