Mowing dry detention basins makes mosquito problems worse

University of Illinois News Bureau: A study of the West Nile virus risk associated with “dry” water-detention basins in Central Illinois took an unexpected turn when land managers started mowing the basins. The mowing of wetland plants in basins that failed to drain properly led to a boom in populations of Culex pipiens mosquitoes, which can carry and transmit the deadly virus, researchers report.

...The team, led by University of Illinois postdoctoral researcher Andrew Mackay, found that mowing down cattails and phragmites, two invasive plants that tend to permeate stormwater basins, adds a lot of plant debris to the water.

“We suspect bacteria quickly colonize the waterborne debris, and mosquito larvae feed on the bacteria,” said Illinois entomology professor Brian Allan, a co-author on the study with Mackay, Illinois Natural History Survey entomologist Ephantus Muturi and U. of I. natural resources and environmental sciences professor Michael Ward.

“After aquatic plants were mowed in the basins, we saw a large increase in the number of Culex pipiens mosquito larvae in the basins, which had relatively few before mowing,” Mackay said. “And perhaps more importantly, we caught about twice as many adult Culex mosquitoes in traps at basins after these plants were mowed, compared with basins where the aquatic vegetation was left intact.”

Mowing phragmites, a tall and sturdy invasive grass, also dispersed a host of bird species that liked to roost in the grass, Allan said.  “We had observed that these phragmites-invaded basins would become colonized by large communa
l roosts of birds,” he said. “And we thought that was important because birds are the natural reservoir hosts of West Nile Virus.” The researchers suspected that a bird roost near a mosquito nursery might increase the West Nile virus risk to people living nearby.

“Instead, we found that the presence of a communal bird roost actually decreased West Nile virus risk,” Allan said. “That may be because these wetland roosts include a variety of bird species, many of which are not good reservoirs of the virus. They don’t amplify the virus like other bird species more associated with residential areas do – the American robin, for example....

Rather than decreasing risk, mowing wetland plants in dry detention basins can exacerbate a mosquito problem, researchers found. Photo by Andrew Mackay

Isolated wetlands have significant impact on water quality

A press release from Indiana University: Geographically isolated wetlands play an outsized role in providing clean water and other environmental benefits even though they may lack the regulatory protections of other wetlands, according to an article by Indiana University researchers and colleagues.

Given those benefits, the authors argue, decision-makers should assume that isolated wetlands are critical for protecting aquatic systems, and the burden of proof should be on those who argue on a case-by-case basis that individual wetlands need not be protected.

“Geographically isolated wetlands provide important benefits such as sediment and carbon retention, nutrient transformation and water-quality improvement, all of which are critical for maintaining water quality,” said lead author John M. Marton, assistant scientis
t at the IU Bloomington School of Public and Environmental Affairs. “We demonstrate that continued loss of these wetlands would likely cause serious harm to North American waters.”

The article, “Geographically Isolated Wetlands Are Important Biogeochemical Reactors on the Landscape,” will appear in BioScience, the journal of the American Institute of Biological Sciences, and is available online. Co-authors include Christopher B. Craft, the Janet Duey Professor in Rural Land Development with SPEA at IU Bloomington, along with researchers from the U.S. Environmental Protection Agency, the University of Western Ontario, the University of Waterloo, the University of Florida and the University of South Florida.

Geographically isolated wetlands are formed by natural forces that create depressions in the landscape, resulting in conditions suitable for wetland plants and soils. They include the prairie potholes of the upper Midwest, the playas of the Southwest, vernal pools in New England and California, and the Carolina Bays.

Citing research literature, the authors say geographically isolated wetlands are highly effective “biogeochemical reactors” that improve water quality. They often retain water longer than protected waters, such as streams and wetlands that are directly connected to navigable water. And they have a higher ratio of perimeter to area, allowing more opportunities for reactions to take place....

