1.1 Introduction

Since the late twentieth century, climate change has undeniably been the world’s most prominent environmental issue. When it first emerged, climate change was discussed exclusively by scientists. However, in recent years, the general public has become much more involved in the concept, with the subject also creating major political repercussions in several countries. The likely consequences of global climate change have reached an alarming state in view of environmental, physical, and socio-economic aspects and pose a critical threat on a global scale. Increased public involvement in climate change discourse, ensuring subsequent awareness of the potential threats and uncertainties associated with the issue, is crucial.

The term ‘climate change’ is used with different implications and perspectives. In its broadest sense, climate change refers to any significant change in the statistical properties of the climate system that persists for an extended period, typically 30 years (IPCC 2014). In order to understand climate change, one has to have an understanding of all of the system’s components (i.e. atmosphere, ocean, land surface processes, cryosphere, and biosphere), climate variables (temperature and precipitation), and climate descriptors (such as the Earth’s surface temperature, ocean temperatures, and snow cover) (IPCC 2001; Weber 2010). This global phenomenon has been created from a combination of natural (such as changes in the sun’s radiation and volcanoes) and anthropogenic (such as burning fossil fuels and inappropriate land use changes) activities (Fröhlich and Lean 1998).

Palaeoclimatologists have been investigating how the climate system, including increasing atmospheric temperature trends, rising sea levels, and increasing atmospheric greenhouse gases, has changed on a global scale over many decades (Easterling et al. 2010). An overwhelming majority in the scientific community conclude that future human-induced climate change is inevitable and will have far-reaching environmental impacts that will affect the ways people live in many parts of the world. It is widely agreed that observed global warming is rooted in climate change. Global warming disturbs natural cycles and causes several irreversible changes over the long term. The main cause of the warming trend is the emission of greenhouse gases (GHGs) from human activity which enhances the ‘greenhouse effect’. The consequences of a continued enhancement of the natural greenhouse effect is likely to result in warming greater than what has been experienced on average over the past century. Warmer conditions will result in more evaporation and precipitation, but different regions will experience these changes at different scales; some will be wetter and others drier (Van Aalst 2006). Moreover, a stronger greenhouse effect increases sea levels, increases ocean heat content, and promotes the loss of ice mass in Greenland, Antarctica, and the Arctic and mountain glaciers worldwide; it generates more intense and longer droughts in many regions, relatively lower mountain glaciers and snow cover in both hemispheres, higher atmospheric water vapour, ocean acidification, and changes in the historical pattern of extreme weather events (Meinshausen et al. 2009; Nerem et al. 2018).

Since the industrial revolution, the average temperature of the Earth has increased; average global surface temperature rose by 0.9 °C between 1880 and 2015 (Rahmstorf et al. 2017). Much of this heat has been absorbed by the oceans, with the top 700 meters of ocean warming over 0.2 °C since 1969 (Levitus et al. 2017). This warming has been driven mainly by increases in all the major GHGs, particularly carbon dioxide (CO2) , methane (CH4) , and nitrous oxide (N2O) . Emissions of these GHGs continue to increase. For example, concentrations of atmospheric CO2 rose from approximately 290 ppm to 430 ppm between 1880 and 2014 (IPCC 2014). The IPCC (2014) report states that CO2 concentrations are likely to rise to around 450 ppm by 2030, and if they continue to increase and reach around 750 ppm to 1300 ppm, the Earth may experience global mean temperature rises of 3.7 °C to 7.8 °C (compared to the 1986–2005 average) by 2100 (Rahmstorf et al. 2017). Net greenhouse gas emissions from anthropogenic activities worldwide increased by 35% from 1990 to 2010. Burning of fossil fuels is still on the rise and is the primary cause of observed growth in GHGs, which accounts for 80% of the overall emissions. Greenhouse gas emissions from agriculture are in the range of 10–15% of the total emissions, and 5–10% of emissions are created from changes in land use patterns. Increased levels of GHGs cause radiative energy to rise and then increase the temperature on Earth’s surface. Higher GHG concentrations increase the amount of heat that the atmosphere absorbs and redirects back to the surface. It has been reported that the Earth currently retains approximately 816 terawatts of excess heat per year, which further increases the surface temperature (Henderson et al. 2015).

Scientific evidence of global warming is unambiguous, and many research organizations have built a comprehensive basis of evidence to understand how our climate is already changing (IPCC 2014). Each of the last three decades has been warmer than any previous decade. Changes have been observed since 1950 in many extreme weather and climate events (Gutowski et al. 2008). Greenland and Antarctica’s ice sheets have declined in volume and area. Data from NASA’s Gravity Recovery and Climate Experiment (NASA 2019) show that, between 1993 and 2016, an average of 286 billion tonnes of ice per year was lost by Greenland, while Antarctica has lost about 127 billion tonnes of ice per year over the same period. Over the past decade, the Antarctic ice mass loss rate has tripled (NASA 2019). Greenland lost 150 km3 to 250 km3 of ice annually between 2002 and 2006, while Antarctica lost about 152 km3 of ice between 2002 and 2005. Glaciers have retreated throughout the world, particularly in the Alps, the Himalayas, the Andes, the Rockies, and Alaska. Declining Arctic sea ice has also been observed over the past several decades (Church et al. 2013). Satellite images show that the extent of snow cover in spring in the northern hemisphere has fallen in the last five decades and that winter snow is now melting earlier than normal (Du Plessis 2018). Over the last century, global sea level rose about 20.3 cm, yet the rate over the past two decades is almost double that of the last century and is slightly accelerating each year (Nerem et al. 2018).

The acidity of ocean waters, particularly surface ocean waters, has increased by about 30% since the beginning of the industrial revolution. This is due to more CO2 being emitted into the atmosphere with concomitant increases in its absorption by the oceans. The amount of CO2 absorbed by the upper ocean layer has been increasing by approximately 2 billion tonnes per year (Sabine et al. 2004; Schmutter et al. 2017). The scientific community generally agrees that global warming needs to be limited to 2 °C above pre-industrial levels by the end of the twenty-first century in order to avoid potentially dangerous impacts. This requires concentrations of atmospheric CO2, estimated at around 430 ppm in 2016, to remain below 450 ppm. Therefore, keeping the Earth within the 2 °C limit requires urgent action. Climate change is a systemic transboundary problem with far-reaching health, security, and prosperity implications for the world. However, despite ongoing efforts to mitigate climate change, global emissions continue to rise. Appropriate approaches will require systematic global efforts to implement systemic changes, and many questions remain as to what form such an effort should take (First 2018).

