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The Environmental Cost of Shoreline Hardening

Wednesday, June 21st, 2017

New study shows hardened shorelines may mean fewer fish and crustaceans. 

by Ryan Greene

A split image. On the left, a bulkhead. On the right, riprap revetment.

A new SERC study shows that both bulkheads (left) and riprap revetment (right) are associated with lower abundance of several species of fish and crustaceans in the Chesapeake Bay and the Delaware Coastal Bays. Credit: SERC

For decades, ecologists have suspected that hardened shorelines may impact the abundance fish, crabs, and other aquatic life. But now they have evidence that local effects of shoreline hardening add up to affect entire ecosystems. A new study by scientists at the Smithsonian Environmental Research Center (SERC) shows that more shoreline hardening means fewer fish and crustaceans in our waters.

Given the predictions for the coming years (i.e. rising seas and more of us living on the coast), this finding is a cause for concern. Many people will likely try to protect their land from flooding and erosion by armoring their shorelines with vertical retaining walls (bulkheads) or large rocks (riprap revetment). But as SERC researchers found in their new paper, published in Estuaries and Coasts, the impact of these hardened shorelines adds up.

Lead author and former SERC postdoc Matt Kornis likens shoreline hardening to littering. While each individual bit of trash isn’t a huge problem, the combined effect can be enormous. Kornis, now a biologist for the U.S. Fish & Wildlife Service, says the same is true of shoreline hardening. Each individual bulkhead or riprap revetment may not be catastrophic, but cumulatively they can contribute to shrunken populations of ecologically—and economically—important species like the blue crab.

“Shoreline hardening can cause loss of habitats important for young fish, like wetlands and submerged vegetation,” Kornis says. “That may be one reason we observed low abundance of many species in estuaries with a high proportion of hardened shoreline.” Click to continue »

Predicting the Future of Migrating Mangroves

Monday, June 19th, 2017

By Joe Dawson

Gfp-mangrove-tree

A stand of mangrove trees in Florida (Credit: Yinan Chen under CC0/Public Domain license)

With their tall, arching roots reaching down like hands into the water, mangrove trees can look downright creepy. And yet they’re critical species for the environment—and humans—on five different continents: They can create their own islands, provide one-of-a-kind habitats for wetland creatures, and store carbon like mad. They also protect shorelines from storms and tsunamis. Unfortunately, and perhaps unsurprisingly, humans are destroying them at a rate that may doom them within a century.

Aquaculture, urban development, tourism, and agriculture are threatening mangrove habitats around the world. Like many natural ecosystems, they are being cut down and destroyed to make way for human endeavors, and human pollution is taking its toll on their growth at the same time. But even as their total acreage decreases, they’re gaining ground in some places. Climate change is causing mangroves to move beyond their tropical habitats and take over neighboring salt marshes, but not always predictably. In North America and South Africa, they are moving toward the poles, while in Australia they are expanding along an east-west axis. All these disappearances and migrations present a riddle for scientists—but one they will need to solve to prevent habitat loss and prepare for a warmer future. Click to continue »

Alaskan Alders Shape Fates of Wetlands, Streams—And Salmon

Monday, May 22nd, 2017

by Joe Dawson

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Dennis Whigham samples horsetail plants in an Alaskan headwater stream. Credit: Ryan King/Baylor University

In Alaska, fish mean serious money. For fishermen, landowners, and the government, learning all they can about the lives of salmon could pay off in future fish harvests. There’s a lot to learn, down to how a single type of tree impacts their habitat.

The story of those habitats and trees, the alders, has been explored by SERC senior scientist Dennis Whigham and colleagues in a new study published May in Science of the Total Environment. The researchers have been studying interactions between watersheds and headwater streams for almost two decades.

Alders are most recognizable for their egg-shaped, serrated leaves. Their bark is used for tanning leather, and their wood to smoke salmon and make Fender guitars. But alders also have an outsized effect on their natural environment, transforming the chemistry and structure of wetlands and streams nearby. Bacteria in alder roots make nitrogen, an important plant nutrient, available in places where it is otherwise scarce. This can send ripple effects through entire ecosystems. In another plot twist, scientists also expect alder trees to expand northward, stirred by warmer temperatures and higher carbon dioxide from climate change. Whigham’s findings highlight the interconnectedness of wetland ecosystems, waterways, and the valuable fish that call Alaska home. Click to continue »

Surprising Tree Emissions Show Forests Consume Less Methane Than Thought

Tuesday, May 9th, 2017

by Ryan Greene

White chambers attached to tree trunks. Multi-colored tubes run from the chambers to a black box in the undergrowth.

