AdaptCost Briefing Paper 3: Coastal Adaptation – Africa Review and New Estimates

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Briefing Paper 3: Coastal Adaptation – Africa Review and New Estimates


The AdaptCost study has reviewed the evidence on the costs of adaptation in Africa. This includes consideration of different aggregation scales and evidence, such as:

  • Aggregated continental level studies and regional studies.

  • Major country initiatives and national studies

  • Sectoral studies (sub-national) and case studies.

As part of this work, the AdaptCost study has also commissioned new specific sectoral work, notably to run the DIVA model to assess coastal effects. This briefing note reports on this review work and summarises the new modelling analysis. Full details are included in a sector report (Brown et al, 2009) that is also available.

Africa has a large and growing coastal population, including a number of important coastal cities.
There are 33 countries with coastlines, and 7 adjacent island nations and territoriesi. The continent’s coastline is estimated to be more than 38,000 km in length, with a further 7,000 km when the adjacent island nations and territories are included.
The coastal zone (defined as the land up to 10m above sea level) around the continent varies in widthfrom a few 100 metres (Red Sea area and mountainous areas) to more than 100km (in the Niger and Nile deltas). This zone includes mangrove forests and swamps, coral reefs, cliffs, sand & mudflats, and tidal marshes, as well as urban settlements.
Africa has around 320 coastal cities (each with more than 100,000 people) and nearly 56 million people (2005 estimate) living in low elevation (<10-m) coastal zones. There is also a growing population and economy and strong trends of urbanisation. Many of these coastal cities are also important ports, which are key to national and regional trade, imports and exports.

All of these coastal zones support significant economic activity, associated with agriculture and tourism, as well as containing commercial and industrial facilities. These zones contribute significantly to wealth and economic activity, as well as providing much wider economic benefits through ecosystem services.

The Impacts of Climate Change on Coastal Zones
Sea-level rise, in combination with changes in the frequency / intensity of extreme weather events is expected to increase the flooding and inundation of coastal areas.
There are potential threats to coastal environments and ecosystems including low-lying coastal plains, islands, beaches, mangroves, coastal wetlands and estuaries. There are also potential threats to infrastructure, transportation, agriculture and water resources within the coastal zone, as well as tourism and provisioning services (fishing, aquaculture and agriculture).
The direct impacts from sea-level rise include inundation of low-lying areas, shoreline erosion, coastal wetland loss, saltwater intrusion and increased salinity in estuaries and coastal aquifers, higher water tables and higher extreme water levels leading to coastal flooding with increased damage. Potential indirect impacts include altered functions of coastal ecosystems and impacts on human activities.
Human-induced pressures on the coastal zone (growing population, water abstraction, etc) are also likely to exacerbate the effects of sea-level rise – though these would also even in the absence of climate change. These are important in the context of future socio-economic change.
With a large and growing population in the coastal zone and a low adaptive capacity due to low national wealth and other development indicators, most African countries appear to be highly vulnerable. Indeed, this has been reported in many previous assessments (e.g. IPCC AR4ii).
This is a particular concern for the large number of rapidly growing coastal cities (see map below).

Figure 1. African cities at risk of sea-level rise
Source: UN-HABITAT, 2008
There are also increased risks of coastal erosion and flooding of low-lying coasts.
However, compared to many other parts of the world, the potential impacts of sea-level rise level in Africa have received less study, particularly a national and sub-national.
In order to address the potential risks of climate change to existing assets and people, some form of protection is required for coastal environments, such as cities, ports, deltas and agriculture areas. Coastal protection to sea-level rise is often a costly, but a straightforward way to overcome the adverse impacts of climate change.
There are a large number of potential adaptation options to address these risks, particularly for protecting market sectors.
These adaptation strategies include coastal defences (e.g. physical barriers to flooding and coastal erosion such as dikes and flood barriers); realignment of coastal defences landwards; abandonment (managed or unmanaged); measures to reduce the energy of near-shore waves and currents; coastal morphological management; and resilience-building strategies.
Planned adaptation options to sea-level rise are usually presented as one of three generic approaches, i.e. retreat, accommodation or protection. The types of options are summarised below.
Table 1. The five major natural system effects of relative sea-level rise, including examples of possible adaptation responses

Natural System Effect

Possible Adaptation Responses

Inundation, flood and storm damage (includes surge (sea) and backwater effect (river)

Dikes/surge barriers [P],

Building codes/floodwise buildings [A],

Land use planning/hazard delineation [A/R].