A vernal pool in the Totts Gap Preserve in Pennsylvania, shot by Nicholas A. Tonelli Nicholas A. Tonelli, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license 

Dartmouth study finds restoring wetlands can lessen soil sinkage, greenhouse gas emissions

EurekAlert via Darmouth College: Restoring wetlands can help reduce or reverse soil subsidence and reduce greenhouse gas emissions, according to research in California's Sacramento-San Joaquin River Delta by Dartmouth College researchers and their colleagues.

The study, which is one of the first to continually measure the fluctuations of both carbon and methane as they cycle through wetlands, appears in the journal by Global Change Biology.

Worldwide, agricultural drainage of organic soils has resulted in vast soil subsidence and contributed to increased atmospheric carbon dioxide concentrations. The California Delta was drained more than a century ago for agriculture and human settlement and has since experienced subsidence rates that are among the highest in the world. It is recognized that drained agriculture in the Delta is unsustainable in the long-term. To help reverse subsidence and capture carbon, there is interest in restoring drained agricultural land-use types to flooded conditions, but flooding may increase methane emissions. Carbon dioxide is the primary greenhouse gas emitted through human activities, but pound for pound, methane's impact on climate change is more than 20 times greater than carbon dioxide.

Researchers at Dartmouth, UC-Berkeley and UC-Davis installed monitoring equipment on three moveable four-meter towers, measuring carbon dioxide and methane concentrations above a pasture and a cornfield that had been drained and a flooded rice paddy, a newly restored wetland and a wetland that underwent restoration in 1997. They found that the drained sites were net carbon and greenhouse gas sources. Conversely, the restored wetlands were net sinks of atmospheric carbon dioxide, but they were large sources of methane emissions, says co-author Jaclyn Hatala Matthes, an assistant professor an assistant professor in Dartmouth's Department of Geography. "However, we do expect that the methane emissions will stabilize over time," she says. "We've seen that emissions tend to increase for the first few years, and that this increase is correlated with the increase in wetland plant growth and spread during this time."...

A brown swamp, shot by the US Fish and Wildlife Service

Just right' plant growth may make river deltas resilient

A press release from Indiana University: Research by Indiana University geologists suggests that an intermediate amount of vegetation -- not too little and not too much -- is most effective at stabilizing freshwater river deltas. The study, "Optimum vegetation height and density for inorganic sedimentation in deltaic marshes," was published online Aug. 24 by Nature Geoscience. The findings may help guide restoration of river deltas, such as those near the mouth of the Mississippi River, which are under threat as sea levels rise.

Authors are William Nardin, a postdoctoral fellow in the Department of Geological Sciences in the IU Bloomington College of Arts and Sciences; and Douglas A. Edmonds, who holds the Robert R. Shrock Professorship in Sedimentary Geology and is an assistant professor of geological sciences.

Vegetation on marsh surfaces in river deltas can slow the flow of water and cause more sediment to be deposited, helping prevent sea-level rise from drowning sensitive marshlands. But the study finds that, if the vegetation is too tall or dense, it diverts water into the river channel, resulting in less sediment being deposited on the marsh.

“In river deltas the effect of vegetation on sedimentation seems to follow the Goldilocks principle,” Edmonds said. “You want the amount of vegetation that is just right -- not too much, but also not too little.”

The world’s river deltas are rich and productive and are home to about 10 percent of the world’s population. But they are threatened by an array of forces, including population growth, pollution, development and erosion, as well as sea-level rise associated with climate change.

...In tidal saltwater marshes, research has shown that vegetation enhances sedimentation. But scientists know less about how vegetation affects sedimentation in freshwater marshes that are common in river deltas. Nardin and Edmonds used sophisticated computer modeling to study how marsh vegetation influences the transport and deposition of sediment in river deltas. They conducted 75 simulations involving varying scenarios of vegetation height and density and rates of water flow.

They found that vegetation of intermediate height and density results in the greatest deposition of sand and mud. However, if the plants are too tall or densely packed, sediment tends to remain in the river channel, bypassing marshes and being carried directly to the sea....

