Archive for Science
Basics of the Basin research symposium discusses past, present and future of the Pontchartrain BasinNovember 6, 2013 | Posted by Delta Dispatches in Mardi Gras Pass, Meetings/Events, Mississippi River Gulf Outlet, Science
By Shannon Hood and Estelle S. Robichaux, Environmental Defense Fund
On October 24-25, 2013, the Lake Pontchartrain Basin Foundation (LPBF) hosted its 11th Basics of the Basin research symposium. Scientists and researchers from academia, non-profit organizations, private consulting groups and federal and state agencies gathered at the University of New Orleans (UNO) on the shores of Lake Pontchartrain to discuss the past, present and future issues of the Pontchartrain Basin. LPBF has hosted these biennial symposiums since 1992, providing an opportunity for students and established researchers alike to share and discuss the most up-to-date research on the restoration and management of Louisiana’s Pontchartrain Basin.
After opening remarks by Dr. John Lopez, executive director of LPBF, the plenary continued with comments and presentations from Phil Turnipseed of the U.S. Geological Survey; Dr. Ioannis Georgiou, Director of the Pontchartrain Institute for Environmental Sciences at UNO; and Dr. Chip Groat, President and CEO of The Water Institute of the Gulf, among others. The conference was grouped into seven general session topics, including hydrodynamic modeling, water quality, storm surge protection, river diversions, wetland restoration, the Central Wetlands Unit and fisheries. Because of the diversity of environmental concerns within the Pontchartrain Basin, broad, interdisciplinary research is essential to effective system-wide restoration and management.
Understanding the present condition of the Lake Pontchartrain Basin requires a look into the history of the lake itself. Dr. Oliver Houck, professor at the Tulane University Law School, provided the storied account of the history of Lake Pontchartrain during his keynote speech. He spoke of the lake’s days as a hot spot for recreation, as well as its decline during the years when the lake was dredged for the clam shells that lined the bottom. This dredging caused a rapid decline in the health and suitability of this lake for wildlife habitat and for recreation. A few brave souls recognized the trauma that the lake was enduring and took on the task of halting the dredging to allow the lake to begin to heal. Through years of dedication, lawsuits and creative thinking, the dredging was successfully stopped, and the healing process began.
Lake Pontchartrain Basin Foundation’s original research was well represented at the conference, with 14 presentations in six different sessions. Eva Hillman presented LBPF’s research into the salinity levels found within wetland soils in the Central Wetlands Unit (CWU), just west of New Orleans. Construction of the nearby Mississippi River Gulf Outlet (MRGO) in 1968 allowed salt water to easily enter these previously freshwater wetlands and lead to severe deterioration of the CWU wetlands. Although the MRGO has been closed since 2009, much of the area still remains highly degraded. LPBF scientists are monitoring soil salinity throughout the CWU to inform restoration efforts, specifically re-vegetation projects.
Research conducted by LPBF scientists on Mardi Gras Pass, a new and evolving distributary of the Mississippi River, was also on display. Dr. Theryn Henkel presented preliminary research on where the fresh water and sediment from Mardi Gras Pass is going once it enters the receiving basin. Results from this study indicate that the deposition of sediment happens well before the influence of fresh water on salinity levels in the receiving basin is no longer observed, and that sediment travels further into the northern areas of the basin than it does to the south. Andreas Moshogianis presented the preliminary findings of ongoing biological assessments in Mardi Gras Pass, most notably that a range of both fresh- and saltwater fishes have been caught during these assessments, often in the same net. LPBF’s research on Mardi Gras Pass is important because it has implications for future restoration efforts throughout coastal Louisiana, as scientists and citizens work to reconnect the Mississippi River with its delta.No Comments
By Alisha Renfro, Coastal Scientist, National Wildlife Federation
The Mississippi River is one of the most managed river systems in the world. However, that management has focused on navigation and flood control needs to the detriment of the economically and ecologically important coastal Louisiana landscape. This week, the U.S. Army Corps of Engineers and Louisiana’s Coastal Protection and Restoration Authority (CPRA) hosted a public meeting in New Orleans to present information and preliminary results of their joint effort on the Mississippi River Hydrodynamic and Delta Management Study. This large-scale, long-term study is developing tools to evaluate different combinations of restoration projects in an effort to address the long-term sustainability of the Mississippi River and its delta while balancing the needs of navigation, flood protection and restoration.