Wetland loss (and change)

Land use planning [A/R],

Managed realignment/ forbid hard defences [A/R],

Nourishment/sediment management [P].

Erosion (direct and indirect morphological change)

Coast defences [P],

Nourishment [P],

Building setbacks [R].

Saltwater Intrusion

a) surface waters

b) ground-water

Saltwater intrusion barriers [P],

Change water abstraction [A/R].
Freshwater injection [P],

Change water abstraction [A/R].

Rising water tables/ impeded drainage

Upgrade drainage systems [P],

Polders [P],

Change land use [A],

Land use planning/hazard delineation [A/R].

[P] – Protection; [A] – Accommodation; and [R] – Retreat

Source: Nichols et al (OECD, 2006iii).

Earlier studies
Previous studies have estimated the potential economic costs of sea level rise in Africa and some estimates of the costs of adaptation.
Nicholls (2006iv) reported that the impacts of storm surges in coastal areas could affect about 30 million people around the African Atlantic and Indian Ocean coasts lives within a hazard zone (i.e. the potentially exposed population), out of which about 2 million people per year could potentially be flooded in the 2020s. Due to the occurrence of tropical storms, the study identified Mozambique, Tanzania and Madagascar as being particularly vulnerable countries to increased flooding.
Nicholls et al. (2008v) estimated the exposure of the world largest port cities to coastal flooding due to storm surge. Using a population criteria of one million people in 2005, they identified 136 port cities globally, of which 19 were in Africa. They estimated African port city’s population exposure at more than 2.6 million people in the coastal floodplain (in 2005) with asset exposure of about US$42 billion (in 2005. Alexandria (Egypt) and Abidjan (Cote d’Ivoire) were identified amongst the top twenty world port cities with high population exposure to coastal flooding in 2005.
Further, the study assessed how these might change in the future with climate change. Taking high-end scenarios of socio-economic, climate and non-climate trends for the 2070s, the total population and assets exposed in Africa in the nineteen major coastal cities was projected to grow to 13.3 million people and US$998 billion of assets, with exposure concentrated in Alexandria, Lagos and Abidjan. Some cities, such as Mogadishu (Somalia) and Luanda (Angola) were also considered to experience a rapid increase in population and asset exposure posing significant challenges for the future.
Dasgupta et al. (2009vi) ranked Egypt, Mauritania, Tunisia, and Benin in the top ten most impacted countries developing coastal countries world-wide (out of a total of 84 countries considered) in terms of the population potentially displaced due to a 1m sea-level rise.
Niang-Diop (2005vii) estimated that the number of people at risk from coastal flooding would increase from 1 million in 1990 to 70 million in 2080, and the costs of adaptation to sea level rise could amount to 5–10% of GDP in African coastal countries.
Ericson et al. (2006viii) considered six major African deltas and relative sea-level rise as part of a global study. The study estimated that about 1.4 million people could be displaced by present rates of relative sea-level rise from 2000 to 2050< with the vast bulk of these people (1.3.million) being in the Nile delta.
Syvitski et al. (2009ix) identified the Nile and Niger deltas as being the most threatened of the African deltas due to subsidence and human interference, with the Limpopo and Congo deltas being much less threatened.
The AdaptCost DIVA Analysis
The AdaptCost study1 has investigated the potential effects of sea level rise using the DIVA (Dynamic Interactive Vulnerability Assessment) model, an coastal integrated assessment model that assesses biophysical and socio-economic impact. Impacts were determined with and without adaptation, so that the benefits and costs of protection could be considered.
This section summarises the analysis. A full technical report is also available
A range of scenarios have been explored, with three scenarios from the IPCC, plus a fourth based on more recent literature which reports an upper bound. This leads to a range of global sea level rise from 0.17m to up to 1.26m from 1995 to 2100. These are shown in the figure below.
These changes have been assessed in conjunction with three IPCC socio-economic scenarios describing population growth and density as well as future GDP (A1FI, A1B and B1).

Figure 2. Sea Level Rise scenarios considered
The impacts were assessed in the years 2000, 2025, 2030, 2050 and 2075, focusing on (1) People actually flooded, (2) Cumulative forced migration, (3) Loss of wetland value, (4) Total residual damage costs, and (5) Total adaptation costs. However, a much wider set of impact categories has been assessed. A full set of results by country is included in the main technical report. The summary results are presented below.
The estimated number of people flooded is shown in the figure below. As an example, this indicates that over two million people in Africa are estimated to be flooded per year by the 2030, rising to 5 million by 2050 (A1B mid-range scenario). In the longer-term these risks increase significantly with approximately 16 million people will be flooded per year in 2100.

