Adapting to rising sea levels in Marshall Islands

The Republic of Marshall Islands, like many Pacific island nations, is leading the world in planning and consideration for climate adaptation, as it looks to urgently respond and adapt to the threat of climate impacts and rising sea levels.

As citizens of a low-lying atoll nation, the Marshallese face an existential threat from climate change-induced sea level rise. This study and visual tool has been produced under the Building Resilience in Pacific Atoll Islands initiative to visualize the long-term climate impacts on Marshall Islands' urban communities and clearly show the adaptation pathways available to the Marshallese under various sea level rise scenarios.

The Republic of Marshall Islands emerged as volcanoes in the Pacific Ocean 70 million years ago. The reefs that formed around the sinking volcanoes became the atolls we see today. They were called

Ad jolet jen Anij ("Our Blessed Inheritance from God")

by the Marshallese - descendants of Micronesian sailors who arrived more than two millennia ago.

The unique physical features and ecology of the atoll with its coral reefs and lagoons enabled a rich and thriving way of life for the Marshallese. Villages and cities grew within the thin strip of land between the lagoon and the ocean, where life and culture adapted to the tides and currents of the sea.

Today, around 60,000 Marshallese live on 182 kilometers (km²) of land spanning an oceanic territory of 200,000 km².

Marshall Islands’ constitution grants all citizens a natural and inalienable right to land. However, climate change and sea level rise threatens to submerge low-lying lands, disrupt coastal livelihoods and uproot traditional patterns of life.

Click through the slides below to view the location of Marshall Islands, the Pacific island nations, and their relationship to sea level rise in the South Pacific Ocean →

However, without any climate adaptation and mitigation measures, Marshall Islands will be one of the first nations to experience sea level rise as a genuine existential threat.

As such, long-term adaptation is critical to giving Marshallese the choice to continue living in the places they have called home for centuries, even as sea levels rise.

In particular, climate adaptation in urban atolls is critical. Today, the urban areas of Majuro and Kwajalein are home to 74% of Marshall Islands’ population, and in the coming decades, these urban atolls are expected to become home to an even greater share of the population.

Long-term climate adaptation planning involves anticipating, limiting, and adapting to the potential impact of sea level rise over the next 100 years. Considering this long time line the planning process needs to prepare for a number of scenarios linked to how high the sea level might rise.

This study modeled and visualized the impact from three sea level rise intervals: 0.5 meters (m), 1m, and 2m. Exactly when Marshall Islands will face a specific sea level rise scenario cannot be determined. However, the likelihood of facing a sea level rise scenario by 2120 depends on the global community’s ability to meet the commitments outlined in the Paris Agreement.

The urban center of Djarrit-Uliga-Delap in Majuro is at significant risk of inundation from 1m sea level rise. Swipe across the image below to view potential impact →

Buildings and communities in the urban atolls of Majuro – Marshall Islands’ capital, with a population of more than 20,000 people –  and Kwajalein are at high risk of inundation from sea level rise. Without any form of adaptation, 37% of Majuro's building stock is at risk of permanent inundation from a 1m sea level rise. In Ebeye, more than half the building stock could be permanently inundated by 1m sea level rise.

To better understand how Majuro's building stock is impacted by different sea level rise scenarios, click through the slideshow below →

Three key questions inform preliminary priorities for long-term climate adaptation planning in Majuro and Ebeye.

1. How can land and housing stock be protected from various sea level rise scenarios;

2. How many people need to be housed in urban atolls due to growth, displacement or inter-atoll migration; and

3. How much land needs to be developed, raised, or reclaimed to accommodate this demand?

There is a great deal of uncertainty when answering these questions because varying degrees of sea level rise can radically alter land availability and trigger new patterns of migration.

Climate change is introducing unprecedented challenges that disrupt traditional atoll livelihoods like fisheries and agriculture. Faced with warming lagoons and rising sea water, outer atoll communities are now having to consider moving away from their traditional homes. This has led to increased inter-atoll migration towards urban atolls and out-migration to countries abroad; most notably to the United States – which is home to approximately 27,000 Marshallese.

While education, health, and economic opportunities are the main drivers of out-migration today, climate-related stressors may become a dominant driver for migration in the future.

