Download Risks and Effects of Sea Level Rise on Coastal Peoples and

Risks and Effects of Sea Level Rise on Coastal Peoples and
Ecosystems in the Gulf of Mexico Region
www.gulfbase.org
Final Report
May 11, 2007
Ecological Risk Assessment
Chris Beal
Jessica DeBiasio
Peter Spartos
Sarah Wilkins
Executive Summary
As a result of global climate change, scientists are seeing a rise of sea levels around the world.
Although there has been some debate concerning the degree of rise over the next decade, the
impacts will be significant. Warming temperatures are melting polar ice caps, adding large
amounts of water to the ocean which in turn raises ocean temperatures causing thermal
expansion. In addition, subsidence and groundwater depletion cause the shoreline to sink
creating isolated sea level rise conditions. All of these contribute to coastal migration of
populations as the water rises and shores move further inland. The transition of coastal forests
and other ecosystems to higher elevations is often hindered by shoreline development,
effectively isolating these ecosystems and preventing migration. As sea level rises, human
populations will be displaced, adversely affecting tourism industries and local economies; loss of
seaports, difficulties in distribution of public resources and the risks to human health will also
increase. The use of tools such as the coastal vulnerability indices can help identify areas most at
risk to sea level rise and provide the basis for responses and management options to help abate
the effects of rising seas.
2
Table of Contents
Problem Statement........................................................................................................................ 4
Background ................................................................................................................................... 4
Figure 1: Changes in Temperature, Sea Level, and Northern Hemisphere Snow Cover. . 5
Table 1: Observed rate of sea-level rise and estimated contributions from different
sources. ............................................................................................................................... 6
Focal Region .............................................................................................................................. 6
Goal/Purpose Statement ............................................................................................................... 6
Objectives....................................................................................................................................... 7
Approach ....................................................................................................................................... 7
Findings.......................................................................................................................................... 7
Coastal Vulnerability Index ..................................................................................................... 7
Table 2. Coastal Vulnerability Index for the Gulf of Mexico region ................................. 7
Figure 2. Percentage of the U.S. Gulf of Mexico Coast shoreline in each risk category .. 8
Figure 3. Map of coastal vulnerability index and risk rankings…………………............ 8
Ecological Impacts .................................................................................................................... 9
Forest Decline and Saltwater Intrusion ................................................................................... 9
Wetland Loss ........................................................................................................................ 10
Flooding ................................................................................................................................ 10
Coastal Erosion and Barrier Island Loss ............................................................................... 10
Socioeconomic and Cultural Impacts ................................................................................... 10
Commercial Fisheries ........................................................................................................... 11
Agriculture ............................................................................................................................ 11
Oil, Gas, and Chemical Industries ........................................................................................ 11
Tourism and Entertainment, Port Transfer and Shipping ..................................................... 11
Public Resources, Water, and Land ...................................................................................... 12
Displacement of Coastal Peoples and Health Risks ............................................................. 12
Management Opportunities ....................................................................................................... 12
Conclusions and Recommendations .......................................................................................... 13
Works Cited ................................................................................................................................. 13
3
Problem Statement
Sea level rise across the next century will have adverse effects on human populations and
ecosystems in low-lying coastal areas of the Gulf of Mexico.
Background
For years, global climate change has been the focus of debate and speculation between leading
scientists and politicians. The most recent edition of the International Panel on Climate Change
(IPCC), released in April 2007, has cleared up much of this doubt. Scientists have determined
with 95% certainty that human activities are a primary cause of this warming trend and the
associated effects. Global sea levels have risen at an average observed rate of 1.8mm per year
from 1961 to 2003 and at a rate of 3.1 mm per year from 1993 to 2003.1 The total sea-level rise
for the 20th century is estimated to be 170 mm (Alley et al, 2007).