The scope of the study extends from Vicksburg, Miss. south to the Bird’s Foot delta. The study is actually comprised of two coupled, but somewhat distinct, efforts. The hydrodynamic portion of the study will focus on characterizing the dynamics in the river and developing models that can be used to evaluate river-side changes due to proposed freshwater and sediment diversion projects. It will also inform location and design of these projects to maximize their effectiveness and minimize the potential for shoaling in the river’s navigation channel. The delta management part of the study will focus on the basin-side benefits and changes caused by these restoration projects. The delta management portion of the study has not yet begun. Currently, the state of Louisiana and the Army Corps are working to define the depth and breadth of that part of the study.
The afternoon session of the meeting focused on detailed technical presentations on the study. The different tasks of the Mississippi River Hydrodynamic and Delta Management Study include a geomorphic assessment, data collection and an extensive modeling effort. The geomorphic assessment focuses on compiling historical river data, dredging records and satellite imagery to document the historical trends in the river. The data collection effort will compile existing data and conduct field work to fill in gaps in understanding of the water and sediment dynamics that currently exist in the river. The historical data and present data will be integrated into the modeling work to inform the models and to ensure that the models capture the dynamics of the river system. The modeling effort includes a suite of models that each has different strengths and weaknesses. These models will be used to forecast the large-scale, long-term and shorter-term regional changes expected in the river in both a future without river diversions and a future that includes different combinations of diversion projects.
The presentations from the technical meeting indicate that this collaborative state of Louisiana and Army Corps effort has moved forward significantly since it began. The geomorphic assessment has been completed and a final report on its results is expected by the end of this year. The data collection effort is ongoing, having captured the low discharge of the river last year and the higher flow discharge from this past spring. Many of the preliminary model simulations have begun, and the preliminary results presented at this meeting emphasized the dynamic nature of the Mississippi River system, where water discharge, sediment transport and deposition can not only vary greatly from year to year, but also from week to week. The preliminary results also point to the importance of appropriate size, location and operation of sediment diversions in order to maximize sediment conveyance into adjacent wetlands and to reduce potential riverside impacts.
The Mississippi River has been a key feature in the growth and development of the U.S. However, for more than 80 years, the management of the river has focused on balancing the needs of navigation and flood control. A shift away from that management scheme towards one that balances navigation, flood control and restoration is absolutely critical for the survival of the delta ecosystem and, ultimately, the communities and navigation industry that depend on the Mississippi River Delta. The Hydrodynamic and Delta Management study is poised to be the effort that changes the way we think about management of the river and how we build a more sustainable, holistic system for our future.No Comments
By Alisha Renfro, Coastal Scientist, National Wildlife Federation
The unprecedented scale of the 2010 BP oil spill and the further complexity introduced by its deep water location pushed scientists involved in the response effort to apply both old and new research methods to estimate the rate of oil flow from the well and the total volume of oil spilled. Currently in New Orleans, phase II of the BP oil spill trial – which will focus on that very question of how much oil gushed from the well into the Gulf during the 86 days between the initial blowout and when the well was finally capped – is underway. Ultimately, this total volume of oil spilled will play a key role in determining the amount of Clean Water Act penalties BP will pay. The decisions made during this phase of trial will come down on the hard work and innovation of the scientific community’s response to a spill that happened under difficult conditions that didn't have easy solutions.
In an article in the December 2012 issue of Proceedings of the National Academy of Sciences, scientists involved in the response reviewed the different methods used to estimate the flow rate of crude oil from the well. The researchers concluded that the science supports flow rates that ranged from 50,000 to 70,000 barrels of oil per day, resulting in a total release of around 5 million barrels of oil from the well, with 4.2 million barrels making it into the Gulf of Mexico ecosystem due to recapturing efforts by BP.
