3756888 The impacts of sea-level rise on the index nesting beach on Klein Bonaire for three species of Sea Turtle.

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Marine Environmental Management | Jennifer Cheetham Project Supervisor: Dr Sue Willis

Supervisor: Julie Hawkins Organisation: Sea Turtle Conservation Bonaire

3756888 The impacts of sea-level rise on the index nesting beach

on Klein Bonaire for three species of Sea Turtle.

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Acknowledgements

This study has only been possible due to support from Sea Turtle Conservation Bonaire (STCB) who offered me this placement, taught me so much and valued me as a respected member of the team, which allowed me to have such a wonderful experience. I am also thankful to STCB for allowing me access to their database and resources. I would especially like to thank Dr Sue Willis for her support, guidance and generosity during my time in Bonaire as my supervisor and mentor. I am also thankful to Mabel Nava for her leadership and organisation and allowing me to take part in all activities that further increased my knowledge and enthusiasm for sea turtles. I also highly acknowledge the contribution made by supporters of STCB such as the Board of Directors, Beach Keepers & Volunteers without whom, the work of STCB and my research would not have been possible. I am grateful to Dennis and Janice Elloway, Dennis for providing me with essential equipment needed for my research and Janice for her commitment to STCB, enthusiasm and kindness. I would like to express my gratitude to Naima Hall for giving up her time to help with my field work of which I would not have been able to do alone. I would also like to thank Gerrie for taking us to Klein Bonaire on his boat every Thursday free of charge so that I could collect data for my research. I would especially like to thank Nathanial Miller from to Dutch Caribbean Nature Alliance who allowed me the use of his computer and gave up his own time to give me guidance on using Google Earth and GIS. I would also like to thank Eseld Imms and Abigail Lynne for help with GIS. Lastly I would like to thank Elizabeth Downes and supporters of the Alasdair Downes Memorial Fund for providing me with funding towards my summer placement.

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Contents

Acknowledgements ... 0

Abstract ... 3

Introduction ... 4

Species found in Bonaire ... 4

Threats to marine turtles ... 7

Sea-level rise projections ... 8

Methodology ... 8

Collection of nesting data- ... 8

Measuring the beach profile- ... 10

Results ... 12

Sea-level rise scenarios ... 16

Discussion ... 17

Conclusion ... 21

References ... 22

Appendices ... 27

Appendix i. ... 27

Appendix ii... 39

Appendix iii ... 47

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Abstract

Globally, all extant sea turtles species are endangered due to centuries of uncontrolled exploitation, furthermore they face future threats from climate change. The Caribbean is home to six of the seven extant marine turtle species. Sea turtles have various nesting and feeding grounds across the Caribbean but return to their natal beaches to breed. This study focuses on nesting sea turtles in Bonaire, a small island in the south of the Caribbean, which has three breeding species; the Green, Loggerhead and Hawksbill turtle. The index beach is

“No Name” beach on the small islet of Klein Bonaire, which is 800m west of Bonaire.

Global sea-level rise projections range between 0.18-0.59m by 2100 (IPCC, 2007). However, the Caribbean region could experience 25% greater sea-level rise than the global average with suggestions up to 1.6m. Sea-level rise threatens nesting beaches and is expected to negatively impact the sea turtles. This investigation measured beach profiles along “No Name” beach to create contours of elevation. The nests were identified, monitored and plotted onto maps.

Analysis of the distance from the nest to the HTM and elevations of nests indicate that Loggerheads are more at risk from sea-level rise. However for all sea-level rise scenarios there will be beach area and nests lost (using 2012 data). Where natal beaches cannot retreat, they may be lost to sea-level rise; turtles must adapt to climate changes or will face an even greater population decline.

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Introduction

Marine turtle species have existed for millions of years, with over 100 different species, evolving from a single ancestor, over 200 million years ago in the Mezozoic era (Pritchard, 1997; Gulko & Eckert, 2004). However, there are only seven species extant today. Five of the seven species are categorised as “endangered” and two species “critically endangered”

(WWF, 2008; IUCN, 2012). All living turtles share similar characteristics such as late maturation, air breathing, high fecundity and external development but each species is adapted to their specific habitat and diet, so there is little niche overlap (Gulko & Eckert, 2004). Within the Caribbean Sea, there has been a vast decline in the number of sea turtles since records began in the 17th century (Harold & Eckert, 2005). It was reported by historical mariner documents in the 17th and 18th century that populations of turtles were in the millions (IUCN/SSC, 2008). Today the Caribbean is home to 6 of the 7 species, of which all population numbers are significantly depleted in comparison to the historical levels. This depletion is due to centuries of overexploitation and accidental death, including bycatch of fisheries or entrapment from abandoned fishing gear (Bräutigam & Eckert, 2006; Harold &

Eckert, 2005). Habitat loss has also played a contributing factor to the declines in population.

Many reef habitats have lost up to 80% of their coral cover in the past 50 years, due to overfishing, sedimentation, pollution, contamination and climate change. These reefs are critical feeding habitats for Hawksbill turtles. Today many global sea turtles populations have been severely reduced and some local populations made extinct (IUCN/SSC, 2008).

However, the level of protection has increased through stricter law enforcement and better management of coastal habitats and fisheries. This had led to a slight increase in the number of Hawksbill turtles in the Caribbean (WWF, 2008; Halpin et al., 2009).

Species found in Bonaire

Bonaire is a small island in the south of the Caribbean, approximately 80km North of Venezuela. Klein Bonaire was the main study site situated in the crescent of Bonaire mainland.

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Klein Bonaire is approximately 6km2 and is fully protected by law (Fish et al., 2005). There are three species of sea turtle that nest on Bonaire and Klein Bonaire these are the Green, Hawksbill and Loggerhead turtles (Gulko & Eckert, 2004; STCB, 2011). These species do not spend all of their lives in the coastal waters of Bonaire, but complete different life stages in other areas of the Caribbean and migrate back to these waters to breed (IUCN/SSC, 2008). Nesting females return to the same beaches from where they were born, this phenomenon is known as natal philopatry. The coastal habitat around Bonaire does not support adult turtles permanently; they only come to Bonaire to breed. However, juvenile Hawksbill and Green turtles inhabit the coral reefs and sea grass beds around the islands (STCB, 2011).

