The unprecedented volume, depth, and spatial scale of the Deepwater Horizon (DWH) oil spill created many enormous challenges for policymakers. Among these was the difficult task of restoring the ocean and coastal ecosystems of the Gulf of Mexico (GoM) to the condition they would have been in but for the spill. Although multiple state and federal agencies had experience in the restoration of damaged natural resources, no agency had ever been faced with a spill affecting such a wide area and such a broad range of ecosystems.
This report aims to answer the question: in what ways might using an “ecosystem services approach” help these agencies to achieve their mission, as mandated by the Oil Pollution Act of 1990, of “making the environment and the public whole.”1 The ecosystem services approach is different from traditional approaches to damage assessment and restoration (e.g., the Natural Resources Damage Assessment) because it focuses not on the natural resources themselves, but on the valuable goods and services these resources supply to people. An ecosystem services approach can supplement traditional methods of assessing, or valuing, damage to natural resources by estimating flows of goods and services before and after an event. In addition, thinking in terms of ecosystem services can change the ways that the public and agencies conceptualize and discuss restoring natural resources to their former condition. For example, if the goal is to restore the flow of ecosystem goods and services, then how should restoration funds be spent?
The ecosystem services approach is not a panacea, although the committee believes it has great potential to improve natural resource damage assessment and restoration. This report explores both the potential benefits and the limitations of the ecosystem services approach in several ways. After explaining the conceptual basis for the approach and how it might add to current methods, the report examines the obstacles to its application. To illustrate these broad discussions, the report includes several case studies that, together with the more general material, make clear that the ecosystem services approach will add value along several dimensions.
First, by framing damage assessment and restoration as an ecosystem services issue, an ecosystem services approach can change the public’s perception of natural resources and the ways agencies manage for healthy ecological systems. One of the strengths of the ecosystem services concept is that it highlights the ways in which healthy ecosystems support healthy economies. Second, as the report discusses in detail, building workable models for implementing an ecosystem services approach will require both better and novel efforts in collecting data about the interactions within ecosystems and the connections between ecosystems and benefits—both economic and nonmonetized types, such as cultural and spiritual.
These efforts, in and of themselves, will contribute to public understanding of the relation-
1 15 C.F.R. § 990.30 (2012).
ships between humans and the environment; in addition, they will enable the public to inform policymakers about such relationships in the unique context of their own communities. One of the key facts central to this discussion is that communities depend on ecosystem goods and services to differing extents and in very different ways. Finally, success in developing workable models for measuring natural resource damage in terms of ecosystem services will facilitate efforts to make the public whole in the wake of future disasters.
On April 20, 2010, an explosion on the DWH platform, which was drilling the Macondo well in Mississippi Canyon Block 252 in the GoM, killed 11 oil workers and injured 17 others, resulted in the largest oil spill in U.S. history, and inevitably impacted the ecosystem services of the GoM. An estimated 4.9 million barrels (±10 percent), approximately 205.8 million gallons, of oil flowed from the wellhead following the explosion.2 For context, this amount of oil represents approximately one-third of the nation’s daily consumption of oil. The DWH oil spill was unprecedented in both its magnitude (see Figure S.1) and the ocean depth at which oil was released, and the event captured the fears and concerns of the nation during the spring and summer of 2010. Recognizing the complexity and potential impacts of the spill, members of the U.S. Congress requested a study by the National Academy of Sciences to evaluate the impacts of the DWH oil spill on natural resources and ecosystem services in the GoM. The complete statement of task is given in Chapter 1.
Ecosytems contribute to our well-being and enjoyment by, for example, supplying fish for markets, wild game to hunt in coastal marshes, and powdery white sand at which to marvel. Formally, ecosystem services are defined as “the benefits provided by ecosystems to humans that contribute to making human life both possible and worth living.” These services are the result of functioning ecosystems—the interactions of plants, animals, and microbes with the environment—and can be classified into four categories:
• Provisioning services (e.g., material goods such as food, feed, fuel, and fiber);
• Regulating services (e.g., climate regulation, flood control, and water purification);
• Cultural services (e.g., recreational, spiritual, and aesthetic services);
• Supporting services (e.g., nutrient cycling, primary production, and soil formation).