In the days immediately following the April 20, 2010 well blowout, the flow rate of oil from the well was one of the most critical pieces of information needed to inform response efforts and prepare designs and procedures that could be used to try and cap the well. Measuring the rate of flow of oil was more complicated than it may seem as the material gushing from the well consisted of a combination of oil and natural gas. To meet this need, an official technical group was gathered which included experts from a variety of scientific disciplines that would work on estimating flow rate and the total volume of oil released.
Flow rate estimates were calculated from a variety of different methods, including oil collection at the sea surface, acoustic and video observations, sampling and analysis of the composition of the discharge material, infrared imaging from aircraft and from modeling the depletion of the reservoir after the well was capped. Some of these methods yielded what were considered more reliable estimates than others. However, quite remarkably, almost all of the methods reviewed in this article converged on flow rates that ranged from 50,000 to 70,000 barrels per day.
Based on the flow rate of oil and its variability with time, the science team involved estimated that approximately 5 million barrels of oil would have been discharged from the well over the 86 days it remained uncapped. Differences between flow rate measured at the well and flow rates calculated from what was observed at the ocean surface suggest that 2 million barrels of oil never made it to the ocean surface and remain in the deep sea. This suggests that the ongoing effects of the oil spill may not be known for years to come.
As phase II of trial continues this week, expert witnesses will testify on rate of oil flow from the Macondo well, using sound science to support their conclusions.No Comments
By Estelle Robichaux, Environmental Defense Fund
Last week, the Gulf Coast Ecosystem Restoration Council held a public meeting in New Orleans to vote on its Initial Comprehensive Plan: Restoring the Gulf Coast’s Ecosystem and Economy. The RESTORE Act, signed into law in July 2012, established the Council and tasked it with, among other duties, creating a long-term ecosystem restoration plan for the Gulf Coast region in the aftermath of the Deepwater Horizon oil spill.
In his opening remarks, Louisiana Governor Bobby Jindal (Council member and host of the meeting) spoke of the many natural and human-caused disasters that have afflicted Louisiana in recent years: Hurricanes Katrina, Rita, Gustav, Ike and Isaac; and, of course, the BP oil disaster.
Jindal highlighted the need to move restoration projects forward and not let the bureaucratic process delay implementation of projects that have already been sufficiently vetted. Jindal stated he had “directed state officials to commit 100 percent of Louisiana’s RESTORE Act funding to ecosystem restoration and community resilience projects associated with our Master Plan.” While the governor acknowledged Transocean for stepping up by paying their Clean Water Act fines, he called on BP to stop spending millions of dollars in public relations, claiming that they have spent more money on television commercials than on actual restoration, while there are still 200 miles of oiled shoreline along the Gulf Coast.
The chair of the Council, newly appointed Secretary of Commerce Penny Pritzker, spoke following Jindal and stated, “the Gulf Region is part of who we are as Americans” and the Council wants “the world to see the Gulf Coast as a wonderful place to visit, work, play, and live.” Although the Comprehensive Plan in its current iteration is still very general, the Secretary took this opportunity to affirm that science will be integral in the decision-making process. She emphasized that the Council was committed to moving forward with the planning and restoration process, despite uncertainties about the ultimate amount or timing of available funds. The desire for momentum was underscored by the Council’s stated goal to begin selecting and funding projects within the next 12 months.
Justin Ehrenwerth, Executive Director of the Council, presented an overview of the Plan and discussed next steps before the Council unanimously voted to pass the Initial Comprehensive Plan and accompanying documents, including the Programmatic Environmental Assessment, Finding of No Significant Impact and Response to Public Comments. Mimi Drew (Chair of the Deepwater Horizon Natural Resource Damage Assessment Trustee Council), Thomas Kelsch (Vice President of National Fish & Wildlife Foundation’s Gulf Environmental Benefit Fund) and Russ Beard (Acting Director of the RESTORE Act Science Program) gave overviews of their respective programs and how they anticipate coordinating with the Council and the Comprehensive Plan as it moves forward.
