An Approach for Assessing
U.S. Gulf Coast Ecosystem
Restoration

A Gulf Research Program Environmental
Monitoring Report

Committee on Long-Term Environmental Trends in the Gulf of Mexico

Gulf Research Program

A Consensus Study Report of

THE NATIONAL ACADEMIES PRESS
Washington, DC
www.nap.edu

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This activity was supported by the Gulf Research Program of the National Academies of Sciences, Engineering, and Medicine. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any organization or agency that provided support for the project.

International Standard Book Number-13: 978-0-309-26339-9
International Standard Book Number-10: 0-309-26339-5
Digital Object Identifier: https://doi.org/10.17226/26335

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Cover image: Researcher working in a marsh in Mobile Bay, Alabama, courtesy of Bethany Carl Kraft.

Copyright 2022 by the National Academy of Sciences. All rights reserved.

Printed in the United States of America

Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2022. An Approach for Assessing U.S. Gulf Coast Ecosystem Restoration: A Gulf Research Program Environmental Monitoring Report. Washington, DC: The National Academies Press. https://doi.org/10.17226/26335.

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COMMITTEE ON LONG-TERM ENVIRONMENTAL TRENDS IN THE GULF OF MEXICO

HOLLY GREENING (Chair), CoastWise Partners

WALTER R. BOYNTON, Chesapeake Biological Laboratory, University of Maryland

HEIDA L. DIEFENDERFER, Coastal Sciences Division, Pacific Northwest National Laboratory and University of Washington

ALBERT A. GEORGE II, South Carolina Aquarium

KENNETH L. HECK, JR., Dauphin Island Sea Lab and University of South Alabama

BARBARA A. KLEISS, Department of River-Coastal Science and Engineering, Tulane University

CATHERINE L. KLING (NAS¹), Dyson School of Applied Economics and Management, Cornell University

BETHANY A. CARL KRAFT, Volkert, Inc.

LARRY D. MCKINNEY, Harte Research Institute for Gulf of Mexico Studies, Texas A&M University

DEEPAK R. MISHRA, Department of Geography, University of Georgia

KODI GUILLORY, Sustainable Design Solutions²

National Academies of Sciences, Engineering, and Medicine Staff

DEBORAH GLICKSON, Director, Board on Earth Sciences and Resources and Water Science and Technology Board

LAURA WINDECKER, Program Officer, Gulf Research Program

MEGAN MAY, Associate Program Officer, Ocean Studies Board (until January 2022)

THELMA COX, Program Coordinator, Gulf Research Program

___________________

¹ National Academy of Sciences.

² Resigned from the committee in October 2020.

GULD RESEARCH PROGRAM

Division Committee

DAVID E. DANIEL (NAE¹), Division Chair, University of Texas at Dallas

LAUREN ALEXANDER AUGUSTINE, Division Executive Director, Gulf Research Program

R. LYN ARSCOTT (NAE), International Association of Oil Gas Producers (Retired)

REGINA M. BENJAMIN (NAM²), Gulf States Health Policy Center

THOMAS P. BOSTICK (NAE), Bostick Global Strategies

VADM MANSON K. BROWN, U.S. Coast Guard (Retired)

BARBARA ENTWISLE, University of North Carolina

MARY L. LANDRIEU, Van Ness Feldman LLP

KERSTIN A. LEHNERT, Columbia University

MONICA MASON, Core Specialty Insurance

SARA N. ORTWEIN (NAE), Exxon Mobil Corporation (Retired)

AMELIE G. RAMIREZ (NAM), Salud America!, The University of Texas Health Science Center at San Antonio

FRANCIS K. WIESE, Stantec Consulting Services, Inc.

ROY E. WRIGHT, Insurance Institute for Business and Home Safety

Gulf Environmental Protection and Stewardship Board

Staff

DONALD BOESCH, Senior Scholar

LAURA WINDECKER, Program Officer

MEGHA KHADKA, Research Associate

___________________

¹ National Academy of Engineering.

² National Academy of Medicine.

Reviewers

This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making each published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the charge. The review comments and draft manuscript remain confidential to protect the integrity of the process.

