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A Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

January 2011

Authors:

Felicia Chisolm Coleman

Florida State University

Jeremy B C Jackson

Smithsonian Institution

Robert Eugene Turner

Louisiana State University

Show all 18 authorsHide

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants — liquid and gaseous petroleum compounds plus chemical dispersants — poured into eco- systems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional “in-place, in-kind” restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and inter-connected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, we provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future.

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A Once and Future

Gulf of Mexico

Ecosystem

Restoration Recommendations

of an Expert Working Group

Charles H. Peterson

Felicia C. Coleman, Jeremy B.C. Jackson, R. Eugene Turner, Gilbert T. Rowe

Richard T. Barber, Karen A. Bjorndal, Robert S. Carney,

Robert K. Cowen, Jonathan M. Hoekstra, James T. Hollibaugh,

Shirley B. Laska, Richard A. Luettich Jr., Craig W. Osenberg,

Stephen E. Roady, Stanley Senner, John M. Teal and Ping Wang

Pete Peterson wishes to thank his co-authors, in particular Gene Turner, Felicia Coleman,

Gil Rowe and Jeremy Jackson, for their insights and assistance in producing this report.

The authors thank the Pew Environment Group for ﬁnancial support for this project and the

three peer reviewers, whose comments helped to improve the manuscript. We appreciate

the many helpful discussions that we each had with interested colleagues.

Acknowledgments

The views expressed are those of the

authors and do not necessarily reﬂect the

views of the Pew Environment Group,

Campaign for Healthy Oceans or The

Pew Charitable Trusts.

Suggested citation:

Peterson, C. H. et al. 2011. A Once

and Future Gulf of Mexico Ecosystem:

Restoration Recommendations of an

Expert Working Group. Pew Environment

Group. Washington, DC. 112 pp.

A Once and Future Gulf of Mexico Ecosystem

Restoration Recommendations of an Expert Working Group

Contents

The Pew Environment Group is the conservation arm of The Pew Charitable Trusts,

a nongovernment organization that works globally to establish pragmatic, science-based

policies that protect our oceans, preserve our wildlands and promote clean energy.

www.PewEnvironment.org

3 Abstract

5 Introduction

9 Precedents and Principles for Restoring

the Gulf of Mexico Ecosystem

15 Acute and Chronic Stressors on the Gulf

of Mexico Before and After the DWH Oil Spill

37 Recommendations for Resilient Restoration

of the Gulf of Mexico

91 Conclusion

93 Appendices

100 Endnotes

101 References

2 A Once and Future Gulf of Mexico Ecosystem

A Padre Island National Seashore, TX

B Galveston, TX

C Flower Garden Banks

National Marine Sanctuary

D Grand Isle, LA

E Chandeleur Islands, LA

(Breton National Wildlife Refuge)

F Pascagoula River, LA

G Green Canyon area

(near the DWH spill site)

H De Soto Canyon

I Big Bend coastal region, FL, includes

Apalachicola Bay, St. Joe Bay and the

Fenholloway, Suwanee and Ochlockonee

Rivers

J Florida Keys National Marine Sanctuary

K Everglades National Park

Figure 1

The Gulf of Mexico Region

Featured sites mentioned in the report

Corpus

Christi

Padre

Island

Egmont

Key National

Wildlife Refuge

Miami

GULF OF MEXICO

Mississippi

New Orleans

Baton Rouge

Houma

Biloxi

Mobile Pensacola

See map detail Page 28

See map detail Page 31

Galveston

Houston

Tampa

Site of

DWH spill

A Once and Future Gulf of Mexico Ecosystem 3

The Deepwater Horizon (DWH) well blow-

out released more petroleum hydrocarbons

into the marine environment than any

previous U.S. oil spill (4.9 million barrels),

fouling marine life, damaging deep sea and

shoreline habitats and causing closures of

economically valuable ﬁsheries in the Gulf

of Mexico. A suite of pollutants — liquid

and gaseous petroleum compounds plus

chemical dispersants — poured into eco-

systems that had already been stressed by

overﬁshing, development and global climate

change. Beyond the direct effects that were

captured in dramatic photographs of oiled

birds in the media, it is likely that there are

subtle, delayed, indirect and potentially syn-

ergistic impacts of these widely dispersed,

highly bioavailable and toxic hydrocarbons

and chemical dispersants on marine life

from pelicans to salt marsh grasses and to

deep-sea animals.

As tragic as the DWH blowout was, it has

stimulated public interest in protecting this

economically, socially and environmentally

critical region. The 2010 Mabus Report,

commissioned by President Barack Obama

and written by the secretary of the Navy,

provides a blueprint for restoring the Gulf

that is bold, visionary and strategic. It is

clear that we need not only to repair the

damage left behind by the oil but also to

go well beyond that to restore the anthro-

pogenically stressed and declining Gulf

ecosystems to prosperity-sustaining levels

of historic productivity. For this report, we

assembled a team of leading scientists with

expertise in coastal and marine ecosystems

and with experience in their restoration to

identify strategies and speciﬁc actions that

will revitalize and sustain the Gulf coastal

economy.

Because the DWH spill intervened in eco-

systems that are intimately interconnected

and already under stress, and will remain

stressed from global climate change, we

argue that restoration of the Gulf must go

beyond the traditional “in-place, in-kind”

restoration approach that targets speciﬁc

damaged habitats or species. A sustainable

restoration of the Gulf of Mexico after

DWH must:

1. Recognize that ecosystem resilience has

been compromised by multiple human

interventions predating the DWH spill;

2. Acknowledge that signiﬁcant future

environmental change is inevitable and

must be factored into restoration plans

and actions for them to be durable;

3. Treat the Gulf as a complex and inter-

connected network of ecosystems from

shoreline to deep sea; and

4. Recognize that human and ecosystem

productivity in the Gulf are interdepen-

dent, and that human needs from and

effects on the Gulf must be integral to

restoration planning.

With these principles in mind, we provide

the scientiﬁc basis for a sustainable restora-

tion program along three themes:

1. Assess and repair damage from DWH

and other stresses on the Gulf;

2. Protect existing habitats and

populations; and

3. Integrate sustainable human use

with ecological processes in the Gulf

of Mexico.

Under these themes, 15 historically

informed, adaptive, ecosystem-based

restoration actions are presented to recover

Gulf resources and rebuild the resilience of

its ecosystem. The vision that guides our

recommendations fundamentally imbeds

the restoration actions within the context of

the changing environment so as to achieve

resilience of resources, human communities

and the economy into the indeﬁnite future.

Abstract

A Once and Future Gulf of Mexico Ecosystem 5

On April 20, 2010, the eyes of the nation

and the world focused on the northern Gulf

of Mexico and witnessed the beginning of a

human and natural disaster. On that day, a

BP oil well blew out on the Macondo

Prospect 1,500 m below the ocean’s surface

and began gushing crude oil into the

sea. Eleven men died from the explosions

accompanying the blowout and subsequent

ﬁre on the drilling rig, Deepwater Horizon.

The great depth of the well—almost a mile

beneath the ocean’s surface—complicated

efforts to stanch the torrential ﬂow of oil

and natural gas. During the next 85 days,

an estimated 4.9 million barrels of crude oil

ﬂowed into the sea as BP and the U.S. gov-

ernment tried chemicals, concrete, physical

material and other desperate measures

to plug the wellhead. The environmental

tragedy was dramatized in a continuous,

mesmerizing video stream of the turbulent

ﬂow of oil and gas at the seaﬂoor wellhead

and in the satellite and television imagery

of oil covering the sea surface, seabirds and

shorelines. This blowout and spill released

more oil into U.S. waters than any other spill

in history. In terms of human welfare, this

single event severely damaged the Gulf’s

natural resources, harming the economy and

costing lives and jobs in a region dependent

on ﬁshing, tourism and oil-and-gas extraction.

This tragedy, however, is but one of many

environmental perturbations that have

degraded or are still degrading the Gulf

environment. Over the previous ﬁve years

alone, for example, hurricanes Katrina, Rita

and Ike struck the Louisiana, Mississippi and

Texas coasts, causing extensive loss of life

and property. Chronic stressors on the Gulf

ecosystem include overﬁshing and overhar-

vesting of marine life; pollution from agri-

cultural runoff and industry; global climate

change and rising sea level; and alterations

of terrain and rivers for oil exploration and

real estate development. Coastal marsh

acreage, riparian wetlands, and forests

in the drainage basins of the Mississippi

and smaller rivers have declined dramati-

cally, reducing ﬁsh and wildlife habitat and

removing natural water-purifying func-

tions. These changes, in turn, have reduced

the Gulf ecosystem’s ability to provide the

services and resources on which coastal

communities depend.

The success and durability of actions taken

to restore damage caused by the oil release

will depend upon the way Gulf restoration

addresses the impacts of historical ecosys-

tem degradation and anticipates future

changes by creating both social and natural

resilience. Even narrowly focused restoration

actions are unlikely to be sustainable if they

fail to consider the complex and intercon-

nected human and natural ecosystem of the

Gulf. Restoration plans must also compen-

sate for prior impacts to individual resources

and to human economic enterprises and

must consider the full scope of relationships

to historical baseline conditions. Finally,

the ability of restoration plans to anticipate

future dynamic change will determine the

success of those plans over the long term.

Some of these environmental changes, such

as sea level rise and severe weather events,

are occurring faster and having larger

consequences along the Gulf Coast than

anywhere else in the country. Therefore, the

Gulf ecosystem could be a model for how

Introduction

The blowout and spill

released more oil into U.S.

waters than any other oil

spill incident in history.

This tragedy, however, is

but one of many historic,

recent and ongoing

stresses degrading the

Gulf environment.

Oil burns during a controlled

ﬁre after the Gulf oil spill.

Photo: Justin Stumberg/U.S.

Navy/Marine Photobank

6 A Once and Future Gulf of Mexico Ecosystem

to solve multiple social and natural chal-

lenges to achieve sustainability in the face

of dramatic environmental change.

To assess restoration opportunities in the

Gulf, we assembled a team of leading

scientists with expertise and experience in

coastal and marine ecosystems and their

restoration. Together we identify strategies

and speciﬁc actions that will help revitalize

the Gulf Coast ecosystem and economy.

Our scientiﬁc approach is based upon spa-

tially explicit and ecosystem-based insights

derived by inferring the baseline conditions

and controlling functions of the Gulf coastal

ecosystem as they were before major

human modiﬁcations were made. Previous

use of this approach to guide ecological

restorations of estuarine (Lotze et al. 2006),

marine (Jackson et al. 2001) and freshwater

(Scheffer et al. 2001) aquatic ecosystems

have revealed how human-induced modiﬁ-

cations, such as overﬁshing apex predators

and historically dominant ﬁlter feeders,

have led to the loss of ecosystem resilience

when subsequent perturbations occurred,

such as nutrient overloading. Such interac-

tions among multiple stressors can propel

the ecosystem across a threshold and into

an alternative persistent state from which

recovery to baseline conditions is difﬁcult.

For example, the overharvest of suspension-

feeding oysters from Chesapeake Bay and

Pamlico Sound estuaries in the decades

around 1900 disabled the capacity of the

ecosystem to exert top-down grazing

controls on phytoplankton blooms. When

nutrient overloading occurred decades later,

the suspension-feeders were no longer

functionally capable of grazing down

the microalgae and helping to suppress

bloom development (Jackson et al. 2001).

Therefore, our restoration recommenda-

tions address a range of modiﬁcations

to the Gulf ecosystem. Using historical

baselines to guide restoration does not

mean that we advocate the impossible,

such as rebuilding coastlines to match the

locations and elevations of previous times

before substantial subsidence occurred.

Instead, historical ecology guides us toward

restoring previously critical processes that

serve to organize the ecosystem and trig-

ger compensatory internal dynamics that

strengthen resilience.

The DWH well blowout is an obvious trag-

edy, but it appears to have made at least

two positive contributions to the region.

The publicity generated by the oil spill put a

spotlight on the immense value of the natu-

ral resources and communities of the Gulf

Coast. It also drew attention to how little

public or private investment has been made

in restoring the Gulf ecosystem after past

injuries or in creating the natural and social

resiliency required for this unique region to

sustain itself in the face of a dramatically

changing natural environment. Although

government promises of funding for hur-

ricane rehabilitation and restoration have

proved overly optimistic, funds for Gulf res-

toration derived from environmental ﬁnes

for ocean pollution and natural resource

damage will be more substantial. Some of

the funds are restricted to direct compensa-

tion for damage done by the DWH oil spill

to the Gulf ecosystem, its natural resources

and the Gulf coastal economy; however,

the potential uses for the rest of the funds

range broadly.

The federal Oil Pollution Act of 1990

(OPA) dictates criteria for compensatory

restoration projects that can be supported

by monies given in settlement of natural

resource damage claims or awarded by the

court system. OPA then has general jurisdic-

tion over Gulf restoration funds derived

from legal settlements with BP. Under the

provisions of OPA, compensatory restora-

tion projects must be explicitly tied to the

natural resource injuries, either damage to

speciﬁc resources, such as the loggerhead

turtle, or damages to speciﬁc habitats, such

as coastal marsh. Consequently, restora-

tion that draws upon this source of funding

must be justiﬁed by linkage to one or more

injured resources or habitats, such as those

listed in Table 1.

