Mariana Fuentes is a PhD candidate at James Cook University. Her thesis assesses the impacts of climate change to the northern Great Barrier Reef green turtle population. For the past eight years she has been working on environmental conservation and conducting research on various aspects of sea turtle ecology. She has worked at various indigenous communities in Torres Strait, Brazil, Vanuatu and Madagascar educating local communities on sea turtle conservation, resource use and potential impacts of climate change to sea turtles. Although, most of her work has focused on sea turtles, her broader scientific interest includes conservation and management of marine wildlife, spatial risk assessment for conservation and management of threatened species in a changing climate.

School of Earth and Environmental Sciences, James Cook University. Townsville QLD 4810, Australia.  .(JavaScript must be enabled to view this email address)

Vimoksalehi Lukoschek is a postdoctoral researcher working on the molecular ecology, evolution and conservation of marine snakes. She completed her PhD on hydrophiine sea snakes in 2007 and has published >10 peer-reviewed and popular articles on their ecology, evolutionary history, and conservation. Vimoksalehi is the founding co-chair of the IUCN Sea Snake Specialist Group; is actively involved in the first IUCN Red List assessments of extinction risk for all sea snake species; and has nominated two sea snake species for listing under Australia’s Environment Biodiversity and Conservation Act.

Department of Ecology and Evolutionary Biology, University of California, Irvine. CA 92697, USA.    .(JavaScript must be enabled to view this email address)  www.seasnakes.info

Dr Mark Hamann works as a Post Doctoral Research Fellow, James Cook University, in the fields of reproductive biology, physiology, climate change and their relation to the conservation of Australian and South-east Asian turtle species. He is currently involved with the development of community-based projects for the monitoring and management of marine turtles in Torres Strait. Working alongside Torres Strait communities, his project aims to collect biological data from foraging and nesting populations such as sex ratios, breeding rates and hatchling success that can be used to strengthen management options for marine turtles in northern Australia.
He is also actively involved with marine and freshwater turtle research in Queensland along side research staff from JCU and Queensland’s EPA. Specifically, He is interested in the ecology of some of Australia’s less known turtle species in the genus Elseya. He also has strong management and conservation interests and is a member of the IUCN Marine Turtle Specialist Group, serving as a Regional Vice Co-Chair for the Australasia region. He had an active role in developing marine turtle conservation programs in Viet Nam and Malaysia.

School of Earth and Environmental Sciences, James Cook University. Townsville QLD 4810, Australia.  .(JavaScript must be enabled to view this email address)

Temperature
All marine reptiles have life history traits, behavior and physiology strongly influenced by temperature (Janzen 1994). They are all ectotherms, and thus are heavily tied to environmental temperatures for body functions such as digestion, reproduction and metabolism (Spotila and Standora 1985).  Therefore, the distribution of marine reptiles is believed to be linked with their thermal requirements and tolerances (Danvenport 1997, Milton and Lutz, 2003, Hawkes et al., 2009). Distribution in the family Chelonidae appears to be constrained by the 20°C surface isotherm (Davenport 1997), while leatherback turtles (Dermochelidae) are often found in the cooler waters of the Southern Ocean, northern Pacific and northern Atlantic.  Thermal limits are not known for leatherback turtles, but for cheloniids temperatures below 15°C may impair locomotion and alter foraging behaviour (Read et al. 1996). Although there is a lack of data on the thermal range of crocodiles (Hamann et al. 2007), the importance of water temperature and basking behavior in crocodiles for the maintenance of physiological processes and behavior is becoming increasingly apparent (Seebacher and Franklin 2005). Experimental studies show that the swimming ability of crocodiles is also influenced by temperature. An increase in sustained swimming speed occurs in warmer waters (23 to 33°C compared with 15°C) and a decrease as water temperatures rise above 33°C (Elsworth et al. 2003). Little is also known about the thermal requirements and tolerances of individual species of sea snakes. Most of the existing information is for Pelamis platurus, which is the most widespread of all sea snake species. Its latitudinal distribution limits coincide with the 18°C surface isotherm. However, breeding populations of most sea snake species do not occur below the 20°C surface isotherm. Additionally, thermal tolerance experiments indicate that P. platurus, has an upper thermal tolerance of 33.5°C (Dunson and Ehlert 1971) and dies almost immediately at 36°C (Graham et al. 1971). It is likely that other sea snake species have a thermal range within the boundaries of those of P. platurus (Hamann et al. 2007).

