Presentation on theme: "Whither wildlife in an overpopulated world? Chris R. Dickman."— Presentation transcript:
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 billion Growth 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 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 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) r 2 = 0.96 y = 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?
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