Archive for Science
In January of this year, high water on the lower Mississippi River prompted the U.S. Army Corps of Engineers to open of the Bonnet Carré Spillway for the 11th time in its 85-year history. The Bonnet Carré Spillway doesn’t just help lower water levels pressing against the flood protection levees, it’s also a thriving wilderness area that benefits from the periodic opening of the spillway structure and the sediment and fresh water it brings.
Despite initial concerns from redfish and speckled trout anglers when the spill way was opened, the additional sediment and water did not push fish from Lake Pontchartrain. Anglers had successful runs throughout the spillway’s opening, as the fish enjoyed the brackish environment the lake offered. By understanding the history of this structure and the mechanics of its operation, we can better understand the implications of the introduction of river water and sediment into nearby fish and wildlife habitat.
Built in the aftermath of the devastating 1927 flood, urgency saw this 350-bay structure designed and built in just two and a half years. When the Mississippi River above New Orleans is in flood, this floodway can divert up to 250,000 cubic feet of water per second and sometimes more. That’s enough water to fill almost 3 Olympic size swimming pools every second. The water flows from the Mississippi River across the spillway and into Lake Pontchartrain.
When the spillway is opened, water and some sediment is pulled off the top of the river and a portion of this sediment is deposited within the spillway. Fresh water also leaks through the timbers of the structure into the spillway when the river stage reaches more than 15 ft. This periodic introduction of fresh water, sediment and nutrients simulates the natural flooding of the river that once built and help maintain much of southeast Louisiana before levees were constructed. Sediment deposition in the spillway can be seen in sediment cores and with the presence of natural cypress regeneration – a rare sight in most swamps in the region.
Since the spillway only pulls water off the top of the river, and there is typically less sediment at the surface than there is at deeper depths, less sediment moves through the spillway compared to water. This makes the Bonnet Carré different from the planned sediment diversion projects which will be located, designed and operated to maximize sediment capture. However, the periodic introduction of fresh water and some sediment benefits the habitats of the spillway, including bottomland hardwood forest, grasslands, ponds and cypress swamps. The productive habitats of the spillway support an abundance of wildlife, including gray squirrels, whitetail deer, swamp rabbits, alligators, wood ducks, mottled ducks, crawfish and a wide-range of finfish. With more than 7,600 acres of public lands, the Bonnet Carré Spillway provides opportunities for fishing, hunting, camping, boating, cycling, horseback riding, ATV riding, and many other recreational activities.
Alisha Renfro is the staff scientist for the National Wildlife Federation’s (NWF) Mississippi River Delta Restoration program. Based in New Orleans, she provides accurate scientific information to help advocate for the best coastal restoration projects for Louisiana. She also helps translate scientific information for the Mississippi River Delta Restoration Campaign’s public outreach and communication efforts.No Comments
The National Audubon Society invites birdwatchers to participate in the longest-running citizen science survey, the annual Audubon Christmas Bird Count (CBC). From December 14 through January 5, birders and nature enthusiasts in Louisiana will take part in this tradition, many rising before dawn to participate.
“Louisiana is home to millions of birds each winter, including waterfowl, shorebirds, and songbirds. Understanding how the populations of these birds are changing is revealed through CBC efforts, which is critical for knowing how to best ensure their survival,” says Dr. Erik Johnson, Director of Bird Conservation for Audubon Louisiana.
Each year, the Audubon Christmas Bird Count mobilizes over 72,000 volunteer bird counters in more than 2,400 locations across the Western Hemisphere. The Audubon Christmas Bird Count utilizes the power of volunteers to track the health of bird populations at a scale that scientists could never accomplish alone. Data compiled in Louisiana will record every individual bird and bird species seen in a specified area, contributing to a vast citizen science network that continues a tradition stretching back more than 100 years.
To date over 200 peer-reviewed articles have resulted from analysis done with Christmas Bird Count data. Bird-related citizen science efforts are also critical to understand how birds are responding to a changing climate. This documentation is what enabled Audubon scientists to discover that 314 species of North American birds are threatened by global warming as reported in Audubon’s groundbreaking Birds and Climate Change Study. The tradition of counting birds combined with modern technology and mapping is enabling researchers to make discoveries that were not possible in earlier decades.
