Climate Change Adaptation Plan for Australian Birds

By CSIRO PUBLISHING

This is the first climate change adaptation plan produced for a national faunal group anywhere in the world. It outlines the nature of threats related to climate change for the Australian bird taxa most likely to be affected by climate change, and provides recommendations on what might be done to assist them and approximate costs of doing so. It also features an analysis of how climate change will affect all Australian birds, explains why some species are likely to be more exposed or sensitive to it than others, and explores the theory and practice of conservation management under the realities of a changing climate.

Species profiles include maps showing current core habitat and modelled climatic suitability based on historical records, as well as maps showing projected climatic suitability in 2085 in relation to current core habitat.

Climate Change Adaptation Plan for Australian Birds is an important reference for policy makers, conservation scientists, land managers, climate change adaptation biologists, as well as bird watchers and advocacy groups.

2014 Whitley Award Commendation for Zoological Management and Conservation Resource.

• Language: English
• Publisher: CSIRO PUBLISHING
• Release date: May 30, 2014
• ISBN: 9780643108042

Book preview

Introduction

Donald C. Franklin and Stephen T. Garnett

AN UNCERTAIN FUTURE

A climate-change world contains much uncertainty and presents major challenges for those responsible for ensuring the persistence and ecosystem functionality of bird and other wildlife populations (Polasky et al. 2011). There are at least four levels of uncertainty: inherent uncertainty in population dynamics, uncertainty about the response of species to climate change, both individually and in the way they interact, uncertainty about the nature of climate change, and the uncertainty that arises because climate change is an on-going process (Table 1).

Though Earth’s sixth mass extinction event is already upon us (Barnosky et al. 2011), thus far only a few extinctions have been attributed (at least in part) to climate change (Monzón et al. 2011; Szabo et al. 2012). However, very many population declines are already attributable to climate change (Thomas et al. 2006; Møller et al. 2008), and modelled predictions for the future of biodiversity in the face of climate change are grim (Thomas et al. 2004; Şekercioğlu et al. 2008; Maclean and Wilson 2011). Globally, Şekercioğlu et al. (2012) suggested that c. 10% of bird species may go extinct by the year 2100 as a result of climate change. High global extinction rates will doubtless correspond to much higher regional extinction rates, leading to widespread reductions in local and regional biodiversity and loss of ecosystem function (Şekercioğlu et al. 2004).

Many of these trends are also evident or predicted for Australia. Among birds, habitat loss and invasive species, rather than climate change, have been the major drivers of decline and extinction since European settlement (Garnett and Crowley 2008; Garnett et al. 2011). However, substantial impacts of climate change on the geographical distribution, and timing and success of breeding have already been observed among Australian seabirds (Chambers et al. 2011). Climate change may well be responsible for changes to the timing of arrival and/or departure noted for quite a number of Australian birds including both inter- and intra-hemispherical migrants (Beaumont et al. 2006; Chambers and Keatley 2010; Smith and Smith 2012). The body size of at least four Australian passerines has declined with a warming continent (Gardner et al. 2009). Further impacts are likely to have occurred but evidence may be constrained by limited monitoring (Chambers et al. 2005; Olsen 2007) and the difficulty of distinguishing the impacts of climate change from the impacts of interannual and interdecadal variation in climate. Whereas change to the range of birds at higher latitudes in the northern hemisphere have been primarily poleward and altitudinal in response to increased temperature (e.g. Brommer et al. 2012), more spatially diffuse impacts – which are harder to document and to link conclusively to climate change – are to be anticipated in Australia where changes in rainfall may be as important as changes in temperature (VanDerWal et al. 2013). For example, rainfall isohyets in south-western and south-eastern Australia may contract coastward and not necessarily southward. Mac Nally et al. (2009) documented the ‘collapse’ of a regional avifauna in northern Victoria during 12 years of drought, but the capacity of the populations to recover subsequently is unclear, as is attribution of the drought to climate change. Regardless, it is clear that Australia’s climate is changing rapidly and future climates are likely to be markedly different to the present (CSIRO 2007; Suppiah et al. 2007) – as reviewed in our chapter on the exposure of Australian birds to climate change. The consequences for many Australian bird species are likely to be seriously adverse (Chambers et al. 2005, 2011; Olsen 2007; Steffen et al. 2009; this study), though others will doubtless benefit (e.g. Weimerskirch et al. 2012).

