**Dr. Virginia Burkett**

**Chief Scientist for Global Change Research**

**U.S. Geological Survey**

**U.S. Department of the Interior**

**Before the Committee on Science and Technology**

**United States House of Representatives**

**Hearing on the State of Climate Change Science 2007:**

**The Findings of the Fourth Assessment Report by the**

**Intergovernmental Panel on Climate Change (IPCC), Working Group II:**

**Climate Change Impacts, Adaptation and Vulnerability**

**April 17, 2007**

Mr. Chairman and Members of the Committee, as a Lead Author of the
Fourth Assessment Report by the Intergovernmental Panel on Climate
Change (IPCC), Working Group II, I am pleased to present a summary of
the findings found in Chapter 6, "Coastal Systems and Low-Lying Areas,"
of the report. First, I want to acknowledge my co-authors, with whom I
have collaborated over the past three years to develop this assessment
of climate change impacts, adaptation and vulnerability in coastal
systems:

> Robert J. Nicholls (UK), Poh Poh Wong (Singapore), Jorge Codignotto
> (Argentina), John Hay (New Zealand), Roger McLean (Australia),
> Sachooda Ragoonaden (Mauritius), and Colin D. Woodroffe (Australia)

Dr. Nichols and Dr. Wong served as Convening Lead Authors for the
coastal chapter.

I deeply appreciate being nominated by the United States Government to
serve as a Lead Author of the Fourth Assessment Report, as well as the
prior assessment report published by the IPCC in 2001. The charge to the
authors of the Fourth Assessment Report by the IPCC was to develop a
balanced, comprehensive and policy-relevant assessment of current
knowledge, which:

\- evaluates the full range of knowledge (e.g., positive and negative
effects),

\- is policy relevant, not prescriptive,

\- is supported by clear evidence,

\- is clear about underlying assumptions, and confidence levels,

\- emphasizes new knowledge since the IPCC's Third Assessment Report,

\- is more concise than the Third Assessment Report, with better
connections to Working Groups I and III, and with wider use on
non-English sources of knowledge,

\- and is lucidly written.

The IPCC Working Group II contribution to the Fourth Assessment Report
was guided by a complex, open and peer-reviewed process that engaged
several hundred authors and roughly 50 review editors from 47 countries;
and well over 800 expert reviewers. The coastal chapter authors
responded to roughly 1500 comments received during external peer and
government reviews, and many of these comments led us to additional new
literature about coasts and climate change. I estimate that our coastal
chapter writing team reviewed between 500 and 700 scientific journal
articles, books and scientific proceedings published since 2000.

For each chapter of the IPCC report, two or three Review Editors were
selected by the IPCC from the lists of experts nominated by the
governments. The three Review Editors assigned to the coastal chapter
were: Job Dronkers (Netherlands), Geoff Love (Australia), and Jin-Eong
Ong (Malaysia). The main duty of these scientists was to ensure that we
responded appropriately to comments on our draft chapter from experts
and the governments during two separate cycles of review. With each
review the scope of the material contained in the chapter expanded and
the consensus of the authors emerged fairly easily in our case as we
identified the key drivers and their impacts.

Please note that we indicated our confidence levels in these statements
and many of our scientific findings by using endnotes (e.g., High
Confidence) or by using the IPCC accepted terminology for assessing the
likelihood of an outcome having occurred or occurring the in the future.
When IPCC authors use the term "very likely" in a sentence, for example,
the authors have reached a consensus that an outcome has an estimated
probability of 90 to 99 percent. This terminology was used across all of
the IPCC Working Group II chapters. Also, please note that for every
statement made, there is supporting literature cited in the coastal
chapter.

***Key Policy-Relevant Findings***

Since the Third Assessment Report was published in 2001, our
understanding of the implications of climate change for coastal systems
and low lying areas (henceforth referred to as 'coasts') has increased
substantially. In the Executive Summary of the coastal chapter, we
identified six important policy-relevant findings, which are extracted
below from our text:

**1. Coasts are experiencing the adverse consequences of hazards related
to climate and sea level rise (very high confidence).** They are highly
vulnerable to extreme events, such as storms which impose substantial
costs on coastal societies. Annually, about 120 million people are
exposed to tropical cyclone hazards which had killed 250,000 people from
1980 to 2000. Through the 20^th^ century, global rise of sea level
contributed to increased coastal inundation, erosion and ecosystem
losses, but with considerable local and regional variation due to other
factors. Late 20^th^ Century effects of rising temperature include loss
of sea ice, thawing of permafrost and associated coastal retreat, and
more frequent coral bleaching and mortality.