Given these thermal requirements of marine reptiles, it is likely that change in sea surface temperatures could alter or expand their distribution. In fact, the distribution of leatherback turtles in the north-east Atlantic has extended north by around 200 km per decade over the past 20 years due to an expansion of warmer waters (McMahon and Hays 2006). Such trends have not been observed in Australia, despite a warming of sea surface temperatures (Lough 2009 – temperature assessment), for any of the marine reptile groups; however this is most likely the result of lack of baseline data and monitoring efforts.  If marine reptile species can not adapt and shift their distributions, it is likely that localized impacts may occur.  Indeed, it is suggested by Francis (2006) that elevated temperatures, at or above the thermal tolerance limits for sea snakes, is a contributing factor to the reduced numbers of sea snakes (of all species) on Ashmore Reef. The Ashmore Reef complex is relatively isolated and surrounded by deep water. Genetic data suggest that deep water is a barrier to dispersal to reef-associated sea snake species (Lukoschek et al. 2007a, Lukoschek et al. 2008); thus, the three species endemic to these isolated reefs are unlikely to be able to shift distributions in response to increased temperatures. Neighbouring Hibernia and Cartier Reefs, which don’t have extensive reef flats, have not undergone similar overall reductions in sea snake abundances (Guinea 2006, 2007).

Warming temperatures will also influence reproduction.  Timing of marine turtles’ and crocodiles’ reproduction is believed to be determined by a combination of photoperiod and temperature, since they have pineal glands that act via melatonin to interact with other endogenous cues to drive the appropriate time for breeding behaviour (Owens 1980, Hamann et al. 2002). However, the specific cues that underlie reproductive cycles are not well known and deserve further exploration (Hamann et al. 2007).  Marine turtles generally do not breed every year and for green turtles in the Australasian region the interval between breeding seasons is probably resource (food) dependent (Limpus and Nicholls 1988, Broderick et al. 2003) and size of the annual nesting population is strongly linked with climate processes such as El Niño Southern Oscillation (Limpus and Nicholls 1988). Higher proportions of the adult female green turtles breed 18 months following a major El Niño event and a lower proportion of females breed a similar interval after a major La Niña event. This short term variation in nesting numbers is regulated by food availability (quality and abundance), primarily seagrasses and macroalgae, which is in turn are influenced by temperature. Thus increased sea surface temperatures may have positive impact on green turtle populations through alterations to growth rates, age at maturity and reproductive periodicity (for examples see Chaloupka and Limpus 2001, Balazs and Chaloupka 2004, Hamann et al. 2007). In contrast, for loggerhead turtles, warmer foraging grounds are associated with a decrease of ocean productivity and prey abundance (primarily benthic invertebrates and gelatinous zooplankton) and consequently a reduction in loggerhead breeding capacity (Chaloupka et al. 2008). Indeed, changes in nesting patterns, earlier and shorter nesting, of loggerhead turtles in the United States have been linked to warmer sea surface temperatures (Weishampel et al. 2004, Pike et al. 2006), which perhaps reflects conditions in distant foraging areas (Hays 2000,  Solow 2001). Temperature is also a critical determinant for breeding of crocodiles (Webb 1989). In particular, high water levels and cool conditions late in the dry season are the key stimuli required for courtship and mating (Webb 1989, McClure and Mayer 2001, Fukuda et al. 2008).
Egg-laying species of marine reptiles (sea turtles and crocodiles) are strongly influenced by temperature during egg incubation (Spotila and Standora 1985).  Successful egg incubation only occurs within a small thermal range; incubating temperatures above the upper thermal threshold (~34?C for sea turtles) will result in hatchlings with higher morphological abnormalities as well as lower hatching success (Miller 1985, Lang and Andrews 1994).  In addition to this, sea turtles and crocodiles have temperature-dependent sex ratios, where sex ratio of hatchlings is determined by nest temperature during incubation (Spotila and Standora 1985, Lang and Andrews 1994).  For sea turtles, warmer temperatures yield more females while temperatures below the pivotal temperature yield more males (Yntema and Mrosovsky 1980, Davenport 1997). The pivotal temperature differs slightly within and between sea turtle species and is generally around ~29°C.  Crocodiles have a female/male/female pattern, where no males are produced below 29°C and above 34°C (Webb et al. 1987, Lang and Andrews 1994).  Higher sand temperatures also decrease the incubation period of sea turtle eggs (Davenport 1997) thus decreasing hatchling body size (Booth and Astil 2001, Burgess et al. 2006). Smaller body size reduces hatchling survival chances since smaller hatchlings are more susceptible to predation as they cross the reef (Gyuris 1994).  Clearly, even small increases in temperature can have a profound impact on hatchling phenotype, performance and success (Mrosovsky 1980). Indeed, the impacts of warmer temperatures are evident in Mon Repos, an important loggerhead turtle rookery, where sand temperatures at nest depth are now reaching as high as 36oC for weeks at a time during hatching season causing increased debilitation and even death of eggs and hatchlings (Limpus in press).