More than 50 people spoke during the meeting’s public comment portion, which was notably held after the Council had already voted to accept the plan. Many residents of Louisiana and other Gulf Coast states traveled to New Orleans to have their voices heard. Most of them, having watched the natural areas around their lifelong homes degrade in recent years, encouraged, supported and even pleaded with the Council to move forward urgently with Gulf Coast restoration. In the words of the Mississippi River Delta Restoration Campaign’s own David Muth: “Delay is the enemy.”
Some individuals tried to further impress upon the Council the damage that had been done to the Gulf ecosystem, pointing to evidence of the continued presence of oil slicks and suspicious absence of wildlife around Mississippi Canyon block 252, where the Deepwater Horizon oil platform was located. Several staff members and experts from our Mississippi River Delta Restoration Campaign gave statements to the Council, reminding them that Louisiana’s Coastal Master Plan is “not a perfect plan, but it is absolutely the best approach to coastal restoration that has been done.”
Louisiana’s 2012 Coastal Master Plan was developed using a science-based process and examines both present-day and likely-future conditions of the coast. The Master Plan provides a model for how restoration should be addressed Gulf-wide, and the Council should work with Louisiana to prioritize restoration projects set forth in the state’s 2012 Coastal Master Plan.
One of the most passionate speakers, who created the most poignant moment during the almost four-hour-long meeting, was 10-year-old Sean Turner. Sean, the youngest Conservation Pro Staff member of Vanishing Paradise, spoke with conviction about saving coastal Louisiana. “I want to save the coast,” said Sean. “I go fishing. I go hunting. That’s why I care. I want to stay here because Louisiana is Sportsman’s Paradise.” You can watch a video of Sean giving his comments here.
The next crucial step for the Council will be selecting projects that are consistent with the restoration priorities criteria defined in the RESTORE Act and will benefit and restore Gulf Coast ecosystems. The RESTORE Act requires that these projects be designed, selected, prioritized, and implemented using the best available science.No Comments
By Alisha Renfro, Coastal Scientist, National Wildlife Federation
Coastal communities throughout the U.S. are increasingly threatened by rising sea levels and extreme weather events. The conventional approach for protecting people and property along the coast has relied on engineering solutions such as levees, seawalls and bulkheads, which “harden” shorelines. However, not only can these structures be expensive to build and difficult to maintain, but in some cases, they can also increase erosion, impair the recreational uses of the area and reduce water quality.
In recent years, efforts to protect coastal communities have been expanded to recognize restoration and conservation of coastal habitats as ways to help buffer coastlines from waves and storm surge. In a study recently published in Nature, “Coastal habitats shield people and property from sea-level rise and storms,” researchers assessed the risk reduction that natural habitats provide to vulnerable people and property and found that loss of the ecosystems that currently exist will result in greater damage to people and property.
Different types of coastal habitat and shoreline offer varying levels of protection to coastal communities depending on their morphology and previously observed ability to offer protection from erosion and flooding. For example, in this study, coastal forests and high cliff shorelines were classified as providing a higher level of protection when compared to marsh and oyster reef habitat, with barrier beach shorelines and areas with no habitat offering the lowest level of protection.
To provide a nationwide view of the risk reduction that could be provided by natural coastal habitat, the researchers in this study compiled a coastal habitat map for the U.S. and compared model runs with and without the habitats under present-day and future sea level scenarios. Their modeling results indicated that, today, 16 percent of the U.S. coastline is classified as a “high hazard” area. When the same conditions were modeled without the presence of protective coastal habitats, the results suggested the extent of U.S. coastline that would be considered vulnerable to storms and sea level rise would double.
Compared to the West Coast, the low-relief Gulf and eastern coasts of the U.S. are more vulnerable to both sea level rise and storms. In order to better protect these vulnerable regions, the authors of this study suggested that large expanses of coastal forests and wetlands, oyster and coral reefs, dunes and sea grass beds are critical.