Nevertheless, there is considerable uncertainty surrounding the magnitude, direction and nature of biodiversity change to be expected both in Australia (Steffen et al. 2009) and globally (Pereira et al. 2010). It has been argued that global models over-predict decline and extinction because their coarse spatial resolution fails to detect topographic and other refugia (Willis and Bhagwat 2009; Sears et al. 2011). Luoto and Heikkinen (2008) suggested a more complex outcome in which models that ignore topography cause a 2-fold overestimation of loss of species in mountainous areas, but a 2-fold underestimation of loss in flat lands – which is ominous for Australia, the flattest of all continents. Further, climate space and other biodiversity models may seriously underestimate species loss because they don’t account for interaction with other stressors (Jetz et al. 2007; Brook et al. 2008).

Table 1. A hierarchy of ecological uncertainty in the management of species under climate change.

Is this a situation without hope for biodiversity? In a pre-eminent review, Pereira et al. (2010) argued not, concluding that the uncertainty surrounding biodiversity outcomes arise ‘partly because there are major opportunities to intervene through better policies’. At a conceptual and practical level, we outline some of these intervention options in our chapter about conserving Australia’s birds. But before we can consider management, we must assess the risks – the vulnerability of Australian birds to climate change. This is a major function of this book.

ASSESSING VULNERABILITY: EXPOSURE AND SENSITIVITY

To be vulnerable to climate change, a species must be both exposed to change and sensitive to that exposure (Foden et al. 2008; Williams et al. 2008; Dawson et al. 2011). Exposure ‘refers to the extent of climate change likely to be experienced by a species’ (Dawson et al. 2011). Sensitivity may be understood as species-specific properties that modify the potential impact experienced from exposure (sensu Williams et al. 2008). However, application of sensitivity and alternative or complementary terms such as susceptibility, adaptability, resistance and resilience (also vulnerability) varies considerably through the literature. In particular, some view adaptability as a third dimension of vulnerability (e.g. Chin et al. 2010; Summers et al. 2012), whereas we have treated adaptability as the converse of sensitivity consistent with Fig. 3 in Dawson et al. (2011), noting that the relevant traits are often simple inversions. For example, a species that is highly specialised with regard to habitat is likely to be sensitive to climate change as a result, whereas one that occupies a broad range of habitats is likely to be adaptable.

The vulnerability dichotomy (exposure and sensitivity) has its roots in the general principles of risk analysis (Burton et al. 1978; Blaikie et al. 1994). An example that has nothing to do with climate change illustrates it well. When petrol contained lead, many of us were exposed to lead, but the extent of exposure varied depending on how far we lived from a busy road. Given equal exposure, children were more likely to suffer poisoning than adults (i.e. children are more sensitive) because ‘their gut absorbs lead more readily than an adult’s; and the developing central nervous system is more vulnerable to toxicants than the mature central nervous system’ (Needleman 2004). (Children were also more exposed to lead because of their greater hand-to-mouth activity.)

Thus, for example, a bird species may be exposed to climate change because the habitat features to which it responds disappear or move, and sensitive to that exposure because it has limited capacity to move to new areas and/or is specialised to a particular habitat that may change beyond the species tolerance. Alternatively, a species may be exposed to climate change but relatively insensitive to it because it is adaptable – flexible in its foraging behaviour and habitat selection, for instance, or its nomadic habits predispose it to tracking suitable habitat.

AIMS OF THIS BOOK

For this book, we assessed the exposure and sensitivity of all Australian birds with the aim of identifying taxa that may be at most risk of extinction or severe decline as a result of climate change. As such, our analysis complements that of The Action Plan for Australian Birds 2010 (Garnett et al. 2011) by incorporating climate change as an additional stressor threatening the persistence of bird taxa. We do not attempt to assess the extent of regional avifaunal declines, and our work in no way negates regional assessments that may place greater emphasis on change to communities and regional decline per se rather than immediate threat of extinction (e.g. Williams et al. 2003 for the Australian wet tropics).

