Co Authors: Bradley C. Congdon², Nic Dunlop³, Peter Dann?, Carol Devney?
1 Centre for Australian Weather and Climate Research, Bureau of Meteorology, GPO Box 1289, Melbourne, Vic 3001, Australia.
2 Marine and Tropical Biology, James Cook University, Cairns, Qld 4870, Australia.
3 Conservation Council (WA), 2 Delhi Street, West Perth, WA 6005, Australia.
4 Research Department, Phillip Island Nature Park, PO Box 97, Cowes, Vic 3922, Australia.
5 AIMS@JCU, Marine and Tropical Biology, James Cook University, Cairns, Qld 4870, Australia.
Chambers L.E., Congdon B.C., Dunlop N., Dann P. and Devney C. (2009) Seabirds. In A Marine Climate Change Impacts and Adaptation Report Card for Australia 2009 (Eds. E.S. Poloczanska, A.J. Hobday and A.J. Richardson), NCCARF Publication 05/09, ISBN 978-1-921609-03-9.
Little penguins are altering their breeding time in response to warmer temperatures, and chick growth of tropical and sub-tropical seabirds has slowed in response to less food availability as temperatures warm (LOW confidence)
Warmer temperatures and an El Niño-like future climate are expected to reduce food availability for breeding seabirds leading to a reduction in breeding success (MEDIUM confidence)
Maintain and expand monitoring to improve understanding of drivers of change in seabird populations, and investigate the potential of alterative land-use strategies to increase the ability of nesting birds to cope
Manage breeding habitats and reduce or eliminate non-climate threats to increase resilience and improve the likelihood of natural adaptation; reduce competition from humans for food e.g. through fishery management
Dr Lynda Chambers is a senior scientist within the Centre for Australian Weather and Climate Research (Bureau of Meteorology), where she specialises in climate research and its interface with Australian flora and fauna, particularly birds. She has published extensively on such topics as phenology, migration, species abundance, climate variability and change, climate extremes, and forecasting; including 20 years of research on the Little Penguin. She is a project leader for the National Ecological Meta Database and the citizen science project Climate Watch, in partnership with the Earthwatch Institute, as well as a contributing author to the Nobel Peace Prize winning Intergovernmental Panel on Climate Change 4th Assessment Report (Impacts, Adaptation and Vulnerability).
Dr Nic Dunlop has been a citizen scientist for nearly 30 years, indulging amongst other things a private passion for the ecology of tropical seabirds off the Western Australian coast. Over that period he has also worked as an ecologist / or environmental officer, in research, as a consultant, as an educator, as a mining industry professional and as a State Government regulator. His current day job is as the Citizen Science Program Coordinator with the Conservation Council of WA. He has now been with that conservation NGO for 8 years.
Dr Peter Dann has worked as a wildlife ecologist for 30 years and has published extensively on seabirds and shorebirds in Australasia. He edited “The Penguins: ecology and management” and is currently editor of “Marine Ornithology”. He manages a research group on Phillip Island in southern Victoria specialising in penguin and seal biology. Peter is also a research fellow of the Department of Zoology at the University of Melbourne and the Scott Polar Institute at Cambridge University, Director of the Penguin Foundation and Secretary of Birds Australia.
Carol is finalising a PhD in Conservation Biology & Marine Ecology from James Cook University. Her thesis is entitled ‘Climate variation and population dynamics in tropical seabirds’. She holds a BSc in Environmental Chemistry from the Colorado School of Mines, USA and a Graduate Diploma of Research Methods in Wildlife Management from James Cook University.
Dr Brad Congdon is a Reader in Ecology at James Cook University – Cairns. He is a field ecologist with a special interest in seabird conservation and evolution and over 25 years experience working with seabirds both in Australia and overseas. His research group has recently demonstrated that seabirds are sensitive indicators of multiple, previously indistinguishable, climate-change impacts in tropical marine ecosystems and have established rising sea-surface temperatures as a major conservation issue for seabirds of the Great Barrier Reef.
For seabirds in the Australian region, climatic and oceanographic variation and change has been associated with changes in distribution, success and timing of breeding, chick growth and survival of adults and immature birds, across many foraging guilds and regions.
Currently, there is a low-medium level of confidence in the prediction of potential impacts of future climate change on seabirds. This is due to incomplete knowledge of climate-ecosystem processes, including potential threshold changes, uncertain ability of species to alter phenology and prey species, and often short historical biological data series. However, southward expansion of breeding colonies will be limited by available habitat and the distribution of prey species. Sea level rise is likely to reduce existing breeding habitat, particularly for burrow and surface nesting species on low-lying islands – at least in the short term.