Recently, some coastal protection plans have begun incorporating conservation and restoration of coastal habitat alongside traditional physical structures. Louisiana’s 2012 Coastal Master Plan is an excellent example of a plan that acknowledges not only the value that coastal habitats have for the fish and wildlife of the area, but it also examines how to combine conservation and restoration of these habitats with traditional engineering strategies to enhance protection for the millions of people that call coastal Louisiana home.1 Comment
By Rachel Schott, Environmental Defense Fund
In June, the Joint Ocean Commission Initiative, a bipartisan 16-member council representing diverse ocean interests, released a new report, “Charting the Course: Securing the Future of America’s Oceans.” The report outlines important ocean reform and coastal restoration recommendations for Congress and the Obama Administration. Being an “ocean nation,” the health of the U.S. economy is closely tied to health of its oceans. For Gulf Coast residents, this specifically means the Gulf of Mexico. The report has implications for both the health the Gulf Coast environment and the economies that rely on it.
“Our oceans and coasts are vital to our nation’s economy and security, as well as to the health and quality of life of its citizens,” states the Joint Initiative in the report. No one understands this better than Louisiana and Gulf Coast residents. After the 2010 oil disaster, in 2012, Congress took an important step toward securing the future health and vitality of the region when it passed the RESTORE Act – legislation that dedicates fines from the Gulf oil disaster to the Gulf Coast states for restoration. However, project selection and final authorization of funds has yet to be determined.
The report makes recommendations that advocate for restoring the coast’s natural coastline, strengthening its ability to protect communities from storms and rebuilding natural habitats and ecosystems. These recommendations offer a valid perspective for allocating available RESTORE Act funding and BP oil spill penalties to coastal restoration projects.
In its report, the council – consisting of national, state, and local leaders from diverse government agencies, academic institutions and industries – provided a set of science-based policy recommendations that enhance the long-term security and economic priorities of the nation’s coast. Two actions that would directly affect the Mississippi River Delta and coastal Louisiana are as follows:
- “Enhance the resiliency of coastal communities and ocean ecosystems to dramatic changes underway in our oceans and on our coasts.”
- “Support state and regional ocean and coastal priorities.”
As hurricanes and super storms become more common, it will become vital that policymakers implement programs that increase coastal resiliency. National decision makers must understand the underlying issues and local community priorities to effectively select and implement coastal restoration projects.
As the report underlines, building stronger and more resilient coastlines benefits not just those living near the coast, but the entire nation that depends on healthy coasts and oceans. The Gulf Coast Ecosystem Restoration Council has an unprecedented opportunity to allocate RESTORE Act funds to implementing coastal restoration projects and becoming an integral part of rebuilding the Mississippi River Delta and Gulf Coast and the economies that depend on a healthy Gulf Coast.
This was originally posted on the EDF Voices blog.
By Douglas Rader, Chief Oceans Scientist, Environmental Defense Fund
The third anniversary of the Deepwater Horizon blowout seems a good time to take stock of the damage done to the Gulf of Mexico, and to look to its future.
The drill rig sank in about a mile of water on April 22, 2010, Earth Day, spewing more than 200 million gallons of crude oil into the Gulf. It took almost a hundred days to cap the underwater well. During that time, shifting currents spread oil-based toxic substances far and wide, at many depths in the sea, exposing many forms of sea life to potentially deadly pollution.
Today, storms still churn up oil and perhaps one third of the toxic materials from the blowout remain loose in the Gulf. Scientists are still struggling to estimate the damage done.
Visible and Invisible Damage
From the spill’s first days, the public focus was on direct human effects, on animals that were being visibly “oiled” – sea birds, dolphins and whales – and on coastal habitats onto which the oil might wash. When drifting oil made landfall on beaches and in saltmarshes, that was big news. But the worst impacts of the spill remained largely out-of-sight and out-of-mind.
The blown-out well is located in deepwater right at the edge of the continental shelf, in close proximity to ancient and highly vulnerable deepwater coral reefs. These were bathed in organic pollutants for months, and surveys have revealed devastation in those coral communities, including serious damage to corals that take thousands of years to grow. It will take centuries – or longer – for those reefs to recover.
