Contemporary recreational fishing combines with old WPA project to hasten marsh die-off

Cape Cod, Massachusetts has a problem. The iconic salt marshes of the famous summer retreat are melting away at the edges, dying back from the most popular recreational areas. The erosion is a consequence of an unexpected synergy between recreational over-fishing and Great Depression-era ditches constructed by Works Progress Administration (WPA) in an effort to control mosquitoes. The cascade of ecological cause and effect is described by Tyler Coverdale and colleagues at Brown University in a paper published online this month in ESA's journal Frontiers in Ecology and the Environment.

A large male purple marsh crab (Sesarma reticulatu) clipping cordgrass with its claws. The burrow opening in the photograph leads to a large, communal burrow inhabited by 10-15 crabs. These crabs are nocturnal and typically reside in burrows during the day to stay moist and avoid predators. Credit, Tyler Coverdale

"People who live near the marshes complain about the die-off because it's not nice to look at," said Coverdale. "Without cordgrass protection you also get really significant erosion, retreating at sometimes over a meter a year." The die-back is ugly, but it is also a substantial loss of a valuable ecological resource.

When fishermen hook too many predatory fishes out of the marsh's ecosystem, the fishes' prey go on fruitfully multiplying, unchecked. The reverberations down the food chain can result in uncomfortable environmental changes for human residents. The problem for Cape Cod is the native purple marsh crab (Sesarma reticulatum), which burrows in the mud along the inner shorelines of the marshes, and dines almost exclusively on the tall and fast-growing low marsh cordgrass (Spartina alterniflora) that lines the marsh edges.

The tall and sturdy cordgrass is an essential buffer against the friction of tides and storms. Without it, soft banks erode out from under the other plants and the water line retreats farther and farther back into the marsh. The unchecked multitudes of purple marsh crabs have taken a visible toll on the developed areas of the Cape. By 2008, 50 percent of the creek banks in the marsh had worn back. Old drainage ditches have expanded from nearly invisible threads to open channels - some nearly 30-40 meters wide - with muddy, exposed edges.

The purple marsh crabs need tidal creek edge habitat to thrive, and do not venture into the inner heart of the marsh, where a shorter cordgrass species (the closely related, but squattier Spartina patens) and other high marsh plants dominate. The old WPA mosquito ditches also fulfill the crabs' habitat requirements. Once benign, the ditches nucleated dramatic reconstruction of the landscape with the loss of blue crab, striped bass, and smooth dogfish, and the subsequent boom of purple marsh crabs.

One of the remarkable features of the cordgrass die-off is its tight locality. Some areas of undeveloped marsh as close as a kilometer to the denuded banks around private residences and public docks appear healthy and unaffected. Mosquito ditches that can only be reached by a hard slog through undeveloped marshland do not display the striking die-off and bank erosion. The pattern cued the researchers to the possibility that recreational fishing was the trigger, Coverdale says. Few people wade into the swamp to fish.

Marshes are excellent model systems for observing the intersection of human impacts that can trigger environmental degradation, the authors say, because they have been exploited by humans for centuries, if not thousands of years, and are easily studied from aerial and satellite images.

"Marshes are one of the most heavily utilized resources worldwide," said Coverdale. "They are easily accessible, and provide shellfish, fuel, baitfish and opportunities for recreational anglers. A lot of those harvests are probably sustainable."But he is interested in the tipping points at which use of the marsh becomes unsustainable. The revelation of the slumbering menace of the mosquito ditches raises the prospect of other submerged impacts that may surface under the influence of new, contemporary pressures.

In the early twentieth century, Cape Cod was a very different place from the summer vacation destination it is today. As land use shifted from agriculture toward tourism, the local chamber of commerce funded an effort to draw off standing water through drainage ditches to suppress the mosquito population. The program was probably not very effective at controlling mosquito-borne disease, Coverdale says, but it did put a lot of people to work, and they were industrious. Over 2400 kilometers of old ditches stripe the marshes of the long, low-lying peninsula. The Cape Cod Mosquito Control Project continues ditch-dredging under the Barnstable County Department of Health and the Environment.