We do so using the vulnerability framework outlined above and detailed in chapters on exposure and sensitivity. Climate space models (also known as climate envelope models, bioclimatic models and species distribution models) are a key quantitative tool we have employed in assessing exposure for terrestrial birds. These have been heavily criticised by some (e.g. Low 2011). However, we avoid many of their limitations by: considering outputs on a taxon-by-taxon basis; considering and incorporating other aspects of exposure (albeit mostly qualitatively); and evaluating the sensitivity of taxa as well as their exposure.

Further, it is not our aim to provide a definitive list of taxa at risk. Even with a much more detailed treatment of each taxon than is possible in a work of this size, no definitive list would be forthcoming – there are too many uncertainties. Rather, we aim to identify some taxa that warrant more detailed consideration, and more generally to highlight the nature of the risks to Australia’s birds and other biodiversity. Each bird taxon we consider in detail can be thought of as a hypothesis which will be tested in time. In providing a chapter on management options, we wish also to provide evidence that wildlife managers are not helpless in the face of climate change.

Finally the recommendations for management detailed for individual taxa are built on the values embodied in current legislation. Thus we consider that each subspecies has equal merit regardless of its taxonomic distinctiveness, the marginality of the population in Australia or the difficulty in retaining it. However, shifts in distribution arising from climate change will mix subspecies that are currently distinct, and the costs of the adaptation strategies needed to retain taxa are likely to be high. This will not only challenge our technical and financial capacity to undertake the actions, but will raise much more fundamental questions about the overall objectives of biodiversity conservation. Will society hold the same value for a taxon that persists only in captivity because it can no longer survive in the wild in the new climates we have created? Can subspecies be retained in their current form? We do not attempt to answer such questions. Rather we provide a range of scenarios which suggest such questions need to be considered by society and may affect legislation and policy in the future.

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The exposure of Australian birds to climate change

Donald C. Franklin, Glenn Ehmke, Jeremy VanDerWal and Stephen T. Garnett

INTRODUCTION

Exposure of species to climate change may be defined as ‘the extent of climate change likely to be experienced by a species’ (Dawson et al. 2011). In descriptive terms this is relatively straightforward: in the places that a species occurs and for a given time frame, the climate is projected to change in a prescribed manner (for example mean temperature rising by 2°C and mean annual rainfall decreasing 10% over a period of 50 years). However, this may have quite different consequences for different species (Foden et al. 2008). For example, whilst reptiles (being ectothermic) may respond relatively directly to temperature (Kearney et al. 2008), birds (being endothermic) generally do not – the most notable exception being to extreme heat waves (McKechnie and Wolf 2010). However, temperature change may influence the persistence of bird species indirectly via several pathways (below). The Australian avifauna is ecologically diverse, ranging from small largely sedentary passerines to highly nomadic waterbirds and large wide ranging pelagic seabirds, and the experience of climate change will clearly differ between them.

Climate change will be measurable as much more than changes to temperature and rainfall. Bellard et al. (2012) suggested five major components of relevance to biodiversity, with numerous measurable sub-components, whilst acknowledging that the list was unlikely to be complete (Fig. 1). The exposure to climate change experienced by any given Australian bird taxon is likely to be a combination of a range of components linked to their life histories and populations by often complex pathways. For predictive purposes, identifying the relevant components and projecting them into the future is a substantial challenge. In this chapter, we explore some of these issues and explain how we have appraised the exposure of Australian bird taxa.

WHAT CLIMATE CHANGE COMPONENTS ARE AUSTRALIAN BIRDS POTENTIALLY EXPOSED TO?

In this section, we briefly review the likely major components and pathways to exposure and the groups of taxa for which each is relevant. Prowse and Brook (2011) also provide a useful review of the elements of projected climate change likely to impact on biodiversity in Australia. Cahill et al. (2013) reviewed the as-yet-limited evidence about the proximal causes of decline or extinction in plants and animals resulting from climate change, noting that indirect effects mediated in particular by food supply appear far more widespread than direct responses to climate itself.

Increased temperature

All of Australia is predicted to experience increases in mean temperature by 2070 of between c. 1.8 and 5.5°C depending on location and emissions scenario (Suppiah et al. 2007). The greatest increases are likely to be in the interior of northern and especially north-western parts of the continent, and the lowest in western Tasmania and the far south of south-western Australia. Temperatures will also become more variable in time. A greater frequency, intensity and length of heatwaves will arise – and has already occurred (Meehl and Tebaldi 2004) – as a result of this combination of increase in the mean temperature and its variance (Schär et al. 2004) as illustrated schematically in Fig. 2.