From the IU website: This image shows freshwater marsh vegetation in Wax Lake Delta, La. Aquatic vegetation on low-elevation marshes is pictured in the foreground, while woody vegetation occupies a levee on the left. The open water in the distance is a deltaic distributary channel. Photo by Elizabeth Olliver

NOAA analysis reveals significant land cover changes in US coastal regions

A press release from NOAA: A new NOAA nationwide analysis shows that between 1996 and 2011, 64,975 square miles in coastal regions -- can area larger than the state of Wisconsin -- experienced changes in land cover, including a decline in wetlands and forest cover with development a major contributing factor.

Overall, 8.2 percent of the nation’s ocean and Great Lakes coastal regions experienced these changes. In analysis of the five year period between 2001-2006, coastal areas accounted for 43 percent of all land cover change in the continental U.S. This report identifies a wide variety of land cover changes that can intensify climate change risks, such as loss of coastal barriers to sea level rise and storm surge, and includes environmental data that can help coastal managers improve community resilience.

"Land cover maps document what's happening on the ground. By showing how that land cover has changed over time, scientists can determine how these changes impact our plant’s environmental health," said Nate Herold, a NOAA physical scientist who directs the mapping effort at NOAA's Coastal Services Center in Charleston, South Carolina.

Among the significant changes were the loss of 1,536 square miles of wetlands, and a decline in total forest cover by 6.1 percent. The findings mirror similar changes in coastal wetland land cover loss reported in the November 2013 report, Status and Trends of Wetlands in the Coastal Watersheds of the Conterminous United States 2004 to 2009, an interagency supported analysis published by the U.S. Fish and Wildlife Service and NOAA.

...Development was a major contributing factor in the decline of both categories of land cover. Wetland loss due to development equals 642 square miles, a disappearance rate averaging 61 football fields lost daily. Forest changes overall totaled 27,515 square miles, equaling West Virginia, Rhode Island and Delaware combined. This total impact, however, was partially offset by reforestation growth. Still, the net forest cover loss was 16,483 square miles.

Tropical and northern wetlands likely to blame for greenhouse gas increases

A press release from the University of Guelph: A surprising recent rise in atmospheric methane likely stems from wetland emissions, suggesting that much more of the potent greenhouse gas will be pumped into the atmosphere as northern wetlands continue to thaw and tropical ones to warm, according to a new international study led by a University of Guelph researcher.

The study supports calls for improved monitoring of wetlands and human changes to those ecosystems – a timely topic as the Intergovernmental Panel on Climate Change prepares to examine land use impacts on greenhouse gas emissions, says Prof. Merritt Turetsky, Department of Integrative Biology.

Turetsky is the lead author
of a paper published today in Global Change Biology based on one of the largest-ever analyses of global methane emissions. The team looked at almost 20,000 field data measurements collected from 70 sites across arctic, temperate and tropical regions. Agnieszka Kotowska, a former master’s student, and David Olefeldt, a post-doc at Guelph, also were among 19 study co-authors from Canada, the United States, the United Kingdom, Finland, Germany and Sweden.

One of the strongest greenhouse gases, methane comes from agriculture and fossil fuel use, as well as natural sources such as microbes in saturated wetland soils. The amount of atmospheric methane has remained relatively stable for about a decade, but concentrations began to rise again in 2007. Scientists believe this increase stems partly from more methane being released from thawing northern wetlands.

Scientists have assumed that wetland methane release is largest in the tropics, said Turetsky. “But our analyses show that northern fens, such as those created when permafrost thaws, can have emissions comparable to warm sites in the tropics, despite their cold temperatures. That’s very important when it comes to scaling methane release at a global scale.”....

US Fish and Wildlife Service photo of tundra in the Arctic

Future-proof UK coastal areas against rising sea levels, says National Trust

The Guardian (UK) via Press Association: A clear national strategy is "urgently needed" to help future-proof coastal areas from rising sea levels and extreme weather, according to a report published by the National Trust on Friday. The trust, one of the UK's biggest coastal owners, says many of its sites have been "battered" by storms and "hit hard" by high tides this winter.