The Gulf ecosystem has been buffeted and

so deeply modiﬁed by such a wide variety

of anthropogenic and natural stressors that

merely following traditional government

guidelines for “in-place, in-kind” com-

pensatory restoration under OPA or other

statutes is unlikely to provide sustainable

beneﬁts. For example, the combination of

subsidence, global sea level rise, shoreline

erosion by major hurricanes, and ero-

sion and ﬂooding facilitated by numerous

navigation channels cut through the wet-

lands could easily lead to submersion and

drowning of Spartina marsh constructed

at most or all sites where the DWH oil spill

The ability of restoration

plans to anticipate

future dynamic change

will determine the

success of those plans

over the long term.

1900 Overharvesting of oysters

from the Chesapeake Bay and

other estuaries contributed

to dramatic changes in their

ecosystems. Above, the oyster

ﬂeet in Baltimore Harbor, circa

1885. Photo: Collection of

Marion Doss

A Once and Future Gulf of Mexico Ecosystem 7

destroyed previous marsh habitat. Conse-

quently, at a minimum, compensatory resto-

ration of injuries caused by DWH oil and

collateral damage from emergency response

actions should contemplate expected

dynamic change to ensure durability of

restoration projects. At best, the long-term

Gulf restoration plan would redress past

insults and restore a resilient Gulf ecosystem

similar in functioning to its historic base-

line condition, within which compensatory

restoration of habitat and natural resources

injured by the DWH oil release could be

self-sustaining. President Obama’s mandate

to address historical and immediate ecologi-

cal damage in the Gulf provides an oppor-

tunity for this ideal restoration strategy; the

Mabus Report, commissioned by President

Obama and written by Secretary of the

Navy Ray Mabus, provides a broad and bold

vision for how to proceed with important

aspects of fulﬁlling this mandate.

Fortunately, the compensatory damages

funds do not represent the only source of

support for DWH oil spill and broader Gulf

restoration, so the limiting criteria laid out

in OPA need not apply to all restoration

actions that are taken in the wake of the

Deepwater Horizon incident. For example,

under the federal Clean Water Act of 1972

(CWA), the uses of monies from water pol-

lution penalties for illegal discharge of oil

into the ocean are not similarly constrained.

CWA penalties are based on volume

discharged with an additional multiplier

for negligence. Particularly if negligence

is established as a signiﬁcant factor to the

blowout, CWA penalties may represent the

bulk of the DWH restoration funds. The

$500 million transferred from BP to the

Gulf Coast Alliance does not appear to be

controlled by provisions tying the use of

those funds to injured resources. Finally, it is

likely that other major grantors will emerge

as the restoration process takes shape;

these grantors may help to multiply the

synergistic beneﬁts from related restoration

projects.

Our restoration guidance is therefore

intended to target administrators of several

funding sources. Funding institutions

will value aspects of the Gulf of Mexico

variously; for this reason, we have not

prioritized the restoration actions that we

develop. Nor have we made detailed esti-

mates of the costs of these 15 restoration

actions. Costs of compensatory restoration

actions will vary with the scale of injuries

from the oil spill that require compensa-

tion. The multiple funding sources will have

different goals and constraints. Many of our

suggested actions address long-standing

modiﬁcations of the Gulf ecosystem that

ﬁt well into the strategies articulated in

initial expert responses to the spill (e.g., the

Mabus Report). Others are directly related

to oil spill damage and compensatory res-

toration. We offer these recommendations

to help guide allocation of resources while

plans are still being developed. Guidelines

for use of the funds provided by BP as an

initial payment to jump-start restoration are

now vague and will be developed by the

administrators. Details of how water pollu-

tion ﬁnes will be allocated are likely to be

determined by Congress. Consequently, our

strategy is to offer what we conclude are

the most inﬂuential and justiﬁable actions

to take, while emphasizing the principles of

restoration that must guide all expenditures

so as to maximize likelihood of success,

achieve synergies of integration based upon

ecosystem connections, re-create lost eco-

system processes associated with historical

ecological baselines, and enhance resilience

through knowledge of ongoing and inevi-

table environmental change.

1970s Passage of the

Clean Water Act provided

the framework for regulating

environmental stressors on

the Gulf ecosystem, such as

oil and natural gas spewing

from a broken cap in Bayou

St. Denis in Louisiana. Photo:

Carrie Vonderhaar/Ocean

Futures Society/National

Geographic Stock

A Once and Future Gulf of Mexico Ecosystem 9

The interdisciplinary ﬁelds of restoration

ecology, conservation biology, and com-

munity and ecosystem ecology all offer

scientiﬁc guidance for restoration projects.

Basic research in community and ecosystem

ecology sheds light on the mechanistic

functions of habitats and the roles of direct

and indirect interactions between species in

organizing communities. Conservation biol-

ogy offers strategies for protecting habitats,

species and their interactions in ecosystems.

Restoration ecology tends to move ahead

through practice, rather than via elabora-

tion and subsequent testing of theory (Allen

et al. 1997, Pal mer et al. 1997, Peterson and

Lipcius 2003). These ﬁelds offer related

approaches to restoration, but no overarch-

ing theory of restoration has emerged. The

absence of a compelling theory that could

be applied to species or habitat restora-

tion implies that empirical assessment of

successes and failures of previous restoration

actions should guide new decision-making

and that small-scale tests of restoration

concepts should be conducted before decid-

ing on larger-scale projects (Bernhardt et al.

2005). Because so much was done under

the banner of restoration after the Exxon

Valdez oil spill, learning from that history

seems prudent before restoration decisions

are made to compensate for DWH injuries to

natural resources of the Gulf and to restore

its ecosystem services (see box, Page 11).

Learning from the Exxon

Valdez restoration efforts

In response to the DWH oil spill, Dennis

Takahashi-Kelso, executive vice president

of Ocean Conservancy, wrote a letter in

August 2010 to the government trustees of

the DWH case, offering practical guidance

based upon experiences from the Exxon

Valdez restoration process. Addressed to

Deputy Secretary of the Interior David Hayes

and Under Secretary of Commerce Jane

Lubchenco, this letter drew upon a panel

of scientiﬁc experts that included two of

us, Senner as panel lead and Peterson as

participant, each with extensive experience

in habitat and species restoration after the

Alaskan oil spill. In this letter, Dr. Takahashi-

Kelso quotes President Obama’s June 15,

2010 charge to Navy Secretary Ray Mabus

and pledge to develop a long-term Gulf

Coast restoration plan. Dr. Takahashi-Kelso

offered support for a plan that acknowl-

edges the importance of the National

Resources Damage Assessment (NRDA)

restoration process, which is the process

used for OPA’s “in-place, in-kind” approach.

But he stressed that restoration must also

go beyond those constraints. We agree

that recognition of the dual mandate of

the president’s wider plan and the narrower

compensatory restoration process driven

by OPA is critically important to achieving

sustainable restoration. We build upon this

overarching concept to design and advo-

cate our speciﬁc restoration suggestions.

Based in part on his own Exxon Valdez

experiences and those of Senner, Peterson

and others, Dr. Takahashi-Kelso makes

several fundamental points about the

process of restoration after natural resource

damage that should be applied to the DWH

oil spill restoration process. We modify and

expand upon these points to formulate our

Precedents and Principles for

Restoring the Gulf of Mexico

Ecosystem

Oyster reefs and mangroves

(shown on Sanibel Island, FL)

serve important functions in

the Gulf ecosystem. Photo:

Brian Kingzett

Because so much was

done under the banner

of restoration after the

Exxon Valdez oil spill,

learning from that history

seems prudent before

restoration decisions are

made to compensate for

DWH injuries to natural

resources of the Gulf

and to restore its ecosys-

tem services.

10 A Once and Future Gulf of Mexico Ecosystem

suggested ecosystem-based restoration

guidance (Appendix I). A summary of the

most relevant points from the Takahashi-

Kelso letter follows:

• The restoration process should be trans-

parent to the public and should engage

the public in meaningful dialogue over

potential actions from an early point.

• Quick settlement of damage claims

without a legal mechanism to achieve

compensatory funding for restoration

of unexpected, delayed injuries is not in

the public interest. The legal settlement

language is critical because it dictates

the scope of restoration possibilities.

• Restoration should be broad to allow

enhancement of injured resources over

and beyond their status and condition

at the time of the oil spill so as to be

responsive to the need to account for

past degradation and, in the process,

create a self-sustaining system more

similar to historic baselines.

• The scope of possibilities to be consid-

ered for restoration should be clearly

deﬁned and, for the compensatory

restoration fund, limited to resources,

habitats and systems that were injured

by the hydrocarbon releases. Otherwise,

public expectations can be misguided

and overly expansive, which unnecessar-

ily causes disappointment and bitterness.

• Care must be taken to avoid harming

the ecosystem and its services by imple-

menting untested projects that could

result in negative rather than positive

net impacts on resources.

• The restoration program or programs,

separating the Gulf ecosystem restora-

tion from compensatory restoration

for spill injuries, should be ecosystem-

based, integrating component projects

into a comprehensive restoration plan

across the northern Gulf.

• Division of restoration funds into state

“block grants” would not achieve the

synergies possible, resiliency needed

and scope required to address the most

critical challenges in sustaining Gulf

ecosystems and their services, because

those bigger challenges tend to be

regional in scope and require coordi-

nated responses.

Restoration must also be based upon sci-

ence and developed using peer review by

independent scientists without conﬂicts of

interest. Some of the science needed to

conduct successful restoration of important

natural resources in the Gulf ecosystem,

including the injuries caused by the Deep-

water Horizon disaster, is not complete and

needs further development before restora-

tion can be conﬁdently achieved (Bjorndal

et al. 2011).

The Mabus Report

In addition to the Takahashi-Kelso letter,

we take guidance from the Mabus Report

(2010), which was prepared by the secre-

tary of the Navy in response to the Presi-

dent’s charge. Fundamentally, we endorse

the recommendation of the Mabus Report

that an informed and independent funding

structure is necessary “to lead to long-term

ecosystem, economic, and health recovery

in the Gulf” (Mabus, Page 5).

Speciﬁcally, the Mabus report recom-

mended the establishment of a Gulf Coast

Recovery Council that “should work with

existing federal and state advisory com-

mittees, as appropriate, to ensure that

relevant scientiﬁc and technical knowledge

underpins recovery planning and decision

making, and that research, monitoring,

and assessment efforts are organized. The

Council should also provide oversight and

accountability into Gulf of Mexico recovery

efforts by developing quantiﬁable perfor-

mance measures that can be used to track

progress towards recovery goals” (Mabus,

Page 8). However, we recommend that the

(perhaps inadvertently) restricted focus on

state and federal agencies be broadened to

include academics and nongovernmental

agencies. We enthusiastically concur with

the ﬁve guiding principles for restoration

(see box, Page 12) presented in the Mabus

report, though we offer several cautions.

We note that sediment management issues

are complex, and some suggested interven-

tions may be so narrowly focused as to be

counterproductive. Additionally, monitoring

conditions and processes is necessary, and

the metrics of success must be identiﬁed

and used to adapt the restoration actions as

needed to achieve their goals.

1989 A worker operates

respirator hoses during an oil

dispersant application test on

Smith Island in Prince William

Sound after the Exxon Valdez

oil spill. Photo: Alaska Resources

Library and Information Service

A Once and Future Gulf of Mexico Ecosystem 11

Cormorants sit on stakes

placed by researchers next to

newly planted sea grass in the

Florida Keys. The birds’ drop-

pings serve as fertilizer for the

plants. Photo: Florida Fish and

Wildlife Commission

Ecosystem Services

Natural ecosystems and their constituent

organisms engage in a wide variety of

processes. Some of these processes serve

needs of other organisms, communities

of organisms, and ecosystems; these clus-

ters of beneﬁcial processes are known as

ecosystem services. Valuable ecosystem

services have historically been taken

for granted and therefore not properly

considered in the process of permitting

development projects. One example is

the pollination of crops by honeybees.

If farmers had to pay for the services of

pollination instead, the costs of produc-

ing crops would be much higher. The

recent decline of honeybee populations

highlights our need to protect valuable

ecosystem services as we modify natural

systems.

Coastal wetlands have for decades

been recognized for the high value of

their many ecosystem services, and the

importance of this delivery of goods and

services has been reﬂected in federal

and state legislation for the protection of

coastal wetlands. The mantra of “no net

loss of wetlands” has guided approaches

to estuarine management for decades.

Tidal marshes are valued, protected and

restored in recognition of their ecosystem

services (MEA 2005), which include:

• high primary productivity of emer-

gent vascular plants as well as single-

celled benthic microalgae and habitat

provision supporting the food webs

leading to ﬁsh and wildlife;

• serving as a buffer against storm

wave damage to the adjoining veg-

etation and human development on

higher ground;

• shoreline stabilization and erosion

protection;

• ﬂood water storage;

• water quality maintenance, including

ﬁltering out sediments, nutrients and

pathogens;

• biodiversity preservation, especially

of a suite of endemic, often threat-

ened or endangered vertebrates;

• carbon storage as peat is accumu-

lated, buried and stored, thus buffer-

ing greenhouse gas emissions; and

• socioeconomic beneﬁts, such as sus-

taining the aesthetics of coastlines,

maintaining a heritage and historical

culture, supporting ecotourism, serv-

ing as a living laboratory for nature

education, and promoting psycho-

logical health and supporting ﬁshing

and waterfowl hunting.

12 A Once and Future Gulf of Mexico Ecosystem

Mabus Principles (2010)

Our committee’s reactions are in italics; details appear later. The following serve as ideal and guiding

principles to restoration toward states to which the Gulf can realistically aspire. The Mabus Report asserts

that they “serve as the drivers for achieving the vision of resilient and healthy Gulf of Mexico ecosystems”

(Mabus, Pages 38-39).