Due to consistent out-migration, the Pacific Community (SPC) projects a reduction in the national population by 2050. While Marshall Islands’ population is likely to decline over the next hundred years due to out-migration, the growth trajectory of urban atolls like Majuro and Ebeye will be more varied and complex. The image below summarizes the demographic trends that climate adaptation needs to consider.

Over the planning horizons of 30, 50, and 100 years, the resilience of Majuro and Ebeye's communities will be tested by fluctuating housing demands and sea level rise.

Communities in Majuro and Ebeye face multiple coastal hazards with varying intensities and frequency. The Marshallese are already seeing coral bleaching, more frequent flooding, more intense cyclones, and droughts. As oceans warm, Marshall Islands' water and food security will soon be threatened by collapsing reefs, saline intrusion into the aquifer, and more frequent storm surges or recurring king tides that damage agro-forestry systems. Sea level rise will exacerbate existing hazards and introduce new risks to urban atoll communities.

Every household is within reach of the ocean or lagoon and their exposure to coastal flooding or permanent inundation can vary greatly due to the form of the atoll lands, reef bed structures, and small differences in elevation. Atolls are mostly low-lying, with land along the ocean side often rising to between 3 and 4 meters. The lagoon side of atolls is more sheltered from waves but much lower in elevation.

Click through the slideshow to view the typical climate change hazards urban atolls may face under various sea level rise intervals without adaptation measures in place →

The small differences in land width and height above sea level will inform the urgency and viability of adaptation pathways in Majuro and Ebeye.

In Majuro, the urban center of Delap-Uliga-Djarrit – the most densely populated area of Marshall Islands – is spread along a narrow land mass with a low-lying lagoon side and a relatively elevated ocean side ridge. Rairok spans over an islet fewer than a few hundred meters wide. In Laura, the land fans out more than a kilometer wide and is sheltered by elevated ridges on both sides. All the settlements in Majuro are connected to critical facilities and the airport by the Lagoon Road. This lifeline corridor is quite exposed to inundation from 1m sea level rise.

The urban settlements of Ebeye in Kwajalein atoll span a consistently narrow and uniformly low-lying atoll and highly exposed to 1m sea level rise.

With relatively limited land at higher elevations, the focus of this study is to identify options that limit loss of housing by protecting the coast and raising or reclaiming land for development that are relatively safe from sea level rise. To prioritize investments towards these pathways, multiple places in Majuro and Ebeye have been visualized.

The visualizations offer an intuitive reading of hazards and assets at risk of exposure under three sea level rise scenarios. They offer a place-specific understanding of land elevations and potential settlement exposure, but are not meant to portray exact location of impact.

The slides below illustrate the impact of inundation and coastal flooding in Delap-Uliga-Djarrit under various sea level rise scenarios →

There are a number of proven, robust, and resilient adaptation options that Marshall Islands can embrace and implement to withstand the long-term impacts of climate change. However, there is a great degree of uncertainty around the magnitude of sea level rise over 100 years, the success of global climate mitigation efforts, and the amount of financing that will be made available for climate adaptation.

This study uses the Dynamic Adaptive Policy Pathways to suggest adaptation pathways that are able to deal with deep uncertainties. It explores sequences of decisions or mitigation measures under multiple futures, and illuminates any path-dependencies between multiple adaptation strategies.

The specific conditions of Marshall Islands' urban atolls make the following adaptation pathways viable:

1) Protect, 2) Raise, 3) Reclaim, 4) Relocate, and 5) Migrate.

These pathways supplement no-regret adaptation strategies like Early Warning Systems and investing in Nature-based Solutions.

Protecting urban atolls from the effects of sea level rise requires non-structural and structural measures with uncertain design lives that may fail sooner as conditions change. A Dynamic Adaptive Policy Pathways approach uses the 'Metro-map' decision tree (seen below) to visualize multiple pathways that would enable Marshallese to continue living on their land under various sea level rise intervals.

Each adaptation pathway has a limit to their effectiveness or 'tipping point' before which, preparation to transition to a different track is advised. Adaptation pathways can be followed sequentially or simultaneously.

While certain pathways can withstand even extreme sea level rise scenarios of two meters or more, they are usually very expensive to implement. It is important to weigh the trade-offs between different adaptation pathways and consider the sequence of investments to make the right transition around tipping points while retaining the flexibility to respond to changing rates of sea level rise. For example, prioritizing robust but costly actions early on may turn out to be an overinvestment or lock-in strategies with negative environmental and cultural impact.