Moreover, toxicants now cover a wide range of seafloor habitats, where they are being consumed and processed by myriad creatures that make their living by eating sediments and digesting organic matter found there. These small creatures, carrying their poisonous payloads then enter food webs when they are eaten by fish. This will be a long-term problem with no easy solution. Recent reports from the field of eyeless shrimp and fish covered with sores suggest that significant amounts of toxic substances are indeed still loose in the Gulf food chain.
Damage also was concentrated in the middle depths of the sea. This so-called “deep scattering layer” is home to swarms of small animals, so dense that they reflect radar signals. This abundant soup of life is the food target zone for deep-diving fishes and mammals – tunas and billfishes, dolphins and great whales. The deep-scattering layer is especially important in the “spill kill zone” of the Northern Gulf, where a large population of sperm whales lives.
Deep scattering layer animals were very likely obliterated for a wide distance around the well site by vast underwater plumes of dissolved and dispersed oil-derived toxicants, nearly certainly made worse by the use – including underwater – of two million gallons of dispersants. The dispersant/oil mixture has since been shown to be up to fifty times as toxic for many sea creatures as the oil by itself. Dispersant use certainly spread the toxic brew much more broadly under the sea.
On the surface, birds and other large animals were oiled and killed, but immeasurably greater numbers of floating baby sea creatures died as well. The oil – and the toxic dispersant brew – covered large areas of sea surface, where buoyant eggs and larvae drift, between the spawning areas at the edge of the coastal shelf and the coastal nurseries (wetlands, tidal creeks and even sandy beaches). For many key species, those larvae drifted through during the peak of the spill.
In addition, the Gulf Loop Current acts as a sea highway for drifting larvae of Atlantic Bluefin tuna, groupers, snappers spiny lobsters and a host of other species spawned far upcurrent. These larvae, too, drifted through the BP “kill zone” during the time of the spill.
As the spill progressed, many observers expressed great relief that the oil stayed offshore, and that it was apparently consumed by microorganisms, including “oil-eating” bacteria that were said to have eliminated the threat. In truth, however, there is no free lunch, even in the sea. It’s true that populations of naturally occurring but normally rare microorganisms exploded, using oil as a feed-stock. This altering ecosystem conditions along many lines. The explosion in bacteria sucked oxygen from the sea and liberated carbon dioxide, deoxygenating and acidifying mid-depth oceans waters and altering food webs in ways that may never be fully quantified.
The Spill’s Bottom Line
The damage done to sea life by the blowout cannot be quantified today. No one knows how many baby reef fish and lobsters died, or how those losses will affect regional fisheries. It may turn out to be possible to make an informed estimate down the road, if extensive modeling is done to compare the numbers of adults that came from 2010 spawning to what might have been expected for at least some of the most economically important animals (perhaps red snapper and some groupers).
I suspect that serious reductions in so-called “year class strength” – the relative number of animals reaching the size where they enter fisheries – occurred for many important species, like shrimp, blue crabs, menhaden and others.
Still, with so much unknown, providing economic loss estimates for the damage done by the spill is challenging. Besides, how do you value pelicans, sea turtles, and dolphins? How do you value – much less replace – a million-year-old coral mound?
When one puts all of these pieces together, it is clear that the Gulf took a real body blow, probably much worse than people understand. Fortunately, there are forces at work that provide hope for the future of the Gulf. I’ll address some of these forces in my next post, but until then you can help make BP pay.
By Rachel Schott, Mississippi River Delta Restoration Campaign
Dead zone. Words that bring images of military exercises or deserted, war-torn areas of land, but certainly not an acceptable description of a region that contains some of the nation’s most vibrant and diverse ecosystems, wildlife and habitats. Right?
Recent studies released by the National Oceanic and Atmospheric Administration (NOAA) and conducted by Louisiana State University, Louisiana Universities Marine Consortium, and University of Michigan scientists forecast a “record-setting dead zone” for the Gulf of Mexico this summer. The studies suggest that the 2013 dead zone area could be anywhere between 7,286 and 8,561 square miles, which would be substantially larger than last year’s dead zone of almost 2,900 square miles.