**2.** **Coasts will be exposed to increasing risks over coming decades
due to many compounding** **climate-change factors (very high
confidence).** Anticipated climate-related changes include: an
accelerated rise in sea level of up to 0.6 m or more by 2100; further
rise in sea surface temperatures by up to 3°C; an intensification of
tropical and extratropical cyclones; larger extreme waves and storm
surges; altered precipitation/run-off; and ocean acidification. These
phenomena will vary considerably at regional and local scales, but the
impacts are virtually certain to be overwhelmingly negative. Corals are
threatened with increased bleaching and mortality due to rising sea
surface temperatures. Coastal wetland ecosystems, such as salt marshes
and mangroves, are especially threatened where they are sediment starved
or constrained on their landward margin. Degradation of coastal
ecosystems, especially wetlands and coral reefs, has serious
implications for the well-being of societies dependent on the coastal
ecosystems for goods and services. Increased flooding and the
degradation of freshwater, fisheries and other resources could impact
hundreds of millions of people and socio-economic costs will escalate as
a result of climate change for coasts.

**3. The impact of climate change on coasts is exacerbated by increasing
human-induced pressures** **(very high confidence).** Utilization of the
coast increased dramatically during the 20th century and this trend is
virtually certain to continue through the 21st century. Under the
Special Report on Emissions Scenarios (SRES), the coastal population
could grow from 1.2 billion people (in 1990) to 1.8 to 5.2 billion
people by the 2080s, depending on assumptions about migration.
Increasing numbers of people and assets at risk at the coast are subject
to additional stresses by land-use and hydrological changes in
catchments, including dams that reduce sediment supply to the coast.
Populated deltas (especially Asian megadeltas), low lying coastal urban
areas, and atolls are key societal hotspots of coastal vulnerability,
occurring where the stresses on natural systems coincide with low human
adaptive capacity and high exposure. Regionally, south, south-east and
east Asia, Africa and small islands are most vulnerable. Climate change
therefore reinforces the desirability of managing coasts in an
integrated manner.

**4. Adaptation for the coasts of developing countries will be more
challenging than for coasts of** **developed countries, due to
constraints on adaptive capacity (high confidence).** While physical
exposure can significantly influence the vulnerability for both human
populations and natural systems, a lack of adaptive capacity is often
the most important factor that creates a hotspot of human vulnerability.
Adaptive capacity is largely dependent upon development status.
Developing nations may have the political or societal will to protect or
relocate people who live in low-lying coastal zones, but without the
necessary financial and other resources/capacities, their vulnerability
is much greater than a developed nation in an identical coastal setting.
Vulnerability will also vary between developing countries, while
developed countries are not insulated from the adverse consequences of
extreme events.

**5. Adaptation costs for vulnerable coasts are much less than the costs
of inaction (high** **confidence).** Adaptation costs for climate change
are much lower than damage costs without adaptation for most developed
coasts, even considering only property losses and human deaths. As post
event impacts on coastal businesses, people, housing, public and private
social institutions, natural resources, and the environment generally go
unrecognized in disaster cost accounting, the full benefits of
adaptation are even larger. Without adaptation, the high-end sea level
scenarios combined with other climate change (e.g., increased storm
intensity) are as likely as not to render some islands and low-lying
areas uninhabitable by 2100, so effective adaptation is urgently
required.

**6. The unavoidability of sea level rise even in the longer-term
frequently conflicts with present day human development patterns and
trends (high confidence).** Sea level rise has substantial inertia and
will continue beyond 2100 for many centuries. Irreversible breakdown of
the West Antarctica and/or Greenland ice sheets, if triggered by rising
temperature, would make this long-term rise significantly larger,
ultimately questioning the viability of many coastal settlements across
the globe. The issue is reinforced by the increasing human use of the
coastal zone. Settlement patterns also have substantial inertia, and
this issue presents a challenge for long-term coastal spatial planning.
Stabilization of climate could reduce the risks of ice sheet breakdown,
and reduce but not stop sea level rise due to thermal expansion. Hence,
it is now more apparent than in the Third Assessment Report that the
most appropriate response to sea level rise for coastal areas is a
combination of *adaptation* to deal with the inevitable rise, and
*mitigation* to limit the long-term rise to a manageable level.

***Human Development Patterns Interact***

***with Climate Drivers and Impacts on Coastal Systems***

Coasts are very likely to be exposed to increasing risks due to climate
change and sea level rise and the effect will be exacerbated by
increasing human-induced pressures on coastal areas. One of our main
conclusions is that the influence of human development activities in
coasts and adjacent watersheds generally had a more important influence
on coastal systems than did climate change during the past century.
Utilization of the coast increased dramatically during the 20^th^
Century, a trend that seems certain to continue through the 21^st^
Century. Coastal population growth in many of the world's deltas,
barrier islands, and estuaries has led to widespread conversion of
natural coastal landscapes to agriculture, aquaculture, silviculture, as
well as industrial and residential uses. It has been estimated that 23
percent of the world's population lives both within 100 km distance of
the coast and less than 100 m above sea level, and population densities
in coastal regions are about three times higher than the global average.

The top bar in the figure below lists the six climate change drivers
that are likely to affect coastal ecosystems, which are generally
influenced by a combination of natural processes and human development
activity. During the preparation of the coastal chapter of the IPCC
Third Assessment report, sea level rise was the focus of the available
literature relating to climate change and coastal impacts. Sea level
rise still dominates the literature on coastal areas and climate change,
but our review shows that more information is now available regarding
the effects of increases in temperature, storm intensity and waves,
increased carbon dioxide (CO~2~) concentration, and changes in run-off.