Hawksbill turtles (Eretmochelys imbricata) are one of the smallest species of marine turtle.

They can be identified by having a narrow head with a beak like jaw and overlapping scutes (4 lateral scutes) (Ripple, 1996; WWF, 2008; Lutz & Musick., 1997). They are also among the most endangered species of marine turtle being classified as “critically endangered”

(facing extremely high risk of extinction in the wild in the near future) by the International Union for Conservation of Nature and Natural Resources (IUCN, 2012; Mortimer &

Donnelly, 2008). This species faces a global crisis, with the IUCN estimating that there was an 80% decline in the population in just three generations, mainly due to human threats, especially poaching. The tortoiseshell carapace is commercially valuable worldwide for jewellery and ornaments (Reuter and Crawford 2006; IUCN, 2007). Hawksbill turtles occupy a wide region and range of tropical habitats, from terrestrial where they hatch and nest to coral reefs where they spend their adult lives. Sea turtles experience a variety of temperature changes and external environments throughout their lives (WWF, 2008). Adult Hawksbills feed on sponges, anemone and squid. Their nesting season on Bonaire is usually between June and December (STCB, 2011). Mature females breed every two to four years, with three to six nests per season (14-16 day intervals) and an average of 100-200 eggs per nest. Each nest has an eggs chamber at least 50cm deep in the sand (Gulko & Eckert, 2004). The eggs

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incubate over 50-60 days. The current global population estimate is 22,900 nesting females (Sea Turtle Conservancy, 2011).

Loggerhead turtles (Caretta caretta) are one of the most migratory species of sea turtle with some individuals crossing the Atlantic or Pacific oceans (Bolten et al., 1998; Nichols et al., 2000). They can be identified by their large head with strong jaws and reddish-brown heart shaped carapace that doesn’t have ridges or overlapping scutes (there are 5 lateral scutes). The adult carapace is 80-110cm in length. Loggerheads inhabit coastal bays and shallow coastal waters where they can feed on their preferred food source of bottom dwelling shellfish including crustaceans and molluscs (Gulko & Eckert., 2004). Individual adults nest every couple of years laying 3 to 6 nests per season with an average of 100-130 eggs per nest. The eggs incubate for approximately 60 days. Their nesting season on Bonaire is between May and August (STCB, 2011). Loggerheads are listed as “Endangered” by the IUCN red list of endangered species (IUCN, 2007; IUCN, 2012; Marine Turtle Specialist Group, 1996).

Incidental capture in fisheries has been a significant part of Loggerhead population decline in recent years. There are currently an estimated 44,560 nesting females in the world (Sea Turtle Conservancy, 2011).

Green Turtles (Chelonia mydas) also nest on Bonaire and Klein Bonaire, however this species has the fewest nests compared to Loggerheads and Hawksbills. Green Turtles can be identified by having a pair of prefrontal scales, a small blunt head with a serrated jaw (Gulko

& Eckhert, 2004). The carapace is large and the scutes do not overlap (4 lateral scutes). The carapace colour varies from different shades of green to browns and yellows, with a length of 80-115cm (Gulko & Eckert, 2004). Green turtles have a wide range of habitats and are found in both temperate and tropical regions. However this species is listed as “Endangered” by the IUCN and face a very high risk of extinction in the wild in the near future (IUCN, 2012;

Seminoff, 2004). Adult Green turtles have a serrated jaw, which allows them to tear vegetation such as algae and sea grasses. The population of green turtles in Lac Bay on the

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east coast of Bonaire has the fastest growth rates in the Caribbean. For Green turtles the mean growth rate of recaptured turtles in Lac bay (since monitoring began in 2003) was 6.2cm/yr compared to outside the bay in the reefs of Bonaire & Klein Bonaire which was 3.2cm/yr (STCB, 2011). The nesting season is usually between July and September in Bonaire and Green turtles return to their nesting grounds approximately every two to five years to breed (STCB, 2011). There are usually 3-5 nests laid per season with each nest averaging 75-115 eggs (Gulko & Eckert, 2004). The nests are approximately 90cm deep, so require beaches with soft deep sand. They incubate for around 60 days. The current population estimate is 88,520 nesting females (Sea Turtle Conservancy, 2011).

Threats to marine turtles

Marine Turtles face many threats both natural and man-made; natural threats include predators and climate fluctuations and anthropogenic threats include pollution (rubbish and oil spills), fishing activities, invasive species, destruction or modification of habitat, harvesting (eggs, shells and meat), artificial lighting, disease or parasites and human induced climate change (Choi & Eckert, 2009; Gulko & Eckert, 2004; Knowles et al., 2009). Survival to adulthood is low (IUCN/SSC, 2008). Anthropogenic threats occur within all population ranges, all species are threatened and because they are highly migratory, when localised populations decline this could be due to local or foreign threats, so prove difficult for study for scientists to target the source of the decline. The Wider Caribbean Sea Turtle Conservation Network (WIDECAST) has found that all species are affected by coastal development, pollution, invasive species and erosion (WIDECAST, 2008; Knowles et al., 2009). Anthropogenic pressures can increase stress levels to turtles throughout their life histories and cause reduction in population size and reduce their resilience to climatic fluctuations (WWF, 2008). These threats are a global problem, and because turtles have long life stages before they are sexually mature and can reproduce, they are not reproductively

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successful. Without adaptation to these threats, conservation efforts and mitigation, recovery of sea turtle populations will be difficult to accomplish.

Sea-level rise projections

The Caribbean has a tropical climate, and in the future this is expected to experience regional differences in temperature, precipitation and sea-level rise. The level of global average sea- level rise varies between different scenarios and considerations, the IPCC estimates a sea- level rise in the range of 0.18 to 0.59m by 2100 (IPCC, 2007). However this does not consider regional changes. The IPCC estimates that the Caribbean will experience a greater sea-level rise than the global average and that small islands will be threatened and sea-level rise could be up to 25% greater than the global average. When thermal expansion and melting of global frozen freshwater stores contribute to rising sea-levels, estimates of sea-level rise should be higher. The Dutch Delta committee estimates that the maximum sea-level rise for the BES islands (Bonaire, Saba, Sint Eustatius) could be up to 1.6m and that this estimate should be used for adaptation (Debrot & Bugter, 2010). Sea-level rises are likely to accelerate beach erosion rates, further increasing the loss of sandy beaches. Tidal surges are expected to become more frequent, further accelerating coastal erosion and inundation of coastal habitats due to higher wave energy (Hawkes et al., 2009).