Ocean currents
Dispersal of loggerhead and green turtles from the southern Great Barrier Reef rookeries occurs via offshore currents (Hecht et al. 1974, Hamann et al. 2007).  Thus, changes to ocean circulation can change post-hatchlings migrations and distribution (Limpus in press, Boyle 2006, Hamann et al. 2007).

Extreme events (cyclones)
Processes associated with cyclones can impact sea turtles. In the long-term, over several generations, they may remove or alter nesting habitat (i.e. through beach erosion) and in the short-term, incubation period, hatchling phenotype and the success of nests may be altered (Milton et al. 1994; Martin 1996; Pike and Stiner 2007). In addition, because both incubation length and gender of sea turtle hatchlings is affected by the sand temperature during incubation (Miller and Limpus 1981, Morreale et al. 1982, Limpus and Reed 1985), cooling from increased rainfall and cloud cover during cyclonic events can play a role in dictating hatchling phenotype and/or sex ratios from beaches (Reed 1980). The more intense the cyclone and the stronger the storm the lower the hatching success, especially when coupled with large tides and storm surges, since the chances of nest inundation are higher (Van Houtan and Bass 2007). Historically, Australian sea turtle populations nesting in Torres Strait, such as the hawksbill, and the Gulf of Carpentaria flatback turtle population have been the least exposed to cyclones while the Coral Sea green turtle population has been the most exposed to cyclonic activity (Fuentes unpublished data). Changes to cyclone frequency, intensity and distribution will also impact crocodile populations by washing away nests or nest material, inundating eggs and disrupting normal nest attendance behaviour during flood events (Hamann et al. 2007). Similarly, changes in cyclones may also affect reef-associated sea snake species, such as Aipysurus laevis and Emydocephalus annulatus. These two species appear to have undergone recent local extinctions (at the level of individual reef) in the offshore Swain Reefs complex, southern Great Barrier Reef, where a trend for the absence or loss of snakes on outer exposed reefs was found (Lukoschek et al. 2007b). It is suggested that strong wave action associated with frequent storms may be affecting these species but the reasons for the localised population declines are unknown (Lukoschek et al. 2007b).