Principle 1: Coastal Wetland and Barrier Shoreline Habitats

are Healthy and Resilient. In order to sustain the many ecosystem

services upon which humans rely, coastal habitats must be healthy

and resilient. Reversing ongoing habitat degradation and preserving

the remaining healthy habitats is a key principle. It must be recog-

nized that even the healthiest ecosystems are dynamic, so a restora-

tion effort should not focus entirely on a ﬁxed “footprint.” A key

objective of this principle is to bring greater balance to managing

the Mississippi River and other rivers for ﬂood control, navigation,

and ecosystem restoration. Another objective is to retain sediments

in coastal wetlands, before they leave the river channel to the Gulf

(Mabus, Page 38).

We concur with this guidance,

although we express serious con-

cern about whether the Mississippi

River, with all its channelization

and engineering constraints such

as levees and dams, brings enough

sediment to sustain wetland

elevations beyond the immedi-

ate footprint of the river-mouth

delta. We suggest that the organic

soils of the inter-levee area can be

harmed by the high concentration

of nutrients in the river. We also

suggest that ﬁlling dredged chan-

nels and preventing new wetland

losses will be much more effective

and less expensive than alternative

restoration approaches.

A Foundation for

Durable Restoration

With guidance from Dr. Takahashi-Kelso’s

letter to government leaders, from pub-

lished papers on ecosystem-based restora-

tion, and from our own experience, we

feel that restoration in the Gulf must rest

on a solid foundation that acknowledges

the past, is realistic about the future, and

recognizes the interdependence of habitat,

species, and human beings in the ecosys-

tem. Therefore, durable and successful

restoration in the Gulf of Mexico must:

1. Recognize that ecosystem resilience has

been compromised by multiple human

interventions predating the DWH spill;

2. Acknowledge that signiﬁcant future

environmental change is inevitable and

must be factored into restoration plans

and actions for them to be durable;

3. Treat the Gulf as a complex and inter-

connected network of ecosystems from

shoreline to deep sea; and

4. Recognize that human and ecosystem

productivity in the Gulf are co-depen-

dent, and that human needs from and

effects on the Gulf must be integral to

restoration planning.

A Once and Future Gulf of Mexico Ecosystem 13

Principle 2: Fisheries are Healthy, Diverse and Sustainable.

The Gulf is home to the largest commercial ﬁshery in the contigu-

ous United States. The total trip expenditures for recreational ﬁshing

in the Gulf states in 2008 were nearly $1.5 billion. Key objectives of

this principle may include incorporating testing and other mecha-

nisms for seafood safety to ensure that ﬁsh and shellﬁsh are safe for

human consumption, and working through regulatory and other

conservation mechanisms to restore populations of ﬁsh and shellﬁsh

(Mabus, Page 38).

We concur that conservation regu-

lation will be required to render

ﬁshing sustainable in the Gulf,

but we also identify habitat protec-

tion as a major additional process

needed to develop the ecosystem

support for resilient ﬁsh and shell-

ﬁsh populations.

Principle 3: Coastal Communities are Adaptive and Resilient.

The needs and interests of Gulf communities vary and the most

effective solutions will be based on local conditions. Given that much

of the land affected by the oil spill is privately held, full restoration

will rely on local citizen support. The impacts of climate change,

including sea level rise and more frequent and intense storms,

will likely alter the landscape signiﬁcantly, forcing communities to

reassess their priorities. Key objectives of this principle may include

providing coastal managers with information and tools to make

better land use and public health decisions, and increasing aware-

ness of the connection between ecosystem and community resilience

(Mabus, Page 38).

We concur and go further to add

that a long-term process of social

engagement with local communi-

ties to encourage understanding

of the scope of unavoidable

future change is required to sup-

port development of community

resilience.

Principle 4: A More Sustainable Storm Buffer Exists. Persistent

coastal land loss, compounded by sea level rise, is deteriorating

natural lines of defense, leaving coastal communities vulnerable to

tropical storms. Natural and engineered systems are necessary to

reduce exposure and ensure protection. Key objectives of this prin-

ciple may include maintaining and expanding natural storm buffers

such as wetland and barrier islands and improving decision-making

with regard to structural protection and navigation interests so that

these complement and enhance restoration of natural systems.

Another objective is the reduction of risk posed to people and pri-

vate property through effective planning, mitigation, and balancing

of interests (Mabus, Pages 38-39).

We concur while recognizing

that hardened erosion protection

structures and beach nourishment

degrade barrier island ecosystem

services and require compensatory

restoration of impacts to natural

resources.

Principle 5: Inland Habitats, Watersheds and Offshore Waters

are Healthy and Well Managed. Communities across the nation

rely on our ability to maintain healthy, resilient, and sustainable

ocean, coasts, and Great Lakes resources for the beneﬁt of present

and future generations. Additional stressors on the health of these

systems and the resources they support include overﬁshing, pollu-

tion, and coastal development. Further, ocean and coastal resources

are directly and indirectly impacted by land management and use

decisions in the watersheds that drain into the Gulf of Mexico. Key

elements of this principle include improving management of agricul-

tural and forest lands; restoring ﬂoodplains and wetlands to improve

water quality by uptake of nutrients, reduce ﬂood risks, and enhance

wildlife habitat; reducing erosion and nutrient runoff from agricul-

tural and developed land; and using state-of-the-art planning tools

to deliver comprehensive, integrated ecosystem-based management

of resources (Mabus, Page 39).

We concur with every point.

A Once and Future Gulf of Mexico Ecosystem 15

The Deepwater Horizon well blowout

occurred April 20, 2010, resulting in explo-

sions and ﬁres on the drilling rig that killed

11 men, injured many more and led two

days later (ironically on Earth Day, April 22)

to sinking of the rig to the seaﬂoor about

1,500 m below the surface. On April 22,

substantial amounts of orange-brown crude

oil appeared at the surface, conﬁrming

that a well blowout had occurred at the

drill site. As the oil continued to ﬂow for

85 days, totaling an estimated 4.9 million

barrels, the nonproﬁt organization SkyTruth

assembled and posted satellite images from

infrared and radar sources depicting the

location of the surface oil slick. By June 25

and 26, the slick had covered more than

24,000 square miles of the sea surface in

the northern Gulf of Mexico (Norse and

Amos 2010). By July 16, the day after all oil

ﬂow from the stricken well had ended, an

area of about 68,000 square miles of the

Gulf surface had been covered by oil (Norse

and Amos 2010).

In late April, winds in the Gulf typically

switch to the seasonally characteristic,

southwesterly onshore direction, which

would have brought the oil quickly and

heavily onto shore and into shoreline habi-

tats. Fortuitously, the spring of 2010 was

not typical and lacked the spring period of

onshore winds. In addition, much of the

surface oil was caught up in an eddy that

helped keep it at sea and prevent its trans-

port via the Loop Current southward to the

Florida Keys and then into the Gulf Stream

and Atlantic Ocean. As a consequence, oil

was not detected reaching shore until

June 3 in Alabama. Oil ultimately grounded

on hundreds of miles of beaches, marshes,

sea grass beds, tidal ﬂats and oyster reefs,

despite intensive response efforts to prevent

and minimize this outcome. These efforts

included massive applications of dispersants

both on the sea surface and injected into

the plume emerging from the seaﬂoor,

skimming ﬂoating oil from the sea surface,

burning it at sea, installing booms along

marshes and other sensitive shorelines,

diverting freshwater river discharges into

marshes in an attempt to prevent intrusion

of oil slicks, and dredging and ﬁlling to

construct artiﬁcial berms on the coastline.

Although no damage assessment test data

are available, ﬁeld observations suggest that

these response actions caused some level

of collateral injuries to wildlife and habitats,

which therefore represent indirect damage

attributable to the Deepwater Horizon

blowout (Table 1).

Despite the emergency response efforts, the

oil fouled many acres of the most valuable

marsh edge habitat, fouled ocean beaches,

forced closures of shellﬁsheries and ﬁn-

ﬁsheries and decimated the economically

vital Gulf tourism industry, extending at

least as far as southwest Florida (Table 1).

Many birds of several species were killed

along shore, including brown pelicans and

other species that were nesting during that

spring-summer season, and marsh residents

like rails. Lesser amounts of oil entered low-

energy muddy habitats of marshes and mud

ﬂats, where it can persist without com-

plete weathering for years. Consequently,

the Deepwater Horizon oil release also

The skyscrapers of New Orleans

are visible behind houses

ﬂooded by Hurricane Katrina.

Photo: Tyrone Turner/National

Geographic Stock

The DWH Oil Spill in the Gulf of Mexico

Acute and Chronic Stressors on the

Gulf of Mexico Before and After the

DWH Oil Spill

The state of the Gulf and

its coastal zone imme-

diately before the DWH

incident was far from

pristine, with countless

stressors having already

altered and degraded the

ecosystem.

16 A Once and Future Gulf of Mexico Ecosystem

resembled earlier shallow-water oil spills

by affecting shoreline habitats of value to

wildlife and to human enterprise.

Differences between DWH

and other oil spills

As anticipated, the Deepwater Horizon

blowout led to the oiling of sea-surface

and shoreline habitats and to consequent

damage to natural resources. In contrast

to previous spills, however, the majority

of the oil and gas released at the well-

head remained far below the sea surface.

An estimated 500,000 tons of gaseous

hydrocarbons — perhaps half of all hydro-

carbons released by the blowout (Joye et

al. 2011) — entered the ocean yet were

metabolized by heterotrophic bacteria in

the deep ocean, and only 0.01 percent was

vented into the atmosphere (Kessler et al.

2011). A large fraction of the oil was also

retained beneath the sea surface because

of the unique physical chemistry created by

the deepwater blowout conditions. Under

conditions of high-pressure deepwater dis-

charge of hot oil and gas, the entrainment

of cold seawater, caused by violent and

turbulent ﬂows at the wellhead, created a

variety of dispersed phases, including ﬁne-

scale oil droplets, gas bubbles, dissolved

gas, oil-water emulsions and gas hydrates.

The collective buoyancy of this mixture of

oil and gas created a rising plume, from

which much of the oil and gas separated

and was trapped by ocean stratiﬁcation at

depths of 800 to 1,200 m and subsequently

deﬂected and transported by ambient cur-

rents (Joye et al. 2011). Massive production

of methanotrophic bacteria was associated

with the oil and gas in this depth stratum,

causing a detectable depression of oxygen

levels, but it did not approach anoxia (Joye

et al. 2011).

The natural dispersal of oil induced by pro-

cesses at the wellhead may have rendered

the application of 1.8 million gallons of

toxic Corexit dispersant unnecessary, but

the net effect was the novel dispersal of the

oil in very ﬁne droplets and retention of a

large percentage of the oil droplets in the

mesopelagic and bathypelagic depths of

the deep sea. Such dispersal and reten-

tion of oil in the water column as ﬁnely

dispersed droplets exposes organisms

living there or passing through to bioavail-

able, toxic oil, affecting copepods, salps,

invertebrate larvae and other particle-

consuming, mesopelagic zooplankters.

Subsequent agglomeration of oil particles,

sediments and marine snow, possibly medi-

ated by release of muds from the well and

by sticky bacterial exudates (Hazen et al.

2010), facilitated the transport of this oil to

the seaﬂoor, where observations of dead,

soft corals and crinoids on hard bottom

and polychaetes and brittle stars on soft

bottom were associated with dark deposits

of hydrocarbon-enriched sediments (Fisher

2010). Consequently, the process of dis-

persing the oil led to widespread exposures

of particle-feeding organisms of the deep

pelagic and seaﬂoor realms. This oil stimu-

lated massive production of microbes, with

unknown consequences to deep-ocean

food webs, in part because of the likely

mortality and feeding incapacitation of the

particle feeders that might consume these

microbes (Table 1).

Clearly, the Deepwater Horizon oil release

differs so dramatically from all previous,

well-studied crude oil spills that it requires

development of a completely new concep-

tual model, applicable not only to this spill

but also to all future deepwater releases

(Peterson et al. in press). Elaboration of

this emerging model for deepwater well

blowouts, including rigorous ecotoxicologi-

cal models, is urgently needed to document

and understand the deep-ocean impacts of

this oil spill, and especially to allow for the

effective compensatory restoration of lost

ecosystem services.

What DWH indicates about

failures in the deep-sea oil

drilling program

The National Commission on the BP Deep-

water Horizon Oil Spill and Offshore Drilling

(Graham et al. 2011a) provides an insightful

and comprehensive account of the many

factors over multiple time scales that led to

the well blowout on the Macondo Prospect

and the resulting loss of life, environmen-

tal contamination, and impacts to human

enterprise along the northern Gulf Coast.

The commission concluded that the spill

was preventable. According to the commis-

sion, the immediate causes of the calamity

were failures in management by BP,

Halliburton, and Transocean on the Deep-

water Horizon rig at the end of the drilling

process. Communications failures among

The DWH oil release

differs so dramatically

from all previous, well-

studied crude oil spills

that it requires develop-

ment of a completely

new conceptual model.

A Once and Future Gulf of Mexico Ecosystem 17

Damage from surface oil at sea

Resource Damage

Seabirds Tens to hundreds of northern gannets, brown pelicans,

laughing gulls, terns, black skimmers and many others

were killed and experienced ﬁtness losses that reduced

reproductive capacity.