Figure 3. Estimated number of people flooded due sea-level rise and socio-economic change from 2000 to 2100 in Africa
Graph shows four sea-level scenarios studied with no additional adaptation measures employed
The values are higher for the A1F and more extreme (Rahmstorf) scenarios, though much lower for the B1 low range.
The analysis also finds that as sea-level rises more rapidly, coastal wetlands (saltmarshes, mangroves, high and low unvegetated wetlands, mangrove areas and coastal forest areas) will decline in area. These losses have also been expressed in monetary values.
The study has estimated the economic costs associated with migration, land loss due to erosion and flooding, salinisation and costs associated with sea and river floods. These reveal significant economic costs, shown in the figure below.

Figure 4. Total costs due sea-level rise and socio-economic change from in Africa
Figure shows for the four sea-level scenarios studied with no additional adaptation measures employed. 1995 prices.
For example, without adaptation, the total costs for the A1B scenario are estimated at US$ 1.6 billion/year in 2030 (1995 prices), rising rapidly to potentially $7.5 billion/year by 2050 (1995 prices). In the longer-term for the A1B mid-range scenario there is an estimated total damage cost of US$38 billion per year in 2100 (1995 prices). The values are higher for the A1F and more extreme (Rahmstorf) scenarios, though significantly lower for the B1 low range.
The results confirm that without adaptation, the physical, human and economic impacts will be significant. Moreover, it is important to note that sea-level rise will not be the only factor shaping Africa’s coast in the 21st Century. Other climate change impacts such as increased storminess, higher temperatures and reduced precipitation also have immediate or secondary impacts of the coast. These have not been considered in this model, but could have important effects such as more intense tropical storms hitting the coast of East Africa (Mozambique, Tanzania and Madagascar). Finally, there are many anthropogenic factors influencing the coast, such as the conversion of wetland to agriculture uses or the reduction of sediment and water fluxes to deltas, often combined with enhanced subsidence. While these factors were not considered here due to lack of data, they should be considered in future studies.

The DIVA model has also considered the potential costs of adaptation for coastal zones in Africa, and the benefits of adaptation in reducing the physical impacts and economic costs estimated above. The DIVA model includes costs for two types of adaptation options, to inundation and coastal erosion, based on technical costs for an increase in flood defence dike heights and application of beach nourishment.
With adaptation in place, the impacts and economic costs above fall significantly. The model estimates that with optimal adaptation (based on meeting acceptable coastal risk levels for flooding, and based on a cost-benefit algorithm for beach nourishment), the number of people flooded per year is reduced significantly. As an example, for the A1B mid scenario in 2030, the number of people flooded reduces from 2 million (no adaptation) to 200,000 – an order of magnitude reduction. The numbers of people flooded in later years actually reduces below this level as adaptation becomes more effective.
Adaptation also reduces the economic costs associated with migration, land loss due to erosion and flooding, salinisation and costs associated with sea and river floods. The resulting economic costs – the residual impacts after adaptation – are shown in the figure below.

Figure 5. Total residual costs due sea-level rise and socio-economic change in Africa
Figure show four sea-level scenarios studied with adaptation measures employed. 1995 prices.
As an example, under the A1B scenario the economic costs are reduce from $ 1.6 billion/year in 2030 (1995 prices) to around $1 billion/year with adaptation. Benefits in later years are much greater with the reduction in economic costs in 2050 falling from $7.5 billion/year by 2050 (1995 prices) to $2.3 billion/year with adaptation. In the longer-term the high damage costs in 2075 to 2100 are largely avoided.
The costs of adaptation to achieve these benefits are relatively low in comparison, shown below.

