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Pacific islands are long-settled by mankind, dating back several hundreds to thousands of years ago since discovery by islanders traveling by boat. Amongst these islands are atoll islands, which are small coral islands that lie at a low elevation and are usually part of a ring-like coral reef formation. Past and present islanders collect water from rainwater catchments and groundwater wells, with rainwater used primarily for drinking water and groundwater used as a supplement for wash water. Unfortunately, this region can experience severe drought, over-wash events during strong tropical storms, and typhoons, all of which threaten the freshwater supply for these islands. Due to rising concerns over climate change, there is interest in studying the water security of these especially vulnerable land forms. This thesis evaluates the reliability of the water supplies on four atoll islands in Yap, Micronesia by modeling the reliability of the two main sources. To first analyze rainwater catchment performance, Ifalik Island is evaluated using data collected on the island in 2015 by a collaborative research field team and a water balance model. Second, the results are used to develop design curves as a tool for rainwater catchment design and improvement. The fresh groundwater source is also modeled for each of the four islands to test the effects of varying climate conditions on the shallow, freshwater lens. Rainwater catchment systems on Ifalik Island are evaluated for their performance using a mass balance model that quantifies water storage through time. Performance is quantified primarily by reliability, which is a term to represent the percentage of days a rainwater catchment supplies sufficient water to the users. Based on the data from the Ifalik field survey, ii the average household rainwater catchment system on Ifalik uses a 16.5 square meter guttered roof with a 2,000 liter storage tank and serves seven individuals at 12 liters per capita per day. As a result of a rainwater catchment system sensitivity analyses based on the average rainwater catchment conditions, the most important factors in performance are effective roof area size, water demand, and gutter-downspout efficiency. Further analyses using the mass balance model found that the performance of each individual catchment is sufficient to provide water to the community during conditions similar to the severe drought year of 1997-1998, as well as projected rainfall conditions for the next 30 years. Therefore, analyses suggest Ifalik Island has sufficient rainwater catchment performance to provide water for the community. However, to introduce a conservative measure for water security, it is recommended that the catchment area be extended to the full size of the roof area. This would thereby increase the storage supply for the community by 25 cubic meters on the day of lowest supply under the 1997-1998 severe drought conditions.

Marine pollution is widely recognised as one of the four major threats to the world’s oceans, along with climate change, habitat destruction and over-exploitation of living marine resources. Spills of oil and other chemicals into the marine environment, both from ships and land-based sources, is a significant source of pollution. In a region sometimes called ‘Oceania’, the health of the ocean is fundamental to the sustainability of all aspects of Pacific island life. The importance of coastal and marine environments to every aspect of the lives of Pacific islanders cannot be overstated, and the impacts of marine spills constitute a major concern for Pacific island peoples. Because of a lack of major land-barriers throughout the Pacific, combined with a complex pattern of trans-oceanic currents, the Pacific Ocean is perhaps the most highly connected and continuous ocean, in terms of water movement, on the planet. This compounds the seriousness of marine pollution for the region. Events in one area can have implications for other areas, as pollutants and contaminants are carried from their sources by ocean movements.

Coastal communities in the Pacific are without doubt some of the most vulnerable to climate change effects in the world. The limited land area in some countries and low profile of atolls (many only 3m above sea level at high tide) exacerbate the vulnerability of these locations, and the governments and people of these countries have limited capacities and resources to cope at all levels.

As with other small islands developing States (SIDS), Pacific island countries (PICs) are highly vulnerable to climate change and sea level rise owing partly to their small land masses surrounded by ocean, and their location in regions prone to natural disasters. PICs are often characterized by having relatively large populations for the area they occupy with high growth rates and densities; poorly developed infrastructure and limited natural, human and economic resources, and their high dependence on marine resources for their livelihood needs. Most of their economies are reliant on a limited resource base and are vulnerable to external forces, such as changing terms of trade, trade liberalization, and migration flows. Adaptive capacity to climate change is generally low.

As environmental problems continue to increase at an ever more rapid rate, exacerbated by the major threat of global climate change, the need for widespread remedial action is becoming ever more pressing. Scientific consensus on both the root causes of these problems and the measures required to tackle them is growing, while mass media and public interest has reached fever pitch. Of course, while this has put pressure on decisionmakers to take positive action, the realisation of the gravity and extent of the environmental problems has encouraged all those concerned about the state of our world to search for partners around it: one such significant partnership to e­merge in recent years is between those concerned with the conservation of nature –and of its biodiversity– and the custodians of sacred sites, representing both indigenous beliefs and mainstream faiths.

Observational records and climate projections provide abundant evidence that freshwater resources are vulnerable and have the potential to be strongly impacted by climate change, with wide-ranging consequences for human societies and ecosystems. Observed warming over several decades has been linked to changes in the large-scale hydrological cycle such as: increasing atmospheric water vapour content; changing precipitation patterns, intensity and extremes; reduced snow cover and widespread melting of ice; and changes in soil moisture and runoff. Precipitation changes show substantial spatial and inter-decadal variability. Over the 20th century, precipitation has mostly increased over land in high northern latitudes, while decreases have dominated from 10°S to 30°N since the 1970s. The frequency of heavy precipitation events (or proportion of total rainfall from heavy falls) has increased over most areas (likely). Globally, the area of land classified as very dry has more than doubled since the 1970s (likely). There have been significant decreases in water storage in mountain glaciers and Northern Hemisphere snow cover. Shifts in the amplitude and timing of runoff in glacier- and snowmelt-fed rivers, and in ice-related phenomena in rivers and lakes, have been observed (high confidence).

Coral reefs are the most structurally complex and taxonomically diverse marine ecosystems on earth, providing ecosystem goods and services for millions of people worldwide. These reefs are seriously threatened by a variety of anthropogenic threats, particularly overexploitation of marine resources, destructive fishing practices and runoff from poor land use practices. Over half of the world's reefs have already been lost or are under threat from these activities, with serious and widespread declines in reef health reported from around the world. Climate change also represents a new and increasing threat to coral reefs and associated ecosystems. Major threats include rising sea temperatures, rising sea levels and changes in ocean chemistry. Urgent action is now required to halt or reverse these threats and declines in coral reef health. One approach to the protection of reefs during this period of change is to manage for resilience.

Small island developing States (SIDS) are highly vulnerable to climate change and sea level rise owing partly to their small land masses surrounded by ocean, and their location in regions prone to natural disasters. SIDS are often characterized by having relatively large populations for the area they occupy with high growth rates and densities; poorly developed infrastructure and limited natural, human and economic resources, and their high dependence on marine resources for their livelihood needs. Most of their economies are reliant on a limited resource base and are vulnerable to external forces, such as changing terms of trade, trade liberalization, and migration flows. Adaptive capacity to climate change is generally low.

Small island developing States (SIDS) are highly vulnerable to climate change and sea level rise owing partly to their small land masses surrounded by ocean, and their location in regions prone to natural disasters. SIDS are often characterized by having relatively large populations for the area they occupy with high growth rates and densities; poorly developed infrastructure and limited natural, human and economic resources, and their high dependence on marine resources for their livelihood needs. Most of their economies are reliant on a limited resource base and are vulnerable to external forces, such as changing terms of trade, trade liberalization, and migration flows. Adaptive capacity to climate change is generally low.