Methodology

Collection of nesting data-

“No Name” beach on Klein Bonaire is the index nesting beach Bonaire (Figure 1). It is monitored by Sea Turtle Conservation Bonaire (STCB) three times a week during the nesting season (May to November). STCB is a non-profit, non-governmental organisation that conducts research and conservation activities to ensure the protection of sea turtles in Bonaire and throughout their natural range. When turtle activity was seen, termed a “crawl”, the tracks

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were investigated to discover whether the tracks led to a nest, a false crawl or an unsuccessful attempt at nesting. When a nest was found, the location was recorded using a GPS point with the location stakes providing distance along the beach (these are located every 50m along the beach). The vegetation type around the nest, freshness and observers were also recorded. In order to confirm the nest, the body pit created was carefully dug and if the eggs were found it is marked as a confirmed nest. If the nest was confirmed the distance from the HTM was also recorded. There were 70 nests (end of September) on Klein Bonaire both confirmed and unconfirmed, used in this study.

Figure 1: Image from Google Earth showing Bonaire and Klein Bonaire.

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Measuring the beach profile-

Figure 2: Image from Google Earth showing Klein Bonaire and the location of "No Name" which was sampled in this study.

Figure 3: Image from Google Earth of "No Name" beach and the location of the HTM, stake and transects every 50m along the beach.

The study site was the Bonaire’s index beach for nesting marine turtles called “No Name”

beach on Klein Bonaire, measuring 2000m in length (Figure 2 & 3). The beach had permanent location stakes every 50m along the beach marking the distance along the beach.

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At each 50m location stake, beach profiles were taken. Transects were laid out with a measuring tape, perpendicular to the sea line from the High Tide Mark (HTM) up to 20m along the profile (this was not always possible where vegetation was very dense). The HTM marks the highest water level of the sea usually seen by a line of marine debris or a line in the sand or rocks. Coordinates of the HTM & location stake were taken using a handheld global positioning system (Garmin GPS 72H) which is WAAS-enabled, giving accuracy up to 3m (Garmin LTD., 2009).The distance between the HTM and location stake was also taken. At every 2m along the profile the elevation of the land was taken using a measuring pole and a support stick with a level balanced on top to read the change in height of the land at 2m intervals (Figure 4) (Emery, 1961). Also at every 2m interval a fixed-point photograph was taken (at 30cm above the ground facing the left side of the transect) in order to create a merged photograph of the entire profile. The vegetation type along each profile was also recorded. Each beach profile was then drawn with Microsoft Excel to show the gradient of each slope.

The GPS points of the transects were then plotted onto Google Earth and imported into ArcMap (ESRI, 2011) for computer analysis and building 3D models of “No Name” beach.

Using the elevations between transects, contours of land heights were created. Nest locations Figure 4: The Emery method was used to measure the beach profile (Emery, 1961). This measures the elevation between two points. In this study elevations were taken every 2m along the transect (up to 20m). The measuring poles were 2m apart, a Level was placed on top of pole A, the observer at A looked through the level and read the horizontal measurement on pole B which gave the elevation d.

The cumulative elevation along the transect gave the beach profile shape.

2m d

HTM Up to 20m

A

B

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were added by species specifying whether the nests were confirmed or unconfirmed. Using GIS software (ESRI, 2011), projections were made to predict how much of the beach would be lost at different sea-level rise projections, this used the samples of the elevations of the beach profiles and analysed how many were below each sea-level rise projection in relation to the overall number of elevation samples collected. An analysis was also made to find the most vulnerable species to sea-level rise at various projections. This compared the nest location on the beach profile for each species by measuring distance from the HTM to the nest and the expected elevation of the nests.

Results

Figure 5: ArcMap showing the GPS points of the nest sites with some anomalies.

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The GPS points for each of the 70 nests were plotted into Arc Map. However there were some anomalous points (Figure 5) which may have been due to human error, such as typos during data entry or not waiting until the GPS had transmitted the satellite signal. In Figure 5 the cluster of nests indicates the actual position of “No Name” beach (top left) and there are approximately 13 observed anomalies (i.e. nests not lying within the beach area). The Garmin GPS tracker used was accurate to 3m. However there can be occasional signal errors if the receiver does not pick up a signal.

Toward the west of “No Name” beach there are an even spread of Hawksbill and Loggerhead nests (Figure 6). However from approximately 1000m to 1850m along the beach the nests mostly belong to Hawksbills. This section of the beach area is steep and highly vegetated with a lot of hard vegetation especially Oleifi (Bontia daphnoides), which is unsuitable nesting

Figure 6: The Location of all the nests on "No Name" Beach, Klein Bonaire

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habitat for other species (STCB, 2011). The Loggerhead turtles nests were largely concentrated in the dune areas.

Figure 7: The HTM of "No Name" beach (A) with the nest locations (B)

The locations of the nests were plotted on maps of Klein Bonaire, with Figure 7 showing the position of the nests in relation to the HTM (Figure 7 (A & B). These distances were only measured for ‘confirmed’ nests and they varied for each of the three species. Patterns showed that the Loggerhead turtles nested closer to the HTM than the Hawksbills, this is what was expected. The average distance from the nests to the HTM for Loggerhead turtles was 6.01m,

(A)

(B)

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for Hawksbill turtles was 8.98m and Green turtles was 14.00m (Figure 8). There is a statistically significant difference (P =0.01) in the means when comparing the Hawksbill and Loggerhead position of the nests in relation to HTM (Appendix iii).The evidence suggests that the Green turtles nested much higher up the beach than the other two species but this is not significant due to there only being 3 green turtle nests on Klein Bonaire, compared to 24 nests from Hawksbill turtles and 22 from Loggerhead turtles.

Figure 8: The mean distance from the confirmed nests to the HTM for three species of turtle;

Hawksbill (Ei), Loggerhead (Cc) and Green Turtles (Cm).

However, using the distance from the nest to the HTM does not provide the adequate information on how sea-level rise will affect the nests, so beach profiles were also measured.

