Brandon McNulty 18 December 2015

Sea Level Rise in Kirabiti: Cause for Adaptation or Relocation?

Background: Kiribati is an island nation in the tropical pacific. It is made up of 33 atolls, 23 of

which are inhabited. They are typically no more than a meter above sea level, or more than a few hundred meters wide. Consequently over 90% of Kiribati’s population of 100,000 as well as its infrastructure is situated less than 100 meters from shore and less than a meter above sea level. This near-absent elevation out of the Pacific has made Kiribati’s residents among the world’s most vulnerable to climate change risks-specifically sea level rise.

Most sea level rise projections range from 20-100 cm by 2100. Estimates outlined below are from the IPCC AR5 and Kiribati Climate Adaptation Plan.

   

  There is a fair amount of discrepancy so both sources are considered in this analysis.

However, the clear takeaway from both estimates is that sea level rise increases the already substantial vulnerability of Kiribati to flooding from storm surges, ENSO-related sea level oscillation, and even high tides. Flooding damages infrastructure and contaminates limited freshwater resources. This looming threat challenges Kiribati to prepare for sea level rise through either aggressive adaptation measures such as constructing sea walls and protecting groundwater lenses, or else leaving their home behind to relocate entirely.

Problem:

This report aims to determine which of these options, adaptation versus relocation, is more strategic. The decision will be informed by analysis of each option’s costs under

consideration of uncertain sea level conditions as well as accounting for aversion to incurring potentially disastrous risks.

Relevant Questions and Data:

An informed analysis of this problem requires estimated costs of adaptation, estimated costs of relocation, parameterization of sea level rise categories, and probabilities for each of those sea level rise categories. Adaptation costs: Kiribati’s government has reported costs for its adaptation plan through both its Climate Adaptation Plan and National Adaptation Programmes of Action. The adaptation plan they are pursuing currently is estimated to cost $103 million dollars and is designed for adaption to 20-60 cm of sea level rise by 2100. Despite thorough planning, damages are expected to be incurred from 20-60 cm of sea level rise. This analysis has assumed these mitigated damages to cost roughly one quarter of expected damages without adaptive measures, or $4 million per year of the $16 million per year estimated for average annual damages without adaptive planning. Therefore this report operates under adaptation costs of $103 million for less than 20 cm of sea level rise, and $103 million plus $4 million per year for 20-60 cm of sea level rise.

The IPCC’s AR5 suggests significant possibility of sea level rise beyond 60 cm. In this case the current adaptation plan seems likely to be ineffective. Kiribati has previously estimated comprehensive, robust adaptation to extreme sea level rise to cost $2 billion. This analysis adopts this estimate of $2 billion for adaptation costs in the event of sea level rise above 60 cm. Relocation costs: No formal estimates for relocation of Kiribati’s residents have been published, or at least not made readily available to the public. Relocation costs were therefore approximated based on reported costs of $7,200 per person for relocating three Tahitian villages. Scaled to Kiribati’s population of 100,000, relocation costs for this analysis have been assumed to be $720 million. Sea level parameters: As previously mentioned, Kiribati has designed its adaptation plan to prepare for 20-60 cm of sea level rise. This report’s decision analysis has chosen to define sea level parameters based on these figures to most accurately represent adaptation costs under various sea level rise conditions. Therefore sea level categories considered here are below 20 cm, 20-60 cm, and above 60 cm. Sea level probabilities: Likelihood of each of the sea level probabilities has been approximated by averaging projections and margins of error published by the IPCC’s AR5 and Kiribati’s Climate Adaptation Plan. No stated figures on the probability of each level were found, rather based on margin of error around each report’s projections this analysis decided to assume a 10% likielihood of under 20 cm, 40% likelihood of 20-60 cm and 50% likelihood of above 60 cm of sea level rise by 2100. Methods:

1. Establish estimated costs and condition probabilities for decision tree. Outlined above.

2. Calculate EMV of expected costs a. Note that smaller EMV is preferred since EMVs reflect expected costs

not benefits 3. Establish utility function

a. A cube root utility function has been chosen to reflect extreme risk aversion

b. Utility function has been scaled up to 100 for ease of interpretation c. Utility function has also been subtracted from 100 to account for

calculation of costs not benefits. This way the higher utility is the preferred option, which is more intuitive and therefore facilitates accurate interpretation of results

4. Compare expected utility of each plan to determine strategic option Analysis: Expected Costs Low SLR by 2100

< 20 cm = (10%) Medium SLR by 2100 20-60 cm = (40%)

High SLR by2100 60+ cm= (50%)

Relocation $720 M $720 M $720 M Aggressive Adaptation

$103 M $103 M + ($4 M/yr*85yrs) = $443 M

$2,000 M

Utility Low SLR by 2100

< 20 cm = (10%) Medium SLR by 2100 20-60 cm = (40%)

High SLR by2100 60+ cm = (50%)

Relocation 0.69 0.69 0.69 Aggressive Adaptation

0 0.56 1

Expected Costs = p(< 20cm)*costs(< 20cm) + p(20-60cm)*costs(20-60cm) + p(> 60cm)*costs(> 60cm) Expected Costs (Relocation) = 0.10*$720 M + 0.40*$720 M + 0.50*$720 M = $720 M Expected Costs (Adaptation) = 0.10*$103 M + 0.40*$443 M + 0.50*2,000 M = $1,188 M U(X) = 100 - 100[(X – Low Cost)/(High Cost – Low Cost)]^1/3 Low Cost =$720 M High Cost = $2 B Expected Utility = p(< 20cm)*U(< 20cm) + p(20-60cm)*U(20-60cm) + p(> 60cm)*U(> 60cm) Expected Utility (Relocation): 100 – 100[ 0.10[(720M – 103M)/(2B-103M)]^1/3 + 0.40[(720M – 103M)/(2B-103M)]^1/3 + 0.50[(720M – 103M)/(2B -103M)]^1/3] = 100 – 100[0.10 (0.69) + 0.40 (0.69) + 0.50 (0.69)] = 100 - 69 EU(Relocation) = 31

Expected Utility (Adaptation): 100- 100[ 0.10[(103M – 103M)/(2B-103M)]^1/3 + 0.40[(443M – 103M)/(2B-103M)]^1/3 + 0.50[(2B – 103M)/(2B-103M)]^1/3]

= 100 – 100[0.10 (0) + 0.40 (0.56) + 0.50 (1)] = 100 - 73 EU (Adaptation) = 27

Results: The expected costs and utility of relocation proved superior to those of adaptation. Conclusion: The results of this decision analysis proved consistent with literature on the subject, which frames the question of not if the people of Kiribati will have to relocate, but rather when they will relocate. This is an unfortunate reality of climate change, however a useful conclusion to reach given its apparent inevitability. In addition to its adaptive planning, Kiribati has begun small scale preparation for relocation including purchasing of land in Tahiti and job training for prospective first wave of e-Kiribati to relocate. At the recent COP21 in Paris, Tahiti’s government provided reassuring news that they are willing to welcome the entire e-Kiribati population if and when it becomes necessary for them to abandon Kiribati. Further preparation on this front is necessary, and given Kiribati’s proactive approach thus far on this issue it can be expected to develop over the next decade. The Kiribati population has expressed concern over maintaining their identity and culture in a new home country and this should be featured in this upcoming relocation planning.

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