Many scientists are concerned that the impacts of global warming have developed much more rapidly than expected. Hence the scientific community, the government bodies, and the media have paid considerable attention to climate change and related issues. Signatories to the UNFCCC, the Kyoto Protocol, and the Paris Agreement are discussing how best to tackle this problem, in particular by developing mitigation and adaptation strategies to prevent excessively negative impacts for future generations and to reduce the world’s vulnerability to these changes (Saxena et al. 2018; Schelling 2002).

The world is addressing climate change in two ways: mitigation and adaptation. Mitigation involves a reduction in greenhouse gas emissions to alleviate the acceleration of climate change, whereas adaptation involves learning how to live with existing climate change and protecting ourselves against unavoidable future climate change effects (IPCC 2014). The growing body of scientific evidence has led to a clear global consensus on the need for action. UNFCCC commits parties to address climate change by ‘preventing dangerous anthropogenic interference with the climate system’ by stabilizing GHG levels. Yet the implementation of strategies to mitigate or survive under turbulent climatic conditions requires a broad acceptance/awareness of climate change. A broadened perspective on adaptation and mitigation strategies could help all nations understand the adjustments or actions that can ultimately increase resilience or reduce vulnerability to expected climate and weather changes (IPCC 2014, 2018).

1.2 Impacts of Climate Change

1.2.1 Global Warming of 1.5 °C

In 2018, the IPCC published a special report on the impacts of exceeding 1.5 °C global warming. The report prescribed that limiting global warming to 1.5 °C would need rapid, far-reaching, and unprecedented changes in all aspects of society (First 2018). By limiting global warming to 1.5 °C compared to 2 °C, for example, the negative impacts of climate change would be significantly reduced. While previous estimates focused on estimating the damage where average temperatures were to rise by 2 °C or more (New et al. 2011), this report shows that there will still be many adverse effects of climate change at 1.5 °C. For example, by 2100, global sea-level rise would be 10 cm lower with global warming of 1.5 °C compared to 2 °C. With global warming of 1.5 °C, coral reefs would decline by 70–90%, while almost all would be lost with a 2 °C increase (Hoegh-Guldberg 2014). Global net human-induced CO2 emissions would have to fall by approximately 45% from 2010 levels by 2030, reaching ‘net zero’ by 2050, in order to limit global warming to 1.5 °C (First 2018).

1.2.2 Global Warming and Sea-Level Rise

Given the current concentrations and ongoing greenhouse gas emissions, the global mean temperature is likely to continue to rise above pre-industrial levels by the end of this century. This has resulted in extensive melting of ice sheets, both in the Arctic and Antarctic, resulting in rising sea levels regionally and globally. The Arctic Ocean is anticipated to become essentially devoid of summer ice before the middle of the twenty-first century as a result of the warming. Rates of sea-level rise have accelerated since 1870 and now average around 3.5 mm per year (Chen et al. 2017). The average sea-level rise is projected to be 24–30 cm by 2065 and 40–63 cm by 2100 under various scenarios compared to the reference period of 1986–2005 (Allen et al. 2014; Pachauri et al. 2014).

Accelerated sea-level rise will result in higher inundation levels, rising water tables, higher and more extreme flood frequency and levels, greater erosion, increased salt water intrusion, and ecological changes in coastal flora and fauna. These will lead to significant socio-economic impacts, such as loss of coastal resources, infrastructure, and agricultural land and associated declines in economic, ecological, and cultural values (Church et al. 2013). An important issue concerning rising sea levels is that it could submerge parts of low-lying coastal lands which are the habitat of an estimated 470–760 million people (Dasgupta et al. 2007). A number of islands are already submerged, including 11 in Solomon Islands and several in Pohnpei (Federated States of Micronesia (Albert et al. 2016; Nunn et al. 2017). It is predicted that between 665,000 and 1.7 million people in the Pacific will be forced to migrate owing to rising sea levels by 2050, including from atoll islands in the Marshall Islands, Tuvalu, and Kiribati (Church et al. 2013). Very large proportions of the population of Bangladesh (46%) and the Netherlands (70%) are likely to be forced to relocate. By 2100, coastal properties worth $238 billion to $507 billion in the United States alone are likely to be below sea level, with particular risk of inundation and flooding in major cities including Miami, Florida, and Norfolk, Virginia (United Nations 2017).

1.2.3 Changing Weather Patterns and Extreme Events

Climate change will also lead to more frequent and/or severe extreme weather events (Trenberth et al. 2007) and possibly even large-scale, abrupt climate change (Alley et al. 2003). Extreme weather events occur when an individual climate variable (such as temperature or rainfall) exceeds a specific threshold and forces significant divergence from mean climate conditions. The world has already witnessed direct and indirect impacts of climate forcing on extreme events such as storms, hurricanes, tornadoes, severe thunderstorms, floods, and hail, and this trend is expected to continue (Walsh et al. 2016).

Climate change is an urgent threat to the entire human population, contributing to a range of increases in natural disasters. Global rainfall patterns are shifting with rising temperatures. Since the late 1990s, Somalia, Kenya, and other East African countries have experienced lower than average rainfall, contributing to a 30% drop in crop yields and famines in 2010, 2011, and 2016 (Henderson et al. 2015). Hurricanes and other destructive weather events have also increased in prevalence. For instance, the worst typhoons (tropical cyclones) recorded in the Philippines occurred in 2013, resulting in more than 6000 deaths and a displacement of almost four million people (Acosta et al. 2016). Since the early 1980s, the intensity, frequency, and duration of North Atlantic hurricanes and the frequency of the most severe hurricanes have increased (Kossin et al. 2013). Hurricane-related storm intensity and rainfall rates are projected to rise as the climate keeps warming. Storm surges, flooding, and coastal erosion threaten coastal settlements and associated infrastructure, transportation, water, and sanitation (IPCC 2007).

1.2.4 Pressure on Water and Food

Food production is closely related to water availability. In 2014, 16% of the Earth’s croplands were irrigated as opposed to rain-fed farming, yet the irrigated land accounted for 36% of global harvest (Pimentel 2012). It is estimated that by 2020, approximately 75–250 million people could be affected by increased water stress in Africa, while rain-fed agriculture-related yields could decrease by up to 50% in some regions (Moriondo et al. 2006). In Pakistan and India, the warming Earth combined with water shortages has been blamed for threatening the viability of the region’s agriculture (Henderson et al. 2015). Without significant GHG emission reductions, the proportion of the world’s land surface in extreme drought could rise by 2090 to 30%, compared to the current 1–3%.