Methane flux chambers keep track of how much methane a tree trunk releases or consumes. Credit: Pat Megonigal/SERC

Rainbow-colored tubes snake through the undergrowth. White acrylic chambers sit mounted to tree trunks like giant bleached snails. At first glance, it’s not quite clear what the heck is going on. Cryptic as it may seem, these tubes and chambers are the key to a recent study showing that trees in upland forests are capable of emitting the planet-warming greenhouse gas, methane.

Scientists have long considered upland forests to be methane sinks due to the presence of methane-hungry microbes called methanotrophs in their soils. But new research by Pat Megonigal, an ecosystem ecologist who heads up the Biogeochemistry Lab at the Smithsonian Environmental Research Center (SERC), and Scott Pitz, a graduate student from Johns Hopkins, has shown that when it comes to upland forest methane cycling, soil isn’t the only game in town. Trees and their emissions are part of the equation too.

In a recently published study in New Phytologist, Megonigal and Pitz found that trees in upland forests are actually capable of emitting methane through their trunks. This means that some of the methane absorbed by methanotrophs in the forest soils may be offset by tree emissions.

Why, though, does any of this even matter?

When researchers think about global climate change, they need to think about heat-trapping greenhouse gases like carbon dioxide (CO2) and methane (CH4). Specifically, they’ve got to track these gases to see where they’re coming from (their sources) and where they’re getting stored (their sinks). Carbon dioxide receives much of the spotlight (and rightfully so, given its enormous impact on the global climate), but it’s also critical to keep an eye on methane. Although methane stays in the atmosphere for far less time than carbon dioxide, it’s capable of trapping up to 45 times more heat. In other words, methane is a big deal. If temperate forests are consuming less of it than we thought, as Megonigal and Pitz’s research suggests, that could be a big deal too. Click to continue »

Ships Struggle To Battle Invasive Species As Global Trade Surges

Monday, March 20th, 2017

Strategy To Flush Invaders From Ballast Water Coming Up Short

by Kristen Minogue

Woman descends gangway of large cargo ship.

SERC marine biologist Jenny Carney descends the gangway of a giant bulker ship in Virginia. When ships export coal and other goods, they return loaded with ballast water from foreign ports—and often inadvertently bring invasive species with them. (Credit: Kim Holzer/SERC)

In the battle against invasive species, giant commercial ships are fighting on the front lines. But even when they follow the rules, one of their best weapons is coming up short, marine biologists from the Smithsonian Environmental Research Center (SERC) discovered in a new study published in PLOS ONE Monday.

As ships move goods around the world, they often inadvertently ferry invasive species as well. These new species can come over in the ships’ ballast water—the water ships pump on board for stability, to keep them from becoming top-heavy. But when the ships arrive to port, they often discharge their ballast water from distant global regions, along with the unseen, unwanted hitchhikers.

Shipping companies and biologists have known about this problem for decades and are still struggling to combat it. Currently, their main strategy is called “open-ocean exchange.” The idea is to flush out ballast water from their original port in the open ocean, to remove most coastal organisms, and replace it with water more than 200 nautical miles from shore. When they arrive at their destinations and discharge their new ballast water, any open-ocean organisms they picked up are unlikely to survive in ports and coastal waters.