Relationships between seabirds and climate are generally poorly known, and documented responses often vary by location and species. For many seabirds and regions limited information is available on prey distributions and biology, foraging and movement patterns, and the ability of species to alter prey species or life-cycle timing. All of these factors make generalisations about adaptive capacity in seabirds difficult. This suggests that, in many cases, regional or more localised assessments of resilience or adaptive capacity may be required, with data obtained specifically for that purpose. Examples of adaptation options include: managing breeding habitats to increase resilience to climate change, reducing or eliminating non-climatic threats to improve the likelihood of autonomous adaptation and reducing anthropogenic competition for resources. Further research and monitoring of key species are clearly required including the determination of which species and systems are more vulnerable to climate change, where generalisations about impacts and adaptation can be made and which species may serve most effectively as indicators of climatic impacts on higher trophic predators.
Seabirds consume significant amounts of marine resources and play an important functional role in marine ecosystems, such as nutrient transfer from pelagic and offshore regions to islands, reefs and coasts, dispersal of seeds and movement of organic matter through the soil layers, particularly by burrow-nesting species (Congdon et al. 2007). Seabirds are upper trophic level marine predators and their demographic and reproductive parameters are often related to changes in trophic and oceanographic conditions (Congdon et al. 2007, Cullen et al. 2009).
Australia, and its external territories, has a diverse seabird fauna of 110 species, covering 12 families (Ross et al. 2000). The majority of these (69%) breed in the region; with the remaining species being either regular or occasional foraging visitors during the non-breeding season (Ross et al. 2000). Alternative definitions of seabirds (e.g. Ross et al. 1996) also include coastal feeding species, some or all individuals of which depend on marine life along or close to the shore, e.g. Eastern Reef Egret Egretta sacra, Osprey Pandion haliaetus, Black-faced Sheathbill Chionis minor, Chlidonias species, and species which breed on offshore islands, e.g. Cape Barren Goose Cereopsis novaehollandiae. This report will concentrate on birds which forage in the Australian marine environment, with some additional notes on species using the coastal zone for at least some of their life cycle, or who are otherwise likely to be directly impacted upon by changes in the marine system.
There are many environmental and anthropogenic threats to seabirds in the Australian region, including changes to the climate system.
Variation in, and changes to, the marine environment are known to affect seabirds globally, influencing prey density and seabird abundance, distributions, productivity and behaviour (Ainley et al. 1988, Crawford and Jahncke 1999, Velarde et al. 2004, Congdon et al. 2007, Cullen et al. 2009). This is particularly true in regions where local sea surface temperatures (SSTs) and marine productivity are influenced by upwelling and boundary currents (Ainley et al. 1988, Crawford and Jahncke 1999, Velarde et al. 2004). Any changes in availability of prey items are likely to have flow on effects to seabird abundance, distribution, migration patterns and to the community structure at higher trophic levels (Richardson et al. 2006).
Table 1. provides a confidence assessment summary of observed impacts of climate processes on Australian seabirds (additional information by region and species is detailed in the Appendix Table A1).
Temperature and solar radiation
Warming of land and oceans are expected to expand or shift seabird and seabird prey distributions southwards (polewards) and to alter reproductive timing and success, foraging areas and possibly prey species (Chambers et al. 2005, Poloczanska et al. 2007, Cullen et al. 2009). In the central and eastern Pacific, Indian Ocean, southern Africa, and in the Southern Ocean, warmer surface waters have been linked to reduced breeding success, later breeding, and increased mortality in a number of seabird species (Ainley et al. 1988, Crawford and Jahncke 1999, Velarde et al. 2004, Ramos et al. 2006). In contrast, cooler surface waters in the north-west Atlantic have been associated with reduced breeding success of surface-feeding seabirds (Regehr and Montevecchi 1997, Sandvik et al. 2008).