Figure 6. Costs of adaptation due sea-level rise and socio-economic change in Africa
Figure shows four sea-level scenarios studied employing a risk based and cost-benefit approach. 1995 prices.
Under the A1B scenario, the costs of adaptation are estimated at approximately $ 2 billion / year over the time period 2030 - 2100. These costs rise significantly with higher sea level scenarios, up to $5 to 8 billion/year by 2100 under some of the higher scenarios. Nonetheless, coastal protection appears to substantively reduce the threat imposed by sea-level rise at a relatively low cost, and in the analysis here, the benefits of adaptation outweigh the costs.
However, even with adaptation, there are some residual damages. Moreover, some additional factors are important. Adaptation is likely to be more costly and difficult than the headline numbers above suggest. This reflects several factors: (1) adaptation costs are partial, (2) there is a large adaptation deficit, reflecting that Africa is poorly adapted to today’s climate, and (3) there is low adaptive capacity. Moreover, while it possible and probably desirable to protect many areas of coasts through adaptation, this does not fully capture the full role of the coastline. Under projected climate change and sea level rise, coastal ecosystems will be threatened. These habitats could be severely reduced or disappear during the 21st century.
The results shown demonstrate that the higher the rate of sea-level rise, the higher the impact and economic costs for Africa. They also show that the socio-economic scenarios are important in determining impacts. This has been examined in the main report through the consideration of a scenario with socio-economic change only and no climate change. This analysis shows future socio-economic change (e.g. population growth) broadly contributes around half the total economic costs shown, i.e. even in the absence of climate change, around half the increase in the economic costs to coastal zones would occur.
The falling population after 2050 under the A1/B1 scenario means that impacts grow less rapidly from 2050 onwards than an alternative population scenarios such as the A2 scenario, or a scenario of net coastward migration.
As a continent, Africa appears highly vulnerable to sea-level rise – though comparison against the global DIVA data set shows that economic costs are much lower than for Asia.
For the A1B mid-range scenario by 2100 (a 43-cm rise scenario) if there is no upgrade of defences there are significant additional impacts estimated, with 14 million people per year are at risk of flooding, nearly 10 million people are at risk of being displaced over the century (to 2100) and a residual damage of nearly US$38 billion per year. If beach nourishment and higher dikes are introduced, these damages can be greatly reduced and most importantly, forced population displacement is nearly entirely avoided. The incremental adaptation costs for Africa are estimated at nearly US$2 billion per year.
It is important to note that the adaptation will not avoid all impacts, and there will be need to be other investment such as port upgrade, measures to counter salinisation, and extensive river dikes in the coastally-influenced reaches of rivers. Additionally, this infrastructure will require maintenance which has not been costed here. Lastly, there is the issue of the adaptation deficit as many African countries are poorly adapted to today’s climate. This is not taken account of in this analysis, and the adaptation deficit implies more investment will be required to meet the adaptation needs of today before addressing future challenges. The value of US$2 billion per year is therefore a likely minimum adaptation cost.
It is also highlighted that as well as sufficient funds, there is a need for greater capacity to implement the necessary adaptation.
Analysis of Individual Countries
The full analysis has also produced DIVA results for each individual coastal country in Africa. These are included in the main report. A summary of key countries is included below
A selection of the economic costs and costs of adaptation are shown in the figures below, showing values for 2030 and 2050. In each case, the figures show socio-economic change (alone), socio-economic and climate change before and after adaptation, and the costs of adaptation.

Costs of adaptation per year ($Million/year) to sea level rise and socio-economic changes for selected countries in Africa – A1B mid range scenario for 2030 and 2050.
Source produced by Paul Watkiss on basis of DIVA model results

Considering the relative ranking of countries in absolute terms, the highest impacts for people-based impacts are Mozambique, Cameroon, Tanzania, Morocco and Egypt. For economic damages, the highest economic costs of sea level rise are found in Algeria, Egypt, Morocco, South Africa, Tunisia, Libya and Cameroon.

The highest adaptation costs (in the figure above) vary with the time period, but generally occur in Madagascar, Mozambique, Guinea, Guinea-Bissau, Nigeria, Somalia and South Africa. Note that high impact costs and adaptation costs are not automatically correlated.