These beach profiles could be used to find the elevation along the beach and create contours to estimate the elevation of each nest, which gives a better indication of the risk from rising sea-levels.

The profiles were drawn in Excel and photos taken along each transect put together to provide visualisation of each profile (Appendix i). These can be used to show the loss of beach area at various sea-level rise projections if beach dynamics remain the same. From 200-1000m the beach is mostly sand dune habitat and from 1000-1800m the profile is steep and highly vegetated. After 1800m to 2020m the profile of the beach rose up in the dunes to a maximum

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elevation of 0.6m then decreased to below the level of the HTM. A large area behind the dunes is vulnerable to flooding with sea level rise above 0.4m.

Measuring the elevation of beach profiles at regular intervals along the beach allowed contours to be created on maps that allow estimations of height of entire beach. GIS has been used to create these contours at 0.2m intervals using the elevations recoded during beach profiling (Figure 9). These contours were then used to estimate the height of each nest and estimate of the impact of sea-level rise on “No Name” beach by identifying the percentage of nests and beach area that would be at risk under the different sea-level rise scenarios.

Figure 9: Contours of 0.2m elevation increase from the HTM for the profile of "No Name"

beach, Klein Bonaire. Contours include; HTM (Orange line with cross poles), 0.2m (Bright Yellow dashed line), 0.4m (Fusia Pink dashed line), 0.6m (Lime Green dashed line), 0.8m (Blue dashed line), 1m (Black line), 1.2m (Red dashed line), 1.4m (light pink dashed line) and 1.6m (White/Yellow dashed line).

Sea-level rise scenarios

A 0.2m rise in sea-level will not severely impact many nests (Appendix ii: Figure 12), 19% of the beach area would be lost along with 7 % of nests using 2012 data (Table 1). Loss of beach area will only occur between 500-1000m and 1850-2050m. With an increased sea-level rise

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up to 0.4m, 34% of the beach are will be affected (Appendix ii: Figure 13 & 14) and 14% of current nests would be at risk especially the ones between 1850-2050m (Table 1). With a 0.8m sea-level rise most of the sandy beach area is expected to be flooded, this is 70% of the Loggerhead habitat and 56% of total nests using 2012 data (Appendix ii: Figure 17 & 18).

Most of the area between 1850-2050m will be flooded as the dunes only reach a maximum of 0.6m above the HTM. For the maximum projected scenario projected for the Caribbean by the end of the century (1.6m sea-level rise), 98 % of nests and 98% of beach area would be at risk (Table 1; Appendix ii: Figures 25 & 26).

Table 1: This table gives a summary of the percentage of nests lost during various sea- level rise scenarios, using the data from 57 nests, both confirmed and unconfirmed (2012 nesting data). 13 of the nests had anomalous GPS points as the location did not appear upon “No Name” beach, so these were not used in this analysis. The percentage of beach area lost was determined by comparing the number of elevations recorded below various sea-level rise scenarios against the overall number of elevations recorded during sampling of beach profiles.

Discussion

The climate of the Earth is changing at a significant rate that has never been seen before in the Earth’s history. This is likely to be caused by acceleration in consumption of fossil fuels and the release of anthropogenic atmospheric emissions (Johns et al., 2003; The Royal Society, 2010; Hoegh-Guldburg et al., 2007). Such rapid climate changes will negatively impact sea turtles and their habitats world-wide (WWF, 2008). The changes in climate since 1996 have been much greater than expected (Rahmstorf et al., 2007; Witt et al., 2009). Since 1850 global temperatures have increased by 0.8°C (±0.2°C), future projections predict an increase

Sea-level rise

(m) % of nests lost % beach area lost

0.2 7 19

0.4 14 34

0.6 25 53

0.8 56 67

1.0 72 80

1.2 81 91

1.4 95 95

1.6 98 98

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of 2.4°C to 6.4°C by 2100, depending on the scenario (IPCC, 2001; The Royal Society, 2010). As the world warms, glacial melt and thermal expansion are expected to cause a rise in sea-levels and increase of extreme weather events are likely to produce more frequent tidal surges, which are expected to impact the nesting beaches of marine turtles.

For all marine turtle species, success is dependent on the availability of nesting habitat (Hawkes et al., 2009). Sea-level rise is likely to significantly reduce the number and size of nesting beaches especially where coastal squeeze is imminent i.e. where retreat of beaches is inhibited by coastal development or on islands that may be submerged with increasing sea- levels (CCCCC, 2009; Fish et al., 2005). Some species of turtle may be more affected by sea- level rise than others depending on their nesting characteristics. In this study there was statistically significant evidence that Loggerhead turtles nested closer to the HTM than Hawksbill turtles suggesting that they could be at more risk from sea-level rise. However, the distance from the nest to HTM was only measured if the nest was confirmed, so this reduced the number of nests in the analysis. Nevertheless, the outcomes of this analysis fitted what was expected, that Loggerheads nest further down the beach profile i.e. in the sand dunes, compared to the Hawksbills that prefer to nest in the vegetation further along the profile and steeply sloped beaches (Horrocks & Scott, 1991). This was also observed when analysing the estimated elevations of the nests, where there were a greater number of Loggerhead nests at lower elevations than Hawksbill nests.

This investigation also analysed the area of “No Name” beach that would be lost under various sea-level rise projections. An earlier study by Fish et al. (2005) on Bonaire’s nesting beaches suggested that 30% of nesting habitat is expected to be lost by a 0.5m sea-level rise and that there would be a 50% loss of Hawksbill nesting habitat with a sea-level rise of 0.9m.

Another study in Hawaii by Baker et al. (2006) predicted a 40% decline in Green turtle nesting area if sea-level rose by 0.9m. Within the Caribbean research showed that by 2006, approximately 20% of nesting sites had already been lost and another 50% were threatened

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(McClenachan, 2006). During this study, there was evidence that a 0.8m sea-level rise would put 70% of the Loggerhead nests at risk. Sea-level rise is expected to impact large sections of the beach whereby a 19-53% beach area is estimated to be lost with a 0.2-0.6m sea-level rise by 2100 (IPCC, 2007). If the maximum sea-level rise scenario of 1.6m is reached by the end of the century then 98% of beach area and 98% of nests would be lost. These projections assume that the current beach morphology and profile is maintained (Debrot & Bugter, 2010;

Fish et al., 2005).