We thank the following individuals for their review of this report:

Although the reviewers listed above provided many constructive comments and suggestions, they were not asked to endorse the content of the report nor did they see the final draft before its release. The review of this report was overseen by Barbara Schaal (NAS), Washington University in St. Louis, and John Boland, Johns Hopkins University. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.

___________________

¹ National Academy of Sciences.

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Preface

On April 20, 2010, the Deepwater Horizon (DWH) drilling rig exploded in the Gulf of Mexico, resulting in the tragic loss of 11 lives and the discharge of at least 3 million barrels of oil. Oil reached over 2,100 km of coastline Gulf-wide and impacted all five U.S. Gulf states. The resulting civil and criminal litigation from the DWH oil spill led to over $16 billion in fines and penalties to be applied to economic recovery and environmental restoration-related activities in the Gulf region. Funds are administered through three major programs: the DWH Natural Resource Damage Assessment Trustees, the National Fish and Wildlife Foundation Gulf Environmental Benefit Fund, and the Gulf Coast Ecosystem Restoration Council (commonly known as the RESTORE Council).

As part of multiple legal settlements, the federal government requested that the National Academies of Sciences, Engineering, and Medicine (National Academies) establish the Gulf Research Program (GRP) to fund and conduct activities to advance three program areas: offshore energy safety; health and resilience; and environmental protection and stewardship.

The goals of the restoration activities are broader than recovery from the oil spill impacts alone, encompassing land acquisition, restoration of coastal and offshore habitats and the Gulf ecosystem, recovery of species, and water quality improvement. More than 10 years after the DWH explosion the Gulf Coast continues to recover from the impacts of the oil spill, and a multitude of academic studies, agency reports, and nongovernmental organizations assessments track ongoing impacts and the effects of recovery efforts. The tracking process is complicated by the presence of long-term background trends, such as those associated with climate change and land use changes, which can obscure the effects of the spill and subsequent restoration efforts.

In early 2020, GRP initiated this study, which is intended to be the first study in a series on environmental protection and stewardship. The study series is focused on long-term environmental trends in the Gulf and is intended to advance GRP’s strategic approach to monitor progress and change and document how environmental conditions in the Gulf evolve over time. This report addresses monitoring and assessment of the cumulative effects of restoration projects beyond the project scale within the context of long-term environmental change. The study scope builds on research results and publications from many sources, including the previous National Academies reports Effective Monitoring to Evaluate Ecological Restoration in the Gulf of Mexico; Understanding the Long-Term Evolution of the Coupled Natural-Human System: The Future of the U.S. Gulf Coast; and the Progress toward Restoring the Everglades report series. The committee’s 10 members brought to the study expertise in a variety of fields, coastal ecosystem restoration and cumulative effects; natural resource management and policy; coastal ecosystem ecology, including wetlands, benthic, and fisheries ecology; water quality; ecosystem modeling; remote sensing and emerging technologies; river science and engineering; environmental economics; and data management and synthesis.

The study scope was broadly defined, with an option of focusing on restoration projects within a geographic region to keep the scope manageable. After deliberation, the committee decided that the geographic scope should include all five U.S. Gulf states, with a focus on assessing the cumulative effects of landscape-scale efforts encompassing multiple restoration projects in coastal areas. The committee hopes to reach a broad audience, including regional program managers, state resource managers, federal agencies, and other Gulf-wide entities with an interest in restoration. Entities particularly positioned to consider the recommendations of this report include those entities funded by the DWH settlements and agreements.

The committee held four information-gathering meetings in 2020 and multiple meetings in closed session in 2021 to develop this report. All meetings and discussions were held virtually due to the COVID-19 pandemic. The committee members heard presentations from representatives from state and federal agencies, nonprofit organizations, and academia. Speakers shared their knowledge and expertise in Gulf environmental trends, restoration, ecology, and DWH settlement-funded restoration programs.