Warmer temperatures , increased CO2 levels, and extreme weather events also affect global food production. Agriculture and fisheries depend on specific climatic configurations. Increased CO2 or warmer weather has the potential to accelerate crop growth or increase yields in some crops; however, crop yield starts to decrease above an optimal temperature that varies from crop to crop (Pimentel 2012). On the other hand, some plant species can respond favourably to increased atmospheric CO2 and grow more vigorously and more efficiently using less water (Bowes 1993). Higher temperatures and changing climate trends can affect the composition of natural plant cover and change the areas where crops grow best (Rahmstorf et al. 2017). Warmer weather facilitates for the spread of pests, weeds, and parasites, while extreme weather has the potential to harm farmlands, crops, and livestock. Climate change could have a direct and indirect impact on livestock production (Thornton 2010). The warmer climate, particularly heatwaves, has a negative impact on livestock. Drought will impact pasture and feed supplies, posing a risk to livestock retention, while increased prevalence of pests and diseases will affect livestock negatively. Temperature changes could affect fisheries by changing the natural habitat and migration ranges of many aquatic creatures (Brierley and Kingsford 2009).

1.2.5 Human Health Risks

Higher temperatures increase the possibility of injury and death related to heat. In the 2003 European heatwave, as many as 70,000 people died, and in 2010, more than 50,000 died in a heatwave in Russia (Parry 2011). Thousands more have been affected by severe heatwaves in India in 2015, in Europe in 2006, and in other regions around the world (Parry 2011). Water and vector-borne diseases are also projected to increase in a warmer world as insects and other carriers move into higher latitudes and altitudes (Benitez 2009; Conn 2014). Mosquito-breeding regions will also change, leading to potentially greater threats from mosquito-borne diseases (Khormi and Kumar 2014, 2016). A warmer climate also tends to increase lung-related health risk, while fossil fuel burning can lead to premature deaths. The World Health Organization found that, in 2012, seven million people died from air pollution worldwide (Lee and Dong 2012).

1.2.6 Impact on Wildlife and Ecosystems

Climate change also harms many natural habitats and increases many species’ risk of extinction (IPCC 2014; Van Aalst 2006). The current extinction rate is 100 times the normal rate, and some scientists predict that the Earth is heading for the sixth mass extinction event in its history (Barnosky et al. 2011). By 2100, 30–50% of the world’s terrestrial and marine species may be extinct. Climate change also has significant ocean-related effects (IPCC 2014). Oceans absorb about 25% of CO2 emitted from the atmosphere, leading to the acidification of seawater. Over the past 100 years, warming has raised near-surface ocean temperatures by about 0.74 °C and has made the sea considerably more acidic, likely affecting marine animal reproduction and survival. As a result of various factors, coral coverage is only half of what it was in the 1960s in some places, and scientists predict that the world’s coral reefs could become completely extinct by 2050 (Henderson et al. 2015). Projected future increases in sea surface temperatures of around 1–3 °C are very likely to result in more frequent coral bleaching events and widespread coral mortality if corals are unable to acclimatize or adapt (First 2018).

Ecosystems will continue to change with climate, with some species moving further poleward or becoming more successful at adapting to changes, while some species may be unable to adapt and could become extinct (Parmesan 2006). Changes in temperature and rainfall and extreme events may affect the timing of reproduction in animals and plants, animal migration, length of cropping season, distribution of species and population sizes, and availability of food species. Increased acidification and catastrophic flooding could reduce marine biodiversity and mangrove wealth (Hoegh-Guldberg 2014; Pearson et al. 2019; Schmutter et al. 2017).

1.3 The Pacific Ocean: Location, Size, and Distribution

The Pacific Ocean is the world’s largest ocean, with an areal extent of 165 million km2 and average depth of 4000 m, covering more than 30% of the Earth and bordering 50 countries or territories’ coastlines (NOAA 2018). The equator divides the Pacific Ocean into the North Pacific Ocean and the South Pacific Ocean. The South Pacific Ocean is generally taken to be located between 0° and 60°S latitude and 130°E and 120°W longitude. The Pacific Ocean plays host to a wide range of habitats, such as coral reefs, mangroves, seagrass, and seamounts, and accounts for much of the world’s marine biodiversity (Cheung et al. 2010) while also playing a key role in regulating global climate and biogeochemical cycles (Cheung and Sumaila 2013).

The islands in this region cover nearly 528,090 km2 of land (0.39%) spread throughout the ocean, with a combined exclusive economic zone (EEZ) of approximately 30 million km2 (Carlos et al. 2008) and a total coastline of 135,663 km. Islands are distributed unevenly across the Pacific basin, most being located in the western, especially in the south and western tropical regions, and the fewest in the northeastern quadrant (Fig. 1.1) (Nunn et al. 2016b). The islands belong to a mixture of independent states, semi-independent states, parts of non-Pacific Island countries, and dependent states. The massive realm of islands of the tropical Pacific Ocean includes approximately 30,000 islands of various sizes and topography. In general, the size of the islands in the Pacific decreases from west to east. New Guinea, the largest island, accounts for 83% of the total land area, while Nauru, Tuvalu, and Tokelau have an area less than 30 km2. Most Pacific Island nations are comparatively small with total areas less than 1000 km2.

Fig. 1.1
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The Pacific region with distribution of the main countries and territories

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The ocean and its resources play a significant role in the livelihoods of the people of the Pacific Islands. Oceania’s terrestrial diversity and endemism per unit area are among the highest on the planet (Keppel et al. 2012; Kier et al. 2009). The region encompasses three global biodiversity hotspots with more than 30,000 plants and 3000 vertebrate species.

Pacific Island countries have been traditionally grouped along the lines of ethno-geographic and cultural lines as Melanesia, Micronesia, and Polynesia. This grouping excludes the adjoining continent of Australia, the Asian-linked Indonesian, Philippine, and Japanese archipelagos as well as those comprising the Ryukyu, Bonin, Volcano, and Kuril arcs which project seaward from Japan.