In the Australian region, oceanographic variations have been related to changes in seabird breeding participation and success, as well as mortality and distribution shifts. In Western Australia, stronger ENSO events tend to correspond to reduced breeding participation and success in Wedge-tailed Shearwaters and tropical terns (Dunlop et al. 2002, Surman and Nicholson, in press). For the tern species, breeding has also tended to be later in El Niño years (Surman and Nicholson, in press). ENSO events have also been associated with prospecting and nesting of tropical seabirds outside their former breeding distributions. As a consequence it is hypothesized that in philopatric species ENSO-related marine productivity failures may drive dispersal of pre-breeders to foraging areas away from natal colonies during the breeding season (Dunlop, in press). Tropical seabird prey and seabird frontier sub-colonies may then be able to persist at more southern latitudes, as has been seen in recent years, as a result of background rises in sea temperature (Dunlop, in press). On Christmas Island, sustained periods of low SSTs result in higher breeding success of Abbott’s Booby Papasula abbotti (Reville et al. 1990, Garnett and Crowley 2000, DEH 2004).
Increased SSTs have also been associated with reduced breeding success in the Great Barrier Reef region, mainly through a reduction in provisioning rates (Smithers et al. 2003, Peck et al. 2004, Congdon et al. 2007). Data from this region indicate that there are SST limits above which provisioning rates become so low that many species, such as Sooty Tern Sterna fuscata, Black Noddy Anous minutus and Wedge-tailed Shearwater Puffinus pacificus, have zero or negative chick growth (Congdon et al. 2007).
In south-eastern Australia, warmer SSTs in the month of March, prior to the Little Penguin Eudyptula minor breeding season, result in earlier egg laying, more and heavier chicks (Cullen et al. 2009). However, over the last 40 years these penguins have been laying later (~0.65 days / year, p = 0.021). Increased survival of first year Little Penguins has also been associated with warmer SSTs, while the reverse appears to be true for adult survival (Sidhu 2007).
For Little Penguins breeding in eastern Australia, there is an inverse relationship between the latitude of the breeding colony and breeding success, perhaps the result of the reduced positive effects of the East Australian Current at higher latitudes (Fortescue 1998). Although no direct evidence was presented, warming SSTs have also been implicated in the growth and expansion of Australasian Gannet Morus serrator colonies in south-eastern Australia (Bunce et al. 2002).
Increased land temperatures may increase heat stress and mortality, leading to reduced breeding success, particularly for surface dwelling birds (Stahel and Gales 1987, Cullen et al. 2009). Many seabirds, including Little Penguins, are unable to withstand prolonged exposure to air temperatures above 35 ºC (Stahel and Gales 1987). Exposure to even a few hours of burrow temperatures above this level may lead to dangerously high Little Penguin body temperatures (Stahel and Gales 1987) with heat stress currently accounting for ~0.2% of annual adult mortality (Dann 1992). Winter breeding occurs in Pied and Black-faced Cormorants (Phalacrocorax varius and P. fuscescens) in south-eastern Australia, unlike the majority of seabirds in this region (Norman 1974, Taylor 2007), and it has been suggested that this is to avoid warmer land temperatures and the associated heat stress for young and adults (Taylor 2007). Drought and high air surface temperatures have also resulted in death from starvation and heat stress in Cape Barren Geese on the Archipelago of Recherche, Western Australia (Halse et al. 1995, Garnett and Cowley 2000).
Ocean currents, mixed layer depth and ocean stratification
Alterations in currents, mixed layer depth and ocean stratification have the potential to impact on seabird distributions, migration and foraging through their impacts on the supply of nutrients and light and, therefore, prey species and subsurface predators, that force and maintain prey at the surface (Poloczanska et al. 2007, Devney et al. 2009a).
Marine productivity and seabird distributions in the Australian region are strongly influenced by the East Australia Current, the Subantarctic Convergence and the Leeuwin Current (Blaber et al. 1996). Typically, surface waters of the East Australia Current are low in nutrients but exhibit significant spatial and temporal variability, with highest nutrient concentrations at locations of encroachment onto the continental shelf (Roughan and Middleton 2002). Satellite tracking data from the Great Barrier Reef suggest that nutrient hotspots important to seabirds are few in number and located adjacent to Coral Sea mounts and along the eastern edge of the continental shelf (Congdon et al. 2007). The breeding success of seabirds may be dependent on the continued stability of a small number of these highly productive areas (Congdon et al. 2007).
Changes in ocean stratification as variation in depths of warm and cold water masses are well known precursors to El Niño events (McPhaden and Yu 1999). El Niño events have been linked to catastrophic breeding failure in both temperate and cold tropical seabird breeding populations (Schreiber and Schreiber 1984, Bertram et al. 2005) through severe impacts on nutrient upwelling. However, in warm tropical regions such as the Great Barrier Reef and adjacent Coral Sea, upwelling is aseasonal and nutrient-rich waters are localised (Andrews and Gentien 1982). Here changes in key ocean characteristics (surface chlorophyll concentration and depth of the 20?C thermocline) that occur up to a year in advance of ENSO indices registering a formal event, appear to drive breeding participation of pelagic foraging tern species (Sooty Terns and Common Noddies A. stolidus), but not inshore foraging species (Crested Terns S. bergii) (Devney et al. 2009a).