In addition to counting up some of our more common birds, Louisiana CBC participants also look for vagrants – birds that normally spend the winter elsewhere, but made a wrong turn somewhere along the way. Last winter, Louisiana CBC volunteers found a total 254 species of birds, including amazing vagrants like Lucy’s Warbler, Ferrugineous Hawk, and Brown Boobies. What unusual birds will be found this winter?
Birders of all ages are welcome to contribute to this fun, nationwide citizen science project, which provides ornithologists with a crucial snapshot of our native bird populations during the winter months. Each individual count is performed in a count circle with a diameter of 15 miles. At least ten volunteers, including a compiler to coordinate the process, count in each circle. The volunteers break up into small parties and follow assigned routes, counting every bird they see. In most count circles, some people also watch feeders instead of following routes.
Want to get involved?
- To find a count near you visit christmasbirdcount.org.
- Counts are open to birders of all skill levels and Audubon’s free Bird Guide app makes it even easier to chip in.
- There is no fee to participate and the quarterly report, American Birds, is available online.
By Alisha Renfro, Staff Scientist, Restore the Mississippi River Delta Coalition, National Wildlife Federation
There’s less sediment moving down the Mississippi River than there used to be. Much of that missing material is trapped behind dams built upriver of Louisiana. Despite the reduction in sediment it carries, the Mississippi is still mighty with approximately 90 million tons of sediment passing the city of Belle Chasse, La. each year1. Tragically, much of that mud and sand will be carried past the sediment-starved wetlands and barrier islands of the delta – where it could have great benefits – and out into the Gulf, leaving us with a missed opportunity to restore health and resiliency to our coast.
The new sediment counter, published on the homepage of our website, shows the tons of sand and mud in the water that moves pass the USGS gage in Belle Chasse, La every second. For this counter, the sediment is estimated using the relationship between sediment and the flow of the Mississippi River at Belle Chasse for years 2008 to 2010, as described by Mead Allison, Ph.D. and others in the appendix of their 2012 paper, “A water and sediment budget for the lower Mississippi–Atchafalaya River in flood years 2008–2010: Implications for sediment discharge to the oceans and coastal restoration in Louisiana.” For more specific details, see “How we calculated uncaptured sediment.”
While there is no single solution for restoring our coast, it is vital that we treat sediment as the precious resource it is and maximize its capture and use for coastal restoration. The 2012 Coastal Master Plan identified two types of projects, marsh creation and sediment diversions, that use sediment to build and maintain land. Marsh creation projects dredge and pipeline sand from the river to strategically build new land. However, reliance on this project type alone means missing out on the mud that makes up at least 70 percent of the sediment that the river carries. Sediment diversion projects tap into both the sand the mud carried by the river to build new land and to help sustain the existing wetlands, that in the absence of sediment input, would continue to rapidly disappear.
Using these two types of restoration projects we can use the sand and mud – the foundation and lifeblood of the delta – to create a healthy and more resilient future for coastal Louisiana.No Comments
By Ryan Fikes, Staff Scientist, National Wildlife Federation, Gulf Restoration Campaign
It’s been more than five years since the Deepwater Horizon oil rig exploded. Since that time, a council of federal and state Trustees have been extensively investigating the impacts of the disaster on wildlife and habitats, but that information has been kept under wraps—for use in litigation against BP. Now that the case has settled, this research has finally been made public in a draft Programmatic Damage Assessment and Restoration Plan.
The impacts to wildlife and their habitats are shocking and far reaching. Despite clean-up efforts and the natural weathering processes over the five years since the spill, oil persists in some habitats where it continues to expose resources in the northern Gulf of Mexico. In many cases, the damage to wildlife and habitats was more severe than previously understood. The ecological linkages of these habitats and communities and their connectivity to the larger Gulf of Mexico ecosystem can result in cascading impacts, influencing the overall health and productivity of the Gulf of Mexico ecosystem.
Together, the National Wildlife Federation and Ocean Conservancy scientists have worked to dig in to the massive report and digest its findings. Here is a snapshot of the types and severity of impacts outlined in the draft report.