Birling Gap, part of the Seven Sisters chalk cliffs in East Sussex, experienced seven years of erosion this winter – leaving its cafe and shop teetering metres from the edge. Part of the footpath down to the golden sands of Rhossili on Gower, South Wales – recently voted the UK's best beach – has been washed away by storms.

The charity says it has been forced to "fast-track" decisions over how to adapt coastal areas in the months ahead, rather than years or decades.  Simon Pryor, natural environment director at the National Trust, called for the government to ensure strategies to future-proof the coastline are implemented.

"There is a natural inclination to want to defend the coastline with concrete, but our coastline is dynamic and the forces of nature that have forme
d it are part of its beauty," Pryor said. "Hard defences will always have their place, but the winter storms that hit many coastal places hard have provided a valuable reminder that they have a limited life.

"Where we can we need to give natural processes that have formed our coast the space to work, and create areas where the coastline can realign as the sea levels rise. Natural habitats such as sand-dunes and salt marshes can act as buffer zones that absorb the impact of storms and very high tides."...

The Seven Sisters chalk cliffs in East Sussex, pre-erosion, shot by StephenDawson, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 2.0 Generic license

China's water squeeze worsens as wetlands shrink 9 per cent

Reuters: China's wetlands have shrunk nearly 9 percent since 2003, forestry officials said on Monday, aggravating water scarcity in a country where food production, energy output and industrial activity are already under pressure from water shortages.

China has more than a fifth of the world's population but only 6 percent of its freshwater resources, and large swathes of the nation, especially in the north, face severe water distress. Since 2003, wetlands sprawling across 340,000 sq. km. - an area larger than the Netherlands - have disappeared, officials of China's State Forestry Administration (SFA) told reporters.

"The investigation shows that China is facing various problems with wetlands protections," Zhang Yongli, vice director of the forestry body, told a news conference, adding that loopholes in protection laws imperil the shrinking wetlands.

The lost wetland areas have been converted to agricultural lands, swallowed by large infrastructure projects or degraded by climate change, the forestry administration said. Wetlands lost to infrastructure projects have increased tenfold since the government's last survey in 2003, Zhang added....

Namsanwai, a wetlands in China, shot by Kevinhksouth (I think), Wikimedia Commons via Flickr,  under the Creative Commons Attribution 2.0 Generic license

Humans threaten wetlands' ability to keep pace with sea-level rise

Terra Daily via SPX: Left to themselves, coastal wetlands can resist rapid levels of sea-level rise. But humans could be sabotaging some of their best defenses, according to a Nature review paper published Thursday from the Virginia Institute of Marine Science and the Smithsonian Environmental Research Center.

The threat of disappearing coastlines has alerted many to the dangers of climate change. Wetlands in particular-with their ability to buffer coastal cities from floods and storms, and filter out pollution-offer protections that could be lost in the future.

But, say co-authors Matt Kirwan and Patrick Megonigal, higher waters aren't the key factor in wetland demise. Thanks to an intricate system of feedbacks, wetlands are remarkably good at building up their soils to outpace sea level rise. The real issue, they say, is that human structures such as dams and seawalls are disrupting the natural mechanisms that have allowed coastal marshes to survive rising seas since at least the end of the last Ice Age.

"Tidal marsh plants are amazing ecosystem engineers that can raise themselves upward if they remain healthy, and especially if there is sediment in the water," says co-author Patrick Megonigal of the Smithsonian Environmental Research Center. "We know there are limits to this, and worry those limits are changing as people change the environment."

"In a more natural world, we wouldn't be worried about marshes surviving the rates of sea level rise we're seeing today," says Kirwan, the study's lead author and a geologist at the Virginia Institute of Marine Science. "They would either build vertically at faster rates or else move inland to slightly higher elevations. But now we have to decide whether we'll let them."...