Prior to the Industrial Revolution, anthropogenic contributions of greenhouse gases (carbon
dioxide: CO2, methane: CH4, and nitrous oxide: N2O) to the atmosphere were low compared to
current levels (Alley et al, 2007). The dramatic increase in CO2 has been linked to intensified
fossil fuel use. In the 1990’s, average annual CO2 emissions were estimated at 22.0-25.0 Gt CO2
per year. This grew to 25.3-27.5 Gt CO2 per year in 2000-2005 and emissions continue to rise.
The 4th IPCC concluded that the increase in CH4 is very likely due to human industries, namely
agriculture and fossil fuel use, while N2O increases are primarily caused by agricultural
activities. As shown in figure 1, global average temperature and sea level have increased
dramatically since 1950 (Alley et al, 2007).
1
Uncertainty exists as to whether this was decadal variability or the advent of a longer-term trend.
4
Figure 1: Changes in Temperature, Sea Level, and Northern Hemisphere Snow Cover.
Observed changes in (a) global average surface temperature; (b) global average sea level rise from tide
gauge (blue) and satellite (red) data and (c) Northern Hemisphere snow cover for March-April. All
changes are relative to corresponding averages for the period 1961-1990. Smoothed curves represent
decadal averaged values while circles show yearly values. The shaded areas are the uncertainty intervals
estimated from a comprehensive analysis of known uncertainties (a and b) and from the time series (c)
(Alley et al, 2007).
5
The effects of global warming are becoming increasingly evident. The changes in air and ocean
temperatures along with decreases in annual snow and ice cover have contributed to a slow but
steady rise in sea-level. Direct contributors to sea level rise and their annual contribution in
millimeters are shown in Table 1. The largest observed source of sea level rise is the melting of
glaciers and ice caps (Figure 1).
Table 1: Observed rate of sea-level rise and estimated contributions from different sources (Alley et al,
2007).
Models have produced various scenarios supporting the connection between a continued rise in
global temperatures and sea level. The IPCC-SRES models low and high scenarios give ranges
for global sea level rise of 0.18-0.38 meters with a 1.8ºC increase in global temperature and 0.260.59 meters with a 4.0ºC increase (Alley et al, 2007).
Focal Region
The Gulf Coast region is one of the nation’s largest ecological systems and is a significant
contributor to the nation’s economy. Sea-level rise poses great risks to these important entities.
States at risk include Alabama, Florida, Louisiana, Mississippi, and Texas, as well as a reach of
the Mexican shoreline. Many variables play into sea-level rise and all must be considered in
order to comprehend the magnitude and scope of this dynamic issue (Ning et al. 2003).
Gulf States have been adversely affected as a result of this rise. For the ten year period from
1985 to 1995, states in the southeastern U.S. lost over 32,000 acres of coastal marshlands as a
result of natural subsidence, human development, erosion and sea-level rise (Ning et al. 2003).
Goal/Purpose Statement
This report focuses on characterizing the risk of impacts, as a result of sea level rise, on
ecosystems, cultures/societies, and economies in low-lying areas of the Gulf of Mexico region.
In addition, this report explores the management options available to deal with these risks.
6
Objectives
This project is designed to characterize the effects of sea level rise. A risk characterization
clarifies the relationship between stressors, effects, and ecological entities in order to guide
management (GERA, 1998).
This report reviews various papers that explore the following:
 Direct impact of sea-level rise on ecosystems and the impact of relative sea-level and
tidal effects.
 Explore economic impacts on industry, and ecosystem services.
 Human health impacts and displacement of coastal communities.
Approach
Methodologies include literature collection and the review of scientific journals and various
reports, government documents and the most recent publication on climate change by the IPCC.
Findings
The first section of the findings describes the ecological impacts associated with sea level rise in
the Gulf of Mexico region. The second portion of the findings describes the secondary impacts
on human populations including, but not limited to, the listed socioeconomic and cultural effects.
It is important to remember that none of the impacts listed act in isolation. Each is
interconnected to others and complex in nature. Included throughout this section are
management opportunities provided in the reports reviewed in this document.
Coastal Vulnerability Index
Table 2. Coastal Vulnerability Index for the Gulf of Mexico region (Thieler and Hammar-Klose, 2000).