Temperatures above c. 45°C sustained for several hours can cause death in birds either directly by hyperthermia or through unsustainable rates of water loss (McKechnie and Wolf 2010). Smaller species are more vulnerable to unsustainable rates of water loss because of their higher body surface to volume ratio, though the converse might apply with hyperthermia in that larger birds may be less able to dissipate heat rapidly. Field temperature and time thresholds will doubtless vary between species and the buffering opportunities provided by the environments they occupy. Mass mortality during heatwaves has been reported in the Australian arid-zone and elsewhere, generally associated with air temperatures greater than 45°C (reviewed in McKechnie et al. 2012). On the south coast of south-western Australia, maximum temperatures of 47.6 and 48°C were associated with major mortality events in Carnaby’s Black-cockatoo (Calyptorhynchus latirostris) (Saunders et al. 2011). Heat waves that occur whilst birds are nesting can also cause substantial direct mortality of eggs or nestlings, especially in species that nest in the open and on the ground (e.g. Krogh and Schweitzer 1999; Sherley et al. 2012).

Fig. 1. Some abiotic components of exposure to climate change. Reproduced from Bellard et al. (2012, part Fig. 1) with permission.

Fig. 2. Schematic illustration of the effect of change to the mean and variance of temperature on the frequency of heat waves. For the purpose of this illustration, a heat wave is defined as any temperature above 45°C. Compared to a hypothetical baseline (A), heat waves conditions are 4.2 times as frequent under scenario B (increase in mean temperature of 2°C) and 13.0 times as frequent in C (increase in mean as in B, and increase in variance). An increase in the skewness of the distribution may further accentuate the trend (IPCC 2012).

Numerous indirect effects of increased temperature on birds, with potential adverse consequences, have also been noted and are perhaps the more pervasive form of temperature-related exposure. Non-lethal spells of hot weather can reduce foraging efficiency, and likely also foraging time, causing loss of body mass (Bauchinger et al. 2011; du Plessis et al. 2012). Heat waves that are assumed to be non-lethal depressed some bird populations, particularly those that occur across narrower thermal ranges (Jiguet et al. 2006), in hotter areas and that were resident and/or nested on the ground (Albright et al. 2011). Temperature may directly influence food supplies (Pearce-Higgins et al. 2010), for example by killing prey or forcing prey to seek cover, or by drying nectar supplies. It may also alter the timing of breeding and the timing and extent (proportion of population) of migration, as shown by experimental studies that tease out temperature from other climate effects (Pulido and Berthold 2010; Schaper et al. 2012). Temperature may influence the growth and drying of vegetation (Bradstock 2010), in turn influencing fire regimes which are critical for several Australian bird species (Woinarski and Recher 1997; Garnett et al. 2011). Poleward and altitudinal shifts in the range of many birds (e.g. Parmesan and Yohe 2003; Forero-Medina et al. 2011; Brommer et al. 2012) are likely attributable primarily to temperature increases though other climate change components may also be involved (Tingley et al. 2009). Higher and/or more variable temperatures appear to have already favoured selection for smaller body size in a range of bird species (Gardner et al. 2011; Goodman et al. 2012) including several Australian passerines (Gardner et al. 2009). The potential pathways for the impact of temperature on birds are diverse and this treatment is most unlikely to be comprehensive.