“Ballast-water exchange provides a stop-gap measure until new technologies can be implemented to further reduce species transfers,” said Greg Ruiz, SERC senior marine biologist and a co-author of the new study. Since 2004, the U.S. Coast Guard has required most commercial ships entering the U.S. from overseas to do open-ocean exchange before discharging ballast in ports. However, this strategy has some serious limitations and may not be as effective as scientists and policymakers once hoped. Click to continue »

Once-Threatened Trumpeter Swans Spotted on SERC Campus

Wednesday, February 15th, 2017

by Sara Richmond

Not long ago, a trumpeter swan sighting was nearly unheard of in the Chesapeake Bay region—or many places in the United States, for that matter. After being hunted to near-extinction in the early 1900s, the birds, who can boast an 8-foot wingspan and are the largest waterfowl in the world, struggled to recover. Now the swans are starting to reappear, including two spotted recently at the Smithsonian Environmental Research Center (SERC).

close-up of trumpeter swan head and beak

Unlike tundra swans, the other native swans in the Chesapeake, trumpeter swans have a small triangle of feathers above their beak. (Tyler Bell)

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Natural Gas Trade Opens Door for Invasive Species

Friday, January 20th, 2017

by Kristen Minogue

Two scientists look at water sample on ship.

Marine biologists Kim Holzer (right) and Jenny Carney sample ballast water from a cargo ship in Virginia’s James River.
(Kim Holzer)

The U.S. is on the brink of a natural gas boom—but that could expose its shores to more invasive species, Smithsonian marine biologists report in a new study published this winter.

Over the last decade, U.S. natural gas imports have dropped as the country tapped into its own resources. Now, thanks to new technology that makes it easier to extract and store natural gas, it’s poised to be the world’s third largest exporter of liquefied natural gas by 2020.

“We’ve hit an inflection point,” said Kim Holzer, lead author and biologist at the Smithsonian Environmental Research Center (SERC). Exports haven’t yet reached historical import highs, but they are climbing.

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Ten Reasons We’re Earth Optimists After 2016

Friday, January 13th, 2017
Dawn Miller in forest

Ecologist Dawn Miller surveys trees in a SERC forest. (SERC)

by Kristen Minogue

The Smithsonian has a new resolution for 2017: Earth Optimism. This is the year the Smithsonian is celebrating environmental success stories, and shifting the focus to how we can fight battles to save species and preserve our planet—and win. Despite breaking a wide swath of climate records, 2016 gave us reasons for optimism as well. In our 2016 Year in Review, we’ve pulled out the most encouraging stories and discoveries at the Smithsonian Environmental Research Center from the previous year. Here are the top 10 that make us hopeful about the planet’s future:

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Dormant Orchids Need Fungi to Rise Again

Friday, January 6th, 2017

by Kristen Minogue

Green small whorled pogonia plant with flower

Small-whorled pogonia orchid, Isotria medeoloides.
(Melissa McCormick/SERC)

If you are a plant, when life aboveground turns harsh, you have few options. Some orchids respond by going dormant, spending years to decades underground before reemerging aboveground. But an army of the right fungi may help jolt them out of dormancy, ecologists from the Smithsonian Environmental Research Center (SERC) discovered in a new study published in the American Journal of Botany Friday.

Smithsonian scientists have been working to understand the ecology of one particular orchid – including why it enters and exits dormancy. The small-whorled pogonia is widely regarded as the rarest orchid east of the Mississippi. Federally listed as threatened, the orchid has vanished from Maryland and is endangered in 16 other states.

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Jekyll or Hyde? The Many Faces of Phragmites

Friday, December 16th, 2016

by Kristen Minogue

Scientist beside a Phragmites experiment on the water.

Pat Megonigal studies the invasive reed Phragmites australis on the Smithsonian’s Global Change Research Wetland.
(Tom Mozdzer)

It’s easy to dislike Phragmites. The invasive brown reed can grow over 15 feet tall and tends to crowd out anything in its shadow. But in the story of global change, Phragmites is a gray character, like Mad Men’s Don Draper, or the enigmatic Professor Snape. Beneath the surface, Phragmites australis—a European reed sweeping over East Coast wetlands—can empower wetlands to grow higher soils and possibly survive rising seas. Biogeochemist Pat Megonigal of the Smithsonian Environmental Research Center (SERC) prefers an analogy from classic literature: Jekyll and Hyde.

“The Jekyll part is that Phragmites helps marshes maintain elevation and keep pace with sea level rise,” he said. “The Hyde part is that they are poor habitat for native plants and animals.”

The latest discovery in Megonigal’s lab could tip things in favor of Mr. Hyde. Phragmites’ deep-growing roots were once thought an advantage that helps wetlands build soil. But those same roots could be disturbing ancient soils deep underground—triggering them to release planet-warming carbon dioxide (CO2).

Click to continue »