According to NOAA, dead zones are not uncommon for waterways and estuaries, as they have recorded 166 dead zones along United States coastlines. As the Gulf of Mexico is at the receiving end of the country’s largest river system, the Mississippi River’s discharge is one of the main causes of the Gulf dead zone. Unfortunately, a dead zone is exactly what it sounds like: an area normally teeming with wildlife and vegetation is infiltrated by pollutants, fertilizer chemicals and industrial runoff. When the river’s more buoyant fresh water enters the Gulf of Mexico, it lies on top of the denser, saltier water, causing a stratification that isolates the deeper waters from receiving a necessary amount of oxygen.
The Coastal Wetlands Planning, Protection and Restoration Act (CWPPRA) explains that the influx of these unnatural substances and nutrients results in the overgrowth of algae and marine organisms on the surface of the water. At the end of their life cycle, they sink to the bottom and are decomposed by bacteria, a process that depletes the oxygen supply from the water, making the existence of life nearly impossible. Every type of marine life is affected, from Gulf fish to tiny marine organisms, which are all essential parts of an interdependent ecosystem necessary for maintaining the balance of life in the Gulf of Mexico.
In scientific terms, the low oxygen is known as hypoxia and has severe effects on the future health and growth of ecosystems. TIME Magazine recently reported that the Gulf of Mexico may soon become an “aquatic desert” and attributes the problems to recent weather conditions in the Midwest: heavy rainfall and flooding increases the levels of nutrients and pollutants in the river. All of these compounding problems will contribute to the 2013 possibly record-setting dead zone.
Scientists state that the dead zone would be less severe if a tropical storm were to enter the area, which would mix up the Gulf’s waters and facilitate oxygenation. The irony of this fact is that it leaves Louisiana residents in a less-than-ideal situation.
To read more about the causes and effects of dead zones, check out NOAA’s State of the Coast website: http://stateofthecoast.noaa.gov/hypoxia/dead_zone.html.1 Comment
By Alisha A. Renfro, Ph.D., Staff Scientist, National Wildlife Federation
Worldwide, rising global temperature is a threat to coastal communities in the form of rising sea levels and stronger hurricanes. Last week, the Louisiana State Museum in New Orleans hosted a presentation by Virginia Burkett, Ph.D., Chief Scientist for Global Climate and Land Use Change at the United States Geological Survey. In Dr. Burkett’s presentation, “Climate Change and Sea Level Rise: Implications for New Orleans,” she discussed the science of climate change and the threats sea level rise present to the vulnerable low-lying landscape and communities of coastal Louisiana. Louisiana’s 2012 Coastal Master Plan acknowledges these threats and outlines a 50-year plan for protection and restoration that takes into account subsidence, sea level rise and increased storm frequency and intensity.
Global sea level rise is a consequence of water influx from melting glaciers and ice sheets and the expansion of ocean water as it is heated. During the 20th century, global sea level rose approximately eight inches, but satellite data indicates that the annual rate of sea level rise has almost doubled over the last 20 years. As the different processes that affect melting of large ice sheets are still the subject of intense scientific study, the range of predicted sea level rise in this century ranges from 0.6 to 6.6 feet, but the most likely range of sea level rise is between one and four feet.
While the predicted rate of global sea level rise is enough to cause concern for many coastal regions, in Louisiana, the threat is intensified as not only is sea level rising, but the land is also sinking. Subsidence can occur due to natural geological processes, such as dewatering and compaction of deposited river sediments over time, but it can also be increased by human actions, such as groundwater withdrawal and oil and gas extraction. Subsidence rates across Louisiana’s coast vary, but in many areas, the rate of subsidence far exceeds the global rate of sea level rise. The combination of global sea level rise and local subsidence means that the local sea level will rise sooner and higher in Louisiana than in most other places in the world.
At the conclusion of her talk, Dr. Burkett had a few recommendations for actions we here in Louisiana can take to adapt to sea level rise and increase the resiliency of our coastal communities and coastline. For coastal communities, elevating and flood-proofing infrastructure are important steps for adapting to the increased threat of inundation from sea level rise and hurricanes, but in some cases, retreat from low-lying coastal areas may be necessary.