Sea turtles Hundreds of loggerhead, Kemp’s ridley, green and

leatherback turtles (all threatened or endangered spe-

cies) experienced ﬁtness loss or were killed.

Marine mammals Bottlenose dolphins were killed.

Sargassum community Plants were soaked with oil, hatchling sea turtles oiled,

juvenile game ﬁsh exposed, forage ﬁsh and inverte-

brate prey exposed, resulting in community mortalities

and ﬁtness losses.

Fish and crabs Blue crab in early life stages took up oil and dispersant

with likely effects on ﬁtness; ﬁsh in early life stages

were similarly exposed.

Cannonball jellyﬁsh

and smaller gelatinous

zooplankton

Physical fouling likely resulting in loss of life and

ﬁtness.

Damage from oiling of shoreline habitats

Resource Damage

Coastal marsh habitat Loss of ecosystem services from hundreds of acres of

heavily, moderately and lightly oiled marsh

Ocean beach habitat Some mortality from fouling of feeding apparatus of

mole crabs, bean clams, amphipods and polychaetes

(prey for surf ﬁsh and shorebirds, reducing their pro-

ductivity)

Sea grass bed habitat Some mortality of sea grass with loss of its ecosystem

services and mortality of sensitive species such as crus-

taceans and echinoderms

Tidal ﬂat habitat Many areas of partial loss of ecosystem services of

producing ﬁsh, crabs and shrimp

Oyster reef habitat Polycyclic aromatic hydocarbon contamination of oys-

ters and likely slower growth and production; probable

deaths of some resident crustaceans such as amphi-

pods, shrimp and crabs.

Nearshore species More bird deaths, including rails, pelicans, terns, black

skimmers, shorebirds, gulls, wading birds; reptile

deaths including terrapins and alligators; deaths of

marsh mammals such as river otters

Table 1

Major Natural Resource Damage From DWH Well Blowout

An oiled pelican stands on a

rock jetty at Grand Isle, LA,

after the Deepwater Horizon

spill. Photo: Eileen Romero/

Marine Photobank

Oil from the spill is visible on a

marsh. Photo: NOAA

18 A Once and Future Gulf of Mexico Ecosystem

Dying corals have been found

near the Deepwater Horizon

site. Photo: NOAA OER and

Bureau of Ocean Energy

Management, Regulation and

Enforcement

Two ﬁshing vessels drag an oil

boom after trapped oil is set

ablaze in the Gulf. Controlled

burns were conducted to

prevent the spread of spilled

oil. Photo: Jeffery Tilghman

Williams, U.S. Navy/Marine

Photobank

Damage from subsurface dispersed oil and gas

Resource Damage

Pelagic suspension feeders Ingestion of particulate oil and fouling of feeding

apparatus caused widespread mortality of deep-sea,

mesopelagic and benthopelagic guilds of particle feed-

ers (e.g., salps, appendicularians, jellies, zooplankton),

altering energy transfer through the food web

Benthic suspension feed-

ers on hard bottoms and

suspension and deposit

feeders on soft bottoms

Ingestion of particulate oil and fouling of feeding

apparatus caused widespread mortality of soft corals,

crinoids, bryozoans, brittle stars, polychaetes — the

benthos of both hard and soft bottoms

Heterotrophic microbial

production throughout the

water column, especially in

800–1,200m of water

Massive organic carbon enrichment resulted in

localized oxygen reductions and disruptions in the

food web.

Collateral damage caused by response actions

Activity Damage

Soot releases into

the atmosphere and

deposition on the seaﬂoor

from burning oil

Wildlife health effects of respiring soot and possible

benthic effects of its ocean deposition

Use of mechanical skim-

mers to remove surface oil

Contact with skimmers resulted in wildlife injuries and

fatalities

Dredging and ﬁlling to

create berms offshore in

attempts to block oil from

grounding on natural

habitats

Mortality of benthic invertebrates, which serve as key

prey for shrimp, crabs and demersal ﬁsh, and mortality

of seabird and sea turtle eggs

Intensive repeated beach

excavations and raking to

remove tarballs

Simultaneous mortality of benthic invertebrates such

as mole crabs and bean clams—important prey for surf

ﬁshers and shorebirds—plus removal of wrack, which

serves as habitat for small crustaceans and insects

consumed by plovers and other shorebirds

Sea turtle nest relocations

from Gulf Coast to eastern

Florida beaches

Risks of imprinting survivors to return to live along and

nest on a different coast

Boom deployment off-

shore of marsh shorelines

Direct physical damage to marsh plants as booms

break loose and are driven by waves into the marsh;

occasional trapping of oil and waterbirds together,

resulting in oiling and enhanced mortality of the birds

Use of 1.8 million gallons

of Corexit

There is uncertainty about Corexit-generated chronic

exposures to pelagic organisms, and likely ﬁtness

losses and direct mortality of particle feeders.

A Once and Future Gulf of Mexico Ecosystem 19

separate specialists and failure to recognize

the seriousness of inherent risks were part

of a complex sequence of multiple fail-

ures that facilitated an improbable event.

Although the blowout may have been

improbable, an underlying and long-stand-

ing culture of indifference within both the

petroleum industry and the federal regula-

tory agency (the former Minerals Manage-

ment Service) set the stage for the blowout

and made such an event inevitable (Graham

et al. 2011a).

As the most accessible oil reservoirs are

being depleted while the demand for

oil increases, the petroleum industry has

extended exploration and production into

progressively deeper waters. This pro-

cess has required remarkable engineering

innovation for successful drilling in ocean

waters over a mile deep and extraction of

oil several miles deeper below the seaﬂoor.

Oil at such depths exists under far greater

pressures than oil extracted from shal-

low depths, thereby increasing the need

to control pressure in the well. Despite

remarkable advances in engineering for oil

exploration and production in deep water,

corresponding progress has not occurred in

blowout prevention, emergency response,

clean-up and mitigation technologies. Some

of the same crude tools used to respond to

the oil release at the surface of the ocean

by the grounded Exxon Valdez tanker in

1989—skimming and surface booming—

were applied again 21 years later. Neither

the industry nor government regulators had

developed effective new technology for

shutting down a deepwater, high-pressure

blowout, as evidenced by the well-pub-

licized and remarkably rapid conceptual

development, construction and testing of

tools and approaches by the industry in the

weeks after April 20, 2010.

Industry complacency, failure to recognize

risk and the differences between deep and

shallow oil releases, and the conﬂicted

mission of the federal regulatory agency

charged with promoting development and

production of oil and gas while simulta-

neously acting as regulator meant that

appropriate advances were not made in

environmental safeguards to match the

heightened risks and challenges of deepwa-

ter drilling. The development and testing of

effective and reliable technologies to cap a

runaway blowout of a deep or ultra-deep

well should have preceded the emergency

need for them. Application of dispersant

at the wellhead should at least have been

tested in mesocosms under conditions

mimicking a deepwater blowout before the

decision to use it for the DWH. Toxicity tests

using the unique deep-sea particle feeders

at risk to ﬁnely dispersed oil should have

been conducted in advance of the decision

to use dispersants. In addition, scientiﬁc

advances needed to understand the biologi-

cal communities of the deep pelagic and

benthic oceans and the physical transport

regime that carries oil after release into the

environment in deep water had also stalled.

As a consequence, assessment of oil spill

impacts from deepwater blowouts was seri-

ously compromised.

As tragic as the DWH blowout was, it offers

an opportunity. As with the 1969 blowout

in the Santa Barbara Channel,1 which led

to passage of the National Environmental

Policy Act (NEPA), and the moratorium on

oil drilling off the California coast and other

states, the DWH blowout could stimulate

interest in protecting the economically,

socially and environmentally critical Gulf

region of the United States.

Ecosystem and natural

resource impacts of oil and

gas release

Before the Deepwater Horizon blowout,

the prevailing paradigm of maritime oil

behavior, biological exposure pathways

fate, and consequent impacts to natural

resources was based upon syntheses of past

shallow-water, largely nearshore oil spills

(e.g., NRC 2003). In such spills, crude oil

remains at the surface, unless mixed into

the water column by strong surface waves.

If discharged below the sea surface, the oil

rises rapidly to the surface because of its

buoyancy. Gaseous hydrocarbons such as

methane also rise to the sea surface, primar-

ily as bubble plumes, and disperse rapidly

into the atmosphere. The crude oil on the

sea surface is viscous and sticky; it fouls

the feathers of seabirds and the coats of

fur-bearing marine mammals, causing high

rates of mortality by disrupting thermoregu-

lation and through ingestion of toxins as

these birds and mammals preen feathers or

fur (Rice et al. 1996). Other organisms that

use the ocean surface, such as sea turtles,

Despite remarkable

advances in engineer-

ing for oil exploration

and production in deep

water, corresponding

progress has not occurred

in blowout prevention,

emergency response,

clean-up and mitigation

technologies.

Ships clean up oil in the Gulf of

Mexico using the same crude

tools that were used after the

Exxon Valdez spill 21 years

earlier. Photo: James Davidson

20 A Once and Future Gulf of Mexico Ecosystem

are exposed to physical fouling, potentially

resulting in death. Smooth-skinned marine

mammals, such as killer whales and harbor

seals, risk mortality and sublethal effects on

growth, reproduction and behavior from

inhalation of oil globules while breathing

through their blowholes and from inhaling

the more volatile toxic hydrocarbons in the

atmosphere. The ﬂoating oil is transported

by winds and surface currents and can end

up grounded on shores, where it exposes,

fouls and kills intertidal and shallow subtidal

organisms, including salt marsh plants, sea

grasses, macroalgae and oysters that pro-

vide important biogenic habitat (Teal and

Howarth 1984). Oil that penetrates into the

sediments sufﬁciently, so that sunlight does

not reach it and oxygen cannot be readily

resupplied from the atmosphere, can persist

for many decades without degradation

(Boufadel et al. 2010), exposing animals

that excavate those sediments to form bur-

rows (Culbertson et al. 2007) or to uncover

infaunal prey. This exposure can cause

sublethal losses of ﬁtness that can have

population-level consequences for several

years (Peterson et al. 2003b).

The DWH well blowout indeed led to

substantial coverage of the sea surface and

consequent fouling and killing of seabirds,

sea turtles, bottlenose dolphins and perhaps

other marine mammals, as expected from

traditional shallow-water spills (Table 1). The

seabirds that experienced the most loss of

life include northern gannet, brown pelican,

gulls, terns and the black skimmer. Aborted

bottlenose dolphin fetuses were observed.

Surface oil also collected in the ﬂoating

Sargassum, a large brown alga that forms

a unique ﬂoating nursery habitat in the

Gulf and other seas. Sargassum supports

large numbers of small ﬁshes, including

A menhaden ﬁshing boat in

Empire, LA. Photo: Louisiana

Sea Grant College Program/

Louisiana State University

Oil that penetrates into

the sediments sufﬁciently,

so that sunlight does

not reach it and oxygen

cannot be readily resup-

plied from the atmo-

sphere, can persist for

many decades without

degradation.

The Menhaden Fishery in the Gulf of Mexico

The Gulf menhaden ﬁshery dates to

the late 1800s and remains economi-

cally important today. With landings of

468,736 tons in 2004, the Gulf men-

haden landings comprise 11 percent

of all U.S. ﬁshery landings, and Gulf

menhaden support the second-largest

commercial ﬁshery in the United States

(Pritchard 2005). The menhaden catch

records for years before World War II

are incomplete, but annual landings

from 1918 to 1944 probably ranged

from 2,000 to 12,000 tons (Nicholson

1978). Landings appeared to increase

from the late 1940s through 1970, with

a peak of 521,500 tons landed in 1969

(Chapoton 1970, 1971). Landings con-

tinued to increase through the 1970s

and 1980s, exceeding 800,000 tons for

six consecutive years (1982 to 1987)

and peaking at 982,800 tons in 1984

(Smith 1991). Since 1988, the land-

ings have ranged from 421,400 tons in

1992 to 761,600 tons in 1994, show-

ing no apparent trend. Although the

menhaden landings do not appear to be

declining further from the 1982–1987

levels, the potential for overﬁshing is

still a concern and must be consid-

ered in the future management of this

important ﬁshery. Because menhaden is

a forage ﬁsh for many predatory pelagic

ﬁshes, seabirds and marine mammals,

reductions in stock levels by ﬁshing

may have consequences for the health

and viability of populations of higher

trophic-level predators (Botsford et al.

1997). To the extent that these higher-

order predators are protected by law,

these indirect ecosystem-based issues

associated with menhaden harvest are

likely to represent a critical manage-

ment concern. The menhaden ﬁshery’s

history indicates limited consideration

for ecosystem-based impacts, yet as

the ocean environment continues to

change, management of this highly pro-

ductive ﬁsh stock will need to take into

account a broader range of factors that

drive menhaden dynamics, including

DWH oil spill impacts, and a wider range

of consequences of ﬁshing, including

impacts on threatened and endangered

species and on species injured by the

oil spill. Menhaden represent one of

many ﬁsh stocks for which ecosystem

consequences of ﬁshing need to be

considered in a context of the changing

Gulf environment so that sustainability is

incorporated into management.

A Once and Future Gulf of Mexico Ecosystem 21

juvenile blueﬁn tuna, cobia and wahoo, as

well as crustaceans and other invertebrates

that help feed juvenile predatory pelagic

ﬁshes. In addition, this is the critical habitat

for juvenile loggerhead, Kemp’s ridley and

other sea turtles from the time of leaving

the nest until they return to coastal waters.