If the beach area cannot retreat, nesting area will be significantly reduced. This may be observed where flood defences or coastal development are present and coastal squeeze in inevitable or on low-lying islands which may be submerged by sea-level rise. In this scenario if similar numbers of nesting females return to nest, nesting areas could reach a carrying capacity and further nesting attempts are likely to be closer together, risking turn out of previous nests (Mazaris et al., 2009; Hawkes et al., 2009). If the beach cannot retreat there will be more nests closer to the

HTM, so there is an expected increase in the number of nests that are vulnerable to tidal inundation (Fish et al., 2005). Nests may also face increased risk of water-logging from below, whereby rising sea-levels may cause the groundwater saturation to increase and the water table to rise, reducing the success of the clutch (Witt et al., 2009; Wetterer et al., 2009). In this instance the species that lay nests closer to the HTM or that lay deeper nests are more at risk, evidence from this study suggests that Loggerhead nests would be most at risk. The choice of nesting site by turtles is dictated by a variety of factors including sand type, distance from the HTM, salinity, ventilation, vegetation and sand depth (Kamel & Mrosovsky, 2006). If there is not sufficient optimal nesting area at a reasonable distance above the HTM, the number of nests will be reduced. Success of a site depends on the number of turtles that return to their natal beaches to breed, so this decline might not be identified for many years.

However, on Klein Bonaire there is no development so nesting beaches have the possibility to retreat and beach morphology dynamics could allow creation of new nesting habitat. In this

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study no beach morphology changes were recorded however, this investigation allows morphological changes to be studied in the future by observing changes in the beach profile via the profiles recorded and the photographs taken. There has been much speculation about the effects of sea-level rise on the rates of beach accretion and erosion (Pethick, 2001). Sea- level changes will alter the wave energy gradients both perpendicular and parallel to the shore. In 1962 Bruun predicted that beach profiles would respond to sea-level rise by maintaining their morphological characteristics relative to the water level. This was expected due to the movement of eroded material, supplying sediment to build the beach profile at other places on the beach but only if there was net sediment balance (Bruun, 1962; Bruun, 1988; Schwartz, 1967). The vegetation on the beach could also impact the coastal morphological dynamics by altering profile characteristics and stabilising the sand (Hesp, 2008). In this study the vegetation has been recorded along each transect, this can be used for further research observing changes along the profile in subsequent years.

Only data from 2012 was used in this study (May to the end of September, more nests could have been laid since), this does not allow analysis past levels of sea-level rise which has already occurred at a rate of 3.4mm/year using global averages (Rahmstorf, 2007). This data can be used for further study of sea-level changes in the future.

Sea-level rise must not be seen as a single entity it must also be considered along with other climate change factors such as global warming and ocean acidification, to incorporate how all factors might have implications on sea turtle behaviour. Sea turtles display ectothermic characteristics so their body cycles, behaviour and development are dependent on temperature (Gulko & Eckhert, 2004). They are sensitive to fluctuations in the external environment, including temperature, level of precipitation and seasonality (Hawkes et al., 2007).

Temperature affects their life histories from hatchling sex determination (Yntema &

Mrosovsky, 1980) to alteration in adult distribution and migratory patterns, also by altering ocean currents and impacting feeding habitats. Extreme weather events such as increased

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frequency and severity of hurricanes and tidal surges are expected to become more common in the future (Meehl et al., 2000; Knutson et al., 2010). Regional variation in precipitation levels across the Caribbean are expected (CCCCC, 2012). Some areas will experience drought conditions where there will be less precipitation. In these areas sea turtles may find creation of nests difficult due to dryer sand and the external temperatures may get too hot for nest incubation. Higher temperatures will lead to skewed sex ratios and temperatures too great can be lethal (Hawkes et al., 2007). The opposite extreme is that some areas will experience heavy precipitation, whereby nests may become saturated, which could reduce the oxygen content of the sand, lowering the success rate. With the increase in carbon dioxide in the atmosphere the oceans will become more acidic (Hoegh-Guldberg et al., 2007). Acidification could impact the food sources of marine turtles, for example crabs will find it difficult to make their calcareous shells. Also coral reefs could be destroyed by bleaching due to the stresses of unusually warm temperatures and more acidic water (Hoegh-Guldberg et al., 2007;

Orr et al., 2005). These are vital food sources and habitats associated with sea turtles, whereby loss of these habitats will negatively impact turtles. The alteration in the temperature and pH of the oceans may directly affect internal mechanisms and homing ability. Sea turtles may be used as an indicator species of climate change due to their sensitivity to environmental changes (Sea Turtle Conservancy, 2011).

Conclusions

The impacts of climate change and furthermore, sea-level rise will undoubtedly affect the nesting behaviour of marine turtles. The climate change factors must also be considered along with existing human threats in order for adaptation and mitigation strategies to be incorporated into conservation and coastal management plans (Fish et al., 2005). This study has deduced that Loggerheads are more at risk from sea-level rise than Hawksbills. Also that if beach morphology dynamics do not keep pace with current and future levels of sea-level rise, nesting area is likely to be significantly reduced. If sea turtles do not adapt to these

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changes when they return to their natal beach to breed, many turtles may not be able to nest and many populations will decline. This investigation raises further questions, for future research such as, will sea turtles continue to nest on their natal beaches even if they are reduced in area or will they find new beaches? Is climate change happening too fast for them to adapt and will we see an accelerated decline in numbers in the future? Research needs to undertaken each year documenting the changes in nest number, beach area and whether there is increased incidence of extreme weather events that will impact sea turtle nesting behaviour.

The severity of sea-level rise risk to sea turtle populations depends on whether changes in coastal morphology could create new nesting beaches or the ability of sea turtle populations to naturally adapt to climate change.

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References

1. Baker, J., Littnana, C., & Johnston, D. (2006). Potential effects of sea level rise on the terrestrial habitats of endangered and endemic megafauna in the Northwestern Hawaiian Islands. Endangered Species Res. 2: 21-30.

2. Bolten, A.B., Bjorndal, K.A., Martins, H.R., Dellinger, T., Biscoito, M.J., Encalada, S.E. & Bowen, B.W. (1998). Transatlantic developmental migrations of Loggerhead sea turtles demonstrated by mtDNA sequence analysis. Ecological Applications, 8 (1): 1–7.