Change to rainfall

There is much less certainty about impending changes to rainfall than there is to temperature. The useful generality that Australia should anticipate drier times (Suppiah et al. 2007) belies considerable regional and seasonal complexity. The firmest prediction is for a substantial reduction rainfall in south-west Western Australia affecting all times of year (Suppiah et al. 2007). This will be in addition to the substantial drying that has already occurred since c. 1975 (Hope et al. 2006), though drying of the far south-west has been partly matched by an increase in rainfall over the last 40 years in the eastern south coast of Western Australia (Australian Bureau of Meteorology 2012). Most of Australia except Tasmania may experience substantially reduced winter rainfall but the effect on annual totals may be partly offset by increases in summer rainfall (Suppiah et al. 2007). The Wet Tropics region of Queensland may experience a reduction in dry-season rainfall but the direction of change to total rainfall is unclear (Suppiah et al. 2009). Rainfall in the Kimberley and Top End regions of northwestern Australia and adjacent inland areas has increased substantially in recent years, a trend attributed to the seeding affect of particulate pollution from Asia brought south by the monsoon; the longer-term trend is unclear because the predicted impact of greenhouse gas emissions is conversely to reduce rainfall in these regions (Rotstayn et al. 2012). The northern wet season may be abbreviated but more intense in a higher proportion of years (Taschetto et al. 2009; Yeh et al. 2009), potentially enhancing the severity of the dry season. However, in some parts of northern Australia, there has been a shift to an earlier start to the wet season over the last 50 years, possibly associated with shifts in the nature of the El Niño–Southern Oscillation (ENSO; Garnett and Williamson 2010).

Decreases in mean annual rainfall have implications for the frequency and length of droughts. Whether these will be exacerbated by an increase in the interannual variability in rainfall is unclear, as Global Climate Models do not yet adequately deal with inter-annual and inter-decadal variability in any of the major regional climatic phenomena that affect Australia – ENSO (Brown et al. 2013), the monsoon (Fu and Lu 2010) or the Pacific Decadal Oscillation (Lapp 2012). At a coarse spatial scale and using data on evapotranspiration as well as rainfall projections, Kirono et al. (2011) predicted increases in the areal extent and/or frequency of droughts for most of southern Australia commencing in the south-west and spreading as the 21st century proceeds to the remainder of the southern mainland and eventually also to New South Wales and Tasmania. It is not known how such droughts will compare with those that occurred during the much drier glacial period or the warmer interglacial periods of the last 125 000 years and through which most Australian species must have persisted. However, a major difference between then and now will be in areas where habitat has been lost, fragmented or degraded, preventing shifts of species to refugia and subsequent recolonisation.

The most direct – though not necessarily most severe – impact of changes in rainfall including drought is likely to be on aquatic and marsh ecosystems and their birds. A proportionate shift from winter to summer rainfall may increase local run-off because of the greater intensity of summer rainfall, favouring run-on portions of the landscape, including wetlands, at the expense of run-off areas. Wide-ranging wetland birds that breed on ephemeral waters may suffer locally-intense exposure in southern Australia but we do not anticipate major exposure of these species at a national level. The exposure of deep-water specialists may be mitigated by artificial reservoirs. Of greater concern is the exposure of specialists of shallow, permanent, vegetated wetlands in southern Australia such as the Australasian Bittern (Botaurus poiciloptilus) and Australian Little Bittern (Ixobrychus dubius). Rookery-breeding waterbirds that nest in shallow, vegetated wetlands may also be exposed in southern Australia, but are not generally restricted to that portion of the continent.

Australian terrestrial ecosystems and their birds have a long history of coping with drought (Robin et al. 2009). An increase in the frequency and intensity of droughts will shift the balance between boom and bust, tipping some species beyond the capacity to recover, but this is in large part a function of species sensitivities and beyond the scope of this chapter. At an ecosystem level, we would anticipate greatest exposure to drought in semi-arid and drier temperate southern ecosystems, especially in landscapes with limited moisture-holding capacity. In one such ecosystem, the box-ironbark forests of northern Victoria, a 12-year drought caused the ‘collapse’ of the avifauna (Mac Nally et al. 2009).

Ecosystem consequences of drought in medium-rainfall areas can include widespread die-back and mortality of trees including eucalypts (Pook and Forrester 1984; Fensham et al. 2009; Semple et al. 2010). An increase in drought frequency and intensity could conceivably provide ecosystem tipping-points resulting in the generation of new, more drought-adapted (and perhaps less productive) vegetation types, with major consequences for the avifauna that are not easy to predict.

As rainfall is a most fundamental driver of vegetation and its productivity, changes to means as well as extremes must have major consequences with flow-on effects for terrestrial and some other birds. For example, low rainfall is implicated in reducing the flowering of key eucalypt nectar sources for birds (Law et al. 2000; Mac Nally et al. 2009) and the seasonality of rainfall influences the timing of their flowering (Keatley et al. 2002).