We can better manage our coast by factoring our understanding of the natural processes and trends and by getting sediment from the Mississippi River into the wetlands. As one of the most vulnerable areas to sea level rise in the United States, coastal Louisiana will serve as the testing ground for scientific innovation and policy that will likely shape the response of coastal communities throughout the country to the threats of climate change and sea level rise.No Comments
Study demonstrates importance of sediment diversions for building land in the Mississippi River DeltaMarch 27, 2013 | Posted by Delta Dispatches in 2012 Coastal Master Plan, Diversions, Restoration Projects, Science
By Alisha A. Renfro, Ph.D., Staff Scientist, National Wildlife Federation
Last week, an independent scientific panel comprised of prominent scientists from throughout the U.S. released a report, “Mississippi River Freshwater Diversions in Southern Louisiana: Effects of Wetland Vegetation, Soils, and Elevation,” which examines some of the ecological effects of freshwater river diversions. The panel concluded that there is little evidence suggesting that the existing freshwater diversions in Louisiana have appreciably reversed the rate of land loss in the region, and that to reverse the land loss trend, significant inputs of sediment are needed. While most of the existing diversions in Louisiana were built to move fresh water only, many of the diversions included in Louisiana’s 2012 Coastal Master Plan focus on sediment capture and conveyance into coastal wetlands.
Freshwater diversions affect basins by reducing salinities. Extensive dredging of canals throughout the Mississippi River Delta’s wetlands has allowed for salt water from the gulf to intrude into wetlands adapted to lower salinity conditions, resulting in large areas of these wetlands dying and being converted to open water. Wetland vegetation is affected directly by the salinity of the water in wetland soil. High salt concentrations in the soil can affect vegetation by reducing the overall rate of photosynthesis, decreasing nutrient uptake and stunting growth rates. Consequently, the introduction of fresh water into wetland communities damaged by saltwater intrusion is vital in any restoration effort.
Freshwater diversions also increase the amount of nutrients introduced into the receiving basin. While increases in nutrient availability to wetland vegetation would presumably stimulate growth, scientific information collected in Louisiana marsh communities have exhibited varying results depending on plant species, nutrient concentrations and the abundance of different types of nutrients. Increasing the amount of nutrients may also alter the composition of the plant community, as some species of plants have a competitive advantage when it comes to nutrient uptake and growth.
River diversions can also have an influence on wetland elevation. In order for wetlands to persist over time, processes that increase the surface elevation of the wetlands must be equal to factors that increase the threat of submergence (e.g. sea level rise, storms). Diversions have the potential to promote an increase in the elevation of a wetland by adding mineral sediment to the surface and stimulating plant growth both above and below ground. However, the surface elevation of a wetland could decrease as nutrients become less scarce, as the abundance of vegetation roots decline and as an increase in the breakdown of belowground organic material by bacteria takes place. More scientific studies are needed to enhance our understanding of the relationship between marsh response and river input in order to better predict the net effect that sediment and freshwater diversions may have on different marsh types.
This scientific panel found that any freshwater diversion that does not transport a substantial sediment load is unlikely to reverse the current trend of wetland loss in Louisiana. The 2012 Coastal Master Plan recognizes and addresses this reality by focusing on large-scale diversions that would be capable of transporting significant amounts of river sediment into the nearby wetlands. In addition to shifting the focus of diversions from fresh water to sediment, the panel determined that a formal adaptive management scheme is needed for existing and planned diversions where the goals of the project are clear, the pre-diversion conditions of the affected area are well characterized, monitoring in the outfall area is done to measure the progress of the project in relation to its goals and a process exists to adjust the operation of the structure to increase the likelihood those goals are reached.
- Fact sheet: "Pulsed" land-building sediment diversions
- Mississippi River Freshwater Diversions in Southern Louisiana: Effects of Wetland Vegetation, Soils, and Elevation (Technical Panel from the Workshop on Response of Louisiana Marsh Soils and Vegetation to Diversions)