The Héraðsflói,estuary in Iceland, shot by Bromr, Wikimedia Commons,  under the Creative Commons Attribution-Share Alike 3.0 Unported license

Rising sea levels threaten Everglades freshwater plants

Marie Guma-Diaz and Annette Gallagher in Terra Daily via UM News Coral Gables: Just inland from the familiar salt-loving mangroves that line the Southern tip of the Florida Peninsula lie plant communities that depend on freshwater flowing south from Lake Okeechobee. These communities provide critical habitats to many wildlife species, and as salt water intrudes, it could spell problems for freshwater plants and animals alike.

Satellite imagery over the southeastern Everglades confirms long-term trends of mangrove expansion and sawgrass habitat loss near the shore. The trend is related to salt water intrusion caused by sea-level rise and water management practices, according to a new study published in the scientific journal Wetlands.

"I was very surprised at how well the results matched our understanding of long-term trends and field data. Normally, we don't see such clear patterns," said Douglas Fuller, principal investigator of the study.

The findings show large patches of vegetation loss closer to the coast, approximately four kilometers from the shoreline, in and around a vegetative band of low productivity that has been shifting inland over the past 70 years. Growth trends were seen primarily in the interior, at about eight kilometers from the shore.

"Less salt-tolerant plants like the sawgrass, spike rush, and tropical hardwood hammocks are retreating. At the same time, salt-loving mangroves continue to extend inland," said Fuller, professor of Geography and Regional studies in the College of Arts and Sciences at the University of Miami....

A storm over the Everglades, shot by Moni3, public domain

Wetlands more cost-effective in nutrient removal, but multiple payments would be of uncertain value

Space Daily via SPX: Removing nitrogen from the environment "the natural way" by creating a wetland is a long-term, nutrient-removal solution, more cost effective than upgrading a wastewater treatment plant, but it isn't necessarily socially beneficial to offer landowners multiple payments for the environmental services that flow from such wetlands, according to a study conducted at the University of Illinois.

"In the areas we studied in Bureau County with small wastewater treatment plants (WWTPs), it was much cheaper to do pollution control by installing just a few wetlands than it was to have the WWTPs do the upgrades that would be necessary to achieve the same thing," said U of I environmental economist Amy Ando.

Bureau County was selected for the simulation because it is an area that has waterways with heavy nitrogen and phosphorus pollution, and it is a rural area of the state but with some population density and a couple of WWTPs.

"In some ways, it's a poster child for an environment where a program like this could work," Ando said. "There is enough farmland to put in some wetlands, but there are also enough people contributing to the WWTPs that are generating nutrients-so there are parties on both sides that could trade with each other."

The study analyzed the amount of land needed to reduce nitrogen pollution, data on the costs of actual wetland restorations, and other factors such as the opportunity costs to the landowner from no longer farming the new wetland area.

"Wastewater treatment plants can already remove nitrogen, but their current technology is only capable of removing them up to a point," Ando said. "If they wanted to do more nitrogen removal, they would have to make upgrades. The cost of phosphorus removal isn't high, but for nitrogen, the upgrades are pretty expensive."...

Kennekuk Marshes, Lake Vermillion, Illinois, shot by Huw Williams (Huwmanbeing), who has released it into the public domain

Study reveals potent carbon-storage potential of manmade wetlands

Terra Daily via SPX: After being drained by the millions of acres to make way for agriculture, wetlands are staging a small comeback these days on farms. Some farmers restore or construct wetlands alongside their fields to trap nitrogen and phosphorus runoff, and research shows these systems can also retain pesticides, antibiotics, and other agricultural pollutants.

Important as these storage functions of wetlands are, however, another critical one is being overlooked, says Bill Mitsch, director of the Everglades Wetland Research Park at Florida Gulf Coast University and an emeritus professor at Ohio State University: Wetlands also excel at pulling carbon dioxide out of the air and holding it long-term in soil.

