Whither wildlife in an overpopulated world?

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 Effect size following predator removal • 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 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 Capture rate: sandy inland mouse Flood rains Rains Intense per capita predation predation Climate model: red-tailed phascogale Long-term rodent trapping results, Simpson Desert

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?

Whither wildlife in an overpopulated world?