Coastal protection to sea-level rise is often a costly, but a straightforward way to overcome the adverse impacts of climate change. In some countries (for instance Mozambique, Nigeria) high impacts result in high adaptation costs. Other countries, for example Egypt, Tanzania and Morocco, have high impacts but a lower adaptation cost. Thus adaptation may be a greater benefit to the latter countries rather than the former.
The analysis may also miss some of the more important relative changes. For instance, Djibouti has the tenth largest urban population as a percentage of the country’s total population (52%) located in the low elevation (<10m) coastal zone (UN-HABITAT, 2008). As it is a small country, the total costs are relatively low, yet on a country level within, impacts may be high. Similar issues could apply to Liberia and Senegal which also have a high percentage of the total population living in a low elevation coastal zone.
Note that the study has assumed a uniform rate of sea-level rise but this will vary (for example, the Mediterranean has experienced a lower rate of sea-level rise in comparison to the global average).
There is also a need to consider present problems and the local context also needs to be considered. Cameroon, Mauritania, Nigeria and Tanzania are countries which experience relatively high rates of subsidence, and even without climate change they would experience slow relative sea-level rise due to these non-climatic processes. Additionally, local man-induced subsidence may increase rates of relative sea-level rise, especially in deltas (for example, the Nile delta).
Additionally, higher temperatures and lower precipitation would tend to reduce river levels affecting river discharge and water availability. Changes and intensification to farming practices may mean that wetlands are at risk as they are converted to agriculture and industrial use, reducing a natural form of coastal defence.
Further work is required to better understand the implications of sea-level rise for Africa in broad sense, but also to move to national and sub-national assessments. These can also address the issue of adaptation in a local context and the linkages with development, and considering more realistic adaptation measures.
With a large and growing population in the coastal zone and a low ability to adapt because of low national wealth and adaptive capacity, most countries around the continent appear to be highly vulnerable.
Finally, these results focus on future climate change, and there is also a need to consider existing disaster risk reduction as a priority, as well as to start planning for future change now. While development can increase adaptive capacity, there is also the potential for future economic development to increase vulnerability, for example if future population or economic zones are located in areas that have high future risks from sea level rise. This necessitates a need for spatial planning. A key element of long-term planning will also be to ensure flexibility.
Other Aggregate Coastal Costs of Adaptation for Africa
As highlighted in the OECD (2008) study, the most extensive evidence base on the costs and benefits of adaptation is in the coastal sector. This also applies to Africa. There are a series of studies which have been undertaken, many as part of global assessments, which also include analysis of coastal adaptation for Africa.
1) UNFCCC Investment Flows
Work as part of the UNFCCC global study on the costs of adaptation (2007x) assessed coastal zones using the DIVA model, and this provided direct estimates of additional investment needed for coastal infrastructure for Africa in 2030, and assuming anticipation to 2080.
Of the total global value for coastal adaptation costs (of $11 billion), around 12-13% were in Africa, with estimates of $1.2 to 1.3 billion/year in 2030. The more recent analysis with the DIVA model here uses an updated model, and a wider range of scenarios, but the central estimates in the more recent analysis are higher.
2) IIED and Grantham Institute (2009): Assessing the Costs of Adaptation to Climate Change
The UNFCCC estimates were critiqued in IIED/Grantham Institute study on assessing the costs of adaptation (Parry et alxi). This review highlights that the coastal sector was only partially covered and considered that the UNFCCC estimates were a potential underestimate by factor of 3 due to higher potential sea level rise.
3) World Bank EACC
The Economics of Adaptation to Climate Change (EACC) Studyxii also estimated the costs of adaptation, and also used the DIVA model looking at a range of scenarios.
For the analysis, DIVA was extended to include a sensitivity analysis of more intense tropical storms. This influences adaptation costs only for dikes. The maintenance costs of sea and river dikes and port upgrades globally are also computed outside DIVA. Port costs are based on a strategy of continuously raising existing port areas as sea levels rise.
The resulting costs are shown below. These imply higher costs than the DIVA model runs above, due in part to the inclusion of these other cateogories. However, it is also because the medium run cited is for a Ramstorf A2 scenario, rather than the A1B scenario above.
Annual cost of adaptation for coastal zone protection for the medium sea-level rise scenario, by region, 2010–50 ($ billions at 2005 prices, no discounting)

Time period

Middle East and North Africa

Sub-Saharan Africa

Total Africa

















Source: World Bank, 2009.