Writing in the July-August issue of the Journal of Environmental Quality, Mitsch and co-author Blanca Bernal report that two 15-year-old constructed marshes in Ohio accumulated soil carbon at an average annual rate of 2150 pounds per acre-or just over one ton of carbon per acre per year.

The rate was 70% faster than a natural, "control" wetland in the area and 26% faster than the two were adding soil carbon five years ago. And by year 15, each wetland had a soil carbon pool of more than 30,000 pounds per acre, an amount equaling or exceeding the carbon stored by forests and farmlands....

Point Pelee marsh in Ontario, shot by Andrea, Wikimedia Commons via Flickr,  under the Creative Commons Attribution 2.0 Generic license

Researchers advocate a simple, affordable and accurate technology to identify threats from sea-level rise

AlphaGalileo via the National University of Singapore: Potential for method to be used within a network of wetland monitoring programmes in Southeast Asia and globally for assessing shoreline security and stability

A team of researchers led by Associate Professor Edward L. Webb of the National University of Singapore (NUS) is calling for the global adoption of a method to identify areas that are vulnerable to sea-level rise. The method, which utilises a simple, low-cost tool, is financially and technically accessible to every country with coastal wet­lands. The team seeks to establish a network to coordinate the standardisation and management of the data, as well as to provide a platform for collaboration.

...Recognising that some wetlands may be able to keep up with sea-level rise, the research team argues that scientists must quantitatively evaluate which wetlands may persist in the future, and which may be most threatened by sea-level rise.

Although the science behind the tracking of sea-level is well-advanced, a large gap exists in the measurement of the biophysical processes underlying the vertical movement of coastal wetlands, so it remains unknown which coastal wetlands will be most vulnerable to future sea-level rise. Collection of relevant data across global wetlands is critical to informing not only local policies, but to generating more realistic regional-level predictions to inform costal management and policy.

In a bid to address this gap, the research team, comprising members from NUS and the United States Geological Survey, argues for the widespread adoption of a standardised, simple and inexpensive method to measure the vertical movement of coastal wetland surface and its constituent processes that determine whether a wetland can keep pace with sea-level rise. The method utilises a rod surface elevation table (RSET), in which a benchmark rod is drilled vertically through the soil down to the base of the mudflat. A portable horizontal arm is attached at a fixed point to measure the distance to the substrate surface. The RSET is thus a permanent reference point to measure the rate and direction of the mudflat’s surface movement. ...

Nei Lingding Island, view from Hong Kong, shot by Minghong, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Why Everglades restoration really needs to be about adapting to climate change

Tricia Woolfenden in WLRN (Florida): When the Comprehensive Everglades Restoration Plan (CERP) was approved in 2000, it was a historic move to "restore, protect and preserve" water resources in central and south Florida. The 30-year framework was designed with the ultimate goal of restoring historic water-flows to a "dying ecosystem." Project leaders and scientists are now focused on incorporating climate change adaptation into the plans and acknowledging that the Everglades will likely never look the way it once did.

"We were looking back, now we need to look forward," said Eric Bush who is with the U.S. Army Corps of Engineers, one of the partners in CERP and other Everglades restoration efforts.  Bush said when CERP was created, it didn't take climate change into account. Sea level rise and fluctuations in precipitation and temperature will alter Florida's landscape, making it necessary to morph Everglades restoration plans into an "adaptation plan" for climate change.

"I don't think the public really understands the implications of climate change (on South Florida)," Bush said. He said while authorities don't yet know how serious the effects will be, adaptation needs to begin "now, or it will be too late," given the many years it takes to put any significant plan into place.

Bush's sentiments were echoed -- to one degree or another -- by numerous speakers at last week's meeting of the Committee on Independent Scientific Review of Everglades Restoration Progress (CISRERP) in Miami. The committee is part of the National Academies, a nonprofit organization that provides government and public institutions with independent analysis and recommendations on public policy....