Rainfall
Rainfall can influence sea turtles’ incubating environment by moistening sand and by reducing the occurrence of potentially lethal fungi (Phillott and Parmenter 2006).  Female turtle’s nesting success can also benefit from rainfall, since moist sand is easier for females to dig (Seabrook 1989). Thus, decreases in precipitation can affect both nesting and hatching success of sea turtles. Indeed, drier than average years have caused lower rates of nesting success at Raine Island (Limpus et al. 2003, Limpus et al. 2005).  The reproductively periodicity of crocodiles is also influenced by rainfall, since rainfall and cooler temperatures, at the end of a dry season, have been observed to trigger mating and courtship in some crocodile populations (McClure and Mayer 2001, Isberg et al. 2005). Therefore rainfall is an aperiodic factor that shapes intra- and inter-annual variation in reproductive success and embryo development in sea turtles and reproductive periodicity in crocodiles (Hamann et al. 2007). A global examination of all sea snakes also suggested that species richness correlates positively with mean annual precipitation within the Indo–West Pacific tropical region (Lillywhite et al. 2008), but may also correlate with other environmental or habitat variables.

Sea level
Sea-level rise will cause erosion and increased inundation of coastal areas, beaches, mangrove forests and salt marshes, which will impact key sea turtle and crocodile habitats, nesting area stability and hatching success (Daniels et al. 1993, Fish et al. 2005, Baker et al. 2006, Hamann et al. 2007). The combined impact of erosion and flooding of the nesting habitat is expected to cause increased egg mortality and eventually loss of nesting beaches. Reduction of available nesting areas will amplify density-dependent issues at sea turtle nesting grounds, potentially increasing nest infection (Fish et al. 2008) and destruction of nests by conspecifics (Bustard and Tognetti 1969, Girondot et al. 2002, Limpus et al. 2003). Currently, concern exists regarding the impacts of sea level rise to several sea turtle rookeries in Torres Strait (e.g. Bramble Cay), the far northern Great Barrier Reef (e.g. Raine Island) and the Capricorn Bunker group (e.g. Heron Island) based on anecdotal and empirical reports of long-term erosion at these places. Additionally, over the last ten years low hatching success has been observed at Raine Island, which is thought to be caused by rising groundwater and other geomorphic processes (e.g. movement of sand)  (Limpus et al. 2003). However, mangroves, which are a critical habitat for crocodiles, may increase in area in northern Australia as low-lying coastal areas are inundated (see Tidal Wetlands, this volume).

Temperature
The thermal requirements of marine reptiles are expected to result in changes in their distributions as climate change progresses (McMahon and Hays 2006). It is likely that sea turtle distribution, both in terms of coastal and oceanic foraging areas and breeding regions, will gradually expand southwards (polewards). At present, many sea turtle nesting beaches or coastal foraging grounds are on the sparsely-populated tropical coastline of Australia. Southwards shifts in sea turtle distributions will bring turtles into regions where there are site based management may be logistically difficult because of existing coastal development (Hamann et al. 2007, Hawkes et al. 2009). Further, fewer conservation measures may be in place and imposing measures in new regions may be challenging. Similarly, the range of habitats suitable for crocodiles will likely expand, particularly into the sub-tropical parts of Australia. Southwards shifts in crocodile distribution will increase human-crocodile interactions potentially leading to conflicts between conservation management and resident human populations (Hamann et al. 2007).

Sea snake species that occur in inter-tidal and/or nearshore reefal and/or inter-reefal habitats also have the potential to respond to increased sea surface temperatures (SSTs) by extending their distributions southward along Australia’s east and west coasts.  However, the ability for a species to undergo southerly range expansions may depend on corresponding range shifts in the preferred habitat types (coral reefs, mangroves, mudflats) of each species. Given that coral reefs are unlikely to expand southwards and are considered extremely vulnerable to climate change (see Anthony and Marshall 2009 - Coral Reefs assessment), species restricted to coral reefs may be the most vulnerable to climate change. Habitat degradation from coral bleaching may cause loss or reduction of sea snakes from the genus Aipysurus, which occur predominantly in coral reef habitats and feed on small reef fish species. A subset of sea snake species occurs only in the Gulf of Carpentaria and/or Arafura Sea. It is not clear whether there are barriers to dispersal for these species to the east and west coasts, however, if such barriers exist, then species restricted to the northern coastline are less likely to have the capacity to undergo southward range shifts in response to increased temperatures. Because of their isolation it is less likely that the three Australian endemic species restricted to offshore Timor Sea reefs will be able to undertake southward range expansions in response to increasing SSTs. If the already reduced abundances of these species are the result of increased SSTs, then it is likely that these species will continue the downward trajectory in abundance in the face of further temperature increases. Increases in sea surface temperature is expected to more strongly effect species that are restricted to reef flats and shallow water habitats, such as Aipysurus apraefrontalis and Aipysurus foliosquama, as it is likely that increased SSTs will result in increased localised temperatures over reef flats for extended periods and these temperatures may reach sea snakes upper thermal threshold (~ 36oC). Average sea surface temperatures are unlikely to reach these upper thermal limits; thus, most sea snake species in Australia that typically occupy depth ranges that include deeper waters (Smith 1926, Minton and Heatwole 1975, Cogger 2000), are less likely to be directly effected. 