Figure 6.1 in the Coastal Chapter, IPCC Fourth Assessment Report, 2007.

Climate change and the coastal system showing the major climate change
factors,

including external marine and terrestrial influences.

![](media/image1.jpeg){width="5.761805555555555in"
height="2.9604166666666667in"}

Increases of extreme sea levels due to changes in storm characteristics
are generally of more concern for populated coastal areas than mean sea
level rise. The coastal chapter reports that climate models suggest both
tropical and extratropical storm intensity will increase as the
temperature of the atmosphere and sea surface rise \-- this implies
additional coastal impacts than attributable to sea level rise alone,
especially for tropical and mid-latitude coastal systems. An increase in
the intensity of tropical cyclones entering the Gulf of Mexico, for
example, is consistent with the observed changes in sea surface
temperature in the equatorial Atlantic Ocean where Gulf of Mexico
hurricanes form. Changes in other storm characteristics are less certain
and the number of tropical and extra-tropical storms might even reduce.
Similarly, extreme wave heights will likely increase with more intense
storms. Changes in run-off driven by changes to the hydrological cycle
appear likely, but the uncertainties are large. Increases in atmospheric
CO~2~ concentrations can enhance photosynthesis and productivity of
plant communities, but because plants respond differently to the
increase in CO~2~, competition among plant species may alter the
structure of coastal plant communities. Increasing atmospheric CO~2~
levels can adversely affect coral reefs by decreasing the pH of the
ocean, which decreases the carbonate saturation of seawater. The table
below summarizes some of the impacts on coastal systems that are
discussed in our chapter.

Table 6.2 of the Coastal Chapter, IPCC Fourth Assessment Report, 2007.

Trend in climate drivers identified in Figure 6.1 due to climate change
and their main physical and ecosystem effects on coastal systems and
low-lying areas.

(Nature of Change: ↑ increase; R regional variability; ? uncertain).

+---+------------+-----------------------------------------------------+
| * |            | **Main Physical and Ecosystem Effects (discussed in |
| * |            | Section 6.4.1)**                                    |
| C |            |                                                     |
| l |            |                                                     |
| i |            |                                                     |
| m |            |                                                     |
| a |            |                                                     |
| t |            |                                                     |
| e |            |                                                     |
| D |            |                                                     |
| r |            |                                                     |
| i |            |                                                     |
| v |            |                                                     |
| e |            |                                                     |
| r |            |                                                     |
| * |            |                                                     |
| * |            |                                                     |
|   |            |                                                     |
| * |            |                                                     |
| * |            |                                                     |
| ( |            |                                                     |
| c |            |                                                     |
| h |            |                                                     |
| a |            |                                                     |
| n |            |                                                     |
| g |            |                                                     |
| e |            |                                                     |
| ) |            |                                                     |
| * |            |                                                     |
| * |            |                                                     |
+---+------------+-----------------------------------------------------+
| C |            | Increased CO~2~ fertilization; Decreased seawater   |
| O |            | pH (or 'ocean acidification') negatively impacting  |
| ~ |            | coral reefs and other pH sensitive organisms.       |
| 2 |            |                                                     |
| ~ |            |                                                     |
| c |            |                                                     |
| o |            |                                                     |
| n |            |                                                     |
| c |            |                                                     |
| e |            |                                                     |
| n |            |                                                     |
| t |            |                                                     |
| r |            |                                                     |
| a |            |                                                     |
| t |            |                                                     |
| i |            |                                                     |
| o |            |                                                     |
| n |            |                                                     |
| ( |            |                                                     |
| ↑ |            |                                                     |
| ) |            |                                                     |
+---+------------+-----------------------------------------------------+
| S |            | Increased stratification/changed circulation;       |
| e |            | Reduced incidence of sea ice at higher latitudes;   |
| a |            | Increased coral bleaching and mortality (see Box    |
| s |            | 6.1); Poleward species migration; Increased algal   |
| u |            | blooms.                                             |
| r |            |                                                     |
| f |            |                                                     |
| a |            |                                                     |
| c |            |                                                     |
| e |            |                                                     |
| t |            |                                                     |
| e |            |                                                     |
| m |            |                                                     |
| p |            |                                                     |
| e |            |                                                     |
| r |            |                                                     |
| a |            |                                                     |
| t |            |                                                     |
| u |            |                                                     |
| r |            |                                                     |
| e |            |                                                     |
| ( |            |                                                     |
| S |            |                                                     |
| S |            |                                                     |
| T |            |                                                     |
| ) |            |                                                     |
| ( |            |                                                     |
| ↑ |            |                                                     |
| , |            |                                                     |
| R |            |                                                     |
| ) |            |                                                     |
+---+------------+-----------------------------------------------------+
| S |            | Inundation, flood and storm damage (see Box 6.2);   |
| e |            | Erosion; Saltwater Intrusion; Rising water tables/  |
| a |            | impeded drainage; Wetland loss (and change).        |
| l |            |                                                     |
| e |            |                                                     |
| v |            |                                                     |
| e |            |                                                     |
| l |            |                                                     |
| ( |            |                                                     |
| ↑ |            |                                                     |
| , |            |                                                     |
| R |            |                                                     |
| ) |            |                                                     |
+---+------------+-----------------------------------------------------+
| > | Intensity  | Increased extreme water levels and wave heights;    |
|   | (↑, R)     | Increased episodic erosion, storm damage, risk of   |
| S |            | flooding and defense failure (see Box 6.2);         |
| t |            |                                                     |
| o |            |                                                     |
| r |            |                                                     |
| m |            |                                                     |
+---+------------+-----------------------------------------------------+
|   | Frequency  | Altered surges and storm waves and hence risk of    |
|   | (?, R)     | storm damage and flooding (see Box 6.2).            |
+---+------------+-----------------------------------------------------+
|   | Track      |                                                     |
|   | (?,R)      |                                                     |
+---+------------+-----------------------------------------------------+
| W |            | Altered wave conditions, including swell; Altered   |
| a |            | patterns of erosion and accretion; Re-orientation   |
| v |            | of beach planform.                                  |
| e |            |                                                     |
| c |            |                                                     |
| l |            |                                                     |
| i |            |                                                     |
| m |            |                                                     |
| a |            |                                                     |
| t |            |                                                     |
| e |            |                                                     |
|   |            |                                                     |
| ( |            |                                                     |
| ? |            |                                                     |
| , |            |                                                     |
| R |            |                                                     |
| ) |            |                                                     |
+---+------------+-----------------------------------------------------+
| R |            | Altered flood risk in coastal lowlands; Altered     |
| u |            | water quality/salinity; Altered fluvial sediment    |
| n |            | supply; Altered circulation and nutrient supply.    |
| - |            |                                                     |
| o |            |                                                     |
| f |            |                                                     |
| f |            |                                                     |
| ( |            |                                                     |
| R |            |                                                     |
| ) |            |                                                     |
+---+------------+-----------------------------------------------------+