Foraging and breeding success in Little Penguins has also been linked to ocean stratification (Ropert-Coudert et al. 2009).
Wind, storms and cyclones
Changes in breeding success, foraging and nesting habitats have been associated with changes in storm intensity, strong winds and cyclones. Cyclones in particular can cause catastrophic destruction of breeding colonies and deaths of individuals in northern Australia. Indirect effects of cyclones include: wave inundation, erosion under the influence of gale force winds, storm tides and intensified currents (Congdon et al. 2007, Devney et al. 2009b). Non-cyclonic storms and strong winds can also influence breeding success by reducing foraging success, increasing mortality of juveniles and by flooding nests or nest burrows, such as has been seen in Roseate Terns S. dougallii (Blaber et al. 1996). Large areas of seabird breeding habitat can be removed by erosion, driven by wind, wave action, high tides and changing current patterns. This is particularly true for sand cays, often highly unstable and at the mercy of processes of erosion and accretion of their substratum: erosion of one part of the cay often being matched by new sand deposits in another location (King 1996). Storms and cyclones have the potential to seriously affect nesting substrate, vegetation and wildlife on seabird breeding islands, as well as impacting on seabirds at sea (Richardson et al. 2006, Congdon et al. 2007, Devney et al. 2009b).
Cyclonic activity affects the timing of breeding in some tropical seabirds, such as the sub-annual breeding Sooty Tern, which in the short-term influences breeding participation and success (King et al. 1992, Devney et al. 2009b). However, negative impacts from localised direct disturbance associated with six tropical cyclones over a 17 year period, or the associated changes in nesting habitat do not appear to have translated into long-term population declines of species breeding on the northern Great Barrier Reef (Devney et al. 2009b). Impacts of individual cyclones and storms depend heavily on the stage of the breeding cycle in which the cyclones occurs (Congdon et al. 2007, Devney et al. 2009b).
In southern Australia, storm and tidal damage to burrows can locally influence numbers of seabirds, such as Little Penguins at Troubridge Island, South Australia (Ross et al. 1996). Storms can also exacerbate food shortages, or reduced the ability to obtain prey, with mass mortality of seabirds along the Victorian coast often following periods of strong winds (Norman et al. 1996). Stronger westerly winds in January to March correspond to later breeding in Little Penguins at Phillip Island, Victoria (Chambers 2004).
Precipitation, floods, and terrestrial runoff
Rainfall has relatively few direct effects on seabird survival or breeding success: however, occasional heavy rainfall may cause flooding of seabird burrows. Rainfall may indirectly affect seabirds through associated impacts on availability of prey, quality of breeding habitat and fire risk to dead or dehydrated vegetation. Anchovies Engraulis australis, important prey of Little Penguins (Chiaradia et al. 2003), are associated with estuarine conditions when spawning and their productivity may be significantly reduced by declining streamflows into coastal areas (Dann and Chambers pers.comm.).
There is little known regarding quantitative links between observed long-term rainfall changes and changes in the distribution and abundance of nesting seabirds.
Other extreme events (including fire)
Prolonged periods of hot dry conditions can increase the risk of fire, including fires resulting from built up salt and dust on power-pole insulators, such has occurred in recent years on Phillip Island, Victoria (Chambers et al. 2009). Synchronisation of breeding in many seabird species increases the colonies vulnerability to catastrophic events, such as fire, during nesting seasons. Burrow nesting species, such as Little Penguins, shearwaters and petrels, may be particularly vulnerable as they are reluctant to abandon nests or emerge during daylight. Some species, such as Little Penguins, do not avoid fire and will remain under or nearby vegetation until severely burnt or killed (Chambers et al. 2009).
The impact of rising sea level on seabirds is expected to vary with breeding habitat and location, with high rocky islands less at risk than low-lying less stable islands (Bennett et al. 2007). However, there are no known quantitative links between observed sea level rise and changes in the distribution and abundance of nesting Australian seabirds.
There are no known quantitative links between ocean acidification and changes in the distribution and abundance of nesting seabirds. Seabirds feeding on cephalapods are at a higher risk of being affected by acidification (see Poloczanska et al. 2007).