Melanesia is a subregion of Oceania located in the southwestern region of the Pacific basin, north of Australia, and bordering Indonesia to its east. The region includes the four independent countries of Fiji, Vanuatu, Solomon Islands, and Papua New Guinea and New Caledonia which is a French overseas territory. The dominant feature of Melanesia is relatively large high islands; it includes 98% of the total land area of the Pacific Islands and approximately 82% of the total population. Papua New Guinea is the largest among Melanesian countries as well as the largest country in the Pacific realm with total land area of 67,754 km2 followed by Solomon Islands (29,675 km2), New Caledonia (21,613 km2), Fiji (20,857 km2), and Vanuatu (13,526 km2).

Micronesia consists of some 2500 islands spanning more than seven million square kilometres of the Pacific Ocean north of the equator. Micronesia comprises only 0.3% of the total land area of the Pacific Islands and about 5% of the Pacific population. It includes Kiribati, Guam, Nauru, Marshall Islands, Northern Mariana Islands, Palau, and the Federated States of Micronesia (FSM). Kiribati is the largest country in Micronesia with an area of 995 km2, followed by the Federated States of Micronesia (799 km2), Guam (588 km2), Northern Mariana Islands (537 km2), Palau (495 km2), Marshall Islands (286 km2), and Nauru, the smallest single island country of Micronesia with 23 km2.

Polynesia is the largest region of the Pacific, made up of around 1000 islands scattered over 8000 km2 in the Pacific Ocean. It is defined as the islands enclosed within a huge triangle connecting Hawaii to the north, New Zealand to the southwest, and Easter Island to the east. It encompasses more than a dozen of the main island groups of central and southern Pacific groups with large distances between them. Polynesia includes Tuvalu, Tokelau, Wallis and Futuna, Samoa (formerly Western Samoa), American Samoa, Tonga, Niue, the Cook Islands, French Polynesia, Easter Islands, and Pitcairn Islands. Polynesia comprises only about 1% of the total Pacific land area but more than 13% of the total population, excluding Hawaii. French Polynesia is the largest country with 3939 km2 followed by Samoa (3046 km2), Tonga (847 km2), Cook Islands (297 km2), Niue (298 km2), American Samoa (222 km2), Easter Island (164 km2), Tuvalu (44 km2), Pitcairn Island (54 km2), and Tokelau with 16 km2 area.

In terms of geological origin, the islands can be divided into reef islands, volcanic islands, limestone islands, and islands of mixed geological type. The reef islands are generally composed of unconsolidated sediments and commonly form linear groups where a reef has grown above a line of submerged volcanic islands. Examples include most islands in Kiribati, Marshall Islands and Tuvalu, and reef-island groups in the Federated States of Micronesia, French Polynesia, and the western islands of the Hawaii group. They are commonly characterized by their tendency to develop on wide reef surfaces in lower latitudes of the Pacific Ocean (Nunn et al. 2016a).

Volcanic islands are formed when volcanoes erupt (Nunn 1994) and produce islands often with high altitudes in the centre and extremely rugged inner cores. The high island terrain of volcanic islands is characterized by often abrupt changes in elevation (mountains, sheer cliffs, steep ridges, and valleys), with these characteristics varying in altitude and size depending on the island’s age (Keener 2013). High islands receive more rainfall than the surrounding ocean from orographic precipitation. This occurs because of the height of the interior of the island, with the warm ocean air being forced up to the higher altitudes, cooling down and falling as rain. The high island landscape is favourable to the formation and persistence of freshwater streams and soil development capable of supporting large and diverse populations of plants and animals (Keener 2013).

The mixed geology-type islands are formed in various ways, principally as a combination of volcanic and coral reef formation. This commonly occurs when the volcanic island forms a high island and a coral reef forms a doughnut-shaped island around it above the water, serving as a barrier from erosion (these are the makatea island types described by Nunn (1994)). Table 1.1 gives some pertinent details, such as population, land area, political status, colonial connections, and dominant lithology of the main Pacific Island countries.

Table 1.1 Some key characteristics of the main Pacific Island countries
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Sea-level rise will directly impact people living in coastal areas of Pacific Island countries. Population distribution is increasingly skewed and concentrated along or near coasts. This is a worldwide phenomenon that is much more pronounced in the Pacific. Kumar et al. (see Chap. 12) analysed the distribution of populations for 12 countries (Cook Islands, Kiribati, Marshall Islands, Nauru, Niue, Palau, Samoa, Solomon Islands, Tonga, Tuvalu, and Vanuatu) in the Pacific and found that around 55% of the population in these countries live within 500 m of the coast, with 20% residing within 100 m. For some of Pacific Island countries, almost the entire population resides in very close proximity to the shoreline. For example, in Kiribati, Marshall Islands, and Tuvalu, the percentage of people living within 500 m of the coast are 98%, 98%, and 99%, respectively.

1.4 Emissions by Pacific Island Countries

Greenhouse gas emissions are spread very unevenly across the world, with the top ten countries generating more than 73.01% of total GHG emissions, and three countries, China (26.83%), the United States (14.36%), and European Union (9.66%), are by far the largest contributors (IPCC 2014). The world’s poorest countries have made the least per capita contribution to carbon emissions in the world. These countries burn trivial amounts of fossil fuel compared to countries like China, the United States, Russia, and Australia, and yet they have to bear the greatest impact of climate change (Padilla and Serrano 2006).

The Pacific Island region accounts for only 0.03% of the world’s total greenhouse gas emissions but is one of the regions that is facing the greatest impacts of climate change from rising sea levels, warming oceans, drought, coral ecosystem destruction, ocean acidification, and extreme weather (Rogers and Evans 2011). For example, CO2 emissions from Kiribati and Tuvalu are among the lowest of all nations, both in total and per capita terms, yet these are the two countries currently suffering the most from rising sea levels. From Table 1.2, large differences between emissions by the Pacific Island countries and some of the industrialized nations are evident. For comparison, it is more logical to look at CO2 emissions on a per capita basis. For most of the Pacific Island countries, the per capita emissions are below 2.0 t CO2 per year, yet for countries such as Australia and the United States, these figures are 16.75 and 15.85 t CO2 per year, respectively. Australia is one of the world’s highest polluters on a per capita basis.

