Select Committee on International Development Minutes of Evidence

Memorandum submitted by Professor Robert Nicholls, Flood Hazard Research Centre, Middlesex University


1.  The importance of coastal zones

  Low-lying coastal zones are sensitive to climate change, most particular sea-level rise. This is important when considering sustainable development as coastal zones are among the world's most diverse and productive environments and they also provide home to much of the world's population. In 1990, 1.2 billion people (or 23 per cent of the world's population) lived within 100 km and 100 m of a coastline. These "coastal" populations are growing rapidly due to migration to the coast and urbanisation: large increases in coastal population are expected, particularly in south, south-east and east Asia and around much of Africa. Coastal areas are already threatened directly or indirectly by a range of coastal hazards such as erosion, saline intrusion, flooding/storms and tsunamis. Human activity is also producing profound changes to the world's coastal zone such as reducing freshwater inputs, modifying sediment budgets, armouring the coast and direct and indirect ecosystem destruction. Therefore, climate change and sea-level rise are an additional pressure on coastal areas, which will interact adversely with many of these other trends, and will potentially hinder the goal of sustainable development.

2.  Climate change in coastal areas

  Global warming is expected to lead to an increase in global mean sea-level rise due to thermal expansion of warming surface waters and the melting of small land-based glaciers such as those in the Alps. During the 21st Century, Greenland and Antarctica are expected to make little net contribution to sea level. The IPCC Third Assessment Report estimated that global-mean sea levels had risen 10 to 20 cm during the 20th Century and will rise between nine and 88 cm (the mid estimate is 48 cm) from 1990 to 2100[9]. Thus, there is likely to be a significant acceleration of global-mean sea-level rise during the 21st Century. At the regional and local scale, future changes in sea level are more uncertain due to regional climate change effects on sea level and geological processes influencing land uplift/subsidence. As an example, deltaic areas are always prone to subsidence, so higher rates of sea-level rise might be expected in these areas. This has important implications for the densely-populated deltas of Asia.

  Many other climate factors will change in coastal areas such as rising seawater temperature. Of particular interest are possible changes in the track, frequency and intensity of storm events. For instance, it has been argued that in a warmer world more intense hurricanes are possible than occur today. However, the uncertainties remain too large to be confident of the direction of change, if any, and this is an important area for future research.

3.  The impacts of climate change and sea-level rise

  With global warming and sea-level rise, the IPCC Third Assessment[10] concluded that many coastal systems will experience:

    —  Increased levels of inundation and storm flooding;

    —  Accelerated coastal erosion;

    —  Seawater intrusion into fresh groundwater;

    —  Encroachment of tidal waters into estuaries and river systems;

    —  Elevated sea-surface and ground temperatures.

  Without appropriate adaptation, these physical changes will lead to socio-economic impacts on human populations and their activities, such as increasing flood losses and destruction of beachfront investments. Most assessments to date have only considered the potential impacts of sea-level rise on today's world. These studies all suggest that impact potential in many developing countries is large and increasing rapidly. Other studies point to a global tendency for shoreline retreat on sandy shorelines, and the observed sea-level rise during the 20th Century may be a causal factor, although is still widely debated.

  Natural ecosystems such as saltmarshes, mangroves and coral reefs are already widely degraded by human activities. Given sea-level rise, saltmarshes and mangroves may be further degraded or lost. Coral reefs appear more threatened by rising sea temperature, which could cause death of the reef in tropical areas where corals are near the upper limit of their thermal tolerance. In the longer term, rising CO2 levels could cause chemical changes which would reduce the capacity of the reef to build upwards with sea-level rise. In all cases, this will reduce the range of services (eg, storm protection, fisheries, etc) that these ecosystems provide to coastal communities.

4.  Examples: Flood and Wetland Impacts

  The impacts of sea-level rise on the incidence of coastal flooding and coastal wetlands (excluding coral reefs) have been modelled on a regional and global basis,[11] [12]. In 1990, it is estimated that 10 million people/year experienced flooding due to storm surge globally—nearly all these people live in the developing world. Under a scenario of a 40-cm rise in global sea level, business-as-usual socio-economic changes, and no specific adaptation for sea-level rise, this increases to about 90 million people/year or more by the 2080s. Many of these people will experience flooding every year, suggesting severe impacts and possible displacement of these impacted populations. These results show that a relatively small global rise in sea level (about 40-cm) could have significant adverse impacts on coastal populations, if there is no adaptive response.

  By the 2080s, a 40-cm rise in global-mean sea level could cause the loss of up to 22 per cent of the world's coastal wetlands. Based on projecting existing trends, direct and indirect destruction by humans could cause greater losses. In this situation, sea-level rise would reinforce other adverse trends of wetland loss. The largest losses due to sea-level rise will be where the tidal range is lowest such as around the Mediterranean and Baltic, the Atlantic coast of Central and North America and most small islands, including the Caribbean.

5.  Vulnerable Regions

  All coastal areas are vulnerable to these changes to varying degrees. However, the impacts are likely to be felt disproportionately in certain areas reflecting both natural and socio-economic factors that lead to higher vulnerability. In absolute terms, the affected people identified in the flood analysis discussed in 4) are found around Africa, and most particularly, South and South-East Asia, with lesser impacts in East Asia. The vulnerability of Africa reflects rapid population growth, combined with a limited capacity to implement flood management due to economic constraints. The vulnerability in Asia reflects significant population growth within the numerous large deltas, where implementing flood management is much more expensive than in most other coastal settings. The vulnerability of small islands, particularly low-lying coral atolls such as found in the Maldives has been recognised for some time. The flood analysis suggests that the islands of the Caribbean, the Indian Ocean and the Pacific Ocean may experience the largest relative increase in flood risk. This vulnerability reflects the concentration of population around the coast, even on the "high" islands. While they have not been examined in detail, other impacts such as degradation of coral reefs would seem to make these areas especially vulnerable to climate change. Further, adaptation options in many small islands are more limited than other coastal regions.