The Turner River in the Everglades, shot by Chauncey Davis, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

New system to restore wetlands could reduce massive floods, aid crops

Seed Daily via SPX: Engineers at Oregon State University have developed a new interactive planning tool to create networks of small wetlands in Midwest farmlands, which could help the region prevent massive spring floods and also retain water and mitigate droughts in a warming climate.

The planning approach, which is being developed and tested in a crop-dominated watershed near Indianapolis, is designed to identify the small areas best suited to wetland development, optimize their location and size, and restore a significant portion of the region's historic water storage ability by using only a small fraction of its land. Using this approach, the researchers found they could capture the runoff from 29 percent of a watershed using only 1.5 percent of the entire area.

The need for new approaches to assist farmers and agencies to work together and use science-based methods is becoming critical, experts say. Massive floods and summer droughts have become more common and intense in the Midwest because of climate change and decades of land management that drains water rapidly into rivers via tile drains...

Wetlands and farm coexisting in Kossuth County, Iowa. Photo by Tim McCabe, USDA Natural Resources Conservation Service

Research reveals catastrophic loss of Cambodia’s tropical flooded grasslands

A press release from the University of East Anglia: Around half of Cambodia’s tropical flooded grasslands have been lost in just 10 years according to new research from the University of East Anglia. The seasonally flooded grasslands around the Tonle Sap, Southeast Asia’s largest freshwater lake, are of great importance for biodiversity and a refuge for 11 globally-threatened bird species. They are also a vital fishing, grazing, and traditional rice farming resource for around 1.1 million people.

Research published today in the journal Conservation Biology quantifies for the first time the area’s catastrophic loss of tropical flooded grassland.  The grassland area spanned 3349 km² in 1995, but by 2005 it had been reduced to just 1817 km² – a loss of 46 per cent.

Despite conservation efforts in some areas, it has continued to shrink rapidly since, with a further 19 per cent lost in four years (2005-2009) from the key remaining grassland area in the southeast of the Tonle Sap floodplain.

Factors include intensive commercial rice farming with construction of irrigation channels, which is often illegal. Some areas have also been lost to scrubland where traditional, low-intensity agricultural activity has been abandoned….

Tonle Sap lake in Cambodia, shot by 松岡明芳, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Sea level rise could severely affect Caribbean coastal wetlands

Jamaica Observer: A new World Bank study says a rise in sea levels by a metre from climate change could destroy more than 60 per cent of the Caribbean and the developing world's coastal wetlands currently found at one metre or less elevation. The study says this could lead to economic losses of about US$630 million annually.

The World Bank analysis considered a variety of types of coastal wetlands at risk in 76 countries and territories, using a number of databases and satellite maps. According to the data, about 99 per cent of the coastal wetlands, at elevations of one metre or less in the Middle East and North Africa, could disappear, as well as 77 per cent in sub-Saharan Africa, 66 per cent in East Asia, and 39 per cent in Latin America and the Caribbean.

The World Bank said, in recent years, coastal wetlands have been disappearing more quickly than other ecosystems, mainly because of land development The Washington-based financial institution said sea level rise from climate change will exacerbate these losses, adding that the rise in sea levels will lead to wetlands being submerged, pushed inland, or blanketed with salt.

"How those wetlands fare will vary, depending on the slopes and water flows in the surrounding area," the bank said. Susmita Dasgupta, a lead environment economist at the bank's Development Research Group, said the findings are "alarming, because wetlands don't exist just for the birds and plants. People rely on them for water, food, transportation, and other essential goods and services"...

NASA photo of Cuba's Zapata Swamp Biosphere Reserve

Quantifying sediment from 2011 flood into Louisiana's wetlands

Space Daily via SPX: The spring 2011 flood on the Mississippi was among the largest floods ever, the river swelling over its banks and wreaking destruction in the surrounding areas. But a University of Pennsylvania-led study also shows that the floods reaped environmental benefits - transporting and laying down new sediment in portions of the Delta - that may help maintain the area's wetlands.