7
The Coastal Vulnerability Index (CVI), shown in Table 2, allows researchers to quantitatively
evaluate the vulnerability of coastal areas based on characteristics of geomorphology. Coastal
slope, rate of sea level rise, rate of accretion and erosion, average tidal range, and average wave
height are used to rank areas in respect to the risk of impact. Out of 8,058 km of the Gulf of
Mexico coastline surveyed using the CVI, 3,867.84 km are at very high vulnerability, 1,047.54
km are at high vulnerability, 2,981.46 km are at moderate vulnerability, and 644.64 km are at
low vulnerability (Table 2) (Thieler and Hammar-Klose, 2000).
Figure 2. Percentage of the U.S. Gulf of Mexico Coast shoreline in each risk category (Thieler
and Hammar-Klose, 2000).
The majority of the Gulf coast is dominated by barrier islands, lagoons, marshes and deltas
which have a high risk ranking. In addition to the geomorphology of the area, the entire coast is
micro-tidal, meaning that only slight variations in sea level occur between low and high tide
events which yield a high risk ranking as well (Figure 2).
Figure 3. Map of coastal vulnerability index and risk rankings (Thieler and Hammar-Klose,
2000).
8
CVI are necessary for long term coastal planning. At present, development is taking place
without proper consideration of the costs associated with shoreline retreat (i.e. erosion, increased
flooding, and storm damage). Entire communities and their residents have the potential to be
displaced, and many high end real-estate ventures are at risk of damage due to sea level rise. Sea
level rise is eminent as are the effects that will ensue as it continues, however the severity of
these effects are still not clearly understood (Thieler and Hammar-Klose, 2000).
Ecological Impacts
Sea level rise will pose great risks to ecosystems and their ecological integrity. The ecological
impacts include: forest decline and saltwater intrusion, wetland loss, flooding, coastal erosion
and barrier island loss. Management opportunities are included at the end of the report,
highlighting potential steps that managers can take in order to protect vulnerable areas.
Forest Decline and Saltwater Intrusion
Sea-level rise along the Gulf Coast and for some distance inland has caused major stress on
coastal forests. As a result of sea-level rise, salt water intrusion and the duration and timing of
flooding can significantly alter the productivity of coastal ecosystems. Freshwater swamps are
being stressed by saltwater intrusion while bottomland hardwoods are also being killed by
manipulations in the timing and duration of floods events (Ning et al, 2003). In a study
conducted by McKee and Mendelssohn in 1989, salinity stress was shown to lower plant
productivity (Day et al, 1995).
Williams et al. (1999) explores this relationship by studying coastal forests that are affected by
tidal flooding. They wanted to describe the mechanism by which sea-level rise initiates forest
retreat. The authors found that stands of sabal palms that were subjected to more frequent
flooding had more standing dead palms and stunted palms than similar sites with less flooding.
These sites contained highly saline groundwater, while groundwater under healthy palm stands
had lower salinities. The study suggests that the relationship between saltwater intrusion and tree
stands is significant since regeneration often fails several decades before mature canopy
turnover. Future studies therefore, should focus on the rate of tree regeneration, not just forest
canopy health, in order to account for sea-level rise (Williams et al, 1999).
The encroachment of ocean on coastal forests has led to changes in species composition, wetland
boundaries, and the complete loss of some terrestrial ecosystems. This has made the region more
susceptible to destructive insect pests. It is predicted that longleaf and slash pine forests could
expand northward and replace some of the loblolly and shortleaf pine forests located throughout
many of the Gulf States. Along the Gulf Coast in Florida, potential diebacks of entire forests are
possible. Elevated sea levels will prevent lenticel function and oxygen uptake. Mangroves are
also predicted to suffer large diebacks as a result of rising sea levels (Ning et al, 2003).