Warming temperatures may lead to shifts in the reproductive phenology of both sea turtles and crocodiles. Sea turtles may nest earlier and have shorter nesting seasons as a result of warmer sea surface temperatures (Weishampel et al. 2004, Hawkes et al. 2007). Adaptive capacity and the consequences of earlier and shorter nesting seasons for sea turtle populations are still unknown. The reproductive output of both sea turtles and crocodiles will also be affected by increased temperatures, as global warming poses a threat of skewing sex ratios towards a predominantly female output and exposing their eggs to temperatures that exceed thermal mortality thresholds (Mrosovsky 1994, Hamann et al. 2007, Hawkes et al. 2007). Indeed, northern nesting beaches are predicted to produce a higher proportion of females by 2030 and to experience incubation temperature that constantly exceed the upper thermal incubating threshold for sea turtles and crocodiles by 2100; this will decrease hatching success unless the timing of nesting shifts (Fuentes et al. in press a, b).

Additionally, any change in the “El Nino Southern Oscillation” climate pattern or intensity will change the proportion of green and loggerhead turtles that breed each year. However, changes will vary spatially since both species in Australian waters will be exposed to changes in sea temperature to varying degrees throughout their range and there may be population specific impacts. 

Marine reptiles also are likely to be indirectly impacted by increase in temperatures through impacts on their food sources. However, exact mechanisms remain difficult to estimate since there is a lack of information on the finer scale links between temperature and its influence on food availability and dietary processes for all species. This is especially true for carnivorous/omnivorous sea turtle species, as predictions on how invertebrate and benthic communities will respond to climate change are based on limited data. Nevertheless, a recent study by Chaloupka et al. (2008) indicates that increases in regional sea surface temperature can lead to a decrease in loggerhead’s food supply (generally benthic invertebrates), reducing their nesting and recruitment.  More is known about likely impacts on the herbivorous green turtle. Increased sea surface temperatures, in the short-term, will have a positive impact on seagrass growth and distribution (Perez and Romero 1992, Connolly 2009 – Seagrass assessment) and thus will likely improve the digestive ecology of green turtles having positive impacts on turtle growth, age at maturity and reproductive periodicity (Hamann et al. 2007). Some key areas remain data poor (1) the relative importance of algae versus seagrass in the diet of green turtles and whether there are differences in the vulnerability of both groups to climate change (2) whether increased sea temperatures will promote the growth/range/toxicity of toxic algae (see Hallegraff et al. 2009 – Phytoplankton assessment) and whether changes will affect green turtles and (3) digestive ecology and ecosystem role of green turtles.  Any long-term reduction or depletion of food resources will reduced growth rates of immature turtles and reduce the proportion of adult turtles that prepare for breeding migrations (Hamann et al. 2007). 

Ocean currents
Changes to ocean currents can potentially influence (positive or negatively) the ecology of post hatchling and juvenile sea turtles. However the positive/negative aspects are difficult to predict at present. Similarly, the potential impacts of changes in ocean currents to sea snakes are unknown.