The ditching program had a relatively minor impact on the marshes compared to other forms of development, however. Following the Second World War, Cape Cod developed rapidly, nearly tripling in permanent human population between 1940 and 1976, when a new awareness of the ecological and economic benefits of the marsh brought strict limitations on further development. Ditches claimed only 2 percent of the marsh, compared with the 70 percent affected by roads, houses, restaurants, marinas, and other hallmarks of a modern coastal community. Alone, the ditches did not fundamentally alter the marsh ecosystem. The species that colonized the ditches were already present in the marsh; the WPA's remodeling project just moved them around. The additional pressure of recreational fishing changed that equilibrium.

How do Cape Cod residents and local fishing enthusiasts feel about this news? Coverdale says the area has a strong conservation ethic. People remember what the Cape looked like when their parents lived there, and are unhappy with the changes. As a fishing enthusiast himself, Coverdale does not see ecologists and fishermen as opposing forces.

"People enjoy catching fish today, but they come back year after year. They want to see the fish there tomorrow," Coverdale said. He has faith that the tendency of residents and long-time visitors to take the long view will make a solution possible. A system of catch and release could make fishing the Cape sustainable and allow the local community to retain its fishing heritage.

Latent impacts: the role of historical human activity in coastal habitat loss. Tyler C Coverdale, Nicholas C Herrmann, Andrew H Altieri, and Mark D Bertness. Frontiers in Ecology and the Environment (e-view) scheduled for March 2013 print edition. doi:10.1890/120130

Contact:
Tyler Coverdale
Department of Ecology and Evolutionary Biology, Brown University, Providence, RI (all authors)
tyler_coverdale@brown.edu
401-863-2916

Photo:
A large male purple marsh crab (Sesarma reticulatu) clipping cordgrass with its claws. The burrow opening in the photograph leads to a large, communal burrow inhabited by 10-15 crabs. These crabs are nocturnal and typically reside in burrows during the day to stay moist and avoid predators. Credit, Tyler Coverdale.

Josh Miller likes to call himself a conservation paleobiologist. The label makes sense when he explains how he uses bones as up-to-last-season information on contemporary animal populations.

Bones, he says, provide baseline ecological data on animals complementary to aerial counts, adding a historical component to live observation. In his November cover article for the Ecological Society of America’s journal Ecology, he assesses elk habitat use in Yellowstone National Park by their bones and antlers, testing his method against several decades of the Park Service’s meticulous observations.

Now an assistant research professor in the new Quaternary and Anthropocene Research Group in the Department of Geology at the University of Cincinnati, Miller located and recorded the elk bone data while a doctoral student in paleontology at the University of Chicago, and finished analyzing the data during a brief stint at the Florida Museum of Natural History at the University of Florida, in Gainesville. His work with modern animals grew out of curiosity about the fidelity of the fossil record in archiving animals and ecosystems of the distant past.

“It turns out that bones are really informative,” he said. At Yellowstone, bone and antler concentrations mirror patterns of animal landscape use known from years of aerial surveys. “This opened up a completely unexpected opportunity for studying modern ecosystems, particularly for areas where our knowledge of animal populations is more limited.”

Reconstructing animal community structure and habitat use through the bones of past generations is a new idea. Until recently, common knowledge held that, on the landscape, bones just don’t last that long. But Miller has found that they can last for hundreds of years. Bones weather in a stereotypical pattern, from fresh to falling apart. He calibrated weathering in the Yellowstone bones through radiocarbon dating, gaining a familiarity that would allow him to pick up a bone and know it had seen a year, 20 years, or 80 to 100 years or more on the open ground.

Bull elk shed their antlers in late winter, when forage is sparse. Too poor in nutrients to interest most scavengers, heavy, and awkwardly shaped for displacement by the elements, antlers tend to stay where they fall. Miller found that, for the most part, the bones of calves don’t travel far either, even in the mouths of predators. The bones of calves mark the range where their mothers sought plentiful food to fuel months of nursing, and shelter to hide their vulnerable newborns.