Country Studies of the Costs of Coastal Adaptation
The study has also reviewed the existing and emerging national studies, many of which consider the costs of adaptation for coastal zones.
Egypt (OECD, 2004)
A number of previous studies have identified Egypt as at potential high risks from sea level rise. Most recently, Dasgupta et al. (2009) ranked Egypt as the first and second most impacted developing country (of 84 developing coastal nations) by 1m of sea-level rise in terms of potential loss of agricultural land and population displacement, respectively. With this magnitude of sea-level rise, the nation was projected to experience an estimated 6% decrease in GDP resulting in the loss of 28,000 km2 of agricultural land (>13% of the national total), 25,000 km2 of urban area (>5% of the national total) and 24,000km2 of wetland loss (>6% of the national total).
The other extensive study was the OECD study (2004xiii) on the Egypt Nile delta estimated a total loss of land, properties and revenues costing in the range of US$30 billion for the city of Alexandria under a 0.5m sea-level rise of ‘do nothing’ scenario (inundating 30% of the city). The same scenario estimated a total of US$2.9 billion loss from land and property for Rosetta city and US$2.2 billion loss in Port Said.
The study also investigated some adaptation options to respond and ranked these. It considered the costs and cost-effectiveness of options. For Alexandria, the costs of options ranged from $54 million for beach nourishment and groins to $900 million for major land use change. Beach nourishment, technical protection (breakwaters, at a total cost of $468 million) and integrated coastal zone management (at a total cost of $ 550) had the highest cost-effectiveness.
Kenya (SEI, 2009)
Awuor et al, 2008xiv looked at Mombasa, and reported that 17% of the city area could be submerged by a sea-level rise of 30 cm. The study reported that improved irrigation planning further inland and other land management practices could be used for flood management and reducing runoff into the ocean, which could potentially contribute to reducing the impacts of sea-level rise.
The Regional Economics of Climate Change Studies (RECCS) study for Kenya (SEI, 2009xv) included a range of assessments, including analysis of the potential impacts and costs of adaptation for sea level rise. This used the DIVA model outputs, consistent with the study undertaken for AdaptCost above (Brown et al, 2009xvi).
The analysis shows that coastal flooding from sea level rise could affect 10,000 to 86,000 people a year by 2030 (across the scenarios), as well as leading to coastal wetland loss and coastal erosion. The associated economic costs in 2030 are estimated to be $7 - 58 million per year (current prices, no discounting) including flooding. By 2050, these costs could increase to $31 - 113 million per year.
When adaptation was applied, the potential impacts and economic costs above were significantly reduced. The study reported that adaptation has large potential benefits in reducing coastal erosion and inundation. The number of people that could be flooded is dramatically reduced, and is one- two orders of magnitude lower at 2,000 to 11,000 people per year in 2030 across the range of scenarios. The total costs are also significantly reduced.
The cost of adaptation in 2030 is estimated at $28-56 million / year depending on the sea level rise scenario. These costs could rise to $80 million / year by 2050 and higher further in the future. Note even with adaptation, there is some residual damage. The finding is that coastal protection appears to substantively reduce the threat imposed by sea-level rise at a relatively low cost, and in the analysis here, that the benefits of adaptation far outweigh the costs.
Contonou, Benin
Dossou and Glehouenou-Dossou (2007xvii) identifeid the impact on the city of Cotonou in Benin of a rise in sea level. They used the MAGICC IPCC scenario IS92a to construct “Average”, “extreme” and “basic” sea level scenarios.
They anticipate resulting coastal erosion, flooding and salt penetration of water table. Additionally, they project threats to road infrastructure & residential districts, industrial & tourism sectors, ecosystem damage and threats to fishing communities. There is an adaptation plan being developed which currently consists of two options (awaiting funding). One option is to introduce groynes which effectively transfer erosion along coast, away from the city, in tandem with an offer of compensation to those adversely affected. The alternative is to move infrastructure, for example building a new airport on higher ground.
An earlier study (French et al., 1995xviii) estimated that 1m of sea-level rise by 2100, assuming no human response, would threaten 18,000km2 and 3.2 million people would be at risk from flooding, currently costing US$18 billion in Nigeria. These estimates are based on 1992 population.
Protection by hard and soft measures would reduce this risk, but would be costly. For instance, protecting highly developed areas and oil infrastructure from a 1m sea-level rise would, alone, cost US$600-US$700 million. This cost, spread over 50 year (a not unreasonable time scale given sea-level rise projections, and design guidelines for hard structures anticipating future conditions), would cost 0.2-0.3% of the county’s GDP. A 1m sea-level rise would make over 800 villages uninhabitable in the Niger delta, at a cost of US$260million.
Another early study (Dennis et al., 1995xix) estimated that in developed areas in Senegal, accelerated erosion due to sea-level rise could cost more than US$500-US$700 million (12-17% of the country’s GDP at 1995 values) out of which 20-30% represents tourist facilities at risk. It is also estimated that 110,000-180,000 people (1.4% to 2.3% of the 1990 population) could be displaced, the majority of which are located south of the Cap Vert Peninsula.
Protection, such as sea walls and beach nourishment, was estimated to cost US$255-US$845 million (0.7-2.2% of the country’s GDP) over a fifty year period. Beach nourishment was a favoured option, as this would help to maintain the tourist industry, which accounts for around 3% of the GDP.
A study of Dar es Salaam (Mwaipopo, 2000xx) reported very little existing protection. Tourist facilities – hotels and roads are partly protected from erosion by groynes and a sea-wall. The cost for building sea walls to protect important vulnerable areas of the city against a 1-m rise in sea level was estimated as US$ 337 million. The study also projected that on average about 400m landward retreat would occur in Dar es Sallam under a 1-m sea-level rise, and a total of 247km2 land could be lost.
According to the Initial National Communication of Tanania (2003), structures costing US$82 millions in the vulnerable region of Dar es Sallam would also be at risk for a 1-m rise in sea level.
South Africa
There has been extensive work on impacts and adaptation to sea level rise in South Africa. This includes the large study in the Western Cape (Midgley et al, 2005xxi)
There are studies developing adaptation plans (Municipal Adaptation Plan) for Cape Town (Mukheiber and Zievogel, 2007xxii) which include coastal erosion
Most recently, there has been a series of sea-level rise adaptation studies (and costing) in South Africa including local government adaptation planning (Durban and Cape Town
Synthesis of the National Studies
Comparing the aggregate estimates for Africa with information from individual countries is difficult. Broadly speaking, results for some parameters are of the same order of magnitude with previous study estimates (e.g. with Nigeria,), while others show significant differences (e.g. for land loss in Senegal). Much of these differences will arise from the difference in defining coasts and wetland area and the level of aggregation in the analysis.
There are also differences in the framework used to derive adaptation costs. In DIVA, adaptation costs are estimated based on a optimum methods where resources are used where they are most effective. Other studies may have used different methods to calculate levels of protection or different baselines, which may explain the difference in costs. More assessment at the country level is required to enhance our understanding at this important scale of action.
Forthcoming Studies
A large number of forthcoming studies will be available, from the UNFCCC NEEDS project, the UNDP Investment and Financial Flow Assessments, and the World Bank EACC Country Studies. Many of these include adaptation costs for coastal zones. These will all emerge during 2010 and will provide a greater evidence base.
The AdaptCost Project
The AdaptCost Africa project, funded by United Nations Environment Programme (UNEP) under the Climate Change – Norway Partnership, is producing a range of estimates of the financial needs for climate adaptation in Africa using different evidence lines. The study aims:

  • To help African policymakers and the international climate change community to establish a collective target for financing adaptation in Africa.

  • To investigate estimates to adapt to climate change and improve understanding of adaptation processes.

This briefing note was prepared by Paul Watkiss, summarising the Coastal report by Sally Brown, Abiy S. Kebede and Robert J. Nicholls of the School of Civil Engineering and the Environment, University of Southampton, Southampton, UK.

Footnotes and References

1 School of Civil Engineering and the Environment, University of Southampton, UK: Sally Brown, Abiy Kebede and Robert Nicholls

i Cape Verde, Comoros, Madagascar, Mauritius, Reunion (France), Sao Tome & Principe, Seychelles.

ii Boko, M., I. Niang, A. Nyong, C. Vogel, A. Githeko, M. Medany, B. Osman-Elasha, R. Tabo and P. Yanda, 2007: Africa. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge UK, 433-467.

iii OECD, 2006. Metrics for Assessing the Economic Benefits of Climate Change Policies: Sea Level Rise Working Party on Global and Structural Policies. ENV/EPOC/GSP(2006)3/FINAL. Nicholls et al.

iv Nicholls, R.J., 2006. Storm Surges in Coastal Areas. In: M. Arnold, R.S. Chen, U. Deichmann, M. Dilley, A.L. Lerner-Lam, R.E. Pullen and Z. Trohanis (eds), Natural Disaster Hotspots, Case Studies, The World Bank Hazard Management Unit, Disaster Risk Management Series No. 6, Washington, D.C., USA, The World Bank, 79-108.

v Nicholls, R.J., Hanson, S., Herweijer, C., Patmore, N., Hallegatte, S., Corfee-Morlot, J., Chateau, J. and Muir-Wood, R., 2008. Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates. OECD Environment Working Papers, No. 1, OECD publishing, doi: 10.1787/011766488208.

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