Large numbers of sea turtle hatchlings

were recovered dead and dying from the

Sargassum.

The state of the Gulf and its coastal zone

immediately before the DWH incident was

far from pristine, with countless anthropo-

genic stressors having already altered and

degraded the ecosystem. In the Gulf and

other ocean ecosystems, anthropogenic

degradation is a historically cumulative

process (Jackson 1997, 2010, Jackson et al.

2001, 2011), and an understanding of that

degradation process is critical to success-

ful restoration. Stressors can synergistically

intensify their impacts over time and across

systems and species in ways that may result

in alternative and less desirable ecosystem

states (Scheffer et al. 2001). Thus, attempts

to repair the consequences of more recent

disturbances in any ecosystem will neces-

sarily fail unless restoration addresses all of

the drivers of degradation both present and

past. Consequently, the restoration should

incorporate an understanding of the base-

line natural processes of the ecosystem, the

historical degradation of those processes,

and the way in which progressive environ-

mental changes in the ecosystem might

affect restorative actions. The durability of

restoration depends upon consideration of

these factors. This section outlines some

of the major historical and anthropogenic

stressors on the Gulf ecosystem.

Humans have been active in the Gulf

ecosystem for thousands of years, ranging

from centuries of subsistence ﬁshing and

harvesting of nearshore resources by Native

Americans to oil and gas extraction in the

20th and 21st centuries. The impacts of

human activities include bottom habitat

modiﬁcation and population reductions

in targeted ﬁsh and shellﬁsh stocks and in

species killed as bycatch from large-scale

commercial and recreational ﬁshing; chan-

nelization and damming of major rivers

ﬂowing into the Gulf; widespread and rap-

idly accelerating coastal development with

its attendant modiﬁcation of hydrology,

increases in impermeable surface area, and

dredge-and-ﬁll activities in wetlands; extrac-

tions of subsurface ﬂuids such as oil, gas

and groundwater, which induce subsidence;

water quality degradation from agricultural,

urban, and industrial runoff of nutrients;

and the burgeoning impacts of anthropo-

genically induced global climate change.

The Gulf has endured the consequences of

uncontrolled nutrient runoff and eutro-

phication because of agriculture upstream

(Rabalais et al. 2002, 2007); overﬁshing and

associated habitat destruction from trawl-

ing; and loss of habitat because of coastal

development, land subsidence, channeliza-

tion of wetlands, intensiﬁcation of severe

storms, and sea level rise. The historical

context of each of these human modiﬁca-

tions of the ecosystem is presented below.

Centuries of ﬁshing in the

Gulf of Mexico

The ﬁrst signiﬁcant human impact on

the Gulf ecosystem was probably caused

by ﬁshing in coastal estuaries by Native

Americans. Although no recorded evidence

exists, Native American ﬁshing may have

particularly affected accessible species such

as oysters near shore (Jackson et al. 2001,

Lotze et al. 2006). This effect may have

been minimal: From the time of Columbus’s

landing through the early 1600s, there were

accounts of large abundances of ﬁsh, oys-

ters, sea turtles and marine mammals found

in the Gulf and the Caribbean. However,

by the early 1800s, many of these organ-

isms were already being overﬁshed (Jackson

1997, Jackson et al. 2001), and exploitation

increased through the 19th century. The sea

turtle ﬁshery peaked in 1890, when turtles

ranked 10th among ﬁshery products from

Gulf states and ﬁfth in Texas, and declined

sharply after 1892 due to overexploitation

(Doughty 1984).

1890s Green turtles are pre-

pared for shipping to New York

from Key West, FL, in 1898.

The Gulf sea turtle ﬁshery

peaked in the late 1800s and

then declined sharply because

of overexploitation. Photo:

Florida Keys Public Libraries

Damage to the Gulf of Mexico Prior to the

DWH Oil Spill

22 A Once and Future Gulf of Mexico Ecosystem

Advances in ﬁshing technology affected

the Gulf as vessels and catching devices

improved the efﬁciency of ﬁshing. The

transitions from sailing vessels in the late

1800s to steamers in the early 1900s and

then to diesel-powered vessels in the 1930s

each increased the impact that ﬁshing had

on marine populations. The introduction of

purse seines and longlines in the late 1800s,

otter trawls for groundﬁsh and shrimp in the

early 1900s, and more recent advances such

as durable nylon ﬁbers for nets, Loran-C,

and GPS navigation systems dramatically

increased efﬁciency, the ability to target

speciﬁc sites, and the size of catches. Refrig-

eration also helped increase demand by

creating globalization of markets.

These technological advances in the com-

mercial and recreational ﬁshing industry

have contributed to overﬁshing and the

subsequent decline of major ﬁsheries in the

Gulf, including Spanish and king mackerel,

red snapper, several species of grouper, red

drum and many pelagic shark species (UN

FAO 2005, Coleman et al. 2004a, Baum

and Myers 2004). The U.S. National Marine

Fisheries Service reported that in 2002, the

ﬁve Gulf Coast states landed a total of more

than 1.7 billion pounds (771,800,000 kg)

of ﬁsh, including Gulf menhaden (see box,

Page 20) and shellﬁsh, worth more than

$705 million. These landings, however, do

not include the many pounds of bycatch

(including juvenile commercial ﬁshes, forage

ﬁshes, birds, sea turtles and marine mam-

mals) that are associated with many ﬁsheries

(Moore et al. 2009), making the total

extraction of ﬁsh and wildlife from ﬁsheries

much greater.

Gulf landings of shrimps and oysters

account for about 68 and 70 percent,

respectively, of total U.S. landings. Although

impacts of ﬁshing on populations of these

animals are not well documented in the

Gulf, the indirect effects of their harvest

on the benthic habitats and the commu-

nities of invertebrates and ﬁsh that they

support have been well studied in recent

decades. Trawling for shrimp and groundﬁsh

disturbs bottom habitat and reduces the

species diversity, abundance and biomass

of bottom-dwelling organisms that serve as

a food source for many demersal ﬁsh and

crustaceans (Collie et al. 1997). Different

assemblages of ﬁsh and crustaceans can

also be associated with habitats frequently

disturbed by trawling, indicating shifts in

community structure at multiple trophic

levels (Wells et al. 2008). Such bottom

disturbance resets the benthic invertebrate

community to an early successional stage

of small, short-lived invertebrates. When

combined with the loss and degradation of

coastal habitats induced by other stressors,

continued intense ﬁshing pressure and

bottom disturbance associated with trawling

and dredging may cause even more habitat

modiﬁcations and reductions in ﬁsh stocks.

Fishing is a major pillar of the contemporary

Gulf coastal economy. Achieving sustainable

harvest levels at higher stock abundances

would result in millions of dollars’ worth of

enhancement to Gulf state economies. Our

Gulf restoration actions under Theme 3 (see

Page 75) include suggestions for achieving

sustainable levels of extraction of ﬁsh and

shellﬁsh at high yields while also minimizing

impacts on wildlife.

Pollution in the Gulf

Trends in nutrient loading and pollution

Nutrient loading, sedimentation and dis-

charges of other pollutants into the Gulf

has increased over the past 200 years as

a consequence of more intense human

occupation, development and use of land

in the Mississippi River watershed and other

rivers entering the Gulf (Turner 2009). The

concentration of nitrate and phosphorus in

river systems that feed into the Gulf, such as

the Mississippi, increased three- to ﬁvefold

between the early 1900s and the 1990s

and may continue to rise with increas-

ing demands for food and, more recently,

for corn and other crops used in ethanol

production in the Midwest (Figure 2; Turner

et al. 2007). The concentrations of pollut-

ants such as heavy metals have increased

in the sediments, and these increases are

probably associated with oil drilling activities

in the Gulf (Vazquez et al. 2002). Increased

levels of mercury and some other toxic con-

taminants in the Mississippi River and other

rivers leading into the Gulf can be linked

to settlement of the Midwest by European

immigrants in the mid-1800s. Contaminant

concentrations of heavy metals peaked

in the 1960s and have since declined,

primarily in response to environmental laws

enacted in the 1970s such as the Clean

Water Act (Wiener and Sandheinrich 2010).

Late 1800s Sailing vessels

were replaced by steam vessels.

Credit: NOAA

The concentration of

nitrate and phosphorus

in river systems, such as

the Mississippi, that feed

into the Gulf increased

three- to ﬁvefold

between the early

1900s and the 1990s.

A Once and Future Gulf of Mexico Ecosystem 23

Despite regulatory protections, mercury

and organic pollutants, such as DDT and

PCBs, which were released into the Gulf

watersheds before effective regulation, have

gradually biomagniﬁed to concentrations

adversely affecting apex predators (Wiener

and Sandheinrich 2010).

Impacts of nutrient loading

and pollution

Salt marshes, sea grass meadows and

oyster reefs act as ﬁlters for nutrients

and other pollutants, but the process of

trapping excess nutrients, heavy metals

and toxic organic chemicals has ecological

consequences (Dame et al. 1984). Although

nutrient enrichment is not the primary

cause of wetland loss in the Gulf, it appears

to contribute to it. From 1998 to 2004,

370,760 of the 3,508,600 acres of saltwater

wetlands along the Gulf Coast were lost,

more than along any other U.S. coastline

(Stedman and Dahl 2008).

In general, nutrient enrichment of wetlands

results in higher aboveground standing bio-

mass (Morris 1991). However, belowground

production is more critical than aboveg-

round production to sustaining marshes

as sea level rises. The production of roots

and rhizomes elevates the marsh surface at

rates that can help compensate for rela-

tive sea level rise. Results from a 30-year

experiment in salt marshes in Massachusetts

show that eutrophication does not increase

organic matter accumulation belowground

but instead weakens soil strength and may

cause a signiﬁcant loss in marsh elevation

equivalent to about half the average global

sea level rise rates (Turner et al. 2009).

Therefore, sustaining and restoring coastal

emergent marshes is more likely if they

receive fewer, not more, nutrients.

Like wetlands, other biogenic shoreline

habitats have suffered signiﬁcant degrada-

tion and loss from nutrient enrichment

in the decades before the DWH oil spill.

Nutrient loading can cause massive blooms

of phytoplankton, microalgae and macroal-

gae, which can compete with benthic sea

grasses (Hughes et al. 2004, Burkholder et

al. 2007) and corals (Anthony et al. 2011)

for light and oxygen and can interfere with

oyster spat settlement on reefs (Thomsen

and McGlathery 2006). Orth and van

Montfrans (1990) estimated that sea grass

covered 2.47 million acres (nearly one

million hectares) of the Gulf; sea grass habi-

tat losses over the past 50 years, however,

have been estimated at 20 to 100 percent

for most northern Gulf estuaries (Duke and

Kruczynski 1992). Similarly, losses of 50

to 89 percent are estimated for oysters in

the Gulf from baselines ranging from 20 to

130 years ago to the present (Beck et al.

2011). Coral reefs in the Gulf have experi-

enced coral bleaching and disease outbreaks

attributed to anthropogenic stressors in

the past few decades, resulting in losses in

total coral cover on some reefs (Knowlton

and Jackson 2008). Because of the known

stress of excess nutrients on these organ-

isms, we can attribute some aspect of these

losses to nutrient loading. Nutrient loading is

likely to continue to increase in the coming

decades and could interfere with successful

restoration of coastal wetlands and subtidal

biogenic habitats of the Gulf if it continues

unabated.

Dead zones in the Gulf of Mexico:

The consequences of hypoxia

In large part because of nutrient loading,

hypoxia (dissolved oxygen < 2 mg l-1) is a

growing problem worldwide in estuaries

and coastal oceans (Rabalais 2002, Diaz and

Rosenberg 2008). The extent and persis-

tence of hypoxia on the continental shelf

of the northern Gulf make the Gulf’s “dead

zone” the second-largest manifestation of

anthropogenic coastal eutrophication in the

world (Figure 2). Systematic mapping and

monitoring of the area of hypoxia in bottom

waters began in 1985 (Rabalais 2002). The

dead zone size, as measured each year in

July, has ranged between 40 to 22,000 km2

and averaged 16,700 km2 from 2000 to 2007

(excluding two years when strong storms

occurred just before the hypoxia survey).

An Action Plan for Reducing, Mitigating,

and Controlling Hypoxia in the Northern

Gulf of Mexico (Mississippi River/Gulf of

Mexico Watershed Nutrient Task Force

2001) endorsed by federal agencies, states

and tribal governments calls for a long-term

adaptive strategy coupling management

actions with enhanced monitoring, mod-

eling and research, and reassessment of

accomplishments and environmental indica-

tors at ﬁve-year intervals. Several models

summarize the relationship between the

nutrient loading of nitrogen and phospho-

rus and the severity of the hypoxic zone

(Figure 2; Rabalais et al. 2007) and support

1920s–present Widespread

application of pesticides and

fertilizers occurred on agricul-

tural lands beginning in the

1920s and continuing today.

Photo: Willard Culver/National

Geographic Stock

24 A Once and Future Gulf of Mexico Ecosystem

Hypoxic “Dead” Zone

When dissolved oxygen levels reach two milligrams per

liter or less—a condition called hypoxia—most slow-

moving or attached animals suffocate, creating areas

known as dead zones in the bottom waters. The dead

zone in the northern Gulf of Mexico is nearly the largest

in the world, averaging 6,700 square miles (17,300

square kilometers) over the past ﬁve years; it is second

only to the hypoxic zone in the Baltic Sea.