The GoM is a highly productive marine ecosystem that is surrounded by the United States, Mexico, and Cuba. It is the world’s seventh largest peripheral sea, with a surface area of 1.51 million km2 and a volume of 2.4 million km3. The great habitat complexity in the GoM supports the region’s high biodiversity, which consists of endemic and cosmopolitan species. The
2 According to McNutt et al. (2012), BP’s containment efforts captured approximately 800,000 barrels of oil before it reached the marine environment, making the total amount of oil to enter the water column closer to 4.2 million barrels.
FIGURE S.1 Location of the Macondo wellhead and spatial extent of the DWH oil spill in the northern Gulf of Mexico. SOURCE: National Oceanic and Atmospheric Administration.
GoM ecosystem is subject to a number of modern stressors, including habitat loss, overfishing, impacts of flood control on sediment supply, degraded water quality, and pollution resulting from activities such as oil and gas development. Harmful algal blooms and hypoxia frequently drive mobile animals from certain areas or decrease habitat suitability, and increasing coastal development and recent intense hurricanes have been destroying coastal habitats.
ECOSYSTEM SERVICES AND IMPACTS FROM THE DWH OIL SPILL
Given the scale of the DWH oil spill, the potential for disruption of GoM ecosystem services was significant. These services provide direct and indirect benefits to the 20 million people who live in the region; they support, among many other economic activities, one of the nation’s most productive commercial and recreational fisheries, a $50 billion tourism industry, and an energy sector that produces about 30 percent of the nation’s oil and 20 percent of its natural gas.
This report examines the impacts of the DWH oil spill on GoM ecosystem services, the ways in which an ecosystem services approach could help in remediating those impacts, and the challenges and limitations of applying the ecosystem services approach. The key to feasible application of the ecosystem services approach is the development of tools capable of establishing and quantifying causal links between the event, an injury to an ecosystem, the resulting decrease in goods and services provided by that system, and the cost of that decrease to individual communities and society at large.
There are three obstacles to developing and applying these tools. First is the difficulty in establishing a baseline measurement of goods and services produced by the system just prior to the harmful event. Simply put, one cannot assess damages—that is, the difference between conditions before and after the harmful event—if one does not know what the conditions were before the event. Assuming that a baseline is established, a second major obstacle is the difficulty in developing a model that can fully predict the event’s impact on the ecosystem and provide defensible estimates of the costs of reduced production resulting from the release of a given amount and kind of pollutant (or any other human-induced stressor) into that ecosystem. Although existing ecosystem models cannot do this, they might serve as the basis for models that can.
The third obstacle relates to the relative values of various ecosystem services. Some ecosystem goods and services are more easily priced than others. For example, economists are better able to price a decrease in a system’s ability to produce fish for a commercial fishery than a decrease in the deep ocean’s ability to regulate nutrient transport to surface waters. And, even when values can be assigned, resource limitation will force policymakers to prioritize among restoration options. The first scenario raises concerns that more-difficult-to-price services will be discounted or ignored in the decision-making process; the second highlights an important limitation to any approach to damage assessment and restoration.
RESILIENCE AND ECOSYSTEM SERVICES
Ecosystems are subject to natural disturbances such as fires, floods, droughts, and disease outbreaks, as well as human-caused disturbances, including oil spills. Ecosystems are also subject to slowly changing long-term stresses, such as nutrient enrichment and changes in sediment supply, as observed in the GoM. These long-term stresses can affect the ability of the system to respond to a shock such as the DWH oil spill.
A resilience framework focuses attention on shocks (pulse disturbances), long-term stresses (press disturbances), and the response of complex systems to these shocks and stresses. Does a system recover slowly or rapidly from a shock? What factors within the system allow for more rapid and more complete recovery? Do attempts to stabilize certain components of systems lead to reduction in overall system resilience and greater potential for large changes?