3. Bräutigam, A. & Eckert. K.L. (2006). Turning the Tide: Exploitation, Trade and Management of Marine Turtles in the Lesser Antilles, Central America, Colombia and Venezuela. TRAFFIC International, Cambridge, UK. pp. 533.

4. Bruun, P. (1988). The Bruun Rule of Erosion by Sea-Level Rise: A Discussion on Large-Scale Two- and Three-Dimensional Usages. Journal of Coastal Research, 4 (4): 627-648.

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5. Bruun, P. (1962). 'Sea-level rise as a cause of shore erosion.' Journal Waterways and Harbours Division, 88(1-3): 117-130.

6. CCCCC (2009). Climate Change and the Caribbean: A Regional Framework for Achieving Development Resilient to Climate Change (2009-2015). Belmopan, Belize.

7. CCCCC (2012). Caribbean Community Climate Change Center. Belmopan, Belize.

Available at www.caribbeanclimate.bz, Referenced on 14th September 2012.

8. Choi, G.Y. & Eckert, K.L. (2009). Manual of Best Practices for Safeguarding Sea Turtle Nesting Beaches. Wider Caribbean Sea Turtle Conservation Network (WIDECAST) Technical Report No. 9. Ballwin, Missouri. pp. 86.

9. Debrot, A.O. and Bugter, R. (2010). Climate change effects on the biodiversity of the BES islands; Assessment of the possible consequences for the marine and terrestrial ecosystems of the Dutch Antilles and the options for adaptation measures.

Wageningen, Alterra, Alterra-report 2081.

10. Emery, K.O. (1961). A Simple Method of Measuring Beach Profiles. American Society of Limnology and Oceanography, 6 (1): 90-93.

11. ESRI (2011). ArcGIS Desktop: Release 10. Redlands, CA: Environmental Systems Research Institute.

12. Fish, M.R., Cote, I.M., Gill., J., Jones., A.P., Renshoff, S. & Watkinson., A.R. (2005).

Predicting the Impact of Sea-Leval Rise on Caribbean Sea Turtle Nesting Habitat.

Conservation Biology, 19 (2): 482-491.

13. Garmin Ltd. (2009). GPS 72H Owner’s Manual. Garmin Ltd. or its subsidiaries.

14. Gulko, D.A. & Eckert, K.L. (2004). Sea Turtles: An Ecological Guide. Mutual Publishing, Honolulu, HI. pp.128.

15. Halpin, P.N., Read, A.J., Fujioka, E., Best, B.D., Donnelly, B., Hazen, L.J., Kot, C., Urian, K., LaBrecque, E., Dimatteo, A., Cleary, J., Good, C., Crowder, L.B. &

Hyrenbach, K.D. (2009). OBIS-SEAMAP: The world data center for marine mammal, sea bird, and sea turtle distributions. Oceanography, 22 (2): 104–115.

(25)

16. Harold, S. & Eckert, K.L. (2005). Endangered Caribbean Sea Turtles: An Educators Handbook. Wider Caribbean Sea Turtle Conservation Network (WIDECAST) Technical Report No. 3. Beaufort, North Carolina. pp176.

17. Hawkes, L.A., Broderick, A.C., Godfrey, M.H. & Godley, B.J. (2009). Climate Change and marine turtles. Endangered species research, 7: 137-154.

18. Hoegh-Guldberg, O., Mumby, P.J., Hooten, A.J., Steneck, R.S., Greenfield, P., Gomez, E., Harvell, C.D., Sale, P.F., Edwards, A.J., Caldeira, K., Knowlton, N., Eakin, C.M., Iglesias-Prieto, R., Muthiga, N., Bradbury, R.H., Dubi A. and Hatziolos M.E. (2007). Coral Reefs Under Rapid Climate Change and Ocean Acidification.

Science, 318; 1737-1742.

19. Horrocks, J.A. & Scoot, N.M. (1991). Nest site location and nest success in the hawksbill turtle, Eretmochelys imbricate, in Barbados, West Indies. Marine Ecology- Progress Series, 69: 1-8.

20. IPCC (2001). The Scientific Basis, Technical Summary by Workgroup I of the Intergovernmental Panel on Climatic Change; Cambridge Press: Cambridge, UK.

21. IPCC (2007). Intergovernmental Panel on Climate Change. IPCC Fourth Assessment Report (AR4). Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, Geneva, Switzerland. pp 104.

22. IUCN (2012). The IUCN Red List of Threatened Species. Version 2012.1. Available at http://www.iucnredlist.org. Referenced on 8th September 2012.

23. IUCN. (2007). IUCN Red List Status Assessment for the Hawksbill Turtle (Eretmochelys imbricata). Assessors: J.A. Mortimer and M. Donnelly. Marine Turtle Specialist Group, IUCN Species Survival Commission. Washington, D.C. 119 pp.

Available at http://www.iucn-mtsg.org/red

24. IUCN/SSC (2008). A Global Strategy for the Conservation of Marine Turtles.

Prepared by IUCN/SSC Marine Turtle Specialist Group. lUCN Publications Services Unit, Huntingdon Road, Cambridge.

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25. Johns, T.C., Gregory, J.M., Ingram, W.J., Johnson, C.E., Jones, A., Lowe, J.A., Mitchell, J.F.B., Roberts, D.L., Sexton, D.H.M., Stevenson, D.S., Tett, S.F.B. &

Woodage, M.J. (2003). Anthropogenic climate change for 1860 to 2100 simulated with the HadCM3 model under updated emissions scenarios. Climate Dynamics, 20:

583–612.

26. Kamel, S.J. & Mrosovsky, N. (2006). Deforestation: Risk of sex ratio distortion in hawksbill sea turtles. Ecological Application, 16: 357-931.

27. Knowles, J.E., Eckert, K.L., & Horrocks, J.A. (2009). In the Spotlight: An Assessment of Beachfront Lighting at Four Hotels in Barbados, with Recommendations for Reducing Threats to Sea Turtles. Wider Caribbean Sea Turtle Conservation Network (WIDECAST) Technical Report No. 12. Ballwin, Missouri and Bridgetown, Barbados. pp. 128.