We considered how these climate-related variables would influence the
sustainability of each major coastal system and coral reefs. A summary
with examples from our chapter is presented below (note: the specific
examples highlighted here comprise only a few of the impacts described
in the chapter):

***Beaches, rocky shorelines, and cliffed coasts -*** Most of the
world's sandy shorelines retreated during the past century and sea level
rise is one underlying cause. One half or more of the Mississippi and
Texas shorelines eroded at average rates of 3.1 to 2.6 m/yr since the
1970s, while 90 percent of the Louisiana shoreline eroded at a rate of
12.0 m/yr. In Nigeria shoreline retreat rates up to 30 m/yr are reported
and in the United Kingdom 67 percent of the coastline experienced a
landward retreat of the low-water mark over the past century. An
acceleration in sea level rise will widely exacerbate beach erosion
around the globe, although the local response will depend on the total
sediment budget. Even gravel beaches and soft rock cliffs are vulnerable
to climate change via changes in storm intensity, sea level rise and
changes in precipitation patterns, which affect the physical processes
that govern the evolution of these coastal systems. The combined effects
of beach erosion and storms can lead to the erosion or inundation of
other coastal systems as well. For example, an increase in wave heights
in coastal bays is a secondary effect of sandy barrier island erosion in
Louisiana, and increased wave heights have enhanced erosion rates of bay
shorelines, tidal creeks, and adjacent wetlands.

***Deltas --*** Deltas have long been recognized as highly sensitive to
sea level rise. Rates of relative sea level rise can greatly exceed the
global average rate of sea level rise in many heavily populated deltaic
areas due to subsidence, including the Chao Phraya delta, the
Mississippi River delta, and the Changjiang River delta because of human
activities. Natural subsidence due to autocompaction of sediment under
its own weight is enhanced by sub-surface fluid withdrawals and
drainage, which increases the potential for inundation, especially for
the most populated cities on these deltaic plains (i.e., Bangkok, New
Orleans, and Shanghai). Most of the land area of Bangladesh consists of
the deltaic plains of the Ganges, Brahmaputra, and Meghna rivers.
Accelerated global sea level rise and higher extreme water levels may
have acute effects on human populations of Bangladesh (and parts of West
Bengal, India).