Consideration of resilience is especially important in systems that can undergo persistent and fundamental shifts in structure and function following disturbances (“regime shifts”).
Generally speaking, increasing resilience can reduce the risk that the system will cross critical thresholds and undergo a detrimental regime shift. However, in rare instances, decreasing resilience can increase the probability of a beneficial regime shift. The understanding of how to increase or decrease resilience places a premium on knowledge of system dynamics, including feedbacks among system components, as well as of uncertainty and variability in dynamic systems. Can factors that increase system resilience be identified and managed to increase the resilience of a system to a “desirable” state, or the inverse?
System resilience can play an important role in maintaining conditions that will sustain the provision of ecosystem services that contribute to human well-being. However, a narrow focus on managing complex systems to provide a constant flow of ecosystem services may actually reduce system resilience and increase vulnerability. An event such as the DWH oil spill will disrupt service provision, but a resilient ecosystem will allow for a return of services sooner rather than later or never.
Although resilience is an important concept, much like that of ecosystem services, providing practical and specific advice to managers to “increase the resiliency of ecosystem services” is a difficult task at present. As noted above, managing resilience requires understanding of the dynamics of complex and highly variable systems, which is often limited. However, without such an understanding, it can be difficult to predict how management actions will affect resilience in practical contexts. Overall, the committee concludes that consideration of resilience provides a useful conceptual framework and important general guidance but may not always lead to specific recommendations to managers.
THE CASE STUDIES
Because of time and space limitations, this report could not address all of the impacts of the DWH oil spill on all of the ecosystem services of the GoM. Rather, the report illustrates the impacts through four case studies. The spill impacted each of the four ecosystem service categories in the GoM—that is, provisioning, regulating, cultural, and supporting services. Some impacts were ephemeral, some persist, and many are under investigation or unknown at this time. Using the ecosystems services approach, the case studies consider how key ecosystem services may have been impacted by the DWH oil spill, examine methods for making baseline measurements, and explore the adequacy of existing baseline data for the GoM. Additionally, for each case study, the committee offers suggestions for additional measurements that can be made to enhance an ecosystem services approach to damage assessment.
The first case study focuses on coastal wetlands in the GoM, which cover a large region in the northern GoM. Half of the nation’s coastal wetlands are found along the GoM, and, of these, approximately 40 percent are in Louisiana. Unfortunately, many wetlands were among the closest land points (only about 40 miles) from the Macondo well. Coastal wet-
lands, consisting of salt marshes and mangrove plant communities, provide a wealth of supporting, regulating, provisioning, and cultural services that include soil and sediment (shoreline stabilization) maintenance, nutrient regulation and water quality, food provision, recreational opportunities, and hazard moderation.
The wetland case study focuses on the regulating service of hazard moderation (specifically storm mitigation) to illustrate the opportunity that exists in using the ecosystem services approach when the underlying ecosystem science and the particular ecosystem service are well known and supported by a rich literature. The ecosystem service of storm mitigation also benefits from having been monetized; that is, the costs of storm damage and reductions in losses due to wetland buffers can be quantified.
The value of ecosystem services for GoM storm protection is directly related to the total area of wetlands and to plant community composition. Consequently, change in total wetland area is the most direct and practical measurement of change in ecosystem services in Gulf Coast wetlands, typically measured by remote sensing by planes and satellites. Remote sensing is used to efficiently map, monitor, and detect changes in wetlands’ health and vegetation profiles, but verification of these changes at greater resolution by ground measurements is still needed.
During the DWH oil spill, about 1,100 linear miles of coastal salt marsh wetland were impacted at some time during the event. Crude oil can smother vegetation by coating leaf surfaces and can cause toxic effects, particularly the lighter fractions of the oil that are more water soluble. The DWH-sourced oil was already weathered and rendered heavier by the time it reached shore, so many of the impacts were associated with the weight of the oil breaking the plant stems. Oil also coated the leaves and smothered plants and their roots.