In summary, changes in oceanographic and climatic process are having observed impacts on Australian seabirds, across many foraging guilds. Foraging has been shown to be related to sea-surface temperatures in various species, and correspondingly, temperatures have been correlated with the timing and success of breeding in some species.
The available evidence so far suggests that in tropical systems the more strongly affected species share a number of life-history characteristics. They tend to be species with larger breeding populations and are generally more pelagic foraging, synchronous breeders that feed regurgitated food to young at relatively long intervals, rather than frequently provisioning young with whole fish. As a consequence, chicks of these species generally have long pre-fledging periods and slow overall growth rates, characteristics that may make them particularly sensitive to ENSO-associated fluctuations in food availability (Congdon et al. 2007).
Potential Impacts by the 2030s and 2100s:
Seabirds_Supplimentary_Table1.pdfA summary of projected impacts of future changes in climate on Australian seabirds is discussed below (additional information by region and species is detailed in the Appendix Table A1).
Temperature and solar radiation
Many seabirds range many thousands of kilometres and, therefore, may be able to rapidly shift their distributions in response to changes in the climate system. However, this can only occur if they are not restricted by habitat requirements at critical life stages, such as availability of nesting sites and feeding grounds (Richardson et al. 2006). Some species, such as many of the seabirds breeding with the Lord Howe Island Group (DECC 2007), are already at the extremity of their breeding range and travel long distances to obtain food. Any southward shift in prey species, as anticipated under warming oceans, is likely to greatly affect breeding success and abundance of such seabirds. A further southward shift in breeding distribution of several tropical seabirds in Western Australia is expected, together with a decline in Houtmann Abrolhos populations (Dunlop, in press). Some populations south of the Abrolhos may increase. Frontier colonies south of the former breeding range may continue to appear and some may establish, but the overall size of the regional meta-populations will probably be well below historical sizes, as frontier colonies (with the exception of the Bridled Tern S. anaethetus) seem to plateaux out at relatively small sizes (Dunlop, in press).
Most studies of the potential impacts of climate change on seabirds suggest that projected changes in ocean temperatures and ENSO type activity are likely to reduce prey availability during breeding, resulting in reduced breeding participation and success (reviewed by Congdon et al. 2007). In addition, if seabird prey species undergo rapid shifts in distribution, either vertically or horizontally, so as to remain in waters at preferred temperatures they may become less accessible to seabirds on a day-to-day basis, particularly if the abundance of sub-surface predators (e.g. tuna) who move prey towards the surface is also decreased (Peck et al. 2004, Erwin and Congdon 2007).
According to Garnett and Cowley (2000) further increases in SSTs are likely to lower breeding success of Abbott’s Booby on Christmas Island, regardless of the nest’s exposure to other climatic effects, such as strong winds.
Regression models for tropical pelagic species indicate that SST increases of 2-4 ºC above background levels may result in zero (or negative) chick growth. However, the length of time that the SSTs remain high, the stage of chick development, and the species are also important in determining whether such temperature increases lead to chick starvation and colony-wide reproductive failure (Congdon et al. 2007).
In contrast to projected negative impacts of increasing temperatures on northern breeding seabirds, there is evidence that at least some southern species may benefit from increasing SSTs. In southern Australia, models based on long-term datasets suggest that an increase in SSTs may lead to earlier and more successful breeding in Little Penguins, at least in the immediate future (Cullen et al. 2009).
A hotter and drier future could make the Archipelago of Recherche, Western Australia, less suitable for coastal nesting species, such as the Cape Barren Goose (Garnett and Cowley 2000).
There is currently too little information on the likely impacts of increasing incident solar radiation on seabirds to predict future impacts.
Ocean currents, mixed layer depth and ocean stratification
The impact that projected changes in mixed layer depth/ocean stratification will have in the Coral Sea region where depth of the 20 ?C thermocline can be greater than 200m is currently unclear. However, changes in the frequency or intensity of El Niño precursors (including changes to ocean stratification) are likely to affect pelagic seabird breeding participation and population dynamics in the northern Great Barrier Reef.
The Leeuwin and East Australia Currents will transport warmer water further south, carrying sub-tropical species into temperate waters, altering the habitat of a whole range of species. For seabirds, competition with established species for nest sites and foraging habitat is likely to result from these new invasions.