Agricultural sources contribute more than 70%

of the nitrogen and phosphorus delivered to the

Gulf, versus only 9 to 12% from urban sources.

Nitrogen

66% comes from growing crops, espe-

cially corn and soy. Other sources include

atmospheric deposition (16%), urban and

population sources (9%), pasture and range

(5%), and natural land (4%).

Phosphorus

43% comes from crops, especially corn

and soy, and 37% comes from range and

pasture, particularly animal manure. Other

sources include urban and population

sources (12%) and natural land (8%).

Source: Alexander et al. 2008

The maximum area of this dead zone was

measured at 8,481 square miles (22,000

square kilometers) during the summer of

2002; this is equivalent to the size of

Massachusetts.

States that run off into the Gulf

More than 75% of nitrogen and phosphorus runoff

comes from Illinois, Iowa, Indiana, Missouri, Arkansas,

Kentucky, Tennessee, Ohio and Mississippi

Study area

200 km

Galveston

Bay

Mississippi

River

Figure 2

Mississippi River Basin

Rivers, estuaries and tributaries

from the 48 contiguous states

run off into the Gulf via the

Mississippi River basin. Source:

USDOI and USGS 2008

Year-to-year area of Gulf of Mexico

hypoxia, shown in square miles

No data available for 1988 and 1989.

Source: Rabalais et al. 2010

20101985 1990

square miles

years

Year to year area of Gulf of Mexico hypoxia, shown in square miles. Source: NOAA

http://www.gulfhypoxia.net/Research/Shelfwide%20Cruises/

2000

5,000

10,000

A Once and Future Gulf of Mexico Ecosystem 25

the key component of the management

action, which is to reduce nutrient loading

to the Gulf of Mexico so that the average

hypoxic area in summer is 5,000 km2 or

less by 2015. Turner et al. (2008) suggested

that there was an increase in the oxygen

demand of marine sediments arising from

the accumulation of organic matter and

that the accumulation in one year made the

system more sensitive to nitrogen loading

the next year. Remedial actions meant to

reduce the size of the hypoxic zone must

address these future increases in nutrient

loading and today’s legacy of eutrophication.

Land loss along the Gulf Coast

Coastal development

The population of the ﬁve Gulf Coast states

increased by 45 percent between 1980

and 2008. More than 20 million people are

now living on the Gulf Coast, with coastal

counties in Texas and Florida (see box

above) experiencing the largest population

increases (Crossett et al. 2004). Increases

in residential, commercial, industrial and

agricultural development have accompa-

nied this population increase, resulting in

the loss of coastal forests and wetlands

and increases in storm water runoff and

transport of nutrients and sediments into

the Gulf.

Channelization, levee construction and

damming have limited ﬂoodwater ﬂows

onto the ﬂood plains, thereby suppressing

the transport, deposition and retention of

sediments to enrich the soils and vegeta-

tion. Motivated by a desire to create more

waterfront real estate with riparian access

for large boats, aggressive construction of

“ﬁnger channels” (see photos, Page 26)

took place in the mid-1950s to late 1960s

along much of the coast of south Florida.

The dredge-and-ﬁll operations were often

conducted directly over mangrove forests or

oyster reefs, as illustrated in these photos.

In addition to destroying critical ﬁsh habi-

tats, aggressive construction in the estuaries

Figure 3

South Florida Population

Growth Since 1900 South

Florida’s population has grown

from 5,000 in 1900 to a current

population over ﬁve million.

Source: Walker et al. 1997

1000000

2000000

3000000

4000000

5000000

population (millions)

1900 20111950

1980–2008 The population

of the ﬁve Gulf Coast states

increased by 45 percent. Above

is Panama City, FL. Photo: Ray

Devlin

Coastal Development in South Florida

South Florida, consisting of seven coun-

ties, supported a population of only

5,000 people in 1900. By 1930, after

Henry Flagler, a principal in Standard Oil,

completed the Miami railway, the popu-

lation had grown to more than 230,000.

With this population surge came large

increases in agriculture in the ﬁrst half of

the 20th century, with more than 55,000

hectares of farmland by 1943, accom-

panied by the destruction of coastal

mangrove forests and the Everglades

wetlands, and then large increases in

residential and urban development in the

latter half of the 20th century. Massive

ﬂooding in the late 1940s with bur-

geoning mosquito populations caused

the federal government to build dikes

around Lake Okeechobee to provide

ﬂood protection for the growing urban

areas to the south and to build mosquito

abatement ponds throughout the area.

By 1950, the South Florida population

reached 720,000, primarily associated

with migration of retirees into suburban

single-family residences surrounded by

golf courses, pools and urban centers

(Walker et al. 1997). Today the popula-

tion is over ﬁve million, representing one

of the highest growth rates in the United

States from 1900 to the present.

Because of the high rate of develop-

ment, many of the functions of the

ecosystems in South Florida are no

longer being performed. Erosion has

become a major problem on the coast,

largely as a result of severed water and

sediment transport pathways from

upstate down through the Everglades

and to Miami, loss of mangroves on

shore, consequences of channel dredg-

ing, and impacts of subsidence caused

by groundwater extraction. With sea

level rise now threatening to ﬂood all

of South Florida (Figure 8), restoration

efforts in this region must address a suite

of ecological issues to restore long-term

sustainability and resilience of ecosys-

tems and human communities.

26 A Once and Future Gulf of Mexico Ecosystem

reduced the bay size and altered the sedi-

ment dynamics of the tidal inlets and the

nearby ocean beaches (Wang et al. 2011).

Compounding the rapid residential develop-

ment, dredging for oil and gas extraction

has been causally linked to coastal wetland

loss in the Gulf. More than 90 percent of

U.S. offshore oil and gas reserves, past

production and present yields are in the

coastal waters of the Gulf of Mexico, but

the inshore recovery peaked more than a

decade ago. Large-scale efforts to slow or

reverse wetland losses along the Gulf began

in the early 1990s, focused on construction

of river diversions. Such projects make up

the largest and most expensive strategy for

addressing wetland loss in the Louisiana

coastal area, with future costs possibly

reaching several billion dollars. Dredging

navigation routes through Gulf coastal wet-

lands began at least 200 years ago (Davis

1973), but it was the canals dredged for oil

and gas recovery efforts beginning in the

1930s and peaking in the 1960s (Figure 4)

that had demonstrable and coastwide inﬂu-

ences on wetlands. The direct impact of

dredging on wetlands amounted to 1,017

km2 of canals in 1990 (Britsch and Dunbar

1993), with an equal area of spoil banks

stacked on the adjacent wetlands (Bau-

mann and Turner 1990). There is a much

larger indirect impact from canals and the

dredged spoil deposits that is demonstrable

at several temporal and spatial scales. For

example, 1) land loss rates in the deltaic

plain, in similar geological substrates, are

directly related to dredging; 2) the amount

of land loss where dredging is low is near

zero; and, 3) the land loss rates acceler-

ated and slowed when dredging rose and

slowed in the Barataria basin (Turner et al.

2007b).

The rise and fall in dredging is coinciden-

tal with the rise and fall of wetland loss

(Figure 4). Other plausible explanations

for wetland loss are related to the loss of

the accumulated organic matter and plant

stress accompanying an altered hydrology

(Swenson and Turner 1987, Turner 1997,

2004). But the fact that sea level rise, soil

subsidence and the concentration of sus-

pended sediment in the river have remained

about the same from the 1960s to the

present (Turner 1997, Turner and Rabalais

2003) supports the conclusion that the cur-

rent dominant cause of Gulf wetland loss is

dredging.

Dredging is regulated and authorized

through permits issued by state and federal

agencies, and the permitting process

does not appear to reﬂect the foreseeable

consequences for wetland loss. Damage

that is now evident was largely completed

before critical analyses of wetland impacts

of canal dredging were completed. But

even today there is no coastwide restoration

program that speciﬁcally targets compen-

sating for the direct and indirect impacts

of canals and spoil banks on wetland loss.

Existing canals and any future dredging and

canal construction could compromise DWH

restoration efforts if they occur within areas

targeted for restoration.

1950s–1960s Finger channels

were constructed over man-

grove and oyster reef habitats

in South Florida. The reduction

in bay size from ﬁlling also had

a substantial impact on the tidal

inlets and on sediment supply

to adjacent beaches. Photos:

Courtesy of Ping Wang

The rise and fall in

dredging is coincidental

with the rise and fall of

wetland loss.

1918 A canal is dredged in

New Orleans. Photo: Team

New Orleans/U.S. Army Corps

of Engineers

1951 2010

A Once and Future Gulf of Mexico Ecosystem 27

20001850

Land area (km2)

years

Land-loss trends for Horn Island (Mississippi-Alabama barrier island) (left) compared with depths of

shipping channels dredged through the outer bars at the Horn Island Pass. (Source: Morton 2008).

1900 1950

-15

20001850

Outer bar dredging depth (m)

years

1900 1950

-10

-5

Figure 5

Land loss trends for Horn

Island, a Mississippi-Alabama

barrier island (left), compared

with depths of shipping chan-

nels dredged through the outer

bars at the Horn Island Pass.

Source: Adapted from Morton

2008

Figure 4

Relationship between land

loss and canal density in the

Louisiana coastal zone The

study measures land loss over

ﬁve time periods between 1930

and 2000. Source: Adapted

from Turner et al. 2007b

20001930

Land loss (km2)

years

Relationship between land loss and canal density in the Louisiana coastal zone.

What are the 6 intervals?

1950 1970 1990

120

20001930

Canal area added (km3)

years

1950 1970 1990

The sinking coastline: unsustainable oil,

gas and groundwater extraction

Although natural subsidence processes,

such as sediment compaction and down-

warping of underlying crust (e.g., in the

Mississippi River Delta plain, Barataria Basin,

and Atchafalaya Basin) are occurring along

the coast, the withdrawals of subsurface oil

and gas are also major contributors to Gulf

wetland loss in some places (Kennish 2002).

For example, the rates of soil compaction

and eustatic sea level rise along the upper

Texas coast can exceed 13 millimeters per

year (mm yr-1), while human-induced sub-

sidence rates can be as high as 120 mm yr-1

(White and Tremblay 1995). In the Houston-

Galveston area, withdrawal of groundwa-

ter has caused up to three meters of land

surface subsidence, with the rate of subsid-

ence ranging from 10 mm yr-1 to more than

60 mm yr-1 (Gabrysch and Coplin 1990).

Beach nourishment to compensate

for land loss

As sea level rises and hurricanes and other

storms subject barrier beaches to high

wave run-up and beach erosion, the land

forms can change dramatically. With rising

sea level, barrier islands commonly roll

over through the process of over-wash and

become reestablished in a new location

displaced landward (Figures 9, 10). This

process represents a natural dynamic of

sandy shorelines, although the greenhouse

gas-driven high rates of present and future

sea level rise are abnormal. So long as bar-

rier islands and coastal barrier beaches are

not developed and residents do not attempt

to draw permanent property lines, the roll-

over of coastal barriers does not represent

a problem (Figures 9, 10). However, when

houses, roads and other infrastructure and

businesses are constructed on these mobile

28 A Once and Future Gulf of Mexico Ecosystem

Figure 6

Detail of northern coast of

Gulf of Mexico

See Gulf overview map Page 2.

See Barrier Island detail maps

on Pages 34–35 (Isles Dernieres

and Chandeleur Islands).

Dauphin

Island

Site of

DWH spill

De Soto

Canyon

Flower Garden

Banks National

Marine Sanctuary

Grand Isle

Pascagoula

River

Alabama

River

Escambia

River

Atchafalaya

River

Atchafalaya

Bay

Mississippi

River Delta

Mississippi River

New Orleans

Baton Rouge

Isles Dernieres

(see detail map on Page 34)

Houma

Biloxi

Mobile

Pensacola

GULF OF MEXICO

Chandeleur Islands

(see detail map on Page 35)

lands, then engineered hard structures such

as seawalls and jetties or soft solutions such

as beach nourishment are typically pursued

to protect the investments. Stabilizing

costal barriers under the emerging context

of accelerating rates of sea level rise and

enhanced frequency of intense tropical

storms will make occupation of coastal

barriers along the Gulf Coast increasingly

expensive, environmentally damaging and

potentially too costly to maintain, especially

on the rapidly subsiding Mississippi Delta.

Beach excavations to locate and remove

buried oil and tarballs also represent physi-

cal habitat disturbances that can bury and

kill the invertebrate prey for shorebirds and

surf ﬁsh, but this is a brief pulse disturbance

from which recovery should occur within a

year. Removal of plant wrack composed of

marsh macrophytic and sea grass materials

takes away a resource that nurtures insects,

amphipods, isopods and other invertebrates

that serve as prey for shorebirds, especially

plovers. Consequently, this intervention

into sandy beach habitats also represents

degradation of ecosystem services. Potential

impacts on the threatened piping plover are

especially critical to assess.