Extreme events (cyclones)
Projected intensification of storms will cause further destruction to key coastal habitats used by marine reptiles. There will also likely be an increase in the numbers of sea turtles and crocodile nests being flooded and thus decrease hatching success. This will be a particular issue for sea turtle populations that have been historically more exposed to cyclonic activities, such as the Coral Sea green turtle population.

Rainfall
There is not enough precision in rainfall estimates or the likely temporal and spatial variability of these estimates to indicate how vulnerable marine reptiles will be to changes in rainfall patterns. It is, however, likely to remain an aperiodic factor that shapes intra- and inter-annual variation in variation in reproductive periodicity, reproductive success and embryo development of sea turtles and crocodiles. Similarly, there are no data on water requirements for true sea snakes to evaluate whether or not increases in rainfall will impact species.

Sea level rise
Sea-level rise (SLR) will likely impact key habitats used by marine reptiles (Fuentes et al. in press c). Sea turtle nesting areas will be exposed to sea level rise to varying degrees since the vulnerability of nesting areas to sea level rise will depend on their physical characteristics and location. Thus, it is not possible to estimate the degree to which each of the sea turtle species will be affected however nesting beaches that are trapped in the ‘coastal squeeze’ between rising sea-level and coastal development may be particularly vulnerable. Small, tropical low-lying islands, such as coral atolls, especially those that are not vegetated or that lie on exposed reefs in areas of high tidal range are likely to be the most vulnerable to SLR (Woodroffe et al. 1999, Church and White 2006). Females may be forced to shift to alternative nearby regions, such as mainland beaches, if low-islands are completely inundated. Mainland nesting beaches may be of darker (warmer) sands then offshore coral islands, and consequently will produce a higher proportion of females. Thus displaced nesting from cooler islands beaches could lead to a long-term reduction of males. Concerns exist over sea level rise accelerating erosion processes and the frequency of nest inundation at nesting grounds used by the northern Great Barrier Reef green turtle population, which currently experience erosion and changes in morphology (Limpus et al. 2003).  Indeed, predictions are for a loss of up to 38% of the available nesting area across the key rookeries used by the northern Great Barrier Reef green turtle population from inundation as a result of SLR (Fuentes et al. in press, c).

Low-lying rubble cays, mangroves and salt marshes used by crocodiles are also likely to be impacted by predicted SLR. It is also probable that sea level rise will influence the reach of the estuarine zone and expose current crocodile nesting sites in low lying areas of catchments.  Sea level rise may also alter the distribution of key sea snake habitats resulting in a shift in distribution of sea snakes around northern Australia. In particular, sea snakes in the Ashmore Reef complex may undergo local extinctions if coral reef growth does not keep up with the rate of sea level rise. The remote isolated reefs in the Timor Sea have the highest sea snake diversities in Australian waters and include the entire distributions of some Australian endemic reef-associated species. Local extinctions would, therefore, be conterminous with species extinctions.

The impacts of sea level rise will probably be more notable by 2100, however it is suggested that over the longer-term (more than 50 years) sea level rise may also help other coral cays to develop and/or stabilize and thus other areas may become available, or become better suited for marine reptiles.

Multiple stressors
Marine reptiles have the potential to survive /adapt to climate change; marine turtles and crocodiles have been around for millions of years and during this time they have endured and survived dramatic changes in temperature and sea-level rise (Hamann et al. 2007). However, some populations of marine reptiles are now very depleted from past exploitation and/ or are being impacted by a range of anthropogenic activities.  The cumulative impact of multiple stressors on marine reptiles is a major threat to their resilience and capacity to adapt to climate change. Thus, concern exists on whether marine reptiles have the adaptive capacity to satisfactorily respond to present day climate changes, especially given the current rapid rates of warming, while being simultaneously impacted by a wide range of threatening anthropogenic activities (Limpus in press). Coastal development, in particular, is an issue since it hinders the natural evolution of beach systems and may reduce the availability of alternative nesting beaches for marine reptiles to shift to as an adaptative strategy. For example, current distributions of coastal sea snake species include large areas of the relatively remote northern Australian coastline; however, increasing coastal development (both urban and industrial) is reducing habitat availability in this region. Moreover, the ability of sea snakes to undergo southward range-shifts will depend on the availability of suitable habitat (such as inter-tidal mangroves, coral reefs).