9
Wetland Loss
Coastal wetlands are among some of the most productive ecosystems in the world and are home
to numerous aquatic and terrestrial species. Coastal wetlands also act as an important buffer
between the ocean and dry land. In some areas, such as Louisiana, wetlands can actually
suppress storm surges and protect the vulnerable inner coast. With decreased accretion rates due
to channelization of waterways, the excessive use of levees and embankments, and increased
subsidence, existing wetlands are diminishing and their ability to abate storm surges successfully
is being lost (Kennish 2001).
Eighty percent of national coastal wetland loss has occurred in Louisiana alone. Forty-one
percent of the nation’s wetlands occur in Louisiana. The transformation of coastal wetlands to
open water accounts for nearly 60% of wetland loss, the majority of which has been caused by
erosion. In all, 2,500 km² of coastal wetlands have been lost in Louisiana over the past 45 years
(Kennish, 2001).
The reduction of sediment supplies and high rate of sea level rise along the Chenier Coast of
Texas has created major erosion problems. Up to 70% of the Texas coast has experienced
erosion rates of approximately 10m/yr (Kennish, 2001).
Flooding
Rising sea levels reduce the drainage of rivers and streams, increasing flood events (Day et al,
1995). When marshes are flooded frequently soils become inundated with salt and as a result,
plants become physiologically stressed. If soils do not accumulate the adequate quantities of
organic and inorganic matter to compensate for rising sea-levels and subsidence, then marshes
will become open water (Ning et al, 2003).
Coastal Erosion and Barrier Island Loss
The coastal erosion of barrier islands and beaches places immense pressure on ecosystems and
people living in coastal communities. Larger storm surges and rising water levels will lead to the
loss of barrier islands and wetlands that protect vulnerable coastal ecosystems and human
settlements. The low-lying deltas of Mississippi and Louisiana are particularly vulnerable to the
effects of increased erosion and storm damage threats (Ning et al, 2003).
Socioeconomic and Cultural Impacts
Rising sea levels will have major impacts on commercial fisheries, agriculture, oil, gas and
chemical industries, tourism and entertainment, port transfer and shipping, public utilities, and
the displacement of human populations and associated health risks. These impacts will in turn
affect socioeconomic and cultural institutions of the Gulf Coast states. A great deal of
uncertainty remains when determining the full range of risks involved.
10
Commercial Fisheries
As mentioned earlier in this report, sea level rise has resulted in the deterioration of coastal
wetlands throughout the Gulf Coast region. Associated impacts on fisheries are expected due to
the loss of valuable wetland habitat. Estuaries and coastal marshlands are unique ecosystems
that act as nurseries for juvenile fishes and are obligate habitat for commercially valuable
species. Many fishing industries depend on wetlands exclusively to provide valuable harvests.
The loss of wetlands and coastal areas due to erosion, subsidence, and sea level rise will impede
on the ability of fisherpeople to harvest successfully (Ning et al, 2003).
Agriculture
Salinization of irrigation waters will lead to the degradation of agricultural soils, as well as
drastic decreases in crop yields (Ning et al, 2003). Overall warming of the globe is predicted to
be beneficial to agricultural yields, but only within a 1-3°C increase in local average temperature.
Any increase in temperature above this range is predicted to cause a decrease in production. For
lower latitudes such as the Gulf Region, crop production is predicted to decrease with even a
small increase (1-2°C) in local average temperature (Adger et al, 2007).
Oil, Gas, and Chemical Industries
In 2003, eighteen percent of United States oil was produced along the Louisiana coast. The risk
of land loss due to subsidence and rising sea levels threatens 30,000 oil wells and related
infrastructure (NOAA Magazine, 2003). The removal of oil from these areas also exacerbates
sea level rise, by increasing subsidence and increasing the vulnerability of coastal communities
and habitat to strong storm surges. These companies must weigh the costs of protecting the
coastline with the costs of relocating their operations. If they choose to stay, the implications of
coastal protection failure and resulting property loss must also be considered. Dramatic increases
in the cost of insurance associated in areas with a high risk of sea level rise have also occurred
along the coast. Continued increases in premiums may eventually lead to the withdrawal of risk
coverage in these vulnerable areas, especially from private insurers (Adger et al, 2007). Big
industry and oil companies are not likely to change their business practices, especially when
most have seen large increases in profits over these last few years2 (McLean, 2007).