> Sea level rise poses a particular threat to deltaic environments,
> especially when coupled with the synergistic effects of other climate
> and human pressures. These effects are best illustrated in large
> deltas with an area greater than 100,000 km^2^ (called "megadeltas" in
> the IPCC report) due to their often large populations and important
> environmental services. The problems of climate change in megadeltas
> are reflected throughout the IPCC Working Group II Fourth Assessment
> Report where a number of chapters considered their vulnerability from
> complementary perspectives. The coastal chapter describes the
> vulnerability of people living in delta systems across the globe, and
> concludes that the large populated Asian megadeltas are especially
> vulnerable to climate change. The Mississippi River delta is another
> megadelta that is considered highly vulnerable to the impacts of
> climate change. Chapter 10 (Asia Region) examines the Asian megadeltas
> in more detail, while Chapter 5 (Food, Fiber, and Forest Products)
> examines the threats to fisheries in the lower Mekong and Mekong delta
> due to climate change. Hurricane Katrina made landfall on the
> Mississippi delta in Louisiana, and the text box below from the
> coastal chapter considers different aspects of this important event,
> which gives an indication of the likely impacts if tropical storm
> intensity continues to increase. Lastly, the Polar Chapter (Chapter
> 15) considers the specific problems of Arctic megadeltas where the
> advance/retreat of Arctic marine deltas is highly dependent on the
> protection afforded by near-shore and land-fast sea ice, which is
> disappearing rapidly in the Arctic Ocean. The Mackenzie and Lena river
> deltas are fed by the largest Arctic rivers of North America and
> Eurasia, respectively. In contrast to non-polar megadeltas, the
> physical development and ecosystem health of these deltaic systems are
> strongly controlled by cryospheric processes and hence highly
> susceptible to the effects of climate change.

![](media/image2.png){width="5.99375in" height="3.3645833333333335in"}

***Estuaries and lagoons -*** Sea level rise will generally lead to
higher water levels and salt water intrusion in coastal estuaries,
thereby tending to shift existing coastal plant and animal communities
inland. A globally-intensified hydrologic cycle and regional changes in
run-off also portend changes in estuarine water quality. Some of the
greatest potential impacts of climate change on estuaries may result
from changes in physical mixing characteristics caused by changes in
freshwater runoff. Changes in the timing of freshwater delivery to
estuaries, for example, could lead to a decoupling of the juvenile
phases of many estuarine and marine fishery species with available
nursery habitat. Freshwater inflows into estuaries influence water
residence time, nutrient delivery, vertical stratification, salinity,
and control of phytoplankton growth rates in estuaries. Increased water
temperature could affect algal production and the availability of light,
oxygen and carbon for other estuarine species. As estuarine water
temperature increases, algal blooms are likely to become more common.

> An effect of rising sea level in some hypersaline lagoonal systems,
> such as the Laguna Madre of Mexico and Texas, will be greater water
> depths, leading to increased tidal exchange and hence reduced
> salinity. As an analogue, the lowering of salinity in the Laguna Madre
> since 1949, attributed primarily to the dredging of the Gulf
> Intracoastal Waterway and increased drainage from agricultural lands,
> has shifted seagrass species from the highly salt tolerant shoalgrass
> (*Halodule wrightii*) to manatee grass (*Syringodium filiforme*),
> which has a lower salinity tolerance.
>
> A projected increase in the intensity of tropical cyclones and other
> coastal storms could alter bottom sediment dynamics, organic matter
> inputs, phytoplankton and fisheries populations, salinity and oxygen
> levels, and biogeochemical processes in estuaries and lagoons.

***Mangroves, Salt Marshes and Sea Grasses -*** Coastal vegetated
wetlands are sensitive to climate change because their location is
intimately linked to sea level. Several global and regional analyses
suggest significant losses of coastal vegetated wetlands during the
21^st^ Century under scenarios of accelerated sea level rise, with
global losses in one study estimated at 33 percent and 44 percent given
a 36-cm and 72-cm rise in sea level from 2000 to 2080, respectively.
However, wetland processes are complex and the impacts on any particular
tract of marsh or forest will depend upon local rates of sediment
accretion, elevation, vertical land motion (such as subsidence) and
other local processes. Changes in storm intensity can also affect
vegetated coastal wetlands (see box on Hurricane Katrina effects).

> Climate change will likely have its most pronounced effects on coastal
> marshes through the alteration of hydrologic regimes, specifically,
> changes in the timing and volume of water delivered to the coast.
> Other variables - altered biogeochemistry, altered amounts and pattern
> of suspended sediments loading, fire, oxidation of organic sediments
> and the physical effects of wave energy - may also play important
> roles in determining regional and local impacts. Regional losses of
> coastal marsh are expected to be most severe on the Atlantic and Gulf
> of Mexico coasts of North and Central America, the Caribbean, the
> Mediterranean, the Baltic and most small island regions due to their
> low tidal range.
>
> Mangrove communities are likely to show a blend of positive (e.g.,
> from higher levels of CO~2~ and temperature) and negative (e.g.,
> increased saline intrusion and erosion) effects, which will largely
> depend on site specific factors. Increasing salinity has played a role
> in the expansion of mangroves into adjacent marshes in the Florida
> Everglades and throughout southeastern Australia during the past 50
> years. Increased salinity of coastal waters since 1950 has contributed
> to the decline of cabbage palm forests in Florida and baldcypress
> forests in Louisiana.
>
> Changes in salinity and temperature and increased sea level,
> atmospheric CO~2~, and storm activity will alter seagrass
> distribution, productivity, and community composition. Increases in
> the amount of dissolved CO~2~ and, for some species, (bicarbonate)
> HCO~3~^-^ present in aquatic environments will lead to higher rates of
> photosynthesis in submerged aquatic vegetation, similar to the effects
> of CO~2~ enrichment on most terrestrial plants, but these changes in
> aquatic carbon availability can also increase the growth of suspended
> or epiphytic algae that reduce light needed for sea grass survival.