Key Points

• Marine turtles and crocodiles are an ancient faunal group, while sea snakes are a more recent and highly successful radiation of marine reptiles. Marine reptile species have, therefore, persisted through very dramatic changes in climate over time scales ranging from thousands to millions of years. Thus, marine reptiles have the adaptive capacity to respond to temperature and sea level fluctuations and associated shifts in breeding and foraging site locations and ocean currents.
• Marine reptiles will likely be impacted by cumulative impacts and a reduced ability to adapt because of altered marine and coastal habitats.
• Marine reptiles are ectotherms; thus, their body temperatures fluctuate with environmental temperatures.
• Increased air and sea temperatures will likely cause most major direct impacts on marine reptiles as climate change progresses.
• Increases in temperature will likely impact sea turtle’s distribution, foraging ecology, nesting phenology and reproductive output. At current rookeries, as sand temperatures increase, there will likely be a feminization of sea turtle populations and an increase in hatchling mortality rates.
• Impacts of warmer sand temperature are already evident at key Australian sea turtle nesting grounds such as Mon Repos, where high sand temperatures are causing increased debilitation and death of eggs and hatchlings.
• Behavior, physiology, reproductive timing and reproductive output of crocodilians are also linked to temperature and thus can be expected to be affected as temperatures increases.
• There is insufficient information on fine scale distribution of different sea snake species, their thermal requirements and tolerances and fine scale aspects of dietary ecology to estimate how particular species will respond to increased sea temperatures. Potential changes could include changes in distribution of certain species and/or their prey, timing of movements and reproductive events.
• Increased sea surface temperatures in shallow-water habitats may reach the lethal thermal tolerance limits of sea snakes and sub-lethal limits may occur for prolonged periods.
• Severe declines in three reef-associated sea snake species endemic to Australia’s Timor Sea reefs may be linked to increased sea surface temperatures; degradation of coral reef habitats from coral bleaching; and/or reduced availability of preferred prey species (small reef fish or eels).
• Some sea snake species are potentially able to respond to increased sea surface temperatures by southward (polewards) range-shifts along Australia’s east and west coasts.
• Currently, there are insufficient baseline and/or long-term monitoring data to determine/detect any current trends or impacts from recent increases in temperatures on the distribution, nesting phenology and foraging ecology of Australia’s marine reptiles.
• Intensification of cyclonic activities and projected sea level rises may compound impacts to key habitats used by marine reptiles.
• There is not enough precision in rainfall estimates, or the likely temporal and spatial variability of these estimates, to evaluate how vulnerable marine reptiles are to changes in rainfall patterns. Rainfall is, however, likely to remain an aperiodic factor that shapes intra- and inter-annual variation in variation in reproductive periodicity, reproductive success and embryo development of sea turtles and crocodiles.
• There are many knowledge gaps about the basic ecology, physiology, reproductive biology and diets of crocodiles and sea snake species needed to evaluate the actual and potential impacts climate change.

Sea turtles
There is HIGH evidence that breeding rates for green turtles from the two Great Barrier Reef (GBR) populations, and eastern Australian loggerheads are linked to climate processes. Also genetic studies have identified population boundaries which will aid management for most species. There is a HIGH level of agreement that climate processes drive reproductive events for green turtles in the Great Barrier Reef and loggerhead turtles from the eastern Australia.
There is MEDIUM evidence that although the impacts of warmer sand temperatures are already evident at some key Australian nesting rookeries there are still insufficient baseline and/or long-term monitoring data to determine/detect specific trends or impacts from climate change on sea turtles distribution, nesting phenology and foraging ecology for most populations.
There is LOW evidence that climate change is impacting turtle nesting beaches. Although there have been obvious impacts to some Australian sea turtles nesting grounds (e.g. through erosion), there is no direct link or evidence that these result from climate change. Therefore, overall consensus between researchers as to whether sea turtles nesting grounds and/ or sea turtles are being impacted by climate change, as opposed to other geomorphologic processes, is low.
Considering the amount of evidence and consensus on the observed impacts of climate change on sea turtles we have very LOW confidence that most Australian populations are currently being impacted by climatic change.

