Scientific evidence indicates that global warming could well lead to a sea-level rise of 1 meter or more in the 21st century.

A rise in sea levels by a meter from climate change could destroy more than 60 percent of the developing world’s coastal wetlands currently found at one meter or less elevation, according to a World Bank study. That would lead to economic losses of around $630 million per year.

The World Bank analysis considers a variety of types of coastal wetlands at risk in 76 countries and territories, using a number of databases and satellite maps. According to the data, about 99% of the coastal wetlands at elevations of one meter or less in the Middle East and North Africa could disappear, as well as 77% in sub-Saharan Africa, 66% in East Asia and 39% in Latin America and the Caribbean.

Most of the damages would be concentrated in a few countries in East Asia, the Middle East and North Africa. For example, about three-quarters of coastal fresh-water marshes that would be affected by the one-meter rise in sea levels worldwide are located in five countries: Argentina, China, Iran, Mexico and Vietnam. Similarly, 61% of saline wetlands at risk are in Egypt and Libya.

In recent years, coastal wetlands have been disappearing more quickly than other ecosystems, mainly because of land development. Sea-level rise from climate change will exacerbate these losses. The rise in sea levels will lead to wetlands being submerged, pushed inland, or blanketed with salt. How those wetlands fare will vary, depending on the slopes and water flows in the surrounding area.

“The findings are alarming, because wetlands don’t exist just for the birds and plants – people rely on them for water, food, transportation, and other essential goods and services,” says Susmita Dasgupta, a lead environment economist at the Bank’s Development Research Group. She co-authored the study with colleague Brian Blankespoor and consultant Benoit Laplante. “We hope our research can motivate steps to protect wetlands, especially since global warming will for sure accelerate the rise of sea levels.”

The resulting economic losses from coastal wetland destruction will be in addition to other coastal impacts such as the forced relocation of people and infrastructure. An earlier study co-authored by Dasgupta predicted that 60 million people in developing countries would be forced out of their homes if sea levels rise by one meter.

The wetlands study comes as World Bank President Jim Yong Kim is urging the global community to take action on climate change.

The “Sea-Level Rise and Coastal Wetlands” is a paper seeking to quantify how a 1-meter sea-level rise would affect coastal wetlands in 76 developing countries and territories, taking into account how much of wetlands would be submerged and how likely the wetlands would move inland as the coastline recedes.

The paper estimates that approximately 64 percent of the freshwater marsh, 66 percent of Global Lakes and Wetlands Database coastal wetlands, and 61 percent of brackish/saline wetlands are at risk. Two regions would shoulder a large percentage of loss: East Asia and the Pacific, and the Middle East and North Africa. At the country level, the results are extremely skewed with a small number of countries being severely affected. In East Asia, China and Vietnam would bear the brunt of these losses. In the Middle East and North Africa, Libya and Egypt would see the most losses.

The following is part of the paper:

A rough estimate of the economic value of the goods and services produced by Wetlands at risk are approximately $630 million per year in 2000 US dollars.

Coastal wetlands, which are comprised of marshes, swamps, mangroves and other coastal plant communities, provide a large number of goods and services that   contribute to the economic welfare of the local and global communities    (Millennium Ecosystem Assessment, 2005). Examples of ecosystem services   include the protection of shorelines from erosion, storm   buffering, sediment   retention, water   quality   maintenance, nutrient recycling, preservation   of   biodiversity, provision of natural environmental amenities, climate regulation, carbon sequestration, as well as cultural heritage and spiritual benefits.

However, coastal wetlands are declining rapidly.  Recent estimates indicate that   approximately 1% of the global coastal wetland stock was lost each year in the late 20th century.

The causes of wetland loss are numerous and often complex. The rapid loss of   the   global coastal wetland stock in the 20th century was primarily caused by direct land reclamation.  While significant losses due to human actions are likely   to   continue   in the future, it is projected that stresses on wetland areas may be further aggravated in the 21st century due to climate change.  Wetlands face a number of hazards including rise in sea level, increased atmospheric concentration of carbon dioxide, rise in air and water temperature, and changes in the frequency and the intensity of precipitation and storm patterns.

Among these various natural threats of a changing climate, the threat posed by the   rise in sea level has received increased   attention In combination with human activities, it is estimated that a 1m global-mean sea level rise  (SLR) could threaten half of the world’s coastal wetlands, which are designated as wetlands of   international importance, while those that survive could be substantially changed.