Wind, storms and cyclones
Current findings suggest that short-term impacts from individual cyclones on northern Great Barrier Reef seabirds are mitigated in the longer-term by sufficient recovery periods and successful breeding in non-cyclone years (Devney et al. 2009b). However, any increase in the frequency or intensity of storms and cyclones increases both the spatial and temporal potential for them to occur during sensitive reproductive phases, thereby reducing the recovery time and/or potential for successful breeding between events (Congdon et al. 2007).
Non-seabirds, including the endangered Orange-bellied Parrot Neophema chrysogaster (Garnett and Crowley 2000), will also be exposed to increased risks from storms at sea during migration.
In temperate regions, current and projected threats from storms are unlikely to pose a major risk to populations that are large and spread over broad geographic areas. Species or subspecies which have small populations and breed in close proximity are, however, susceptible to catastrophic wind and storm events. Temperate seabirds which fall into the latter category include the Australian populations of the Fairy Prion Pachyptila turtur, Blue Petrel Halobaena caerulea, Gould’s Petrel Pterodroma leucoptera, White-necked Petrel P. cervicalis, Soft-plumaged Petrel P. mollis, Herald Petrel P. heraldica, Round Island Petrel P. arminjoniana, Kermadec Petrel P. neglecta, and Grey-backed Storm-petrel Garrodia nereis (Garnett and Crowley 2000).
Precipitation, floods, and terrestrial runoff
Changes in rainfall patterns, together with sea level rise, are likely to influence seabirds and their reproductive success through their effect on availability of breeding habitat (Congdon et al. 2007). The long-term impact of these will vary according to how each affects the distribution and abundance of species-specific habitat. In tropical and sub-tropical regions, colonising ground cover and woody shrub vegetation types are favoured by annual reductions in rainfall and potential increases in deposition of sand and rubble on windward island edges. In these situations, tree and burrow nesting species may be negatively impacted. The full extent of the impact will depend on how limited by habitat availability the seabird colonies are currently (Congdon et al. 2007).
Flow regimes and discharge patterns for major coastal rivers may affect primary productivity and trophic stability at lower trophic levels, potentially impacting upon seabird populations. These changes may also impact upon erosion and deposition patterns that effect island size and availability of breeding habitat (Congdon et al. 2007).
Based on existing research, it is not possible to predict what global warming-associated changes to precipitation, floods and run-off will have on Australian seabirds.
Other extreme events (including fire)
Any increase in the incidence of hot and dry conditions in southern Australia may increase fire related risk of seabird injury and death, particularly for burrowing colonial seabirds (Chambers et al. 2009).
The impact of rising sea level on seabirds is expected to vary with breeding habitat, with high rocky islands less at risk than low-lying less stable islands (Bennett et al. 2007). Many species of birds are dependent on coastal habitats, which may be at risk from sea level rise, including many species of migratory shorebirds, mangrove nesting and foraging species, and species that breed on low-lying sand cays or beaches, e.g. Little Tern S. albifrons (Richardson et al. 2006, Bennett et al. 2007). The ability of seabirds to alter their nesting locations and inshore foraging habitat and for shorelines to evolve, as a result of sea level rise, may be constrained by coastal development (Richardson et al. 2006).
Seabirds, and other bird species, using lowland parts of many islands, including those of the Torres Strait, Houtman Abrolhos, the Great Barrier Reef, and the Lord Howe Island Group, are at risk from sea level rise from potential inundation of breeding sites and other habitat (Ross et al. 1996, Gannett and Cowley 2000, Congdon et al. 2007, DECC 2007). However, in tropical regions where breeding islands and cays are often composed of coral substrate and sediment, rising sea level will assist coral growth and potentially create suitable ‘replacement’ seabird breeding locations. Whether coral populations will have the capacity to grow in time with potential sea level rises (Hoegh-Guldberg et al. 2007) and whether new nest habitat and particularly vegetation will become available in such instances remains unknown. Increased interspecific competition driven by sea level rise may occur in some regions, e.g. an increase in sand deposition may allow turtles to access the central depression of Raine Island (Great Barrier Reef) currently used by ground nesting seabirds.
There is currently too little information on the likely impacts of changing ocean chemistry on seabirds to predict future impacts. However, ocean acidification is expected to compromise coral reef accretion through impacts on the ability of corals to calcify and grow (Hoegh-Guldberg et al. 2007), thereby changing the composition of coral reef communities. This has the potential to degrade important foraging habitat for nearshore feeding tropical seabirds, and breeding habitat for all taxa of species breeding in coral reef systems such as the Great Barrier Reef, Ningaloo Reef and the Houtmann Abrolhos Islands.