***Coral Reefs*** - Coral "bleaching" refers to the loss of symbiotic
algae and/or their pigments and has been observed on many reefs since
the early 1980s. Slight paling occurs naturally in response to seasonal
increases in sea surface temperature and solar radiation. Corals bleach
white in response to anomalously high sea surface temperature (about
1^o^C above average seasonal maxima, often combined with high solar
radiation). If bleaching is prolonged, or if sea surface temperature
exceeds 2^o^C above seasonal maxima, corals die. The most severe
world-wide bleaching events appear to be associated with El Niño events.
Major bleaching events were observed in 1982-83, 1987-88, 1994-95, and
most extensively in 1998. Since 1998 there have been several extensive
bleaching events. For example, in 2002 bleaching occurred on much of the
Great Barrier Reef and reefs in the eastern Caribbean experienced a
massive bleaching event in late 2005, one of the hottest years on
record.

> There is very limited evidence that corals can adapt to increases in
> temperature; corals and other calcifying organisms (e.g., molluscs,
> foraminifers) are considered extremely susceptible to increases in sea
> surface temperature that are likely during the coming decades.
> Bleaching events reported in recent years have already impacted many
> reefs, and their more frequent recurrence is very likely to further
> reduce both coral cover and diversity on reefs over the next few
> decades. There are other threats to reefs associated with climate
> change apart from coral bleaching, in addition to non-climatic
> stresses such as overfishing, pollution and sediment influxes.
> Increased concentrations of CO~2~ in seawater will lead to ocean
> acidification, which will affect aragonite saturation state and reduce
> calcification rates of calcifying organisms such as corals. An
> increase in tropical storm intensity would further endanger coral
> reefs with impacts ranging from minor breakage of fragile corals to
> destruction of the majority of corals on a reef.

The bleaching of corals above a certain sea surface temperature is a
threshold-type response that illustrates the complex, nonlinear behavior
of coastal systems to changes in climate. Another temperature-related
threshold is the melting of polar permafrost which results in coastal
erosion. Several other types of thresholds characterize the response of
coastal systems to climate change and are reported in the IPCC coastal
chapter. The key message is that while some coastal systems do not
appear to be vulnerable to the rates of change experienced during the
20^th^ century, they each have a limited capacity to adapt to changes in
climate and in many cases there are thresholds at which rapid changes in
coastal systems are likely to occur.

### *Consequences for Human Society*

I understand that Dr. Roger Pulwarty from the National Oceanic and
Atmospheric Administration is testifying today on Chapter 17 of the IPCC
report, titled *Assessment of Adaptation Practices, Options, Constraints
and Capacity*. Dr. Pulwarty focuses on adaptation strategies that
society can use to adjust to climate change, to moderate potential
damages, to take advantage of opportunities, or to cope with the
consequences.

As Dr. Pulwarty points out, adaptation procedures could increase
societal resilience to the negative consequences of climate change in
the future. That said, since much of the world's population is located
at or near the coast and coastal systems provide many valuable goods and
services globally, the changes that we anticipate in coastal systems
will have widespread societal consequences. In our chapter we presented
a synthesis of current knowledge about coastal impacts of climate change
for six different socio-economic sectors, as highlighted below:

1.  *Freshwater resources* -- Saltwater intrusion due to sea level rise
    alone will have serious economic effects for many coastal
    communities. Although the coast contains a substantial proportion of
    the world's population, it has a much smaller proportion of the
    global renewable water supply, and the coastal population is growing
    faster than elsewhere, exacerbating this imbalance. Freshwater
    supply problems due to climate change are most likely in developing
    countries with a high proportion of coastal lowland, arid and
    semi-arid coasts, coastal megacities (particularly in the
    Asia-Pacific region), and small island states.

2.  *Agriculture, forestry, and fisheries* -- Climate change is expected
    to have impacts on agriculture and, to a lesser extent, on forestry.
    Climate variability and change also impacts fisheries in coastal and
    estuarine waters. More frequent extreme climate events, together
    with higher rainfall intensity and longer dry spells, may impact
    negatively on crop yields. Cyclone landfall causing floods and
    destruction, have negative impacts on coastal areas, e.g., coconuts
    in India, or sugar cane and bananas in Queensland. Rising sea level
    is predicted to have negative impacts on coastal agriculture.
    Detailed modelling of inundation implies significant changes to the
    number of rice crops possible in the Mekong delta under 20-40 cm of
    relative sea level rise. Rising sea level potentially threatens
    inundation and soil salinization of palm oil and coconuts in Benin
    and Cote d'Ivoire and mangoes, cashew nuts and coconuts in Kenya.

