1

The evil quartet

If we know what causes biodiversity

loss, we should also know the solutions

Dave Dawson February 2011

Jared Diamond

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

2

David Raup

Jack Sepkoski

Prof. Norman

MacLeod Natural

History Museum

McLeod (2003)

1 2 3 4 5

Stages in geological time

McLeod 2003

The evil quartet

• Over-exploitation

Dave Dawson February 2011

If we know what causes biodiversity

loss, we should also know the solutions

3

Paul Martin

Prehistoric overkill

• Rapid extinction of

megafauna shortly

after arrival of people

•People in small

numbers, but they

were

•Sophisticated, group

hunters

•with advanced tools

Martin (1989)

4

Millennium Ecosystem Assessment

Vitousek et al. (1997a)

World fisheries

Garratt Hardin 1968

The tragedy of the commons

The evil quartet

• Invasive alien species

Dave Dawson February 2011

If we know what causes biodiversity loss,

we should also know the solutions

•Over-exploitation

5

Grass flora of New Zealand

157

31

226

46

Endemic Indigenous Naturalised Transient

Edgar & Connor (2000)

Dove SaxSteven Gaines

6

Sax &

Gaines

(2008)

Plant species on islands

Sax & Gaines (2008)Plant species on well-studied islands

The increase of alien species over time

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)

7

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

• Loss and degradation of habitat

Dave Dawson February 2011

If we know what causes biodiversity loss, we

should also know the solutions

•Over-exploitation

•Invasive alien species

Darlington (1957)

West Indies.

The number of species, S,

relates to the area of the

island, A

D = cAz Preston (1962)

Number of

amphibian and

reptile species,

log scale

Island size, log scale

8

E.O. Wilson, studied ants on New Guinea islands MacArthur & Wilson

(1967) The theory of

island biogeography

Jared DiamondDiamond (1975)

Oceanic islands

in equilibrium

Land bridge islands(connected to New Guinea

10,000 years ago)

Carry an “extinction

debt”

New Guinea satellite islands

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New Guinea satellite islands

Diamond (1975)

Fraction of

near island

number, log

scale

Diamond (1975)

•Bigger better

•Single large better than several

small

•Close spacing better

•Grouping better

•Better linked with corridors = B

•Better compact than thin

1980

Lenore Fahrig

10

Habitat

Habitat fragmentation (Fahrig 2003)

Habitat

Habitat fragmentation (Fahrig 2003)

Matrix

Habitat

Habitat fragmentation (Fahrig 2003)

Matrix

Correlated effects of Habitat loss, after Forman (1997) & Fahrig (2003)

Landscape multicollinearity

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 20 40 60 80 100

Percentage of Habitat Lost

Do

min

an

ce

of

ea

ch

pro

ce

ss

, a

rea

s

an

d n

um

be

rs

Perforation

Fragmentati

onShrinkage

Attrition

Patch size

Core

Isolation

# of patches

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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

McGarigal & Cushman (2002), Fahrig (2003), Ewers & Didham (2005), Kupfer et al.(2006)

Meg Game

George Peterken

Incidence of Dog's mercury in recent woods with distance

from older woods (Game & Peterken 1981)

0

50

100

< 0.2 0.2 - 0.4 0.4 - 0.8 0.8 - 1.6 1.6 - 3.2 3.2 - 6.4

Distance from source (Km, log scale)

Perc

en

tag

e w

ith

Do

g's

merc

ury

(95%

co

nfi

den

ce l

imit

s)

Woodland herbs in central Lincolnshire (after Game & Peterken

1984)

0

20

40

60

80

100

120

140

160

1 10 100

Number of ancient woods (log scale)

Nu

mb

er

of

sp

ec

ies 5ha

15ha

40ha

70ha

150ha

250ha

350ha

600ha

Increasing fragmentation

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Alessio Mortelliti

80% forest coverIncidence of Hazel

Dormouse in 41

landscape blocks

in central Italy

Mortelliti et al. (2011)

Under 10% forest cover

Increasing amount of hedgerows (length in a 4x4 km landscape block)

100%

Proportion

of

landscape

blocks with

Hazel

Dormice

0%

Dr Robert Ewers

Dr Raphael Didham

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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).

45% showed little

or no edge effect.

5% of the species preferred

the grassland matrix

Ewers & Didham 2008

Beetle

population

abundance

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).

38% of the species were affected

up to 50m into the forest

Ewers & Didham 2008

Beetle

population

abundance

Distance (m) 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).

12% of the species were affected

1000m, or more, into the forest!

Ewers & Didham 2008

Beetle

population

abundance

Edge effects reducing

and fragmenting the

core

Ewers & Didham (2007)

15

Extinction debt

Kakamega Forest, Kenya

Brooks et al. (1999)

Extinction debt

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 & Muller-Landau (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)

16

Combined

Priority afforded

by schemes that

focus on:

A (Red), where

most has been

lost or

B (Green), where

most remains,

and so which are

vulnerable in

future

The evil quartet

• Pollution and intensive management

Dave Dawson February 2011

If we know what causes biodiversity loss, we

should also know the solutions

•Over-exploitation

•Invasive alien species

•Loss and degradation of habitat

Fritz Haber Paul Müller

Published 1962, DDT banned in US 1972

17

Ratcliffe (1970)

Year

Eggshell

thickness

Peregrine Falcon eggshell thinning

and organochlorine pesticide use

Anon 2010, see also Gregory et al. (2004)

The second silent spring? Krebs et al. 1999

The second silent spring (Krebs et al. 1999).

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?

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(2007)

The evil quartet

• Climate change

Dave Dawson February 2011

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 and habitat loss

Species’ distribution

Climate envelope

Climate change and habitat loss

Species’ distribution

Climate envelope

Lost habitat

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Climate change and habitat loss

Species’ distribution

Climate envelope

Lost habitat

Climate change and habitat loss

Species’ distribution

Climate envelope

Lost habitat

R.J. Whittaker et al. (2005)

Whittaker et al. (2005)

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Jared Diamond

Diamond (1975)

•Bigger better

•Single large better than several

small

•Close spacing better

•Grouping better

•Better linked with corridors = B

•Better compact than thin

What should the principles be?

1. First, increase the total area of high quality habitats

2. Go for high environmental heterogeneity

3. 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

After Harrison & Bruna (1999), Dawson (2006), Laurance (2008) & Hodgeson et al. (2009)

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”?

21

Millennium Ecosystem Assessment Biodiversity Synthesis

See also Diaz et al. (2006)

The evil quartet

• Us

Dave Dawson February 2011

•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

Dr Paul Ehrlich1978

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Lord (Robert) May of Oxford, President

of the Royal Society 2000-2005

Government Chief Scientific adviser

1995-2000

May 2010

Ecological footprint and biocapacity

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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

May 2010

Intergovernmental Platform on Biodiversity and

Ecosystem Services (IPBES)

Announced December 2010. To be set up this

year

– Will mirror the IPCC

Simon Levin (2010)

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.

Mark Van Vugt

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Averting the Tragedy of the CommonsUsing 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.