28. Knutson, T.R., McBride, J.L., Chan, J., Emanuel, K., Holland, G., Landsea, C., Held, I., Kossin, J.P., Srivastava, A.K. & Sugi, M. (2010). Tropical Cyclones and Climate Change. Nature Geoscience, 3: 157-163.

29. Lutz, P.L & Musick, J.A. (1997). The biology of sea turtles. CRC Press LLC, New York, NY.

30. Marine Turtle Specialist Group (1996). Caretta caretta. In: IUCN 2012. IUCN Red List of Threatened Species. Available at www.iucnredlist.org. Referenced on 8th September 2012.

31. Mazaris, A.D., Matsinos, G. & Pantis, J.D. (2009). Evaluating the impacts of coastal squeeze on sea turtle nesting. Ocean & Coastal Management, 52 (2): 139-145.

32. McClenachan, L., Jackson, J.B.C.& Newman, M.J.H. (2006). Conservation implications of historic sea turtle nesting beach loss. Frontiers in Ecology and the Environment, 4: 290-296.

33. Meehl, G.A., Zwiers, F., Evans, J., Knutson, T., Mearns, L. & Whetton, P. (2000).

Trends in extreme weather and climate events: issues related to modelling extremes in projections of future climate change. Bulletin of the American Meteorological Society, 81 (3): 437-442.

(27)

34. Mortimer, J.A & Donnelly, M. (IUCN SSC Marine Turtle Specialist Group) 2008.

Eretmochelys imbricata. In: IUCN 2012. IUCN Red List of Threatened Species.

Available at www.iucnredlist.org. Referenced on 17th September 2012.

35. Nichols, W.J., Resendiz, A., Seminoff, J.A. & Resendiz, B. (2000). Transpacific Migration of a Loggerhead Turtle Monitored by Satellite Telemetry. Bulletin of Marine Science, 67 (3): 937-947.

36. Orr, J.C., Fabry, V.J., Aumont, O., Bopp, L., Doney, S.C., Feely, R.A., Gnanadesikan, A., Gruber, N., Ishida, A., Joos, F., Key, R.M., Lindsay, K. Maier- Reimer, E., Matear, R., Monfray, P., Mouchet, A., Najjar, R.G., Plattner, G.K., Rodgers, K.B., Sabine, C.L., Sarmiento, J.L., Schlitzer, R., Slater, R.D., Totterdell, I.J., Weirig, M.F., Yamanaka, Y. & Yool, Y. (2005). Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms.

Nature, 437: 681-686

37. Pethick, J. (2001). Coastal management and sea-level rise. CATENA, 42 (2-4): 307- 322.

38. Pritchard, P.C.H. (1997). Evolution, phylogeny and current status. The Biology of Sea Turtles, CRC Press, USA.

39. Rahmstorf, S., Cazenave, A., Church, J.A., Hansen, J.E., Keeling, R.F., Parker, D.E.

& Somerville, R.C.J. (2007). Recent Climate Observations Compared to Projections.

Science, 316 (5825): 709.

40. Reuter, A. and Crawford, A. (2006). Tourists, Turtles and Trinkets: A Look at the Trade in Marine Turtle Products in the Dominican Republic and Colombia. A Report from the Field. TRAFFIC. 12 pp.

41. Ripple, J. (1996) Sea Turtles. Voyager Press, Inc. Vancouver, B.C.

42. Schwarz, M.L. (1967). The Bruun Theory of Sea-Level Rise as a Cause of Shore Erosion. The journal of Geology, 75 (1): 76-92.

43. Sea Turtle Conservancy (2011). Available at www.stc@conserveturtles.org referenced on 20th August 2011.

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44. Seminoff, J.A. (Southwest Fisheries Science Center, U.S.) (2004). Chelonia mydas.

In: IUCN 2012. IUCN Red List of Threatened Species. Available at www.iucnredlist.org. Referenced on 8th September 2012.

45. STCB (2011). Sea Turtle Conservation Bonaire: Research and Monitoring Report 2011. Kralendijk, Bonaire, Netherlands Antilles.

46. The Royal Society (2010). Climate change: a summary of the science.

47. Wetterer, J.K., Wood, L.D., Johnson, C., Krahe, H & Fitchell, S. (2009). Predaceaous ants, beach replenishment and nest placement by sea turtles. Environmental Entomology, 36: 1084-1091.

48. WIDECAST (2008). Wider Caribbean Sea Turtle Conservation Network. Available at www.widecast.org, Referenced on 8th September 2012.

49. Witt, M.J., Hawkes, L.A., Godfrey, M.H., Godley, B.J. & Broderick, A.C. (2009).

Protecting the impacts of climate change on a globally distributed species:the case of the loggerhead turtle. The Journal of Experimental Biology, 213: 901-911.

50. WWF (2008). The Impact of Climate Change on Hawksbill Turtles. WWF Climate Change Programme.

51. Yntema, C.L.& Mrosovsky, N. (1980). Sexual distribution in hatchling loggerheads (Caretta caretta) incubated at different controlled temperatures. Herpetologica, 36:

33-36.

Appendices

Appendix i.

Beach Profiles taken at every 50m along “No Name” beach. These include the slope of the profile in Microsoft Excel, photographs of the profile and how each profile will be affected by different leveld of Sea Level Rise.

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0.2m 0.4m 0.8m 1.2m SLR

SLR 0.2m 0.4m 0.8m 1.6m

0.4m

0.2m 0.8m

SLR 1.6m

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SLR 0.2m 0.4m 0.8m

SLR

SLR

0.2m 0.4m 0.8m

0.8m 0.4m

0.2m

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SLR

SLR

SLR

0.2m 0.4m 0.8m

0.2m 0.4m 0.8m

0.2m 0.4m

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SLR

SLR

SLR

0.2m

0.2m

0.4m 0.8m

0.4m

0.2m 0.8m

0.4m

0.8m

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SLR

SLR

SLR

0.2m 0.2m 0.4m

0.4m 0.8m

0.2m 0.4m 0.8m

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SLR SLR

SLR

0.2m 0.4m 0.8m

0.2m 0.4m 0.8m 1.2m

0.2m 0.4m 0.8m

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SLR

SLR

SLR 0.2m 0.4m 0.8m 1.2m 0.8m 0.4m 0.2m

1.6m 0.8m 0.2m

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SLR

SLR

SLR

SLR 0.2m

0.8m 0.4m

0.8m 0.4m 0.2m

0.4m 0.8m 0.2m

0.8m 0.4m 0.2m

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SLR

SLR

SLR

1.2m 0.8m

0.2m 0.4m 0.8m 0.4m 0.2m

0.4m 0.2m 0.8m

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SLR

SLR

SLR SLR

0.2m 0.4m 0.6m

0.2m 0.4m 0.8m

0.2m 0.4m 0.8m 1.6m

0.2m 0.4m 0.8m 1.2m

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SLR

SLR

SLR 0.2m 0.4m 0.6m 0.2m 0.4m 0.6m

0.2m 0.4m

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Appendix ii

Images taken from ArcMap indicting various levels of sea level rise in relation the location of nests along “No Name” beach.