Table 1.2 Total CO2 emissions per country per year and emissions per capita per year measured in 2017 for representative countries in the Pacific, together with selected larger emitters for comparison
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1.5 Projected Climate Change and Impacts

The IPCC report on the impact of global warming states that, if warming continues to increase at the current rate, it is likely to reach 1.5 °C between 2030 and 2052 (high confidence) and small islands are projected to experience higher risks as a consequence (IPCC 2018). In the Pacific, under the RCP4.5 scenario, sea level is likely to increase 0.5 to 0.6 m by 2100 compared to 1986 to 2005 (Church et al. 2013). The frequency of occurrence of tropical cyclones is likely to remain unchanged or decrease according to the IPCC AR5. On the other hand, the intensity of tropical cyclones is likely to increase with increasing temperatures and precipitation (Christensen et al. 2013; CSIRO 2015). An increase of even 32 cm sea-level rise is projected to have serious consequences for the continued sustainability of ecological and social systems on low coral atolls (Pearce 2000). Wave actions, storm surges, sea-level rise , and river flooding can damage the freshwater supply and in turn have adverse effects on various sectors such as agriculture, tourism, public health, and hydro-electricity production (Campbell and Barnett 2010).

Projected data for Suva, Fiji, show trends of temperature (Fig. 1.2) and rainfall (Fig. 1.3) over the next 80 years to 2100, with the GCMs used in the ensemble modelling shown in Table 1.3.

Fig. 1.2
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Observed (1979–2010) and projected (until 2100) temperature for Suva, Fiji, under an ensemble of 30 GCMs (Table 1.3). Data for the projections of temperature and rainfall was obtained from the Climate Data Factory website (The Climate Data Factory 2019 ) <https://theclimatedatafactory.com/> for the period of 1951 to 2100. Different numbers of Global Climate Models (GCMs) obtained from the official IPCC data portal (ESGF 2009) (ESGF <https://esgf.llnl.gov/>) were used to project climate data

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Fig. 1.3
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Observed (1979–2010) and projected (until 2100) rainfall for Suva, Fiji, under an ensemble of 31 GCMs (Table 1.3)

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Table 1.3 Models used for projection of rainfall and temperature data
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Figure 1.2 compares temperatures for two RCP scenarios and different time periods. Based on historical data, we can see that the temperature in the Pacific Island region increased slowly from 1951 to 1975, followed by a steady increase until 2010. Observed temperature (1979–2010) was also consistent with this trend. The mean historical temperature data derived from GCMs shows a warming of 0.58 °C within the period 1950 to 2010. In the period from 1979 to 2010, the observed average surface temperature increased by 0.14 °C. Observed data confirms that the average temperature of Suva, Fiji, rose by 0.05 °C per decade since 1979. The projected mean surface temperature change for 2050 relative to 2010 under RCP4.5 is 0.7 °C, while it is 0.84 °C under RCP8.5. The temperature change for 2100 relative to 2010 is projected to be 1.19 °C and 2.9 °C for RCP4.5 and RCP8.5, respectively. Temperature increase for the projected period becomes quite prominent under both RCP4.5 and RCP8.5 towards the end of the century. The difference in terms of temperature values between the RCPs will begin to expand after 2025 (Fig. 1.2).

Suva is already experiencing an increased temperature regime that is evident from the observed temperature which is 0.12 °C (median value) higher than the historical period (1951–2010) (Fig. 1.4). By the end of the twenty-first century, under the business-as-usual scenario (no mitigation, RCP8.5), the temperature will increase by 2.59 °C. Even if the mitigation strategies are implemented successfully (RCP4.5), a 1.33 °C increase in temperature will take place compared to the median value of the observed period. Not only does the temperature increase, but also the inter-annual variance increases in the latter half of the century under both the RCPs (see the confidence intervals on the right of Fig. 1.2). This implies that many hot spells will dominate in the future and, in extreme cases, the annual mean temperature can go even higher than 28 °C, while it was below 24.5 °C during the observed period. However, if mitigation policies are properly implemented as assumed by the RCP4.5 scenario, the temperature is likely to stabilize after 2071, with a median value of 25.6 °C.

Fig. 1.4
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Observed time series of annual total number of warm days (red) and cool nights (blue) for Suva, Fiji, indicating a general warming trend. Grey bands around the linear regression line show one standard error of the estimate (Data: Fiji Meteorological Service)

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Suva receives an annual rainfall of around 2800 mm (median = 2846 mm for 1979–2010 period), and the projections show that rainfall will generally remain similar by 2100 under both selected RCPs (Fig. 1.3). The difference between the radiative forcing of RCP8.5 and RCP4.5 (IPCC 2014) will cause only about 10 mm difference in median values of rainfall during 2021–2050 and 2071–2100 for Suva. In the projected period, the average rainfall under RCP8.5 will be slightly higher than that for RCP4.5; rainfall anomalies (inter-annual variability) will also be considerably higher. This may result in more pronounced wetter and drier seasons in the future, which will have implications for flooding and drought.

Over recent decades, the El Niño-Southern Oscillation (ENSO) characteristics have changed quite sharply, even in the absence of obvious external forcing (Cobb et al. 2003). Therefore, it is also appropriate to expect similar abrupt changes in climate variability of the tropical Pacific region in the future, with or without a trigger from ongoing greenhouse forcing (Kleypas et al. 2015). However, under the RCP8.5 scenario, the equatorial Pacific is likely to experience an increase in mean annual precipitation by 2100 (IPCC 2018). The South Pacific is projected to experience changes in precipitation, relative to 1961–1990, ranging from −3.9% to 3.4% by 2020, −8.23% to 6.7% by 2050, and −14% to 14.6% by 2080 (Barnett 2011).

The changing climate will have impacts across the landscape that will be variable. For example, the rising sea levels and changes in currents will result in significant wave height changes that will affect different regions differently (Fig. 1.5). Mean significant wave height (Hs) data obtained from the South Pacific Applied Geoscience Commission (SOPAC) was modelled using two concentration pathways, RCP 4.5 and RCP 8.5, under the Coupled Model Intercomparison Project Phase 5 (CMIP5) model (http://wacop.gsd.spc.int/) (WACOP 2016). The GCMs used were CNRM-CM5, HadGEM2-ES, INMCM4, and ACCESS1.0. An average value was obtained for 2081–2100 by using the above models, and the difference between the projected and the historical scenario (1986–2005) was derived for projected changes in Hs. From Fig. 1.5, it can be observed that there is likely to be considerable variability in changes in Hs across the Pacific, with Hs differences of up to 0.4 m seen by 2081–2100. The highest increase in Hs will be experienced in the north-west Pacific around Palau and Northern Mariana Islands as well as in the south around Tonga and Niue. Several regions in the Central Pacific are projected to experience no changes in Hs. This projected data for Hs shows that the impacts of climate change will be highly variable across the Pacific region, with some areas being impacted considerably more than others.