3.  *Human settlements, infrastructure, and migration* - Climate change
    and sea level rise affects coastal settlements and infrastructure in
    several ways. Sea level rise raises extreme water levels with
    possible increases in storm intensity portending additional climate
    impacts on many coastal areas, while saltwater intrusion may
    threaten water supplies. The degradation of natural coastal systems
    due to climate change, such as wetlands, beaches and barrier islands
    removes the natural defenses of coastal communities against storm
    surge. Hundreds of millions of people are vulnerable to flooding due
    to sea level rise, especially in densely populated and low-lying
    settlements where adaptive capacity is relatively low and which
    already face other challenges such as tropical storms or local
    coastal subsidence. The numbers affected will be largest in the
    mega-deltas of Asia. Africa is also likely to see a substantially
    increased exposure, with East Africa (Mozambique) having particular
    problems due to the combination of tropical storm landfalls and
    large projected population growth in addition to sea level rise.

4.  *Human health -* Coastal communities, particularly in low income
    countries, are vulnerable to a range of health effects due to
    climate variability and long-term climate change, particularly
    extreme weather and climate events (such as cyclones, floods, and
    droughts). Communities that rely on marine resources for food are
    vulnerable to climate-related impacts, in both health and economic
    terms. Temperature changes play a role in determining human health
    risks, such as from cholera and other enteric pathogens (*Vibrio
    parahaemolyticus*), harmful algal blooms, and shellfish and reef
    fish poisoning.

5.  *Biodiversity --* The distribution, productivity, and diversity of
    species in coastal ecosystems is sensitive to variations in weather,
    climate, and sea level. Changes in the ranges of invertebrates and
    waterfowl have already been observed in some coastal regions in
    response to increases in temperature. It is clear, however, that
    responses of intertidal and shallow marine organisms are more
    complex than simply latitudinal shifts related to temperature
    increase, with complex biotic interactions superimposed on the
    abiotic.

6.  *Recreation and tourism -* Climate change may influence tourism
    directly via the decision-making process by influencing tourists to
    choose different destinations; and indirectly as a result of sea
    level rise and resulting coastal erosion. In general, air
    temperature rise is most important to tourism, except where factors
    such as sea level rise promotes beach degradation and viable
    adaptation options (e.g., nourishment or recycling) are not
    available. Other likely impacts of climate change on coastal tourism
    are due to coral reef degradation. Temperature and rainfall pattern
    changes may impact water quality in coastal areas and this may lead
    to more beach closures.

***Key Vulnerabilities and Hotspots***

A comprehensive assessment of the potential impacts of climate change
must consider at least three components of vulnerability: exposure,
sensitivity, and adaptive capacity. The coastal chapter broadly
characterizes the sensitivity and natural adaptive capacity (or
resilience) of several major classes of coastal environments to changes
in climate and sea level rise. Differences in geological, oceanographic,
and biological processes can lead to substantially different impacts for
a single type of coastal system (mangroves for example) at different
locations. Some global patterns of vulnerability among systems became
evident, however, and are listed below, with the first three generally
at a higher level of risk:

-   deltas/estuaries (especially populated megadeltas)

-   coral reefs (especially atolls)

-   ice-dominated coasts

-   low-lying coastal wetlands

-   small islands

-   sand and gravel beaches

-   soft rock cliffs

Our understanding of human adaptive capacity is less developed than our
understanding of responses by natural systems, which limits the degree
to which we were able to quantify societal vulnerability in the world's
coastal regions. Nonetheless, several key aspects of human vulnerability
emerged. It is apparent that multiple and concomitant non-climate
stresses will exacerbate the impacts of climate change on most natural
coastal systems, leading to much larger and detrimental changes in the
21^st^ Century than those of the 20^th^ Century. The table below
summarizes some of the key hotspots of vulnerability that arise from the
combination of natural and societal factors. Note than some examples
such as atolls and small islands and deltas/megadeltas recur in this
table, stressing their high vulnerability*.*

Table 6.6 of the Coastal Chapter, IPCC Fourth Assessment Report, 2007.

Key hotspots of societal vulnerability in coastal zones.