Other extreme events – fire

Changes to the frequency and intensity of fire will be influenced by changes in a range of climate parameters, by the response of fuels present in differing vegetation types to rainfall and drought, and management (Bradstock 2010; O’Donnell et al. 2011; Williams and Bowman 2012). Relevant climate parameters include rainfall, temperature, droughts and wind speed. Climate change projections for wind speed over land in Australia are ambiguous. Of particular relevance to fire risk in southern Australia: ‘extreme winds in summer are likely to be governed more by small scale systems that are not adequately captured by the resolution of the climate models’ (CSIRO 2007).

In some ecosystems such as grasslands and grassy woodlands, a trade-off between changes in fire weather and the production of fine fuels (grass, herbage, leaf litter) lends uncertainty to predictions about changes to fire regimes (Bradstock 2010; Matthews et al. 2012). However, ecosystems in southern Australia such as heathlands, shrublands and forests with a shrubby understorey, where the fuel includes substantial live woody plant material, can expect potentially-substantial increases in the frequency, intensity and areal extent of wildfires with warmer and drier conditions (e.g. King et al. 2013). This generates serious exposure for specialist old-growth inhabitants of these environments such as scrub-birds (Atrichornis spp.), bristlebirds (Dasyornis spp.), ground parrots (Pezoporus spp.), Malleefowl (Leipoa ocellata) and Black-eared Miner (Manorina melanotis).

Scenarios for change in fire regimes in spinifex (Triodia spp.) hummock grasslands are even more complex because this vegetation type occurs across a broad range of substrates (sand, loam, rock), topography (plains, dunes, ranges), and semi-arid climates (from southern regions where winter rainfall predominates to northern, summer-dominated rainfall) (Griffin 1984). Hummock grasslands occupy approximately one quarter of the Australian mainland. Hummock grasses are shrub-like in that they accumulate fuel, and thus the connectivity that enables fire to spread, over many years (Allan and Southgate 2002; Russell-Smith et al. 2010). In some areas, connectivity may be further enhanced by annual or perennial grasses and herbs which, in central Australia in particular, proliferate – and then dry – after heavy rain (Greenville et al. 2009). In others such as the sandstone escarpments of Arnhemland (Russell-Smith et al. 2002) and some mallee and mallee-heaths of southern Australia (Cheal and Parkes 1989), Triodia is associated with shrubs which may desiccate during drought. We suspect that hummock grasslands of the northern interior, along with shrubby mallee and heath with spinifex in southern Australia, are likely to be exposed to higher fire risk, the former because of hotter and potentially wetter conditions and the latter particularly because of more frequent and prolonged drought. This exposure is of great concern for old-growth spinifex specialists such as most members of the genera Amytornis (grasswrens) and Stipiturus (emu-wrens). However, projections for mulga-spinifex ecosystems in central Australia suggest a decrease in the incidence and area burnt (King et al. 2013).

In the longer term, atmospheric changes in the concentration of carbon dioxide may also influence fire regimes by shifting the competitive balance between grass and woody plants (see below).

Other extreme events – cyclones and other storms

The exposure of birds generated by cyclones and other storms can take the form of either death or reduced breeding success, and can occur directly as a result of storm conditions or subsequently as a result of the flow-on effects of habitat damage (Tanner et al. 1991). Examples of direct effects include the death of at least 81 Carnaby’s Black-Cockatoo (Calyptorhynchus latirostris) during a hail storm, and of numerous tern chicks (whether by storm impact or starvation) on a Great Barrier Reef island during or soon after a cyclone (Langham 1986). Flow-on effects of damage to tropical rainforest by cyclones may be greatest via reduced supplies of nectar and especially fruit rather than insects (Tanner et al. 1991), suggesting greatest exposure for specialised frugivores such as the Southern Cassowary (Casuarius casuarius johnsonii; Latch 2007).

Under enhanced greenhouse gas conditions, the frequency of tropical cyclones is anticipated to diminish somewhat but the mean intensity, and especially the frequency of the most severe cyclones, is likely to increase. This projection applies both globally (Knutson et al. 2010) and to Australia (CSIRO 2007). An increase in the frequency of intense cyclones generates exposure for birds of tropical mangroves, the rainforests of Queensland’s Wet Tropics and Cape York Peninsula, and rookery-nesting seabirds. Because the impact of