Oil spill cleanup can also have detrimental effects on marshes, including physical disturbance and compaction of vegetation and soil associated with cleanup activities. Consequently, many portions of the marshes were designated for “no further treatment” (allowing the oil to biodegrade over time) due to access, degree of oiling, and other considerations.
The expectations for long- and short-term effects of oil fouling of marshes depend on the areal extent and magnitude of the exposure. The overall impacts in the GoM wetlands can be summarized as follows:
• Acute effects on marshes, where the biota are not expected to recover, appear to be confined to the edges of bays, canals, and creeks in a limited subset of the oiled wetlands.
• Where the vegetation has died and the root systems have been lost in heavily oiled areas, the erosion of sediment is leading to the conversion of once productive marshland to open water.
• Subsequent tropical storm activity resulted in additional erosion of oiled marshes.
• Based on numerous studies that document a rapid recovery from oiling and a relatively low sensitivity of perennial marsh vegetation to hydrocarbons, GoM marsh vegetation can be expected to suffer little or no long-term impairment
from the DWH oil spill in areas where roots and rhizomes survived the initial impact of oil fouling. If roots and rhizomes did not survive, then an area will not recover on its own.
These impacts need to be viewed in the context of significant and continuing losses of wetlands in the GoM due to many other stressors, including subsidence, canal dredging, salt intrusion, and sediment starvation.
The second case study relates to fisheries, a provisioning service with a rich literature about its valuation and assessment. Fisheries in the GoM provide some of the most important and lucrative services through the production of seafood, industrial fish products, and recreational fishing. In recent times, this service has been considered to be a good candidate for a holistic integration of management at an ecosystem scale that includes ecological and human components. Although the field has been developing this integration through the promotion of an ecosystem approach to fisheries management, it does not yet consider ecosystem services as a guiding principle. Fisheries, however, offer many examples of regular quantification of human impacts on the ecosystem structure and of ecological and economical productivity. This case study explores a provisioning service, the provision of seafood from the GoM, and how the ecosystem services approach may help to quantify the possible impacts of oil spills on seafood production.
The spill’s potential disruption to the provision of seafood can be estimated by examining the spatial extent of the fishery closures imposed by the National Oceanic and Atmospheric Administration (NOAA) in the aftermath of the spill and entry of oil into estuarine waters (Figure S.2). The closures were intended to limit the risk of harvesting contaminated seafood. However, they underestimated the spatial extent of potential impacts, because fish can migrate through the spill area and be caught elsewhere, and larvae that survive direct impacts from the spill may end up as juvenile fish in other regions. Still, by preventing fishermen from accessing resources, these closures alone decreased fishery landings in the GoM by as much as 20 percent and created an immediate economic hardship for fishermen affected by the closures.
Unlike many of the ecosystem services that are provided by the GoM, fisheries have long been researched, monitored, and evaluated quantitatively. Although this research has generally focused on how to best manage individual fisheries, it has also provided valuable insight into marine ecosystem processes and fisheries baselines. Unfortunately, impacts on fishery productivity from oil spills and other stressors are not as well understood. Despite longterm studies and ongoing development of models, the ability to detect spatial and temporal differences in fishery productivity in the GoM is limited. Recent developments in fishery data collection, such as the introduction of vessel monitoring systems in the reef fish fishery of the GoM, could improve estimates of abundance. However, any mortality or reduction in individual
FIGURE S.2 Fishery closure imposed by NOAA to ensure seafood safety, effective May 17, 2010. The closed areas changed daily as NOAA sampled seafood in the area and the geographical extent of the detected oil changed. SOURCE: NOAA.
fitness caused by the spill directly or indirectly may take years or, for some species, decades to transfer through the ecosystem and be observed.
Much like their health and nature, the value of fisheries in the GoM has long been considered, but available data may not provide a complete picture. Federal and state agencies charged with managing fisheries estimate the direct value of commercial fisheries to the fisherman with this straightforward formula: the dockside value of the catch (the amount that the fisherman receives) minus any expenses incurred to capture those fish. The methodology for evaluating the economic effects of an oil spill, like any other type of pollution, on commercial fisheries is also relatively simple in concept. The economic costs of pollution are derived from either reduced production (due to dieoffs or fishery closures) or by reduced consumer demand (due to the perception of reduced fish quality or safety). As stated above, the immediate economic impact was a 20 percent decrease in landings for 2010.