The chemical industry is primarily affected indirectly by sea level rise through the impacts on
raw material supplies from the oil and gas industries (Ning et al, 2007).
Tourism and Entertainment, Port Transfer and Shipping
The loss of valued ecosystems for recreation and tourism could be potentially devastating,
especially for communities and regions that depend nearly exclusively on tourism for local
economic support. The pristine beaches and colorful coral that draw thousands of people each
year are now becoming eroded beaches and bleached coral. Along with vital ecosystem services,
coral reefs attract visitors from all over the United States each year. A study conducted in the
ExxonMobil has nearly quadrupled it’s profits from around to 12 billion USD to up around 39 billion USD from
1997-2006.
2
11
South Pacific concluded that in very extreme cases up to 75% of tourism revenue could be lost,
by and large due to the loss in coral reefs (Duke University, 2001).
Access to ports may also be impaired by changing river flow rates, increased sedimentation and
the need for dredging, while shipping traffic could be affected by severe storms and changing
seabed landscapes (Ning et al, 2003).
Public Resources, Water, and Land
Sea level rise in the Gulf region poses a great risk of potential salt water intrusion to local
groundwater utilized by millions of people. Costs of water transport will increase and water will
need to be brought in from areas not affected by salt water intrusion. This places immense
pressure on drinking water supplies and stress on low-income areas that will be
disproportionately disadvantaged by such problems. As sea levels rise, many land resources will
also be flooded more regularly and severely, as well as permanently in lower lying areas (Adger
et al, 2007).
Displacement of Coastal Peoples and Health Risks
The deterioration of these public utilities will also bring major health risks. Flooding and coastal
erosion will make it increasingly difficult for people to subsist in these areas. Land loss and the
loss of ecosystem services are going to displace large populations of people in areas of high
vulnerability. The continued development in vulnerable areas without consideration of sea level
rise could be potentially costly and detrimental to the persistence of people in the Gulf region.
As seen with Hurricane Katrina, major storm surges and huge flood events associated with sea
level rise could cause the displacement of coastal peoples; increase the risk of water-borne
diseases; create immense pressure on food and water supplies for communities; and create
extremely traumatic scenarios for those living in at-risk areas (Ning et al. 2003).
Management Opportunities
Dealing with sea level rise is difficult and often times management efforts are temporary and
thus become futile in the long-term. Greater attention needs to be paid to natural systems that
provide a buffer between coastal areas and the rising sea. These natural systems, which will
grow and adapt to changing conditions, can provide an array of services and functions widely
beneficial to humans and local ecologies. Much of wetland loss is attributed to decreased
accretion rates. Increasing sedimentation in coastal wetlands will help to combat erosion and
subsidence in these areas. Efforts, such as levee removal along the Mississippi River, can help
bring greater sediment loads to coastal wetlands and increase accretion rates. Protecting
ecological systems will strengthen the resilience of coastal areas and in turn provide
anthropogenic benefits.
Improved wetland management and restoration programs, together with regulatory protection
measures, have reduced the loss of coastal salt marsh habitat in recent years. Additional
12
comprehensive management and restoration efforts must be taken in order to counter the
devastating losses of wetland habitat during the 20th century (Kennish, 2001).
Coastal forests adjacent to open water flood more frequently than those buffered by salt marshes.
Between the forest and the open water, the loss of marshlands may exacerbate forest decline.
Protection of marshlands therefore holds a great deal of potential for reducing retreat due to sea
level rise (Williams et al, 1999).
A range of management opportunities exist for the Gulf Coast. Possible responses to sea level
rise include the building of walls to hold back the rising sea, and allowing the sea to advance and
adapting to it. This would mean actions such as replenishing beach sand as well as elevating
houses and infrastructure away from the rising sea (Ning et al, 2003). The benefits of these
options, while potentially effective, are costly and only consider the short term.