One pathway that needs to be financed and implemented in the short-term is 'Protect'. This involves strategies to reinforce the coastal edges of urban atolls to withstand moderate sea level rise and the elevated risk of coastal flooding.

The slides below show adaptation options under 'Protect' and the benefits, costs, and consequences of implementing them →

The measures under Protect are only effective for low to intermediate levels of sea level rise. With 0.5m sea level rise, around 80km of Majuro and 20km of Ebeye's shoreline need to be protected. As sea-levels continue to rise, and coastal inundation increases, it is likely that more transformational resilience measures will be needed in the medium to long-term.

Protect is a short-term adaptation strategy that buys time to plan for and invest in pathways like Raise or Reclaim. These are expensive but robust pathways that can withstand sea level rise of 1 to 2 meters, or more.

Reclaim adaptation strategies that create new land for development over shallow beds within lagoons are highlighted in the slides below →

The most important objective of long-term climate adaptation for the Marshallese is to ensure future generations can live and thrive on their ancestral atolls. However, under extreme sea level rise scenarios if Marshall Islands could not adequately protect urban shorelines or implement the ambitious raise or reclaim options in time, Marshallese face the difficult pathways of Relocate or Migrate.

As residents of a low-lying atoll nation, the Marshallese are already facing the impacts of climate change, but they do so with adaptation options. Through long-term climate adaptation planning, Marshall Islands can pursue a number of pathways to prepare their urban atolls for increased risk of flooding and inundation from moderate sea level rise. A sea level rise of up to 0.5 m greatly increases risk to coastal hazards but can be managed via multiple pathways by 2120. Moderate sea level rise of up to 1 m brings much tougher but ultimately surmountable challenges, with advanced preparation and ambitious projects.

If global emissions continue unchecked, the Marshallese could experience rising sea level that represent an existential threat to their land and culture. In extreme scenarios where sea level rise levels reach 2 m or more, the only viable options are massive land reclamations, and land raising that includes relocating part of the population. These options would cost billions of dollars and require investments far higher than current adaptation projects. Alternately, the Marshallese would be forced to rely on inter-atoll or international migration as an adaptation option.

The Marshall Islands are at the frontlines of climate change but there are opportunities to avert the worst case scenarios. In the words of former Marshall Islands Foreign Minister Tony De Brum: “If we manage to save my country, we’ll manage to save the world.”

Over the next hundred years, Marshall Islands will have to embark upon ambitious initiatives and make tough decisions that require enormous political will, significant climate financing, and community cooperation.

This project was made possible through support from the World Bank, with funding and technical support from the Global Facility for Disaster Reduction and Recovery.

This product was created as a part of the World Bank’s work, ‘Building Resilience in Pacific Atoll Island Countries ’ which aims to support Pacific atoll island countries to boost their resilience and manage the long-term adverse impacts of climate change.

The World Bank works in partnership with 12 countries across the Pacific supporting 87 projects totaling US$2.09 billion in commitments in sectors like agriculture, health, education and employment, climate resilience and adaptation, energy, fisheries, rural development, economic policy, macroeconomic management, aviation and transport, telecommunications, and tourism.

Coastal flooding due to wind-driven surges, tides and wave set-up was estimated for Majuro and Ebeye for events with return periods of 1, 5, 10, 50 and 100 years using local LiDAR survey data of 5m resolution.

All simulations have been performed by Deltares for the current situation and in combination with fixed sea level rise magnitudes of 0.25, 0.50, 1.0 and 2.0 m.

An interactive webmap produced by GeoAdaptive under this study allows users to explore multiple sea level rise scenarios in Majuro and Ebeye, click below to explore:

The data and visualizations shown in the maps, drawings, and other web tools illustrate the potential risk of inundation and flooding under various sea level rise and storm event scenarios. They are not meant to suggest exact location of impact, and do not account for erosion, subsidence, other geophysical or climate stressors or future development.

The information shown is meant for screening-level decisions by relevant stakeholders in climate adaptation planning or management. All buildings, roads, and their characteristic features should be verified by site visit and surveys. Any risks associated with using this data for purposes other than long-term planning is assumed by the user. These visualizations should be used strictly as a decision support tool and not for permitting, or other legal purposes.