Bottlenose dolphins were chosen as the subject for the third case study for numerous reasons, including their role in three of the four ecosystem services—regulating, supporting, and particularly cultural. This case study allowed for exploration of approaches to estimating the value of passive use and existence, a key, but difficult-to-establish, metric for cultural ecosystem services. Although research is limited, more is known about bottlenose dolphins than virtually any other cetacean. The world’s longest-running study of a wild dolphin population, spanning five generations, focuses on Sarasota Bay in the eastern GoM. Bottlenose dolphins are capable of self-recognition, which ranks them highly on a cognitive scale. They are also apex predators, a role they share with humans, and therefore play a role in regulating the GoM food web. As apex predators, the dolphins’ health and well-being serve as important indicators of the health of the GoM and oceans in general. Their position as the most studied and arguably the most popular and charismatic marine mammal makes them a centerpiece for conservation science, education, and ecotourism. The stranding of hundreds of dolphins in the GoM before, during, and especially after the DWH oil spill have stimulated considerable public concern, which speaks to our cultural needs and sensitivities regarding their “value” as an ecological resource and ecosystem service. If the recent mortality event is determined to be linked to the DWHoil spill, then an opportunity may exist to establish a plan to protect and restore the dolphin habitat as well to reduce dolphin mortality due to human activities.
The Deep Gulf of Mexico
Finally, the deep GoM was selected as the subject for the last case study in part because of its location with respect to the DWH blowout and spill. The deep sea was also selected because of the increasing concern and risk posed by the energy industry’s activities as it works at the leading edge of engineering in the most poorly understood of the impacted habitats. The biota of the surrounding seafloor at 1,500 meters depth and of the water column through which a plume of hydrocarbons and dispersants flowed received the most immediate impact of the uncontrolled discharge.
Knowledge of deep-sea processes and GoM-specific information is sufficient to begin the process of identifying ecosystem services, considering the impact of the DWH oil spill, examining methods to measure baselines, and identifying gaps in current databases. However, the area is so vast and sampling is so sparse that gaps in knowledge of the GoM deep sea inhibit the ability to apply an ecosystem services approach in a quantitative way. Delineating what is and is not known about this extensive subregion can be helpful for identifying relevant processes and uncertainties and thus directions for future investigation.
Based on current understanding, the primary ecosystem services of the deep GoM generally fall in the category of supporting services. The deep GoM resupplies nutrients depleted during photosynthetic activity in the photic (where sunlight is available) zone. Given that the aphotic zone is vastly larger than the photic zone, the deep GoM provides these nutri-
ents at a rate totally independent of the photic zone’s biological demand and is thus a very stable source of nutrients to overlying life. This stability provides the whole GoM with greater resilience.
The deep GoM also provides the important regulatory service of pollution attenuation. For example, natural populations of deep-sea oil-degrading bacteria digested a significant amount of the DWHoil. This ecosystem service is well documented for shallow marine and intertidal environments, but was unknown for the deep-sea water column prior to the DWH oil spill. The release of crude oil from the Macondo well thus created a unique opportunity to study this phenomenon.
THE OIL SPILL RESPONSE EFFORTS
In addition to the impacts of the spill itself, the techniques that were employed in response to the spill had potential impacts on ecosystem services. These techniques included allowing or fostering the natural breakdown of oil (natural attenuation) and using chemical dispersants, in situ burning, and skimmers at sea, as well as booms, berms, and hydrologic modification closer to shore, to prevent spilled oil from reaching sensitive shoreline habitats.