Old bones from past decades outline a range consistent with the living herd. Miller saw only moderate shifts in a few areas, even given the many recent changes at Yellowstone: the prodigious wildfires of 1988, repatriation of grey wolves starting in 1995, and regrowth of willows, aspen, and cottonwoods over the last couple of decades following a long decline during the 20th century.

Because bones can last decades to centuries in the Yellowstone environment, Miller says they can put relatively recent data from direct observation into broader context for managers looking at long-range planning, helping to sort out important changes from the noise of cyclical booms, busts and shifts in landscape use. Bones are a minimally invasive tool for tracking the history of range animals. They are data just lying on the ground, waiting to be collected.

Spatial fidelity of skeletal remains: elk wintering and calving grounds revealed by bones on the Yellowstone landscape (2012) Joshua H. Miller. Ecology 93:11, 2474-2482.

Contact: Joshua Miller Department of Geology & the Quaternary and Anthropocene Research Group, University of Cincinnati.http://homepages.uc.edu/~mille5ju/ josh.miller@uc.edu (513) 556-6704

Photo: The bared vertebrae of an elk lie on a riverbank in Yellowstone National Park. Credit, Joshua Miller.

Journalists and public information officers can gain access to full texts of all ESA publications by contacting the public affairs office. Email Liza Lester, llester@esa.org.

The pressures of global trade may heighten disease incidence by dictating changes in land use. A boom in disease-carrying ticks and chiggers has followed the abandonment of rice cultivation in Taiwanese paddies, say ecologist Chi-Chien Kuo and colleagues, demonstrating the potential for global commodities pricing to drive the spread of infections. Their work appears in the September issue of ESA’s journal Ecological Applications.

After Taiwan joined the World Trade Organization in 2001, active cultivation of rice paddies fell from 80 percent to 55 percent in just three years. The government of Taiwan subsidized twice-yearly plowing of abandoned fields to reduce the spread of agricultural pests into adjacent fields still in cultivation. Compliance has been spotty. Kuo found that, while plowing did not suppress rodent populations, it did inadvertently reduce the presence of the ticks and chiggers that use rodents as their primary hosts.

“The government considers only agricultural pests such as insects and rodents. They don’t think about the disease factors,” said Kuo. But land use policy can have complex and unexpected reverberations in the ecology of the landscape.

Chiggers, the larval stage of trombiculid mites, spread scrub typhus (Orientia tsutsugamushi), a bacterium thatgets its name from the scrubby, dense vegetation that often harbors its flesh-loving host. Scrub typhus is a common culprit underlying visits to Southeast Asian hospitals for flu-like symptoms. Without antibiotics, the infection is often fatal. Ticks (Ixodidae) transmit bacteria spotted fever group rickettsiae, causing fever, aches and rash similar to Rocky Mountain spotted fever. Neither pest prefers to live underwater.

Hualien, Kuo’s study area, is one of the least populous of Taiwan’s counties, yet had nearly the highest incidence of scrub typhus from 1998-2007. The county is a smattering of small villages surrounded by a patchwork of flooded, plowed, and abandoned rice paddies.

Flooded paddies are poor habitat for ticks and chiggers, and so cultivation of rice, which locally means carefully managed flooding of fields to drown agricultural pests, likely suppresses ticks and chiggers as well. Even the seemingly unkillable ticks die after a few weeks of submersion, and chiggers are similarly terrestrial. Though studies are few, limited data indicate that most chiggers die after a month under water.

This study did not assess flooded paddies due to the difficulty of finding and collecting rodents, ticks, and chiggers underwater. Instead, Kuo trapped rodents in fallow and plowed fields and examined their tick and chigger passengers, testing the arachnids for presence of disease-causing rickettsial bacteria. He found 6 times as many ticks on the rodents living in fallow fields – and the proportion of infectious ticks in fallow fields was three times higher, compounding the risk. Chiggers rode rodents at a rate 3 times higher in fallow fields than plowed fields.

