Whither wildlife in an overpopulated world? Chris R. Dickman.
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Transcript of 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
Source: UN Department of Economic and Social Affairs (2012)
Current population ~7.2 billionGrowth rate ~1.1%
World population: projections
Source: UN Department of Economic and Social Affairs (2012)
‘Low’ variant ‘Medium’ variant
‘High’ variant
‘Constant-fertility’variant
Australia: population growth
Current population ~ 23 millionLong 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
Climate model: red-tailed phascogale
Average of Pseudomys hermannsburgensis
0
10
20
30
40
50
60
1990
1991
1993
1999
2001
2002
2006
2008
2011
Capt
ures
(100
trap
nig
hts)
Flood rain → resource pulse → rodents →predators (+ wildfire) → intense predation
Long-term rodent trapping results, Simpson Desert
Capture rate: sandy inland mouse
Flood rains Rains
Intense per capitapredation
predation
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)
r2 = 0.96y = 36.5+0.95x
1950
2009
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?