The techniques applied offshore—in situ burning, skimming, and dispersants in particular—were effective in significantly reducing the volume of oil before it went ashore. Estimates of the reduction range from 17 percent to 40 percent. The public expressed a great deal of concern about the amount and novel subsurface application of dispersants. However, the dispersants effectively broke up the oil both at the surface and in the water column, thereby making the oil much more available for biodegradation by hydrocarbon-digesting marine microbes. Although a number of studies have shown dispersed oil to be toxic, especially to juvenile stages of many marine species, the dilution and mixing effects of the open ocean may have mitigated the toxic effects of the DWH oil spill.
The techniques applied near shore and onshore varied in their effectiveness, with the least effective being the construction of sand berms, primarily because of the timing and scale of the efforts relative to the oil distribution at the time. This report also discusses the operations to clean up the oil that made it to shore, including manual removal of oil, sand washing, and surf washing. The final analysis and assessment of the impacts of the response techniques are dependent on the release of damage assessment data that are presently being analyzed, as well as of long-term monitoring data that may become available after this report is published.
As the nation moves forward after the DWH oil spill, the substantial funding that is and will be available through the criminal and civil settlements offers an unprecedented opportunity to establish a comprehensive baseline and fundamental understanding of the GoM, a critical
component of an ecosystem services approach. To fully implement an ecosystem services approach for the GoM, several key research needs must be addressed.
First, there is a critical need for an overarching infrastructure for organizing and integrating the wealth of data that have been and will be collected in the GoM. This infrastructure is needed to support comprehensive ecosystem models that can be used to evaluate the impacts of human activities on the ecosystem’s ability to provide services. The development of this infrastructure must engage the participation of the academic community, federal agencies, industry, and the public. Furthermore, funding for this infrastructure and its maintenance will need to be stable and long-term.
Second, although a substantial body of data exists to support a better understanding of ecosystem structure and function within the GoM, a comprehensive model that incorporates biophysical, social, and economic data for the GoM is needed for the long term, while models for GoM subcomponents and services are needed for the short term. Data regarding socioeconomics and human dependencies lag far behind. Integration of such data into social-ecological models is essential. For an ecosystem services approach to be successful, this issue must be the focus of additional data collection going forward. Future research efforts must include both the collection and the synthesis of these data so that the appropriate models can include the full range of social and ecological impacts and can be used to better inform decision makers.
Third, research and management focused on resilience both in principle and in specific applications would be useful. Resilience provides a valuable conceptual framework for managing complex systems because it focuses attention on how systems are affected by short-term disturbances and long-term stresses, such as hurricanes and wetland losses. Resilience may be increased through management decisions that incorporate the contribution of biodiversity and the connectivity that sustain and maintain ecosystems. Resilience can also be increased by adaptive management and by improved governance from local to regional scales to enhance the functioning of institutions and to improve social cohesion. In addition, promoting the diversification of local economies will improve the resilience of communities. However, obtaining adequate data for measuring the resilience of a social system is particularly difficult, because the state or “measure” of the baseline social system has not been identified or may continuously change. Still, efforts should be made to maximize the understanding of resilience in these systems. As with ecosystem services, there are tradeoffs: managing for the resilience of a particular service may reduce the resilience of another service.
There will be funding opportunities through multiple venues to achieve better preparedness before another event like the DWH oil spill happens, but there must be coordination so that innovation can be fostered without wasting funds, duplicating efforts, and causing harm. GoM communities and natural resource managers face many challenges as they contemplate and select research priorities and restoration plans. Among these are helping stakeholders to
consider how best to manage multiple ecosystem services across a diverse and large marine ecosystem.
As many in the region have already realized, past decisions that were aimed at enhancing a particular ecosystem service to maximize a particular benefit—for example, energy development, fisheries, or tourism—have resulted in tradeoffs that diminished the capacity of other ecosystem services to deliver benefits. Although the fines, penalties, and outcomes of litigation will help to fund and further our scientific understanding of the GoM ecosystem and how it functions, policymakers and the public should consider potential tradeoffs as they set priorities and goals for restoring and strengthening their communities and the GoM natural resources.The ecosystem services approach is one tool that could be used during these deliberations to more fully capture the value of assorted services in the GoM.