“This study is a great example of the kinds of indirect effects that trickle down from human policies,” said Bob Parmenter, an ecologist unaffiliated with the study. “It tells a nice story about how changes in international trade barriers can have unforeseen consequences.” Parmenter is director of the USDA’s Scientific Services Division at Valles Caldera National Preserve near Los Alamos, New Mexico, and an expert on the influence of ecology on deadly Hantavirus outbreaks, like the current episode in Yosemite National Park (California, USA) that has infected nine visitors and killed three. 
The consequences of economic pressures on land use are also present in the eastern United States, where the small farms of the eighteen and nineteenth centuries have reverted, to a large degree, to forest. With the return of deer and wildlands has come a rise in ticks, and concurrent rise in Lyme disease. Conversely, opening new land to farming or housing can bring its own disease risks.

Many studies have investigated influence of global forces on disease, said Kuo. “Most are focused on how climate change, global travel, or habitat destruction will affect the emergence of vector-borne and zoonotic disease. We show that economic organizations can actually affect human health, by influencing the landscape.”

Title:
“Cascading effect of economic globalization on human risks to scrub typhus and tick-borne rickettsial diseases.” Ecological Applications volume 22 issue 6

Authors:
Chi-Chien Kuo, Geography and Environment, University of Southampton, Southampton, UK
Douglass A Kelt, Department of Wildlife, Fish, & Conservation Biology, University of California, Davis, CA, USA
Jing-Lun Huang, Pei-Yun Shu, Pei-Lung Lee, and His-Chieh Wang, Research and Diagnostic Center, Centers for Disease Control, Department of Health, Taipei, Taiwan, ROC

Contacts:
Chi-Chien Kuo: +44 (0)2380584319, ccckuo@ucdavis.edu
Douglass Kelt: 530-754-9481, dakelt@ucdavis.edu
His-Chieh Wang: +886-2-3393-5054, sjwang@cdc.gov.tw
Robert Parmenter: 505-428-7727, bparmenter@vallescaldera.gov

Journalists and public information officers can gain access to full texts of all ESA publications by contacting the public affairs office. Email Liza Lester, llester@esa.org.

Scott Collins, Regent’s Professor of Biology and Loren Potter Chair of Plant Ecology at the University of New Mexico became President of the Ecological Society of America (ESA) on August 10, 2012. Elected by the members of ESA for a one-year term, Collins will chair the ESA Governing Board, the elected governing body of the Society, which provides vision and guidance on ESA initiatives and future direction.

“It is a great honor to be elected President of the Ecological Society of America. I have been a member of ESA since 1976, my first year in graduate school,” said Collins. “The rapid development of electronic communication, data and information management, and social networking creates some challenges and many exciting opportunities for ESA and its journals. I look forward to working with ESA staff, the Governing Board, and the membership to meet these challenges so that ESA can continue to serve the research community and advance ecological knowledge.”

Collins is an internationally recognized community ecologist. As Director of the Sevilleta Long-term Ecological Research (LTER) program his research focuses on long-term studies of plant community ecology. His work is primarily in grassland ecosystems where he investigates how factors such as climate and disturbance by fire or grazing impact grasslands. The Sevilleta LTER Project is located roughly 80 kilometers south of Albuquerque, NM, in and around the Sevilleta National Wildlife Refuge. Its unique location serves as a model setting to examine how human activities will interact with climatic variation to catalyze change in arid communities and ecosystems.

Collins also serves as Chair of the LTER Network Science Council and Executive Board, and he is a past president of the Association of Ecosystem Research Centers. He was also the original NSF Program Director for the National Ecological Observatory Network (NEON), organizing six NEON planning workshops between 2000-2002. During the 1990s, he worked at NSF, serving as Program Director in various capacities, including the agency’s Ecological Studies and LTER programs.