Crocodiles
There is no empirical (LOW) evidence that crocodiles are currently being impacted by climate change. There is LOW consensus that crodociles are being impacted by climate change. There has been little empirical or theoretical research conducted to determine whether crocodiles have been or are currently impacted by recent climate changes (Hamann et al. 2007).
Given the lack of evidence and consensus on the observed impacts of climate change on crocodiles, there is very LOW confidence that they are being impacted by recent climate changes.

Sea snakes
Although there have been obvious declines in abundance of some sea snake species in Australian waters, there is no empirical (LOW) evidence that these declines have been the direct or indirect result of climate change. There is LOW consensus; there has been little empirical or theoretical research conducted to evaluate the potential effects of climate change for any sea snake species.

There is LOW confidence that sea snakes are being impact by current climate change. A workshop held in Brisbane (February 2009) brought together many of the world’s sea snake experts who conducted the first IUCN Red List Assessments of extinction risk for all sea snake species as part of the Global Marine Species Assessment. These assessments are currently in draft form, however, the workshop highlighted many of the knowledge gaps in sea snake conservation biology, including understanding their potential responses to the effects of climate change. As assessment of the vulnerability of marine reptiles to the various effects of climate change on the Great Barrier Reef also concluded that there was not enough information to assess the risks for sea snakes in this region (Hamann et al. 2007). Nonetheless, dedicated surveys conducted in the Ashmore Reef region have highlighted the precipitous declines of some sea snake species and the potential links with climate change.

Sea turtles
There is MEDIUM evidence that turtles will be affected this century by climate change. There is a growing body of theoretical research that predicts how sea turtles will be affected by climate change based on what is currently known about sea turtle species. Most theoretical studies have focused on the impacts of increasing temperatures to the reproductive output and distribution of sea turtles and/or the impacts of sea level rise to nesting habitats. However, few studies have investigated how other climate changes (e.g. in ocean currents) may affect sea turtles and/or how their foraging ecologies may be impacted. There are few baseline data for most northern and western Australian populations to underpin statistical models so evidence is LOW for these. Although there is a high degree of consensus that sea turtles will be broadly impacted by climate change, there is a low level of consensus on how individual species and populations in Australia will be impacted, therefore, overall the consensus level is MEDIUM.
Although it is generally agreed that sea turtles will be impacted by the affects of climate change, there is LOW confidence on the specifics of how different species and populations in Australia will be impacted.

Crocodiles
There are little empirical, theoretical or modelling evidence (LOW evidence) about how crocodiles will be impacted by climate change. There is a LOW consensus that climate change will affect crocodiles. There are few empirical or theoretical data to determine how vulnerable crocodiles are to future climate changes (Hamann et al. 2007).
Considering the amount of evidence and consensus on the observed impacts of climate change on crocodiles we have very LOW confidence about how vulnerable they are to the effects of future climate changes.

Sea snakes
There is LOW evidence that climate change will impact sea snakes. Based on what is known about the physiology, distribution, habitat and prey preferences of sea snake species it is possible to make theoretical predictions about how sea snakes will respond to the effects of climate change, however, there are no direct observations or statistical models with which to test these predictions. There are few empirical data and no theoretical models that could be used to predict the potential impacts of climate change by 2030 or 2100 for any sea snake species, therefore there is a LOW consensus.

There is LOW confidence. The lack of empirical and theoretical data makes it difficult to predict how the effects of climate change will affect any sea snake species with anything but a low level of confidence. Nonetheless, some species have undergone population declines on some Australian coral reefs, so something is clearly occurring: however, the extent to which the effects of climate change are implicated needs to be established.