Alterations of river systems

that lead into the Gulf of

Mexico

The watersheds in the Gulf contain a range

of habitats that support biologically diverse

and productive ecosystems with both

nursery and feeding grounds for ecologi-

cally and economically important species

(Livingston 1997, MCWMP 2007). Although

representative bays have a number of

morphologic and hydrologic similarities,

they differ in the extent to which they have

been affected by anthropogenic changes

and in their loss of ecological integrity over

the past few decades (NOAA 2009). For

example, the Mississippi Sound, near metro-

politan New Orleans, is heavily affected

by sewage outﬂows, agricultural drain-

age and intensive development, while the

Apalachicola Bay system is still relatively

pristine and is the last bay of that quality

in the northern Gulf of Mexico. A tremen-

dous advantage in the scientiﬁc study of

these systems is that each contains estab-

lished National Estuarine Research Reserves

(NERRs), thus providing investigators with

access to signiﬁcant stores of existing

data, new or recently developed numerical

A sign warns of a pipeline cross-

ing in Louisiana. Because of

coastal erosion, many pipelines

are closer to the surface and in

some cases are even in open

water. Photo: Paul Goyette

A Once and Future Gulf of Mexico Ecosystem 29

models, and guidance of NERR managers

with tremendous expertise in the needs of

coastal and environmental decision-makers.

Research conducted in these reserves can

help to restore unimpeded water ﬂows,

improve water quality and restore and

protect riparian in-stream habitats of high

value. Below are short descriptions of

several Gulf waterways and their known

historic stresses.

The Mississippi Sound System

The Mississippi Sound (drainage area,

69,700 km2) is a shallow estuarine system

that extends from Lake Borgne, Louisiana,

to Mobile Bay, Alabama. It receives freshwa-

ter through marsh habitat runoff and seven

watersheds (from west to east, the Pearl,

Escatawpa, Pascagoula, Tchoutacabouffa,

Biloxi, Wolf and Jourdan Rivers) and occa-

sionally receives large freshwater inputs

via Mississippi River ﬂood control releases

that can cause low-salinity anomalies that

last for months. It exchanges water with

the Mississippi-Alabama-Florida (MAFLA)

Shelf through barrier island passes involv-

ing seven primary islands, including Grand

Island, Cat Island, West Ship Island, East

Ship Island, Horn Island, Petit Bois Island and

Dauphin Island. The shelf-scale hydrography

is dominated by seasonally shifting winds

that inﬂuence salinity patterns, creating

offshore-directed salinity gradients driven by

river discharge. Seasonal differences result in

westward-directed transport over the shelf

during fall and winter, reducing the local

inﬂuence from the Mississippi River, while

low-salinity water spreads over the shelf

during the spring and summer, resulting in

a strong halocline (Morey et al. 2003a, b).

The Pascagoula River (drainage area,

23,310 km2), the second-largest basin in

Mississippi, is the last unimpeded river

system in the continental United States

and the largest contributor of freshwater to

Mississippi Sound. Unobstructed ﬂow and

natural ﬁre regimes are critically important

The Pearl darter, a rare small

ﬁsh, is one of the threatened

or endangered species in the

Gulf region. Photo: Joel Sartore/

National Geographic Stock

Environmental Concerns Related to Petroleum Storage

in Salt Domes

The practice of storing oil in salt domes

throughout the Gulf of Mexico has gone

on for more than 40 years, with active

storage sites in Louisiana and Texas (DOE

2011). Domes are considered ideal stor-

age receptacles because the salt forms

a seal around contained substances,

creating a stable reservoir. But leakages

in similar domes off Weeks Island, LA.,

have proven problematic, resulting in the

removal of petroleum stores and aban-

donment of the site (Neal 1997, Neal et

al. 1998, Kurlansky 2002). Undoubtedly,

heterotrophic microbes exist in the conti-

nental shelf that can degrade petroleum

hydrocarbons relatively rapidly, but if the

oil leakage creates signiﬁcant patches

of ﬂoating oil or contaminates oysters

or other shellﬁsh, then leakage is clearly

unacceptable.

A proposal from the DOE to create a

petroleum reserve site in Mississippi salt

domes, which was recently withdrawn,

threatened the Pascagoula River basin.

The process for preparing the Mississippi

site for oil storage would involve inundat-

ing the dome each day with millions

of gallons of freshwater drawn from

the river to dissolve the salt and then

pumping out the resulting hypersaline

(264 parts per thousand) solution into

a pipeline constructed over 1,500 acres

of wetlands to transport it 80 miles to

the Gulf of Mexico. The activity would

take ﬁve to six years to complete,

severely reduce ﬂow in the Pascagoula

and discharge millions of gallons of

salt brine just south of Horn Island, a

2,763-acre barrier island that is part of

a group of islands along the Mississippi

coast that the federal government has

spent millions of dollars to protect. Other

anticipated damage includes saltwater

intrusion from the Mississippi Sound

up the river, with potentially devastat-

ing outcomes (if the damage caused by

Hurricane Katrina is any indication) and

development of a dead zone near the

outfall from the pipeline. Although the

proposal was withdrawn in March 2011,

it still looms over the river’s future.

30 A Once and Future Gulf of Mexico Ecosystem

in maintaining the high productivity of

bottomland forests, marshes, savannas and

aquatic habitats that support an enor-

mously diverse biota, including 22 threat-

ened or endangered species. Among these

are species found only in Mississippi, includ-

ing the Pearl darter (Percina aurora), a rare

small ﬁsh found only inthe Pascagoula and

Pearl River drainages, the Mississippi sand-

hill crane (Grus canadensis pulla), critically

endangered nonmigratory birds, the yellow-

blotched map turtle (Graptemys

ﬂavimaculata) and the Louisiana black

bear. The river basin also provides habitat

to other species endangered throughout

their range, such as the red-cockaded

woodpecker, swallow-tailed kite (Elanoides

forﬁcatus) and Gulf sturgeon (Acipenser

oxyrhynchus desotoi), among others.

Stresses to the Pascagoula River ecosystem

include invasive plant species; sedimenta-

tion from mining and other activities; water

withdrawal for use in agriculture, industry

and domestic purposes; and direct dis-

charge of pollutants, especially nutrients,

from industrial or municipal wastewater

treatment facilities, mining and waste man-

agement. Although these stresses take their

toll, another concern is a proposal from the

U. S. Department of Energy (DOE) to create

a petroleum reserve site in Mississippi salt

domes (see box, Page 29).

The Perdido River (drainage area 2,937 km2)

provides the primary freshwater source for

Perdido Bay, a relatively small, shallow estu-

ary at the Alabama-Florida border. The bay

is affected by two interwoven problems:

artiﬁcial widening of its mouth in the 1970s

and nutrient loading that started as early as

the 1940s. The widening of the bay mouth

to help retain sediment led to the unantici-

pated consequence of saltwater intrusion

into the bay. This contributed signiﬁcantly

to salinity stratiﬁcation, the development of

hypoxia and ultimately serious declines in

benthic invertebrates and ﬁsh assemblages

in the deeper waters of the bay. The overall

effect was disruption of local food webs.

Nutrient loading created a different set of

trophic problems. The nutrients entered

the bay from multiple sources, including

efﬂuents from a paper mill (operated by

International Paper; efﬂuent enters Eleven

Mile Creek), urban storm water and sewage

runoff (the area around the bay is highly

developed), and agricultural runoff from

Alabama (Livingston 2000, 2001, 2007).

The introduction of different nutrients at

various times of the year stimulates a series

of phytoplankton blooms, with diatoms pre-

dominating in the spring, raphidophytes in

summer and dinoﬂagellates in winter. When

these become coupled with high concentra-

tions of orthophosphate and ammonia from

the mill, the outcome is characterized by

the loss of planktivorous infaunal inverte-

brates. Teasing apart these multiple effects

is quite difﬁcult without intensive food web

modeling that takes into account benthic

conditions, planktonic responses to nutrient

loading, and climate change. Clearly, both

top-down and bottom-up processes act on

this system (Livingston 2007).

The pulp mill adopted some strategies to

reduce nutrient input, and these resulted

in some improvement in the complex of

infaunal species. Although much remains

to be done, the only solution proffered

by the industry (and approved by Florida’s

Department of Environmental Protection

[DEP]) was to build a pipeline that would

move the efﬂuent discharge site from the

upper stretches of Eleven Mile Creek to the

mouth of creek. This would help clean up

Eleven Mile Creek, but it would do nothing

to stop the arrival of pollutants in Perdido

Bay. Within months of approving this plan,

DEP Director David Struhs retired to become

vice president for environmental affairs at

International Paper. This plan illustrates one

of the many challenges of large-scale resto-

ration projects: the intertwining of industry

and government interests in the use of

natural resources.

The Apalachicola System

Apalachicola Bay (drainage area, 50,674

km2) (Figure 7) consists of a large estuary

with extensive wetlands that receive water

from the Apalachicola, Chattahoochee

and Flint Rivers (the ACF watershed). The

Apalachicola River, the largest river in

Florida and among the largest entering

the Gulf of Mexico, provides 35 percent

of the freshwater input to the northeast

Gulf (Richter et al. 2003). Apalachicola

Bay, covering approximately 1,012 km2,

is one of the more productive estuaries in

North America, supplying approximately 90

percent of the oyster landings (Crassostrea

virginica) in Florida and 10 percent nation-

ally It also provides nursery habitat for

The Pascagoula River is the

largest contributor of freshwater

to Mississippi Sound. Photo:

Jennifer Cowley/Plan for

Opportunity

Apalachicola Bay is one

of the more productive

estuaries in North Amer-

ica, supplying approxi-

mately 90% of the oyster

landings (

Crassostrea

virginica

) in Florida and

10% nationally.

A Once and Future Gulf of Mexico Ecosystem 31

numerous economically important ﬁsh and

invertebrate species (Livingston et al. 1974,

Livingston et al. 1997). The adjacent west

Florida shelf, extending along the length of

the Florida peninsula and the panhandle,

makes up 75 percent of the total U.S. Gulf

continental shelf and contains some of the

most diverse and economically important

marine habitats (e.g., salt marsh, sea grass

meadows, coral reefs) and ﬁsheries (e.g.,

snappers, groupers) in the nation (Coleman

et al. 2000, Koenig et al. 2005). Despite its

great importance to Gulf state economies,

this system remains relatively unstudied in

terms of deﬁning its inﬂuence on ecologi-

cally and economically important species in

inshore and nearshore environments.

The major water bodies of the estuary are

East Bay, Apalachicola Bay and St. George

Sound. A series of inlets (one of which is

man-made) allows sediment and seawater

exchange with the Gulf. The Apalachicola

River is the principal source of sediment

for the development of the barrier islands,

despite the presence of a dam approxi-

mately 115 km upstream from its mouth,

with beach sand dispersion having a net

westward transport. Circulation in the bay

is dominated by local winds and tides,

whereas hydrography and salinity are domi-

nated by river ﬂow on multiple time scales

(Conner et al. 1982), although salinity is

also inﬂuenced secondarily by freshwater

drainage from Tate’s Hell Swamp. Tides in

this multiple inlet estuary form a compli-

cated pattern of mixed semi-diurnal/diurnal

tides and have small amplitudes (Huang

and Spaulding 2002).

Like the Pascagoula River, the Apalachicola

River is one of the last free-ﬂowing alluvial

rivers in the continental United States, but

river channelization and damming of its

upstream distributaries affect its ﬂow. The

natural ﬂow of the river provides a sea-

sonally varying supply of nutrients (e.g.,

nitrogen and phosphorus) that enhance

primary productivity from Apalachicola Bay

(Mortazavi et al. 2000a, 2000b, 2001).

Sustained declines in river ﬂow, the result

of drought or upstream diversion, could

lead to fundamental shifts in both trophic

structure and the capacity of the system

to support overall productivity (Livingston

1997). Indeed, ocean color images from

satellite radiometry show an extended

plume of river water emanating from the

watershed southward over the west Florida

shelf during periods of peak river discharge.

This conspicuous biological event, known

as the Green River Phenomenon (Gilbes et

al. 1996, 2002), occurs during late winter

and early spring and persists for weeks to

months, overlapping in time and space with

the spawning season and locations of a

A blue crab prepares to fend

off an intruder among the

rocks in the Florida Keys. Photo

Courtesy of 1stPix

Apalachicola

St. Joe Bay

Ochlockonee

Escambria

Suwanee

Fenholloway

Apalachicola Bay

St. George Sound

Pensacola

Tampa

Figure 7

Detail of northeast coast

of Gulf of Mexico

See Gulf overview map, Page 2

The Big Bend coastal region in

Florida includes Apalachicola

Bay, St. Joe Bay and the

Fenholloway, Suwanee and

Ochlockonee Rivers.

Big Bend

Region

Egmont Key

National Wildlife

Refuge

Caloosahatchee

GULF OF MEXICO

32 A Once and Future Gulf of Mexico Ecosystem

number of important ﬁsh species (Koenig

et al. 2000). Its inter-annual variability is

in part explained by climatic variability

over the ACF drainage basin that inﬂu-

ences freshwater ﬂow (Morey et al. 2009).

Although dedicated investigations are

lacking, we suspect that this plays a key

role in supplying nutrients and ﬁxed organic

carbon that inﬂuences the general structure

and function of estuarine and offshore

oceanic food webs in the northeast Gulf

(Mortazavi et al. 2000a, 2000b, 2001,

Putland and Iverson 2007a, b).

Recent national attention focused on the

management of the ACF drainage system

because of extended drought conditions

over the southeastern United States and

regional conﬂicts over water use. Georgia

and Alabama have drawn an increasingly

larger volume of water for municipal and

agricultural needs over the years that in

concert with regional drought has resulted

in severe declines of ﬂoodplain forests

(Darst and Light 2008) and possibly overall

estuary health. The fact that this conﬂict

remains unresolved despite years of debate

highlights the need for effective science

that can inform policy decisions by address-

ing human needs while sustaining key eco-

system services. There is concern that the

continued alteration of historical pathways

of energy ﬂow will precipitate signiﬁcant

declines in ﬁsheries production (currently

valued at billions of dollars per year) and

potentially undermine the entire food web

in this portion of the Gulf of Mexico. Given

the enormous economic value of these ﬁsh-

eries, such a disruption would be devastat-

ing, and even more so when considered in

light of anticipated growth in coastal devel-

opment and the effects of climate change.