While the Trustees acknowledge that this is a very conservative estimate, the total number of birds killed by the BP oil disaster is from 56,100 to 102,400 birds. At least 93 species of birds across all five Gulf Coast states were exposed to oil.
2. Beach & Dune Habitat
BP oil covered at least 1,300 miles of the Gulf coastline, including 600 miles of beach, dune and barrier island habitat.
3. Lost Human Use
The public lost 16,857,116 days of boating, fishing and beach-going experiences. The total loss of recreational use of the Gulf due to the disaster is worth $528 million to $859 million.
Between 4 and 8.3 billion oysters are estimated to have been lost. Over three generations (minimum recovery time), the dead oysters would have produced a total of 240 to 508 million pounds of fresh oyster meat.
5. Salt Marsh
Louisiana lost up to 53 percent of its salt marsh plants across 350-721 miles of shoreline. In Louisiana wetlands, erosion rates approximately doubled along at least 108 miles of shoreline. The effect lasted for at least 3 years.
Sargassum, a floating seaweed that provides habitat for young fish and sea turtles, was exposed to oil, which may have caused the loss of up to 23 percent of this important habitat.
7. Seagrass Habitat
Seagrass beds covering a total area roughly the size of 206 football fields (272 acres) were lost from the time of the disaster through 2012.
8. Larval Fish
The Trustees estimated that 2-5 trillion larval fish were killed. The loss of larval fish likely translated into millions to billions of fish that would have reached a year old had they not been killed by the BP oil disaster.
9. Sea Trout
Several of species of sea trout, including the spotted (or speckled) sea trout, were severely impacted by the disaster. An estimated 20-100 billion sea trout larvae were killed as a result of the disaster.
The growth of young white, pink and brown shrimp was dramatically affected by oil. The total loss of shrimp production over 2010 and 2011 due to oiling is estimated at more than 2,300 tons.
11. Red Drum
The growth of young red drum fell by up to 47 percent along marsh shorelines in Louisiana that were persistently oiled since 2010, and an estimated 700 tons of red drum were lost. Reduced red drum production persisted through 2013 and is expected to continue.
While nearly all of the species of whales in the footprint of the oil have demonstrable, quantifiable injuries, the most hard-hit was the Bryde’s whale. With only about 50 Bryde’s whales left in the Gulf, roughly half of these animals were exposed to oil—and nearly a quarter were killed. It is unclear if Bryde’s whales will be able to recover.
13. Bottlenose Dolphins
The number of bottlenose dolphins in Barataria Bay and Mississippi Sound—two areas particularly affected by the disaster—is projected to decline by half. The populations are expected to take 40-50 years to recover. In the 5 years after the oil disaster, more than 75 percent of pregnant dolphins observed within the oil footprint failed to give birth to a viable calf.
14. Coral Reefs
The footprint of injury to mid-depth coral reefs is just over 4 square miles. These areas along the continental shelf edge, known as the Pinnacles, showed extensive damage to both the coral colonies and the reef fish associated with them. The larger ecological functions of this habitat were very likely impaired.
15. Sea Turtles
All five of the Gulf’s sea turtles are either threatened or endangered. It is estimated that somewhere between 61,000 and 173,000 sea turtles—of all ages—were killed during the disaster. For the endangered Kemp’s ridley sea turtle, this equals 10-20 percent of the average number of nesting females each year, which would have laid approximately 65,000 – 95,000 additional hatchlings.
16. Deep Seafloor
The footprint of BP oil on the Gulf seafloor around the wellhead is an area more than 20 times the size of Manhattan (over 770 square miles). An additional 3,300 square miles may have been affected.No Comments
By Shannon Cunniff, Deputy Director for Water, Environmental Defense Fund
Coastal zones are the most densely populated areas in the world. In the U.S., they generate more than 42 percent of the nation’s total economic output. These coastal communities, cities and infrastructure are becoming increasingly vulnerable to the effects of climate change. Rising seas and increased storms, as well as ongoing coastal development, have stripped these natural environments of their innate resilience to storms and flooding, leaving coastlines and the people who live there especially exposed.
