Download Chris Dickman - Sustainable Population Australia

Whither wildlife in an
overpopulated world?
Chris R. Dickman
Aims of talk
• World population growth – trends and predictions
• Population growth in Australia
• Consequences for Australian wildlife:
1) the losers: large species, specialists
• Direct impacts – loss of habitat, overkill, pollution, disruption
to life cycles
• Indirect impacts – invasive species, disease, climate change
2) the winners: generalists, resilient native species
• Consequences for people:
• Loss of resources and services, cultural memory loss,
diminishing connection with remaining wildlife and its
environment; accelerating loss of wildlife
• Conclusions: where to from here?
World population: growth
Current population ~7.2 billion
Growth rate ~1.1%
Source: UN Department of Economic
and Social Affairs (2012)
World population: projections
‘Medium’ variant
‘Low’ variant
‘Constant-fertility’
variant
‘High’ variant
Source: UN Department of Economic and Social Affairs (2012)
Australia: population growth
Current population ~ 23 million
Long term growth rate >1.3%
(now 1.8%)
Source: UN Department of Economic and Social Affairs (2012)
Wildlife: recent changes in status
• Worldwide: 270 terrestrial
vertebrates, 62 fishes, 384
invertebrates listed as extinct (IUCN
Red List – 2013)
• Australia: 54 terrestrial vertebrates
listed as extinct, +2 not listed, 290
more rated as threatened (EPBC Act
1999 – 2013); ~3000 ‘ecosystem
types’ also at risk (Keith et al. 2013)
• Background rate of extinction ~1
species per million per year;
exceeded by 1-3 orders of
magnitude by some vertebrate
groups, e.g. Australian mammals
(Dickman et al. 2007)
Photo: T. Prete
Photo:
D. Gialanella
Photo: A. Greenville
Australian wildlife: causes of loss
• Habitat loss: conversion of
natural vegetation for human
food (arable + grazing),
shelter (towns, cities), roads,
industry. Examples:
• 1) Victorian native grassland
reduced by 99% for grazing
and urban infrastructure →
loss of eastern barred
bandicoot
• 2) Logging in Victorian
central highlands for timber
→ decline in Leadbeater’s
possum
• 3) Mining, CSG fracking?
Photo: Museum Victoria
Photo: D. Harley
Australian wildlife: causes of loss
• Direct overkill: targeted
destruction of wildlife to
reduce competition (real or
perceived) with humans.
Examples:
• Thylacine, Tasmania
• Marsupial Destruction Acts,
Queensland and NSW;
bounties, Sydney rat cull
• Indirect overkill: roads,
fence barriers, uncapped
mine shafts kill >100 million
terrestrial vertebrates / year
→ local population depletion
Photo: Murweh Shire Council
Australian wildlife: causes of loss
• Invasive species:
human-associated
sport, companion,
commensal and other
animals have
wrought huge
problems. Examples:
• Rabbit, red fox,
domestic cat, black
rat, common myna,
cane toad
Effect size following predator removal
Salo et al. (2007)
Photos: P. German
Australian wildlife: causes of loss
• Pollution: air, water,
soil contamination;
noise, light pollution
reduce habitat quality
and disrupt species’
life cycles. Examples:
• Frogs (water
pollution), bats, birds
(light pollution);
chronic elevation of
stress hormones in
many terrestrial
vertebrates →
reduced reproduction
Australian wildlife: causes of loss
Climate change, esp.
extreme events: heat
waves, droughts,
floods and climate ×
environment
interactions
Flood rain → resource pulse → rodents →
predators (+ wildfire) → intense predation
Average of Pseudomys hermannsburgensis
Capture rate: sandy inland mouse
60
Captures (100 trap nights)
50
Flood rains
40
Rains
30
Intense per capita
predation
20
predation
10
Climate model: red-tailed phascogale
Long-term rodent trapping results, Simpson Desert
2011
2008
2006
2002
2001
1999
1993
1991
1990
0
Australian wildlife and human
overpopulation
• Australia has the
world’s highest rate
of extinction of native
mammals in the last
200 years + high
rates of loss of native
birds and amphibians
• Rates far exceed
background rates
• Many other
vertebrates are
threatened
• Humans—directly
and indirectly—are
the cause
Where to from here?
• Predicting future
wildlife loss: 13
extinctions of
Australian terrestrial
vertebrates since
1950; 56 in total
• 0.95 species lost with
every million
additional people
• By 2100 (roughly!):
– 63 species (IUCN low)
– 70 species (IUCN
medium)
– 87 species (IUCN
high)
– 124 species (IUCN
constant-fertility)
2009
r2 = 0.96
y = 36.5+0.95x
1950
What will we lose?
Rough estimates suggest
many species (7-68) will
go by 2100, most likely:
– Currently threatened
species
– Specialists (e.g. koala,
high altitude + latitude
frogs and mammals)
– Boom and bust taxa
and other arid-dwellers
– Coast-dependent
species (seabirds,
turtles), island
endemics
– Any species with small
geographical ranges
What will we lose?
• In addition to the species …
• the integrity of ecological communities
• co-evolved relationships
• ecological services (e.g. soil turnover,
dispersal of seeds, fruits, spores of
mycorrhizal fungi, pollination, control of
some ‘pest’ species)
• current economic value (e.g. $1.8 billion / year in
tourism; Hundloe & Hamilton 1997)
• future value (missed opportunity costs)
• aesthetic, inspirational, iconic exemplars of the
Australian identity
What will we have?
Lots of these …
(resilient or generalist
native species)
and these …
(domestic +
invasive
species)
→ biotic
homogenisation
Photo: R. Shine
Conclusions
• Many Australian mammals, birds and other vertebrates
have been extirpated by human activity
• Potentially catastrophic losses of more species,
populations, ecological processes and services are
inevitable as the human population grows
• Cultural memory loss and disconnection to the
environment are likely with more people (and increasing
urbanisation), exacerbating problems for wildlife
• “All environmental problems become harder – and
ultimately impossible – to solve with ever more people”
Sir David Attenborough
• Can we avoid a Down Under dystopia? Solutions?