Effects of ﬂood control efforts

on the Gulf Coast

The ﬂooding regime, freshwater volume

and routes of the major U.S. rivers ﬂow-

ing into the Gulf have been signiﬁcantly

altered through levee construction, dam-

ming and channel rerouting to accom-

modate increases in coastal populations,

agriculture, shipping and industry over the

past century. The reduction in the sedi-

ment supply to many Gulf barrier islands

has affected their morphology (Figure 5,

Morton 2008), and drainage of wetlands

for urban development has led to increased

soil subsidence (e.g., much of New Orleans

is now below sea level). Explosive breaks in

ﬂood protection levees, called crevasses, are

recognized by geomorphologists as being

vastly different from the overbank ﬂood-

ing that occurred before levees were built.

Before the construction of levees, sediment

overﬂowing river banks accumulated near

the river to form a levee parallel to the river

channel not much wider than the river

itself (Frazier 1967). The dramatic release

of ﬂoodwater through ﬂood protection

levees sends sediments farther from the

river levee and sometimes forms a mini-

delta or “splay.” Kesel (1988) estimated that

the amount of sediment ﬂowing over-bank

in an unconﬁned river and through the

ﬂood protection levees was equal to 2.3

and 0.86 percent of the river’s sediments,

respectively. This compares with 12 percent

returned from offshore from hurricane

Figure 8

Lands vulnerable to sea

level rise

This map displays land below

an elevation of 1.5m. The IPCC

estimates that sea level will rise

75 to 190 cm by 2100, resulting

in tidal inundation in the areas

pictured here. Source: Adapted

from Titus and Richman 2001

Land below 1.5 meters

elevation

Scale

100 miles

A Once and Future Gulf of Mexico Ecosystem 33

deposition, primarily within a few kilome-

ters of the seashore.

Hurricane protection levees, increasingly

needed to protect people settled in the

Gulf, will both impound wetlands behind

them and restrict sediment deposition—

each reducing the resiliency of the wetlands

seaward that should function to reduce

storm surge heights. These changes in how

sediments, nutrients and water are redis-

tributed must be quantiﬁed and considered

for each proposed wetland restoration

project to ensure long-term sustainability of

restored areas.

Effects of global climate

change on Gulf ecosystems

Global climate change, occurring as a direct

result of anthropogenic increases in levels

of carbon dioxide and other greenhouse

gases in the atmosphere, is predicted to

continue to increase atmospheric and sea

surface temperatures, acidiﬁcation of the

oceans, rate of sea level rise and frequency

of intense storm events, in addition to

numerous other changes over the next

several decades (IPCC 2007). The long-term

impacts of these changes on the ecosys-

tems will be wide-ranging and potentially

irreversible (Scavia et al. 2002). Although

the rate of eustatic, or global, sea level rise

projected by IPCC (2007) is rapid, we now

know that these projections actually under-

estimated the rate of change by substantial

amounts because the IPCC was unable to

include estimates of increasing melt rates

for the Greenland ice sheets and polar ice

caps. Vermeer and Rahmstorf (2009) show

that under the future global temperature

scenarios of the IPCC (2007) report, predic-

tions of eustatic sea level rise from 1990 to

2100 range from 75 to 190 cm.

The most alarming expected consequences

of climate change for the Gulf Coast are

the combined effects of relative sea level

rise at an already high and escalating rate

and more frequent severe hurricanes. Using

a projection that accounts only for ﬂooding

of low-lying land without including impacts

of storm erosion, large parts of Louisiana

and southern Florida, as well as other

smaller sections of the Gulf Coast, will be

submerged even under moderate estimates

of sea level rise (Figure 8). In addition to

the loss of human settlements, rising sea

levels are likely to result in the “drowning”

of wetlands, some barrier islands, sea grass

meadows, oyster reefs and coral reefs if

they are unable to achieve increases in their

vertical elevation equal to sea level rise.

Mangroves have greater ability to move

inland as seas rise, provided the uplands

are undeveloped and not bulkheaded or

armored in some other way, but the uneven

ability of organisms to adapt to rising sea

levels will shift the balance of the ecosys-

tem in unpredictable ways. It seems highly

unlikely that accretion rates in these critical

coastal habitats will keep pace with sea

Large parts of

Louisiana and southern

Florida, as well as other

smaller sections of

the Gulf Coast, will be

submerged even under

moderate estimates

of sea level rise.

Barrier islands in the Gulf

are threatened by increas-

ing rates of sea level rise.

Houses on Dauphin Island

in Alabama are protected

by sand berms. Photo: Joel

Sartore/National Geographic

Stock

34 A Once and Future Gulf of Mexico Ecosystem

level rise if it increases by a factor of two

or more in the next 50 to 100 years, as

expected (Vermeer and Rahmsdorf 2009).

Indeed, many Gulf wetlands are already

being submerged and subsequently lost

(Day et al. 1995).

Increased water depth will result in

decreased light availability to sea grasses

and hermatypic corals and increased

turbidity for oysters, probably resulting in

increased mortality and decreased growth

rate. Loss of shoreline habitat destroys

its capacity to buffer the shoreline from

wave-driven erosion. Under higher ambi-

ent sea level and more frequent intense

storms, storm-surge ﬂooding of the Gulf

Coast will be more extensive and damaging

to infrastructure, threatening massive loss

of property and life. Effects of hurricanes

on shoreline erosion, damage to struc-

tures, and risk of loss of life interact with

rising sea level and human modiﬁcations

to hydrodynamic regimes. For example, the

loss in area of Gulf coastal barriers from

multiple states is clearly related to hurricane

activity and also to depth of shipping chan-

nels excavated through the barriers (Figure 5).

Ocean acidiﬁcation and increased sea sur-

face temperature are stressors that interact

to affect calciﬁcation in marine organisms,

such as corals, oysters and a host of other

taxa with external or internal skeletons of

calcium carbonate. For example, models

developed by Anthony et al. (2011) based

on the IPCC A1F1 scenario (fossil-fuel

intensive) demonstrated that severe ocean

acidiﬁcation and sea surface warming could

decrease coral reef resilience even under

otherwise favorable conditions of high

grazing intensity and low nutrients. These

results indicate that coral reefs already sub-

jected to overﬁshing of herbivorous ﬁshes

and to nutrient loading are likely to be

even more vulnerable to increasing carbon

dioxide Impacts on larval ﬁshes could be

profound as they struggle to form internal

skeletons that are needed for locomotory

ability when full grown. The thin larval

shells of oysters and other bivalve mollusks

may be unable to form; several studies have

demonstrated increased mortality rates of

juvenile clams and other bivalves during

early development. Shell additions to estua-

rine environments, which would augment

the ability of the mollusks to grow their

shells, may be necessary as a management

adaptation to acidiﬁcation in estuaries to

provide chemical buffers for growing acidity

and to allow sensitive calcifying organisms

to persist.

The effects of climate change on the Gulf

ecosystem extend beyond those discussed

here and it is impossible to outline every

possibility. However, restoration efforts

must address the inevitable environmental

changes to achieve restoration that

is resilient.

Figure 9

Shoreline Changes of the

Isles Dernieres Barrier

Island Arc, Louisiana, from

1887–2005

Source: Adapted from Lee

et al. 2006

Area of islands 2005

Area of islands 1887

0 52.5

Miles

0 52.5

Kilometers

1:75,000

Map Scale 1887

2005

Scale

5 miles

Raccoon Island Whiskey Island

Caillou Bay

Trinity Island

East Island

GULF OF MEXICO

A Once and Future Gulf of Mexico Ecosystem 35

0 52.5

Miles

0 52.5

Kilometers

1:100,000

Map Scale

1855

2004

GULF OF MEXICO

Figure 10

Shoreline Changes of the

North Chandeleur Islands,

Louisiana, from 1855–2005

The area of the islands has

decreased from 6,827.5 acres

in 1855 to 913.9 acres in 2005.

Source: Adapted from Lee

et al. 2006

Area of islands 2005

Area of islands 1855

Scale

5 miles

Chandeleur Sound

Monkey Bayou

Schooner Cove

Freemasons

Islands

New Harbor

Islands

North Islands

Hewes Point

A Once and Future Gulf of Mexico Ecosystem 37

Grass is planted on a newly

created embankment on

Dauphin Island, AL. Photo:

Joel Sartore/National

Geographic Stock

In this chapter, we provide 15 recom-

mendations that can work together to

produce comprehensive and long-term

restoration of the Gulf. Our understanding

of historical and contemporary stresses on

the ecosystem, as described in the previ-

ous chapter, informs these recommended

actions. Restoration of an anthropogeni-

cally damaged ecosystem such as the Gulf

must include not only an understanding of

its basic history and natural processes but

also a realistic and scientiﬁc assessment of

damage, well-deﬁned goals and policies

that accurately reﬂect these realities, and

open communication of all decisions to

educate the public and earn the trust of

local communities. Our recommended

actions, then, reﬂect this exigency for rigor-

ous assessment, deﬁned goals and coopera-

tion with human communities. Taken alone,

each action may be no more effective than

the traditional “in-place, in-kind” approach

to environmental restoration. However, we

have designed our recommended actions

to work in concert, treating the Gulf as a

holistic ecosystem that must accommodate

multivalent, intersecting and sometimes

competing uses by plants, wildlife, micro-

scopic organisms and humans. To treat an

ecosystem holistically—including the lives,

processes and futures of marine animals,

vegetation, microbes and humans—is dif-

ﬁcult but essential for resilient restoration.

Our recommendations stress the need

for rigorous scientiﬁc research, goals that

reﬂect that research, and open communica-

tion and involvement with human commu-

nities in the Gulf. Below, we provide more

detail on these characteristics that we ﬁnd

so fundamental to restoration:

Understand the past.

We need to account for historical baselines,

expected future dynamics and ecosystem

interactions to develop a responsible and

effective restoration program. We need to

recognize the historically pristine condition

and functions of Gulf ecosystems and the

nature of their degradation as the basis

for deﬁning realistic restoration goals. The

purpose is not to return the Gulf to some

idealized pristine condition, but to recog-

nize that restoration will be unsustainable

unless all of the necessary components and

functions of the ecosystem are in place.

We also need to be realistic about the time

frames required to achieve goals in the light

of extreme variations in recruitment and

growth rates of different essential species,

the necessarily enormous spatial scale of

intervention and protection that may be

needed, as evidenced by the recent rezon-

ing and protection of one-third of the entire

Great Barrier Reef (Pandolﬁ et al. 2005),

and the inevitable future consequences of

climate change, sea level rise and intensiﬁ-

cation of hurricanes (Rahmstorf et al. 2007,

Vermeer and Rahmstorf 2009, Jackson 2010).

Acknowledge the future and

restore resilience.

Restoration will require a comprehensive

and integrated plan focused on rebuild-

ing the functional integrity and services of

entire ecosystems that have been harmed

as a consequence of the DWH oil spill, in

addition to responding to the systematic

degradation that has progressively compro-

mised Gulf ecosystems. To ensure sustain-

ability, restoration should be deﬁned to

include enhancement of natural resources

Recommendations for Resilient

Restoration of the Gulf of Mexico

To treat an ecosystem

holistically—including

the lives and processes

and futures of marine

animals, vegetation,

microbes and humans

—is difﬁcult but

essential for resilient

restoration.

38 A Once and Future Gulf of Mexico Ecosystem

over and above pre-DWH levels and should

take explicit account of the highly dynamic

nature of the Gulf environment that will

require adaptive management as conditions

change. The institutional mantra of

“in-place, in-kind” restoration is inappropri-

ate without including analysis of sustainabil-

ity and would probably lead to longer-term

failures without planning for future chang-

ing conditions. Efforts to achieve durable

restoration should not be diluted by calls for

economic and community development.

Recognize the interconnection

between human prosperity and

ecosystem health.

The experience of the Exxon Valdez spill

and some harmful consequences of so-

called restoration actions demand that

the goals for restoration in the Gulf, plans

for their implementation and subsequent

assessment of progress be fully transparent

to the scientiﬁc community and public at

large. The public must be aware of the time

frames and geographic scope of intended

restoration actions as they compare to the

pace of environmental change. It is critically

important to acknowledge, celebrate and

foster meaningful and timely public partici-

pation in the restoration process, especially

because increasing sea levels and increased

frequencies of intense storms will ultimately

require retreat from the Mississippi River

delta. Resilience of human communities

and ecological resources are intimately

connected; therefore, the ecosystem must

be understood as a coupled human-nat-

ural system. A robust model for restoring

ecosystem resiliency holistically combines

environmental with human approaches—

for instance, compensatory habitat restora-

tion combined with a project that redresses

historical anthropogenic injuries that now

jeopardize the sustainability of shoreline

habitats.

Such a wide-ranging restoration program

calls for structuring the recommendations

around general goals. Therefore, we have

organized our 15 recommendations along

three themes:

1. Assess and repair damage from

DWH and other stresses;

2. Protect existing habitats and

populations; and

3. Integrate sustainable human use

with ecological processes in the

Gulf of Mexico.

Recommendation Themes

THEME 1

Assess

A Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

Abstract and Figures