Fig. 1.5
figure 5

Projected differences in Hs values under RCP4.5 (a) and RCP8.5 (b) for 2081–2100 compared to historical scenario of 1986–2005 under CMIP5 and an ensemble of GCMs (CNRM-CM5, HadGEM2-ES, INMCM4, and ACCESS1.0). Maximum Hs values were calculated from modelled monthly data supplied by SOPAC (http://wacop.gsd.spc.int/)

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Anthropogenic CO2 has caused a decrease of 0.06 pH units in the tropical Pacific since the beginning of the industrial era (Howes et al. 2018). Currently, the pH of the tropical Pacific Ocean is decreasing at a rate of 0.02 units per decade, and it is projected to decrease by 0.15 units relative to 1986–2005 by 2050 (Hoegh-Guldberg et al. 2014). In addition, the CMIP5 ensemble model projects a further decrease of 0.23–0.28 pH units relative to 1986 to 2005 by 2100 (Howes et al. 2018). This declining seawater pH level corresponds to a decrease in concentration of dissolved carbonate ions (CO32−) which may lead to a ‘saturation state’, lowering the potential of CaCO3 precipitation. According to IPCC AR5, under the RCP8.5 scenario, the aragonite saturation states in the subtropical gyre region will continuously decrease to around 800 ppm by 2100, which will intensify the calcification process with detrimental effects for many shallow-water organisms (Hoegh-Guldberg 2014). This phenomenon is anticipated to affect the biological and physical complexity of corals; coral cover is projected to decline from the current maximum of 40% to 15 to 30% by 2035 and 10% to 20% by 2050, primarily due to the acidification of the ocean and increasing sea surface temperature (Bruno and Selig 2007; Hoegh-Guldberg 2014). This will also negatively affect the ability of corals to compete with microalgae for space; hence, microalgae are likely to smother a significant proportion of corals by 2035. This pressure on coral reefs will also affect the reproduction of coral reef fish species, numbers of which are projected to decrease 20% by 2050 (Bell et al. 2013).

Climate change will have detrimental impacts on human health directly and indirectly in almost all the regions of the world. Pacific Island countries are particularly vulnerable to health impacts from changing climate due to their unique geologic, social, and economic characteristics (Hanna and McIver 2014; Woodward et al. 2000). Comparatively small size and isolation, their tropical locations, often stagnant economies, and limited health infrastructure are some of the reasons. The direct impacts include damages to health infrastructure, deaths, and traumatic injuries occurring during extreme hydro-meteorological events and physiological effects from heatwaves. For example, in 2015, Cyclone Pam caused severe damages to the health-care system of Vanuatu, destroying 21 of 24 health facilities (hospitals, health centres, and dispensaries) across 22 affected islands in the most affected province (Esler 2015). Indirect impacts occur from the disruption of existing ecosystems, including increased geographic ranges of vectors and increased pathogen loads in food and water (McIver et al. 2012). For example, with the prevailing severe water shortage issue, the changing climate is likely to worsen the diarrheal disease in many Pacific Island countries (Singh et al. 2001). A strong positive correlation was identified between the extreme weather events and outbreaks of dengue fever and diarrhoeal disease in Fiji (McIver et al. 2012). Another foodborne disease of concern is ciguatera, a toxidrome believed to be caused by a toxic dinoflagellate-contaminated reef fish (WHO 2015). Increased incidents of ciguatera in the Pacific Island countries have been reported over the past two decades (Skinner et al. 2011). The ciguatera incidence was linked with marine surface temperatures and ENSO cycles (Llewellyn 2010; Skinner et al. 2011). In addition, the sensitive zones of vectors transmitting pathogens may expand with increases in temperature and alterations in precipitation and humidity (Hanna and McIver 2014).

The biodiversity of Pacific Island regions is also facing pressure from global climate change. Three of 35 global biodiversity hotspots are located in the Pacific Island region, enriched with large numbers of endemic species. The limited amount of suitable habitat and limited capacity for rapid adaptation of small islands make the consequences of accelerating climate change likely to be severe for the region’s biodiversity (Taylor and Kumar 2016). Sea-level rise poses a major threat to the restricted species ranges on smaller and atoll islands. In addition, high-elevation ecosystems such as cloud montane forests are projected to disappear by the end of this century (Taylor and Kumar 2016). In an assessment of 23 countries in the Pacific, Kumar and Tehrany (2017) showed that 674 of the islands hosted at least 1 terrestrial vertebrate species that was either vulnerable, endangered, or critically endangered. A total of 84 terrestrial vertebrate species are endemic to this region, and many of them occupy one island only, increasing their chances of extinction.

Climate change is one of the major threats to the culture and traditions of indigenous communities of Pacific Island countries (Keener 2013). A community’s response to every dimension of climate change including understanding the causes and responses is mediated by culture (Adger 2006). Nowhere has culture already been threatened by climate change than in the small island states of the Pacific Island region, a trend likely to continue for some time (Ede 2003; Funk 2009; Hunter 2002; Patel 2006). Indigenous people of such islands whose culture is intricately connected to their ancestral lands will experience significant cultural disruption (Farbotko and McGregor 2010). For example, in Samoan culture, the place where families and forebears lived plays an important role in their culture and personal identity; yet increasing numbers of islanders are moving inland or to other countries in search of a more secure future, while some are determined to hold their ground (Piggott-McKellar et al. 2019). In this context, relocations and resettlements have been significantly affecting the state of Samoan culture in terms of loss of heritage and sense of being cut off from the ancestral communities left behind. For instance, the personal connection to the sea has subsequently been lost by those who moved inland or offshore where fishing is no longer their primary source of food (Wing 2017). Such impacts on culture and traditions will be more likely in the future with the accelerating pace of climate change.