  National studies also identify hotspots of vulnerability. For instance, Guyana and Suriname have a high impact potential and have similar problems to many of the Asian deltas. This contrasts with a lower vulnerability in most of South America. There is a need for a systematic identification of similar hotspots at a detailed level around the world to focus more detailed work on impacts and adaptation.

6.  Responses

  Responding to climate change and sea-level rise requires identifying the most appropriate mixture of mitigation and adaptation. Mitigation could greatly reduce the risks associated with sea-level rise and climate change, particularly in the long-term. However, some climate change appears inevitable, so we must also be prepared to adapt to these impacts,[13] [14]. Adaptation acts to reduce the impacts of sea-level rise and climate change, as well as other changes (as well as exploiting benefits). Given the large and growing concentration of people and activity in the coastal zone, autonomous (ie, spontaneous individual and market-driven) adaptation processes are unlikely to be sufficient to respond to sea-level rise. Further, adaptation in the coastal context is almost universally seen as a public responsibility. Therefore, all levels of government have a key role in developing and facilitating appropriate adaptation measures. There are three generic planned adaptation options for sea-level rise and climate change:

    —  (Planned) Retreat—all natural system effects are allowed to occur and human impacts are minimised by pulling back from the coast;

    —  Accommodation—all natural system effects are allowed to occur and human impacts are minimised by adjusting human use of the coastal zone;

    —  Protection—natural system effects are controlled by soft or hard engineering, reducing human impacts in the zone that would be impacted without protection.

  However, adaptation needs to be seen as a process rather than just these technical measures. A particular issue of interest is resolving conflicts between sustaining the human use and ecosystem functioning of the coastal zone under climate change and sea-level rise. There is a need to start strategic planning of appropriate responses now, particularly enhancing the technical and institutional capacity of coastal management, which is under-developed in much of the world, including the most vulnerable regions identified here. Given the wide range of existing coastal problems, such planning and capacity building could have immediate benefits.

7.  Conclusions

  The main conclusions are as follows:

    —  Climate change in coastal areas will lead to global-mean sea-level rise, rising seawater temperatures and possible changes in the track, frequency and intensity of storms, among other changes. This is an additional stress on coastal zones, which could hinder the goal of sustainable development.

    —  Most impact assessments have focussed on the impacts of sea-level rise and no other climate change. They identify a high and increasing impact potential in many developing countries.

    —  The most vulnerable regions appear to be Africa and parts of Asia, reflecting high and growing exposure and the low economic base to support adaptation. However, in relative terms, small islands, including the Caribbean, appear most vulnerable, and they have some of the most limited adaptation options.

    —  Coastal ecosystems are also threatened by climate change, although this requires more quantification, particularly for coral reefs.

    —  A more detailed global analysis of the different types of vulnerability is essential to focus work on impacts and adaptation.

    —  An appropriate mixture of mitigation and adaptation would be the best response to climate change. There are a range of effective adaptation options, although they need to be considered within the broad process of coastal management. Therefore, enhancing the capacity for coastal management is a fundamental step in adaptation to climate change and sea-level rise.

  Based on this, DFID could help to promote sustainable development of coastal areas by:

    —  Encouraging efforts to improve our understanding of vulnerability;

    —  Promoting more evaluation of the implications of climate change in coastal areas, particularly in the vulnerable regions identified above;

    —  Enhancing coastal management capacity so that it can deal with the full range of issues, including climate change.

Professor Robert Nicholls, Professor in Coastal Geomorphology and Management,

Flood Hazard Research Centre,

Middlesex University

January 2002

9   Houghton, J T, Ding, Y, Griggs, D J, Noguer, M, van der Linden, P J and Xiaosu, D (eds), 2001. Climate Change 2001. The Scientific Basis. Cambridge University Press, Cambrid. Back

10   McCarthy, J J, Canziani, O F, Leary, N A, Dokken, D J, & White, K S (eds), 2001. Climate Change 2001: Impacts, Adaptation and Vulnerability, Cambridge University Press, Cambrid. Back

11   Climate change and its impacts. Some highlights from the ongoing UK research programme: a first look at results from the Hadley Centre's new climate model. 1998. Department of the Environment, Transport and the Regions, London and the Met Office, Brackn. Back

12   Nicholls, R J, Hoozemans, F M J, & Marchand, M 1999. Increasing flood risk and wetland losses due to global sea-level rise: Regional and global analyses. Global Environmental Change, 9, S69-S. Back

13   Parry, M, Arnell, N, Mcmichael, T, Nicholls, R, Martens, P, Kovats, S, Livermore, M, Rosenzweig, C, Iglesias, A & Fischer, G, 2001. Millions at Risk: Defining Critical Climate Threats and Targets. Global Environmental Change and also avalable at Back

14   Arnell, N W, Cannell, M G R, Hulme, M, Kovats, R S, Mitchell, J F B, Nicholls, R J Parry, M L, Livermore, M T J & White, A 2002. The consequences of CO2 stabilisation for the impacts of climate change Climatic Change, in press. Back

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