ESA is the world’s largest community of professional ecologists and a trusted source of ecological knowledge, committed to advancing the understanding of life on Earth.  The 10,000 member Society publishes five journals, convenes an annual scientific conference, and broadly shares ecological information through policy and media outreach and education initiatives. Visit the ESA website at http://www.esa.org

The Ecological Society of America (ESA) will present its fifth annual Regional Policy Award to Ken Bierly of the Oregon Watershed Enhancement Board during the Society’s upcoming conference in Portland, Oregon. The ESA award recognizes an elected or appointed local policymaker who has an outstanding record of informing political decision-making with ecological science.

“We are delighted to present this prestigious award to Ken Bierly for his long-term commitment to Oregon’s streams, rivers, wetlands and other natural areas,” said ESA President Steward Pickett. “His pioneering initiatives with the Oregon Department of State Lands in developing and implementing wetland regulations and Oregon Watershed Enhancement Board in developing tools for watershed management have enabled Oregonians across the state to use science to help improve and protect the rivers and streams of their communities.”

“I am greatly honored and stand on the shoulders of a great number of researchers, fellow agency staff and citizens of the state who deeply care about and wish to understand more deeply about our precious natural heritage,” said Bierly.

Bierly’s career ties in well with ESA’s 97th annual meeting theme: “Life on Earth: Preserving, Utilizing and Sustaining our Ecosystems.” For over twenty years, Bierly has distinguished himself as a state employee through his innovative approaches to restoring and protecting habitats. Accomplishments include: developing freshwater wetland legislation in 1989, formulating a science-based regulatory program for wetlands, guiding the expansion of the Governor’s Watershed Enhancement Board, and a key team member of Governor Kitzhaber’s administration in the development of the Oregon Plan for Salmon and Watersheds.

As part of the implementation of the “Oregon Plan,” Bierly oversaw the development of a science-based approach to evaluating the condition of the state’s watersheds. Bierly then advocated the development of local watershed councils – who used the assessments with assistance from technical experts to develop action plans for improving fish habitat and water quality in their communities.

Currently, Bierly is Senior Partnerships Coordinator at the Oregon Watershed Enhancement Board (OWEB), a state agency that provides grants to help landowners and others to restore or otherwise enhance natural resources in the state. The agency’s grants are funded from the Oregon lottery, federal dollars and salmon license plate revenue. His most recent responsibilities are to work with grantees and other funding partners in the implementation of three different long-term investments that are expected to produce defined aquatic ecosystem health outcomes in focused areas. These efforts include: a partnership with federal land management agencies to restore watersheds across public-private boundaries, a target initiative to address the necessary physical conditions to support the reintroduction of anadromous fish above dams on the Deschutes River, and a cooperative effort with the Meyer Memorial Trust, a regional private foundation, to make measurable improvements of floodplain and channel dynamics of the Willamette River.

About his work at OWEB, Executive Director Tom Byler states, “As OWEB has grown from its infancy as a grant-making agency, Ken has been an innovator, finding new and unique ways to invest in local watershed restoration. His ability to leverage OWEB funds with those from private and public partners has directly improved Oregon’s environment and benefited local communities.”

ESA President Pickett will present Bierly with the 2012 ESA Regional Policy Award at the start of the Opening Plenary Session on Sunday, August 5 at 5 PM in Oregon Ballroom 201-203 of the Oregon Convention Center. ESA’s conference is expected to draw a record number of participants, with well over 4,000 scientists, educators, policymakers and others attending from around the world.

Media Attendance
The Ecological Society of America’s annual meeting, Aug. 5-10, 2012 in Portland, Oregon, is free for reporters with a recognized press card and institutional press officers. Registration is also waived for current members of the National Association of Science Writers, the Canadian Science Writers Association, the International Science Writers Association and the Society of Environmental Journalists. Interested press should contact Liza Lester at llester@esa.org or 202-833-8773 x211 to register.  In a break from previous policy, meeting presentations are not embargoed.