Throughout 18 months of deliberations, the committee developed an increasing sense of urgency to encourage the synthesis of data and information already collected and use that information to inform future DWH settlement–funded restoration efforts. The DWH Project Tracker website reports that more than 570 environmental restoration projects have been completed or are under way, including 152 focused on habitat restoration and enhancement, 82 on species restoration, and 47 focused on water quality restoration and maintenance (see https://dwhprojecttracker.org/). With committed and expended DWH settlement recovery funds approaching half of the total amount available, and data and information from completed restoration projects becoming available, synthesis and analysis of successful and (especially) less successful efforts is both timely and essential to ensure effective restoration efforts and wise use of the remaining restoration funds. The committee members recognize the challenges facing the Gulf Coast environmental restoration community (several from personal experience), not just recovery from the DWH oil spill, but also from multiple hurricanes and other climatic events. I continue to be amazed at the Gulf Coast communities’ hard work and resiliency in making progress on the recovery efforts in the face of these difficult conditions. Our conclusions and recommendations are provided to assist in supporting successful restoration efforts now and in the future.

This report is the result of the collective expertise and experience of some of the nation’s leading experts in environmental restoration theory and application. I want to express my deep appreciation to every member of the committee for their insight and expertise, as well as their humor, collegiality, and commitment to our collective effort. Consensus is not easy, and all have contributed to ensuring a strong and consistent message. Thank you.

I also want to acknowledge the many individuals who assisted the committee and the National Academies staff in their task to create this report. Over the course of our four virtual information-gathering meetings, the committee engaged with interested colleagues in academia, nongovernmental organizations, and government. The committee greatly appreciated the chance to learn from the participants at these meetings.

On behalf of the entire committee, kudos to our outstanding National Academies staff for their excellent support, guidance, and contributions to the report. Study directors Laura Windecker (Gulf Research Program), Deborah Glickson (Board on Earth Sciences and Resources/Water Science and Technology Board), and Megan May (Ocean Studies Board), as well as program coordinator Thelma L. Cox (Gulf Research Program) were instrumental in coordinating and guiding the committee’s progress throughout and in producing the final report. I have thoroughly enjoyed working with such a professional and dedicated team.

Holly Greening, Chair

Committee on Long-Term Environmental Trends in the Gulf of Mexico

Contents

SUMMARY

1 INTRODUCTION

The Gulf of Mexico

The Deepwater Horizon Oil Spill and Resulting Settlements and Agreements

DWH Restoration Activities

Study Origin and Related Activities

About This Report

Audience

Study Scope and Approach

2 ENVIRONMENTAL TRENDS AND INDICATORS

Introduction

Climate Change Influences on Long-Term Environmental Change

Water, Nutrient, and Suspended Sediment Inflow Trends

Ambient Water Quality of Estuarine and Coastal Receiving Waters

Other Significant Gulf of Mexico Environmental Trends

Summary Table of Trends and Their Implications for Restoration Decision Making

3 ASSESSING CUMULATIVE EFFECTS OF RESTORATION: CURRENT AND EMERGING APPROACHES

Introduction

Antagonism and Synergism in Restoration Efforts

Assessing the Cumulative Effects of Restoration

The Role of Conceptual Models in Developing Hypotheses

An Approach for Considering the Consequences of Large-Scale Restoration

Tools for Gathering Multiple Lines of Evidence

Reflections on Restoration Planning and Endpoints

Case Study of Cumulative Effects in the Annually Recurring Hypoxic Zone in the Gulf of Mexico

A Long-Term View

4 APPLICATION OF SYNTHESIS AND CUMULATIVE EFFECTS ASSESSMENT IN THE GULF OF MEXICO

Introduction

Key Considerations and Information for Gulf Coast Cumulative Effects Assessment

Prior Assessments of the Cumulative Effects of Ecosystem Restoration and Management in the Gulf of Mexico

Meeting the Challenges of Gulf Coast Scale Assessment

Using an Adaptive Management Approach to Assess Cumulative Effects

Gulf-Wide Synthesis: An Example

Integrating Cumulative Effects and Adaptive Management into Restoration: Next Steps

5 MOVING FORWARD

Introduction

Data Resources for Assessing Long-Term Environmental Trends

Key Metrics Necessary for Assessment Beyond the Project Level

Program Level Adaptive Management Strategies

Final Thoughts

Conclusions and Recommendations

REFERENCES

APPENDIXES

A Distribution and Status of Funds Derived from Deepwater Horizon–Related Settlements

B Committee Member and Staff Biographies

C People Who Provided Input to the Committee