1.6 Economic Impacts in the Pacific

Island economies face significant costs due to climate change. According to a recent study by the Asian Development Bank (2013), it is estimated that under the ‘business-as-usual scenario’, climate change could cost 2.2 to 3.5% of the annual GDP of Pacific Island countries by 2050 and 12.7% by 2100. The agriculture sector was identified as one of the most vulnerable sectors, contributing 5.4% of annual GDP loss by 2100 under the high emission scenario. Agriculture is likely to be affected in various ways, including loss of arable land and contamination of freshwater. For example, in Fiji in 2003, Cyclone Ami caused damage to crops to the value of US$ 35 million (McKenzie et al. 2005), while severe flooding occurred in the Wainbuka and Rewa Rivers in 2004, destroying 50–70% of crops (Connell and Lowitt 2019). The World Bank estimates that climate change may cost Tarawa atoll in Kiribati USD 8–16 million, equivalent to 17–34% of current GDP, by 2050 (World Bank 2017).

Regardless of their size and population, the major socio-economic reality regarding small island countries of the Pacific is that their cost of adapting to climate change is significantly higher in terms of GDP than for larger countries, a phenomenon referred to as ‘indivisibility’ in economics. For example, for the construction of a similar coastal protection structure, the unit cost per capita in small island countries is substantially higher than for bigger countries with larger populations. In addition, compared to larger or continental territories, the relative impact of a coastal hazard or extreme event has a disproportionate impact on small island countries’ GDP compared to continental or larger territories where it only affects a small portion of its total land mass (Pachauri et al. 2014). According to the World Bank Climate Vulnerability Assessment Report of Fiji (World Bank 2017), the country’s economic growth has been relatively slow in the last couple of decades because of the impacts of climate change. Fiji is particularly vulnerable to floods and tropical cyclones which have already made a significant impact on the economy. Tropical Cyclone Winston in 2016, with the strongest winds ever recorded in the southern hemisphere, caused damages costing F$2 billion (USD 0.95 billion), equivalent to 20% of Fiji’s GDP. During this event, the average losses of assets due to the tropical cyclones and floods alone are estimated at more than F$500 million (USD 230 million).

Tourism is one of the fastest growing sectors in the world. The tourism sector is a common industry in almost all Pacific Island countries and a major source of employment and foreign exchange, contributing an average 20% of GDP and 15% of total jobs (ESCAP 2010). It is also considered as crucial to poverty alleviation and a pathway for achieving economic security coupled with broader development goals around employment and infrastructure (Everett et al. 2018). Climate change has a profound and negative impact on tourism by reducing the value of attractiveness of the tourism destinations (Becken and Hay 2012). Sea-level rise and storm surges pose threats to coastal assets and infrastructure. Kumar and Taylor (2015) have shown that 57% of all infrastructure in 12 Pacific Island countries are within 500 m of the coast, with 20% being within 100 m. This exposes a very large proportion of national infrastructure in these island countries to coastal climate change impacts.

Oceans are intrinsically linked with the atmosphere as they absorb more than 90% of the surplus heat produced by global warming and about two-thirds of CO2 emitted through anthropogenic activities (Rhein et al. 2013). This affects both the ocean dynamics and ecosystems and consequently has a major impact on the resources they provide to the community (Pörtner et al. 2014). In the Pacific Island countries, fishing and aquaculture contribute substantially to economic development, government revenues, food security, and livelihoods. Climate change impacts on oceans are expected to have major effects on the distribution of fish habitats, the food webs, the fish stocks they support, and, as a consequence, the productivity of fisheries. For example, the combined impacts of increasing temperature, sea-level rise, and alteration of mixing the ocean layer thickness will affect the nutrient supply, lagoon flushing, and ocean acidity and will ultimately affect plankton productivity and survival of corals (FAO 2008; Lal 2004). Stormy weather and more intense cyclones can also make fishing trips unsafe and less productive. This will most likely affect the fish supply, deprive fishermen of income, and potentially threaten the economic security of some island communities (FAO 2008).

1.7 Migration and Displacement Due to Climate Change

Change in the climate system will significantly affect small islands, with severe impacts projected for local economies and livelihoods of people, resulting in human mobility and cross-border displacement and migration (Perch-Nielsen et al. 2008). In certain contexts, particularly in low-lying coastal areas, climate change can be a driving factor in human mobility. Significant migrations from rural atolls to coastal towns and cities or to larger islands have taken place over the past decades in the Pacific Island region (Campbell and Warrick 2014). This has a negative impact on resources in urban coastal areas, and climate change is expected to exacerbate these pressures. In this context, one adaptive strategy for climate change is international migration, especially for the island population who lose livelihood opportunities or whose land disappears or who have limited land. As opportunities and resources diminish, freedom and attraction of movement to other countries or larger islands increase. This, in turn, encourages international migration for those with sufficient resources to move abroad. Therefore, essentially, climate change and rural hardships may encourage people to seek economic opportunities in other countries. Many Pacific Island countries currently have large proportions of their population living abroad; Table 1.4 shows the percentage of population abroad and the main destinations for some Pacific Island countries. Fifty-six percent of the Pacific Islanders who live abroad are settled in New Zealand and Australia, with almost 20,000 more Pacific migrants in the former. North America is the second most popular destination region, with 25% of Pacific immigrants, with the United States having a much larger share than Canada. The special visa schemes for Pacific Islanders in the United States, New Zealand, and Australia provide opportunities for temporary and sometimes permanent migration for people living in climatically vulnerable areas (DESA 2015).

Table 1.4 Pacific Island countries and territories by share of the total population and major destinations domiciled abroad (2015)
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Pacific Islanders have been described as one of the world’s most mobile groups (Ash and Campbell 2016). Global estimates of migrants relocating as a result of rising sea levels vary. In particular, ‘disappearing’ or ‘sinking’ islands force islanders to relocate either within their country or beyond its borders. In fear of future climate change and natural disasters, countries such as Tuvalu, Kiribati, Fiji, Solomon Islands, Vanuatu, and Papua New Guinea have considered new plans for relocations. The move is less challenging when relocation takes place within existing customary land boundaries. However, if relocations occur outside of land boundaries, then the relevant government bodies need to be consulted in order to avoid any conflicts (Ash and Campbell 2016). Kiribati’s government has purchased land in Vanua Levu, Fiji, with speculation that ultimately this land will be used to relocate Kiribati to Fiji. However, the Government of Kiribati’s statements have tended to focus on the potential of the land for agriculture (Hermann and Kempf 2017). Forced displacement from climate change is highly disruptive to livelihoods, culture, and society unless proper and well-planned interventions support people to adapt to the challenges (Gharbaoui and Blocher 2016; Piggott-McKellar et al. 2019).