• For seabirds in the Australian region, climatic and oceanographic variation and change has been associated with changes in breeding distribution, breeding success, breeding timing, chick growth and adult survival.
• Rising ocean temperatures are projected to continue decreasing prey available to many breeding seabirds at their current breeding sites, impacting negatively upon breeding success, chick growth and adult survival, with the possible exception of breeding success and juvenile survival in the Little Penguin.
• Background rises in sea-surface temperature may foster the persistence of tropical seabirds at more southern latitudes.
• Potential for seabirds to shift breeding locations as a result of inundation of breeding sites (sea level rise, increased incidence major storms) and/or degradation of breeding sites (including ocean acidification) is unclear is highly dependent upon the resistance/resilience of coral reef ecosystems and other breeding locations to climate change.
• Projected increases in the frequency/intensity of extreme storm events have the potential to negatively impact upon seabird populations.
• Any increase in fire risk has the potential to severely impact some colony (burrow) nesting seabirds.
• Increased surface air temperatures are likely to increase heat stress related mortality in seabirds.
• High potential for impacts to vary regionally and by species, suggesting that local-based threat assessment, monitoring and management are required.
Confidence levels for potential impacts by the 2030s and 2100s are low-medium due to incomplete knowledge of the climate-ecosystem processes, including potential threshold changes, uncertain ability of species to alter phenology and prey species, and often short historical biological records. Southward expansion of breeding colonies will be limited by available habitat and prey species. Sea level rise is likely to reduce breeding habitat, particularly for some nesting species on low-lying sandy islands – at least in the short term.
Adaptation Responses >
Many aspects of climate’s impacts on seabirds are little known, and documented responses often vary by location and species, making generalisations about adaptive capacity difficult. This suggests that, in many cases, regional or colony by colony assessments of resilience or adaptive capacity may be required, with data obtained specifically for that purpose (Congdon et al. 2007). However, there are some general principals that should aid adaptation across a variety of species and regions (Olsen et al. 2007).
Buffering potential negative effects of climate change through habitat management
The potential exists to buffer some of the expected changes in climate, in the short-term and particularly in terrestrial habitats, by management of the quality of the habitat. For example, vegetation at many temperate seabird breeding sites has been severely modified by grazing, introduced plants and fire regimes. A number of demographic parameters appear to be related to the floristics and structure of vegetation and by managing these to provide the optimal microclimates for breeding success and adult survival, some negative effects of climate change could be ameliorated.
Reduce or eliminate existing non-climate related threats
Many seabird populations are adversely affected by non-climatic pressures, such as pollution, commercial fisheries (including long-line), tourism, feral and invasive animals and plants, etc. By reducing or eliminating these threats to species and ecosystems the aim is to increase resilience, thereby improving the likelihood of successful (autonomous) adaptation and reducing the risk of ecosystem collapse. Both land and sea components need to be considered.
Some examples of how this might be achieved include:
• Marine protected areas, including No-Take Areas, where fishing is prohibited
• Exclusionary fences which limit tourist access to breeding colonies
• Indefinite moratoriums on public access to the breeding colonies following catastrophic events, such as major cyclones or fires
• Nest protection / cages / exclusion zones to reduce predation by introduced species, such as foxes and dogs, and public interference with nest sites / breeding colonies
• Feral / pest animal and plant control plans
• Signage near breeding sites informing the public of the importance of the nesting site and appropriate behaviour (e.g. dogs on leads)
Further research is required to determine which regions and species resilience to climate change would be most benefited by reductions in non-climate change pressures (Chambers et al. 2005).
Research and monitoring
A lack (or uncertainty) of information and science currently constrains the development of effective climate change adaptation actions and decision making (National Biodiversity and Climate Change Action Plan 2004-2007). To redress this, increased research into and long-term monitoring of the impacts of climate change and adaptation options for species and ecosystems are required. Resulting plans and actions will also require monitoring, to determine effectiveness, and adjustments made as new information become available, incorporating the approaches of adaptive management. A list of those seabirds more likely to be negatively impacted by climate change should be compiled to guide research priorities.
Ex situ conservation or translocation
Ex situ conservation and translocation of species are generally not very cost-effective conservation measures, and are often considered a ‘last resort’ methods for species that are unable to self-adapt. Both measures can be expensive, difficult and potentially hazardous activities – raising ethical issues, such as ‘what impact will translocated species have on existing species in the recipient areas?’