Since periodic flooding is the essential characteristic of coastal wetlands, sea-level     rise   (henceforth SLR) can disrupt wetlands in three significant ways: inundation, erosion, and   salt   water intrusion.  The natural impact of SLR causes coastal wetlands to migrate to upland areas. The net change in the area of   total   wetlands depends on   the   slopes   of the wetlands and characteristics of these areas.  If the land has a constant slope all the way through the wetlands  and the upland   areas, then   the   area   lost   to   wetlands   drowning   in the   sea may be equal to the   area acquired by the landward encroachment of high tides. If the slope above is steeper than the wetlands, then   the   SLR   causes   a   net   loss   of   wetland   area.   However, wetland   migration is only possible if the adjacent upland areas are not developed, otherwise all the wetlands may be   lost.

Understanding the impact of SLR on coastal wetlands must therefore take into account factors   that affect the ecological balance of the wetland ecosystem such as the history of sea levels in regard to the development of coastal gradients, relative    geomorphic and sedimentology homogeneity of the coast, the coastal processes   including the   tidal   range   and   its   stability, the availability   of   fresh   water   and   sediment, and   the   salinity   of   soil   and   groundwater.

Even though location-specific studies are    needed    to    define    the    specific    details, experts and scientists agree  that adaptation of wetlands to future sea-level rise depends on its success in landward    progression and is conditioned by the availability of adequate and suitable space for expansion/migration, and a rate of sea level rise that is not greater than the rate at which wetlands can migrate.

This paper is an effort to quantify the coastal wetlands of different types at risk from 1m SLR in 76 developing countries and territories in the five regions of the world.  Our estimates take into account the exposure of wetlands derived from the recent GLWD-3 database to 1m SLR and the estimated capacity of the coastline to retreat and for coastal wetlands ecosystems to move   (or migrate) inland as the coastline   is   receding. Attempts have also been made to estimate the economic loss, which may be associated with adversely impacted wetlands.

Our   estimates indicate that a 1m rise in sea level would lead to a loss of present coastal wetland stocks of 60% or more, depending on wetland type. Human activity   is generally increasing rapidly in coastal areas and thus the coastal wetlands are also likely to be impacted by direct and indirect human actions. However, it is  difficult to predict location-specific socio-economic changes and patterns of land use in the future.  In our study, we refrain from making simplistic assumptions about future states of coastal wetlands.

The sea level will rise gradually over time.  Although there is a scientific consensus that the sea level will continue to rise for centuries due to the time scales associated with climate processes and   feedbacks even if green house gas emissions were to be stabilized today (IPCC 2007), the time profile of SLR   is uncertain. It is difficult to predict the sea level change on a specific date with confidence due to the nonlinearity of the process.

Uncertainty about the time profile of SLR makes valuation of wetland loss over   time difficult. Valuation of a future loss is also complicated due to ambiguity in the rate of time   preference.  In light of these uncertainties, we estimated the economic value of the wetlands at risk for a single scenario of 1m SLR using the current literature on valuation of wetlands. The economic value of the wetlands at risk from 1m SLR in the 76 developing countries considered in this analysis is around USD 630 million per year  (in USD 2000).  It is hoped that the estimates of wetlands at risk from SLR reported in this paper would offer insights into the extent to which countries may be willing to invest to protect coastal wetlands or facilitate their migration as sea level rises.

At the outset, we acknowledge several important limitations of our analysis.  First, we have not assessed the time profile of 1m SLR. We take this scenario as given, and assess the exposure of   the present wetland stock for each of the 76 developing countries and five regions.    Second, the digital elevation  (90m DEM V2) data we use in our analysis gives altitude in 1-meter increments, preventing us from sub-meter SLR modeling. Third, the lack of resolution of spatial data of the wetlands   and digital elevation higher than 90m prevented us from including small islands in   our analysis.  Fourth, our analysis does not estimate potential destruction of   wetlands from direct and indirect human actions.  Fifth, we have not estimated the   net present value of  the coastal wetland loss over a period of time.

To read the whole paper you can download a copy at http://web.worldbank.org/WBSITE/EXTERNAL/NEWS/0,,contentMDK:23365190~pagePK:34370~piPK:34424~theSitePK:4607,00.html