Some Pacific Island countries have agreements with Australia, New Zealand, and the United States which already host large groups of immigrants from these countries. Yet, many of those countries with the greatest migration pressures, including Tuvalu, Kiribati, and Nauru, have the fewest available international destinations (Doherty and Roy 2017). Relocation due to climate change has many economic, social, cultural, and psychological costs, although economic and social reasons may be the primary reasons for migration .

1.8 Adaptation, Adaptive Capacity, and Lack of Information and Information Communication Infrastructure

Improving the adaptive capacity of communities in the Pacific Islands is one way to reduce vulnerability. Adaptive capacity is conventionally assumed to be based on the extent to which people can access, understand, and use new knowledge to inform their decision-making processes. This is true in some sense – the pace and nature of current/future climate change is unprecedented – yet much of this knowledge was generated outside the Pacific Island region and is therefore perceived by many people within the region as ‘alien’, even reflecting a foreign preoccupation that applies to others not to ‘us’ (Nunn 2009). This is one of the reasons for the widespread and conspicuous failure of most external interventions for climate change adaptation in the Pacific Islands over the past 30–40 years (Piggott-McKellar et al. 2019). It is not that the adaptive capacity of people in the Pacific Island region is low; it is rather that the adaptation pathways they are being offered are unfamiliar and underpinned by unfamiliar reasoning.

Yet to have survived on often quite remote islands in the Pacific for three millennia or more, it is clear that Pacific Island people must have evolved effective ways of coping with climate extremes, be these short-onset events or longer-term periods of changed climate (McNeill 1994; Nunn 2007). Evidence for the former abounds. In several Pacific Island societies, it has been demonstrated that there were methods for ensuring food security in the aftermath of tropical cyclones as well as ways of identifying their precursors (Johnston 2015; Lee and Dong 2012). It is also clear that Pacific Island people survived longer-term climate changes such as the AD 1300 event by changing livelihood strategies (Nunn 2007). In today’s globalized world, it is easy for people, especially those outside the Pacific region, to make assumptions about vulnerability and need in an era of rapidly changing climate and to overlook traditional coping strategies. Recently there have been many calls for the renewal and revitalization of such strategies, at least in combination with global knowledge, to help Pacific people cope with the future (Mercer et al. 2007; Nunn and Kumar 2018).

Another reason for adaptation failure that comes as a surprise to many outsiders is that the adaptive solutions being offered to Pacific Island people are invariably secular in nature. These are in conflict with the deeply held religious beliefs through which many decisions, especially around environmental governance, are filtered in Pacific Island communities (Nunn et al. 2016b). Unless adaptation pathways are developed that acknowledge people’s spiritual beliefs, it seems unlikely that external interventions for climate change adaptation can become either effective or sustainable in most instances.

In terms of raising awareness about climate change, education is key; yet, public media reports, which often focus on extreme scenarios, are often more persuasive in a Pacific Island context. Many Pacific Island school students are gaining education regarding climate change through school curricula and are experiencing anxiety and frustration at their elders’ lack of awareness and foresight (Scott-Parker and Kumar 2018). It seems clear that the localization of climate change awareness and knowledge is key to effective anticipatory adaptation in many Pacific Island contexts.

Telecommunications can help ease the isolation experienced by many of the more remote islands and provide significant access to health care, education, and government services. Unfortunately, due to the remoteness and isolation of the islands in the Pacific, these regions face problems such as lack of access to transport, communications, basic services, and economic opportunities (Dornan and Newton Cain 2014). Pacific Island countries have some of the lowest ICT penetration rates in the world in terms of Internet and mobile phone connectivity. Bandwidth is therefore limited and prices for broadband are high (Cave 2012). Significant progress has been made in recent years in improving telecommunications services in the Pacific Islands. Mobile technology has flourished in this environment. By 2013, one in three residents in Fiji, Tonga, and Tuvalu had access to the Internet (Firth 2018). Mobile phone technology advances were clearly a factor in providing remote areas with Internet access. Fiji has shown significant growth in Internet access and mobile telephone services. The geographic location, service culture, pro-business policies, English-speaking population, and well-connected e-society have supported this trend. Fiji has a relatively reliable and efficient telecommunications system with access to the Southern Cross submarine cable linking New Zealand, Australia, and North America relative to many other South Pacific islands.

Without timely and relevant information , developing Pacific Island states will find it difficult to monitor their progress towards sustainable development. A mature ICT infrastructure is critical for enhancing scientific research, upgrading the technological capabilities of industrial sectors, and encouraging innovation. Research and development expenditure as a proportion of GDP and researchers (in full-time equivalent) per million inhabitants are the two indicators chosen by the United Nations to measure progress (UNESCO 2015). Fiji is the only developing country in the South Pacific with recent data on research and development gross domestic expenditure (GERD). In 2012, the National Statistics Bureau cites a GERD/GDP ratio of 0.15%. Research and development in the private sector are insignificant, while government investment between 2007 and 2012 tended to favour agriculture .

1.9 Conclusions

Climate change has been identified as one of this century’s critical challenges for the Pacific region as a whole. The unique vulnerability of the Pacific Island countries to climate change is determined by their geography and environment, frailty of their economic structures, and demographics as well as the interactions between these factors. The vulnerability to climate change in the Pacific Islands is multidimensional and inextricably linked to broader challenges of development. Key impacts include damage to coastal systems, settlements, and infrastructure, undermining recent economic developments, ameliorating existing challenges to water and food security, increasing human health threats, and degrading regional biodiversity (Barnett 2001; Keener 2013). Climate change threatens prosperity and the viability of Pacific Island countries. If the world does not respond effectively to rising greenhouse gas emissions, significant additional stress will be placed on coastal communities, natural ecosystems, water and food security, and the health of islanders in the Pacific. In the face of often menacing climatic conditions, the people of the Pacific have a long history of resilience, and the nations and communities of the Pacific are now actively responding to the new challenges of climate change. With Pacific Island leaders already implementing adaptation measures and looking at relocation options for their climate refugees, islanders will have a better chance of survival if the global warming is limited to a 1.5 °C temperature rise (McNamara and Gibson 2009). The Paris Agreement of the United Nations has committed the world to ‘net zero’ global greenhouse gas emissions, and it is imperative that this is followed through for the long-term survival of many Pacific Island nations.