Other adaptation measures (requiring direct intervention)
A general adaptation measure is to factor the impacts of climate change on seabirds into natural resource management and land-use planning. “Integrating climate change considerations into biodiversity programs is the most cost-effective way of dealing with climate change, as these programs already have the infrastructure, mandate and encapsulated knowledge to address the issues” (National Biodiversity Climate Change Action Plan 2004-2007).
Other examples, which foster population viability and/or adaptation, include: • Encourage establishment of breeding colonies to the south of existing ones, or to another location, through the use of artificial decoys, by translocating young birds or providing artificial islands
• Encourage natural expansion and/or movement of breeding colonies through the removal of introduced predators (e.g. foxes) and optimisation of vegetation type and cover. In some cases, restricted public access may assist this process
• Reduce the potential for erosion by waves, storms or rainfall by protecting or increasing appropriate vegetation and reducing inappropriate vegetation
• Shading nests (either through natural vegetation or man-made structures) or designing insulated artificial nesting burrows to reduce heat stress in nesting seabirds
• Running powerlines underground and implementing a fast-response fire action plan to reduce the risk of fire in seabird colonies close to human settlements or facilities
At least in the short-term, the adaptive capacity of seabirds to respond SST-associated changes in prey availability, will depend on the species’ ability to alter foraging behaviour (including location and prey species), nesting location, breeding timing and/or chick growth: responses which have been seen in recent decades in Australian seabird species. In some species, such as Wedge-tailed Shearwaters, adults breeding in the southern Great Barrier Reef alternate multiple short foraging trips to near-colony, but resource-poor areas, with longer trips to more highly productive, but distant, areas (Congdon et al. 2005, Peck and Congdon 2005). By using this strategy adults are able to breed in areas that would otherwise not support stable breeding populations (Congdon et al. 2005). This implies that for pelagic seabirds, such as these shearwaters, the ability to increase foraging rates may be limited and, as most species have single egg clutches, in any given season they either rear a chick or not. If productivity remains low for a number of years, there is a risk that the colony may become unviable (Congdon et al. 2007).
Some seabirds may be able to adapt to changes in the frequency and intensity of cyclones and storms by adjusting either breeding timing, to avoid periods of peak storm activity, or relocating to less affected breeding sites. The capacity for Australian seabirds to do either of these, in response to these climate drivers, is largely unknown (Congdon et al. 2007).
The adaptive capacity of seabirds to sea level rise and significant rainfall changes depends on their ability to relocate to suitable breeding sites elsewhere (Congdon et al. 2007). The potential for suitable breeding sites to come into existence depends on a complex mixture of factors, including climate change-associated impacts on ocean acidification and coral growth, precipitation, and shifts in key foraging locations.
Knowledge Gaps >
Observed responses to climate variation and change vary by species and location, making generalisations about the adaptive capacity of seabirds difficult and highlighting the need for an improved knowledge base. Some of the critical knowledge gaps include:
• Understanding the drivers of change in seabird populations, including the relative role of natural variability and climate change. This needs to be investigated at the level of species, ecosystems and regions. Which processes and phases of life cycles are most likely to be affected? Need for long-term data and continued/renewed and strategic monitoring.
• Understanding the factors determining the resilience and adaptive capacity of marine ecosystems, including seabirds. E.g. How do/will seabirds respond to climate changes: gradual versus triggers versus thresholds (including physiology)? What level of change can species tolerate and still remain viable? Which species and systems are most vulnerable? The impact of gradual (e.g. SRL, mean temperature) versus extreme (e.g. cyclone, storm surge) climate impacts. Identifying and determining how existing non-climatic threats to seabirds will interact with climate change. To increase resilience, how can we best target money and strategies by characterising interactions and synergies between stresses?
• Some ecosystems and species and regions are better understood than others, and it is unlikely that all will be researched in sufficient detail. So, ideally, we need to know at what level and for what ecosystems and species can appropriate generalisations can be made about climate change impacts and adaptation options.
• Information on seabird movement, including foraging, dispersal, migration and inter-colony movement, and on their diet, including the food chain, prey distribution, prey climate responses and predator responses. We have only a limited knowledge on distributions and feeding of many species outside the breeding season.
• Climate-related species biology and species associations, including quantifying the role of seabirds in ecosystem functioning and the economic and social impacts of climate-related changes to seabird communities.
• Incorporating uncertainties in species distribution changes, changes in species interactions and ecosystem responses into current modelling of climate change impacts on seabirds. The models need to be capable of modelling regional changes at scales appropriate for management programs and reserve design.
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