Protecting coastal areas requires a multipronged approach. Traditional hardened infrastructure, such as levees and floodwalls, should be combined with natural infrastructure, such as dunes and barrier islands, to optimize storm protection. By attenuating wave energy, natural infrastructure measures can enhance the performance of and complement traditional gray infrastructure. And in certain situations, natural coastal infrastructure measures can reverse coastal erosion, help rebuild shorelines and even keep pace with rising sea levels.
Natural coastal infrastructure measures also provide significant co-benefits to communities. In addition to reducing the effects of storm waves and surge, these wetlands and other plant-based means also improve water quality, enhance recreational and commercial fisheries, add to the coastal esthetic and attract tourists. Their installation or restoration can also buy time for communities as they develop long-term strategic plans to cope with sea level rise.
In Louisiana, coastal planners understand the importance of nature-based designs, such as sediment diversions and barrier beach nourishment, when developing coastal restoration and protection plans – the state’s Coastal Master Plan is a combination of restoration, protection and resiliency projects.
But with their myriad of benefits, why aren’t natural infrastructure measures being implemented to a greater degree in other parts of the nation?
In part, the reason is the lack of accepted engineering design guidance – a document that explains the engineering principles, issues, methods, and performance metrics for evaluating, siting and designing features. Lacking such, engineers cannot formally sign off on the designs and risk benefits that will be realized.
How can we quantify the storm risk reduction benefits of nature-based measures, so as to help decision-makers and planners choose the best methods for their needs and find financing to implement these projects? Can we accelerate development of engineering guidance?
Natural Infrastructure Workshop and Report
Seeking to answer these questions, Environmental Defense Fund (EDF) convened a workshop of 19 coastal engineers, scientists, program managers, and financiers to discuss establishing storm risk reduction performance measures of various natural coastal infrastructure solutions.
After completion, EDF produced the report, “Performance of Natural Infrastructure and Nature-Based Measures as Coastal Risk Reduction Features,” which reviews the state of knowledge on the risk reduction performance of natural and nature-based infrastructure, compiled from existing literature as well as workshop participant input. The report includes findings on a host of nature-based measures, including beach nourishment, vegetated dunes, barrier island restoration, edging and sills (living shorelines), oyster reefs, coral reefs, mangroves, maritime forests and coastal wetlands (non-mangroves).
While the report is a bit technical, the authors hope that city planners, coastal engineers and other decision-makers find it useful when determining which storm protection measures to implement in their communities.
For each of the measures, the report summarizes its storm risk reduction attributes (e.g., wave attenuation and storm surge protection); lists its strengths, known weaknesses and uncertainties about utility for risk reduction; and identifies suitable conditions for implementation. The report also indicates where engineering design guidelines already exist (e.g., for beach nourishment and dune building) and whether they can be created by modifying existing guidelines (e.g., oyster and coral reefs function like submerged breakwaters).
For the layperson, Table 1 is a one stop shop for information on how each storm risk reduction measure stacks up next to other methods. The table is a summary of the strategies – natural, nature-based, as well as structural – and how each compares regarding risk reduction performance, costs, climate change mitigation, and adaptability to seal level rise and changing community needs.
To guide further research supporting adoption of natural infrastructure into coastal resilience plans, the report provides the most catalytic and pressing research needs and lists other survey needs gathered from the literature or raised during the workgroup discussion.
Workshop participants – and subsequent consultation with other engineering experts – confirm that there is sufficient confidence in the ability of natural coastal infrastructure measures to reduce impacts of storms and sea level rise to coastal communities, such that these approaches should be routinely considered as viable options by decision-makers.
With what we know now, implementation of these approaches can be facilitated by developing detailed engineering guidelines that provide functional and structural design guidance as well as address other design issues. As projects are built and monitored, we can further expand knowledge of the circumstances where these measures work best; learn more about how traditional structural, nonstructural, natural infrastructure and nature-based measures can optimally work together; understand how coastal processes are effected; and track the measures’ life expectancies in our increasingly dynamic coastal environments.
You can show your support for coastal restoration by taking the pledge to urge leaders to be a powerful voice for coastal restoration. Take the pledge at RestoretheCoast.org!No Comments