SLR

SLR

SLR

0.2m 0.4m

0.2m 0.4m 0.2m

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Figure 2: the nest location in relation to the transect location on “No Name” beach.

Projections

Figure 3: The orange line represents the HTM, the yellow dotted line is the elevation of 0.2m, which will be lost with 0.2m of sea-level rise.

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Figure 4: Pink line shows a 0.4m elevation above HTM, this area of beach will be lost with 0.4cm rise in sea-level.

Figure 5: The 0.4m elevation contour shows how much beach will be lost with 0.4m sea-level rise and which nests would be at risk (using 2012 nest data).

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Figure 6: Lime green dashed line represents a 0.6m elevation contour above the HTM.

Figure 7: The 0.6m elevation contour shows how much beach will be lost with 0.6m Sea-level rise and which nests would be at risk using 2012 nest data.

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Figure 8: The blue dashed line represents an elevation of 0.8m above the HTM

Figure 9: The 0.8m elevation contour shows how much beach will be lost with 0.8m Sea-level rise and which nests would be at risk using 2012 nest data.

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Figure 10: The purple line represents 1m elevation above the HTM.

Figure 11: The 1m elevation contour shows how much beach will be lost with 1m sea-level rise and which nests would be at risk using 2012 nest data.

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Figure 12: The Red dashed line represents a contour 1.2m above the HTM.

Figure 13: The 1.2m elevation contour shows how much beach will be lost with 1.2m sea-level rise and which nests would be at risk using 2012 nest data.

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Figure 14: The contour (pink dashed line) represents an elevation of 1.4m above the HTM.

Figure 15: The 1.4m elevation contour shows how much beach will be lost with 1.4m sea-level rise and which nests would be at risk using 2012 nest data.

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Figure 16: The white/yellow dashed line represents a contour of 1.6m above HTM (the maximum expected SLR by 2100).

Figure 17: The 1.6m elevation contour shows how much beach will be lost with 1.6m Sea-level rise (SLR) and which nests would be at risk using 2012 nest data. 1.6m SLR is the maximum projected SLR for the Caribbean.

Appendix iii

A table to show the number of nests (confirmed and unfirmed) from each species that are impacted by different levels of se level rise. Paired T-tests were used to identify whether the

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mean of the distance between the nest and the HTM is significantly different between the 3 species.

SLR (m)

Ei Cc Cm ?

Confirmed Unconfirmed Confirmed Unconfirmed Confirmed Confirmed Unconfirmed

0.2 1 3

0.4 3 1

0.6 2 1 2 1

0.8 6 3 7 1 1

1 1 2 5 1

1.2 4 1

1.4 5 1 1 1

1.6 1 1

1.6+ 1

Paired Samples Statistics

Mean N

Std.

Deviation

Std. Error Mean

Pair 1 Ei 8.6336 22 3.70003 .78885

Cc 6.0114 22 2.26031 .48190

Pair 2 Ei 12.5333 3 4.31895 2.49355

Cm 14.0000 3 5.04777 2.91433

Pair 3 Cc 6.0333 3 1.05040 .60645

Cm 14.0000 3 5.04777 2.91433

Paired Samples Correlations

N Correlation Sig.

Pair 1 Ei & Cc 22 .076 .736

Pair 2 Ei & Cm 3 .754 .456

Pair 3 Cc & Cm 3 -.126 .919

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Extra-Curricular activities.

During my time in Bonaire I did my PADI open water dive certification and completed a few more dives after that including a clean up dive and night dive. With STCB I also carried out a variety of other jobs that were not to do with my own research, these included in-water snorkel surveys, maintenance of the sea grass beds, beach cleans, rescues, data entry, communicating with the public and Beach Keepers via talks, email and social media. I also helped out with hatchling releases and presentations that were in the evening, encouraging many people to come to these events. I carried out all the tasks of an intern including many admin roles and general tasks that were set such as making Beach Keeper identification badges and selling merchandise, as well as doing my own research.

In my free time I also visited the National Park, Donkey Sanctuary and took Salsa lessons. I also liked to snorkel in my own time, which was very peaceful and I saw so many wonderful species on the reefs. I liked to cycle to many places on the island, visiting the key sites and beaches. I also wrote a blog about my time in Bonaire,

Paired Samples Test

Paired Differences

t df

Sig. (2- tailed) Mean

Std.

Deviation

Std. Error Mean

95% Confidence Interval of the Difference Lower Upper

Pair 1 Ei - Cc 2.62227 4.18622 .89250 .76621 4.47834 2.938 21 .008 Pair 2 Ei - Cm -1.46667 3.35460 1.93678 -9.79995 6.86662 -.757 2 .528 Pair 3 Cc - Cm -7.96667 5.28425 3.05087 -21.09348 5.16015 -2.611 2 .121

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which allowed me to communicate to the world and my friends at home, what I had been doing in Bonaire. I am also going to write a few more blogs on Bonaire to tell of my overall experience.

Overall, I had such a wonderful time in Bonaire especially with the turtles and seeing conservation in action. I especially liked releasing trapped hatchlings that would not have made it without intervention, it was such a wonderful feeling to see them free.

The people were really friendly and supportive and I ended up making good contacts in STCB, CIEE, DCNA, STINAPA and in Dive Friends Bonaire. I always felt welcome and safe, and enjoyed everything I did in Bonaire.

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