The study, led by Ph.D. student Nicole Khan of the Department of Earth and Environmental Science, is the first to quantify the amount of sediment transported to wetlands by a flood on the Mississippi. The results shed light on how floods impact wetlands, and how these effects might be harnessed to purposefully rebuild Louisiana's wetlands, which are sinking from compaction and growing smaller as sea level rises.

...A study by many of the same scientists, published in Nature Geoscience last year, found that the 2011 Mississippi River floods deposited more sediment in the Atchafalaya River Basin, where the waters moved slowly over a broad area, than in the Mississippi River Basin, where levees and control structures funneled the floodwaters into a jet stream that shot water and sediment out into the Gulf of Mexico.

The current study, published in Geology, focuses specifically on the questions of how much sediment was laid down in the river basins affected by the flood and where the sediments deposited the most.

"The marshes may be able to maintain their surface area or height above sea level if they receive significant sediment, either from floods or hurricanes or normal fluvial processes," Horton said. "Ours is the only empirical study to obtain an estimate of how much sediment is deposited by a large-scale flood on the Mississippi."...

A barge on the Mississippi in Louisiana, shot by Ken Lund, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

Marsh plants actively engineer their landscape

EurekAlert via Duke University: Marsh plants, far from being passive wallflowers, are "secret gardeners" that actively engineer their landscape to increase their species' odds of survival, says a team of scientists from Duke University and the University of Padova in Italy.

Scientists have long believed that the distribution of plants within a marsh is a passive adaption in which species grow at different elevations because that's where conditions like soil aeration and salinity best meet their needs. But this team found intertidal marsh plants in Italy's famed Venetian lagoon were able to subtly tune, or adjust, their elevations by producing different amounts of organic soil, and trapping and accumulating different amounts of inorganic sediments as part of a complex interplay with the environment.

"Our study identifies the visible signature of a two-way feedback occurring between the vegetation and the landscape," said Marco Marani, professor of ecohydrology at Duke's Nicholas School of the Environment and Pratt School of Engineering. "Each species builds up the elevation of its substrate to within a favorable range for its survival, much the way corals in the animal kingdom do." The finding may help scientists better predict marsh ecosystems' resilience to climatic changes such as sea level rise. "Obviously, this is not a conscious choice on the part of the plants," Marani said. "It's a natural mechanism -- how marshes work. We just didn't understand it in such detail until now."

...The team used numerical modeling to visualize the dynamic interactions of marsh ecosystems over time, and tested the models against detailed topographical surveys of elevations and distributions of plant species in the Venetian lagoon.

"We've been studying this same marsh for 15 years and, as in similar studies around the world, we were using GPS technology with an accuracy of plus or minus one centimeter in elevation," Marani explained. For the new study, they used a more precise surveying instrument, an electronic theodolite, which measure elevations accurately to within less than one millimeter. "It allowed us to observe differences so subtle that they went unnoticed before," he said....

A digital map of one portion of the Venetian marsh shows the distribution of several species of marsh plants. Courtesy of Marco Marani, Duke University

Planners need to allow for Coastal wetlands migration due to sea level rise, climate change

Indymedia.org (Australia): Coastal Wetlands are under pressure. They face rising seas from climate change, but their biggest obstacle to migrate naturally inland is human development with roads, houses and other infrastructure blocking their way. And our urban planners are largely unaware of this tricky situation.

We all love to live beside the sea, but coastal urban development and rising seas will increasingly threaten sensitive coastal wetlands with no room to move and imperilling the survival of their unique plants, birds and fish.

Our urban planners have taken a stable sea level for granted with development to date, often destroying wetland environments for coastal development, agriculture and aquaculture.

More recent urban planning incorporating sea level rise predictions places an emphasis on the threat to peoples houses, roads, railway embankments and other human infrastructure. But planning also needs to encompass the coastal wetland environments that share our coastlines. These ecosystems will also need to migrate inland as the ocean rises....

Gippsland Lakes in Victoria, Australia, from NASA