+--------------------------------------------+-------------------------+
| **Controlling factors**                    | **Examples from this    |
|                                            | Chapter**               |
+--------------------------------------------+-------------------------+
| Human communities in low-lying coastal     | Atolls and small        |
| areas, especially those facing major       | islands,                |
| technical or economic constraints with     |                         |
| respect to adaptation                      | New Orleans             |
+--------------------------------------------+-------------------------+
| Coastal areas where adaptation will        | Venice, Asian           |
| deliver great benefits but where           | megadeltas              |
| substantial barriers to implementation     |                         |
| exist (costs, institutional,               |                         |
| environmental, etc.)                       |                         |
+--------------------------------------------+-------------------------+
| Coastal areas that are subject to multiple | Mississippi, Nile and   |
| natural and human-induced stresses, such   | Asian megadeltas,       |
| as subsidence or declining natural         | Netherlands,            |
| defenses                                   | Mediterranean, Maldives |
+--------------------------------------------+-------------------------+
| Coastal areas already experiencing adverse | Coral reefs, Arctic     |
| effects of temperature rise                | coasts (USA, Canada,    |
|                                            | Russia), Antarctic      |
|                                            | peninsula               |
+--------------------------------------------+-------------------------+
| Coastal areas exposed to significant storm | Bay of Bengal, Gulf of  |
| surge hazards                              | Mexico/Caribbean, Rio   |
|                                            | de la Plata/Parana      |
|                                            | delta, North Sea        |
+--------------------------------------------+-------------------------+
| Coastal areas where freshwater resources   | W. Africa, W.           |
| are likely to be particularly and          | Australia,              |
| adversely affected by climate change       |                         |
|                                            | Atolls and small        |
|                                            | islands                 |
+--------------------------------------------+-------------------------+
| Coastal areas where economies are highly   | Caribbean,              |
| dependent upon tourism and major adverse   | Mediterranean, Florida, |
| effects on tourism are likely              | Thailand, Maldives      |
+--------------------------------------------+-------------------------+
| Highly sensitive coastal systems where the | Many developed coasts,  |
| scope for inland migration is limited.     | Low small islands,      |
|                                            | Bangladesh              |
+--------------------------------------------+-------------------------+

The coastal chapter contains an assessment of the costs of sea level
rise, storm damage and erosion in the world's coastal regions. Since the
IPCC Third Assessment Report there has been significant progress in
moving from classical cost--benefit analysis to assessments that
integrate monetary, social, and natural science criteria. Under current
climate conditions developing countries bear the main human burden of
climate related extreme events, but it is equally evident that developed
countries are not insulated from disastrous consequences.

Tropical cyclones have major economic, social and environmental
consequences for coastal areas. Up to 119 million people are on average
exposed every year to tropical cyclone hazards. Worldwide, from 1980 to
2000, a total of more than 250,000 deaths have been associated with
tropical cyclones, of which 60 percent occurred in Bangladesh. (This is
less than the 300,000 killed in Bangladesh in 1970 by a single cyclone.)
The death toll has been reduced in the past decade due largely to
improvements in warnings and preparedness, wider public awareness and a
stronger sense of community responsibility. The most exposed countries
have densely populated coastal areas, often located on megadeltas
(China, India, the Philippines, Japan, Bangladesh).

Between 1980 and 2005, the United States sustained 67 weather-related
disasters each with an overall damage cost of at least US\$1 billion.
Coastal States in the southeast United States experienced the greatest
number of such disasters. The total costs including both insured and
uninsured losses for the period, adjusted to 2002, were over US\$500
billion. There are differing views as to whether climatic factors have
contributed to the increasing frequency of major weather-related
disasters along the Atlantic and Gulf coasts of the United States, but
the 2007 IPCC Working Group I report and several independent experts
support the view that storm intensity has increased in some ocean basins
(such as the North Atlantic) and this will continue with global warming.
Whichever view is correct, the damage costs associated with these events
are undisputedly high, and will increase into the future, especially if
development in coastal areas continues. The following figure from the
coastal chapter shows the differential vulnerability of developed and
developing nations to the effects of sea level rise:

Figure 6.10 of the Coastal Chapter, IPCC Fourth Assessment Report, 2007.

Causes, selected consequences (dryland and wetland loss, people
displaced) and the total costs of an assumed sea level rise, for
developing and developed countries, and as a global total (based on Tol
2006).

![](media/image3.wmf){width="5.675694444444445in"
height="3.9277777777777776in"}

Our chapter concludes with a review of adaptation practices, options and
constraints for human settlements in coastal zones. The concept of
integrated coastal zone management is discussed with many examples given
to illustrate adaptation practices that will help sustain natural
coastal systems, their ecological services and the human communities
that depend upon them. We do note, however, that recent studies suggest
that there are limits to the extent to which natural and human coastal
systems can adapt even to the more immediate changes in climate
variability and extreme events. For example, short of mitigation, there
is little that humans can do to ameliorate the effects of increased sea
surface temperature on coral reefs \-- other than reduce the non-climate
related pressures of human activity. Without either adaptation or
mitigation the impacts of sea level rise and other climate change such
as more intense storms will be substantial, suggesting that some small
islands and low-lying coastal areas may become uninhabitable by 2100.

Two things became immensely clear to us as we concluded this
assessment: 1) it is much more costly to consider the effects of climate
change after the fact than to incorporate climate change into adaptive
coastal management now and 2) poor communities (and the poorer parts of
communities) and developing coastal and island nations are particularly
vulnerable to the impacts of climate change. Poorer coastal societies
have a limited ability to adapt or cope with change because they tend to
be concentrated in relatively high-risk areas, they have more limited
financial and institutional capacities needed for adaptation, and they
are often more dependent on climate-sensitive resources such as local
water and food supplies.

Thank you, Mr. Chairman, for inviting me to summarize our coastal
chapter findings. I will be happy to try and answer any questions that
you may have.