Conclusions and Recommendations
Dealing with the impacts of rising sea level is and will be one of the greatest challenges facing
Gulf states over the next century. Numerous uncertainties remain and it is extremely difficult to
judge which impacts will be most severe. The loss of valuable wetlands, coastal forests, wildlife
habitat, beaches, displacement of communities and damage to economies will all have negative
impacts. Recommendations include assessing the specific areas at risk, and the existing
vulnerability of shoreline and infrastructure. Once this is accomplished, regional planners should
be conscientious of future planning and building in vulnerable areas. Additionally, managers
should work in conjunction with federal, state, and local regulations for economic support to
protect existing infrastructure and prevent further shoreline degradation. Regulations to decrease
coastal zone development are necessary to protect coastal ecosystems and the functions they
provide. Through the implementation and enforcement of these regulations, managers have the
opportunity to increase ecosystem resilience and in turn protect vulnerable human populations in
the region.
Works Cited
Adger, Neil; Aggarwal, Pramod; Agrawala, Shardul; et al. 2007. Climate Change 2007:
Climate Change Impacts, Adaptation and Vulnerability, Summary for Policymakers.
The Fourth Intergovernmental Panel on Climate Change (IPCC) Working Group II.
Brussels.
Alley, Richard; Berntsen, Terje; Bindoff, Nathaniel L.; et al. 2007. Climate Change 2007: The
Physical Science Basis, Summary for Policymakers. The Fourth Intergovernmental Panel
on Climate Change (IPCC) Working Group I. Paris.
Day, J. W.; Pont D.; Hensel P. F.; Ibanez C. 1995. Impacts of sea-level rise on deltas in the Gulf
of Mexico and the Mediterranean : the importance of pulsing events to sustainability.
Estuaries. 18(4): 36-647.
13
Duke University. Coastal Communities: Sector Impacts. 2001. Retrieved on 11 April 2007 from
source: http://www.biology.duke.edu/bio217/2001/sealevel/page7.html
Guidelines for Ecological Risk Assessment. 1998. (GERA) Environmental Protection Agency.
Retrieved on January 2007 from source:
http://cfpub2.epa.gov/ncea/cfm/recordisplay.cfm?deid=12460
Kennish, M.J. 2001. Coastal Salt Marsh Systems in the U.S.: A Review of Anthropogenic
Impacts. Journal of Coastal Research. 17(3):731-748.
McLean, Dan. 2007. Gas prices rise on 10-week tear. Burlington Free Press.
NOAA Magazine. 2003. Subsidence and Sea Level Rise in Louisiana: A Study in Disappearing
Land. Retrieved on 2 April 2007 from source:
http://www.magazine.noaa.gov/stories/mag101.htm
Ning, Z. H., R.E. Turner, T. Doyle, and K.K. Abdollahi. 2003. Preparing for a Changing
Climate: The Potential Consequences of Climate Variability and Change: Gulf Coast
Region. U.S. Climate Change Research Program, published by the Gulf Coast Climate
Change Assessment Council (GCRCC) and Louisiana State University (LSU) Graphic
Services. Retrieved on 6 March 2007 from source:
http://www.usgcrp.gov/usgcrp/Library/nationalassessment/gulfcoast/gulfcoast-brief.pdf
Thieler, E.R., and Hammar-Klose, E.S., 2000. National Assessment of Coastal Vulnerability to
Future Sea-Level Rise: Preliminary Results for the U.S. Gulf of Mexico Coast. U.S.
Geological Survey, Open-File Report 00-179, 1 sheet. Retrieved on 6 March 2007 from
source: http://pubs.usgs.gov/of/2000/of00-179/
Williams, K; Ewel, KC; Stumpf, RP; Putz, FE; Workman, TW. 1999. Sea-level rise and coastal
forest retreat on the west coast of Florida, USA. Ecology. 80(6): 2045-2063.
14