Friday, October 30, 2009
Tuesday, October 27, 2009
Sustainable Design
Saturday, October 10, 2009
in CategoryResearch Briefs | DateSep 21, 2009
Palustrine wetland with rooted emergent vegetation. Image credit, Howard Weamer.
Working in conservation, most of us have been trained to view biodiversity as an essential aspect of a successfully functioning ecosystem. But new research from wetland scientists at Halmstad University in Sweden challenges this common assumption. The study has provided evidence indicating that vegetative biodiversity in wetlands can actually inhibit nitrogen removal -- a desirable and vital wetland process. The study showed no support for vegetative biodiversity supporting ecosystem function.
One highly beneficial function of wetlands is their ability to remove nitrates from nutrient rich river water before it enters the ocean. For years, eutrophication has been a major environmental concern due to the fact that it causes numerous “dead zones” within our oceans. Wetlands filter out these nutrients preventing harmful algal blooms and preserving the dissolved oxygen for its rightful recipients: the aquatic fauna.
Methods
The study examined nitrogen removal (denitrification) and vegetative species diversity (Shannon diversity method) in 18 experimental wetlands. The researchers left six of those wetlands unplanted to develop freely. In six of the wetlands they added tall emergent vegetation (Phragmites australis, Glyceria maxima, & Phalaris arundinacea) and in the other six they added plantings of submerged vegetation (Elodea Canadensis, Myriophyllum alterniflorum, and Ceratphyllum demersum). An inlet pipe released water with 11 milligrams of total nitrogen per liter into the wetlands. Water escaping an outlet pipe was then tested for nitrogen concentrations. The wetlands were monitored over the course of 3 years.
Results
Although the unplanted wetlands initially had the lowest biodiversity, as the study progressed, the other twelve wetlands gradually became less and less diverse. Where the tall emergent species were planted, they ultimately dominated by outcompeting the previously established plants. While these wetlands became the least diverse, they contained the densest vegetation and the water leaving them contained lower nitrogen concentrations than the submerged vegetation wetlands (P < 0.001) or the free development wetlands (P = 0.002).
There are several explanations for these results: The tall vegetation wetlands (1) provided higher amounts of organic matter needed for the denitrifying bacteria, (2) offered more litter for the bacteria to attach to, and/or (3) contained dense vegetation that limited sunlight from reaching the water column, promoting anaerobic conditions necessary for the denitrification process.
Implications
While ecosystem managers commonly set a goal of species heterogeneity, low-diversity wetlands, dominated by tall plant life, seem to aid nitrogen removal. To eliminate detrimental nitrogen concentrations, managers may want to reconsider the common practice of thinning dominant species to promote biodiversity. This low-diversity may actually benefit ecosystem functioning!
--Reviewed by Evyan Borgnis
Weisner, Stefan, & Thiere, Geraldine (2009). Effects of vegetation state on biodiversity and nitrogen retention in created wetlands: a test of the biodiversity-ecosystem functioning hypothesis Freshwater Biology DOI: 10.1111/j.1365-2427.2009.02288.x
Fish and boxing gloveMeeting US goals for biofuel production will increase nutrient run-off to the Gulf of Mexico, making it more difficult to reduce the size of the gulf’s “dead zone,” scientists say in Environmental Science & Technology.
US energy policy dictates that 36 billion gallons of renewable fuel must be produced annually by 2022. But a task force led by the Environmental Protection Agency is also aiming to shrink the Gulf of Mexico’s hypoxic zone, a low-oxygen area that can reach 14,600 square kilometers. Excess nitrate from agricultural run-off is thought to play a large role in hypoxic zone formation, which kills and disrupts marine life each year.
The authors calculated the nitrate output of various crop combinations that could be used to meet the US biofuels mandate. Relying on crops for cellulosic ethanol, such as switchgrass, rather than corn would cut nitrate output by 20 percent, they found. But that still wouldn’t be enough to reach the EPA’s goal of reducing the hypoxic zone to 5,000 square kilometers by 2015, the team concluded.
To meet that target, the US will need to undertake an “aggressive nutrient management strategy,” they say. Possible solutions could include constructing wetlands or building buffer zones to intercept run-off. – Roberta Kwok
Source: Costello, C., Griffin, W., Landis, A., & Matthews, H. (2009). Impact of Biofuel Crop Production on the Formation of Hypoxia in the Gulf of Mexico Environmental Science & Technology DOI: 10.1021/es9011433
Image © MichaelUtech, iStockPhoto.com
Filed Under Marine, Socio-political issues |
in CategoryResearch Briefs | DateSep 23, 2009
Kawai Nui Marsh, sunset. Image credit, Jason Turse.A new study compares natural wetlands in Hawai‘i against those that have been restored and created. While all three wetland types had similar vegetation characteristics, natural wetlands had very different soil properties. These results indicate that wetlands created and restored as compensatory mitigation under the Clean Water Act may not adequately replace the function of natural wetlands lost to development.
The study is also important because it represents the first assessment of costal lowland wetlands in Hawai‘i. Invasive species dominated the vegetation cover in natural, created, and restored wetlands. According to the researchers:
"Our findings suggest that the vegetation of costal low wetlands in Hawai‘i needs more intensive management and invasive species control. These results also suggest that it may be difficult to use vegetation to locate ‘‘reference’’ sites for costal lowland wetlands in Hawai‘i due to the pervasive nature of invasive species regardless of wetland status. From a management perspective, however, there are a few sites (e.g., Lawai Kai, Nu‘u, Kamilo Point) that have mostly native vegetation and could be considered the least-impacted."
From a global perspective, this research adds to a growing list of studies showing that restored and created wetlands do not replace soil properties of natural wetlands. This study found that natural wetland had lower bulk density and pH and higher soil organic matter, silt, total nitrogen and total carbon versus created and restored wetlands.
The researchers list the likely explanations for the differences in soil properties:
1) The use of heavy machinery in wetland creation and restoration leads to compaction of soils, resulting in higher bulk densities.
2) Higher bulk density and lower soil organic may be an artifact of excavation into subsurface soil horizons that are compacted and have lower organic matter content.
3) Organic matter accumulation is a function of time, established vegetation, and hydrology. Organic matter accumulation is favored in natural wetlands due to the inhibition of decomposition caused by the long-term anaerobic conditions typical of natural wetlands.
4) The low pH and high total carbon and total nitrogen values observed in natural wetlands were likely the result of saturated soils, low oxygen levels, and subsequent inhibition of organic matter decomposition.
The study offers the following recommendations for wetland mitigation:
1) An effective method for reducing soil compaction of created and restored wetlands is to use a chisel plow to mechanically rip both the topsoil and subsoil layers, prior to planting.
2) Amendments such as compost, mulch, or other organic material have proven to be effective methods for increasing soil moisture.
3) Due to the greater similarities between the soil properties of natural and restored wetlands, it will likely take longer for created wetlands to develop functions characteristic of natural wetlands. Therefore, given the option between restoration and creation, restoration should be the preferred mitigation option in Hawai‘i.
--Reviewed by Rob Goldstein
Bantilan-Smith, M., Bruland, G., MacKenzie, R., Henry, A., & Ryder, C. (2009). A Comparison of the Vegetation and Soils of Natural, Restored, and Created Coastal Lowland Wetlands in Hawai‘i Wetlands, 29 (3), 1023-1035 DOI: 10.1672/08-127.1
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Dave Munger Dave Munger is editor of ResearchBlogging.org. He also blogs at Cognitive Daily. Each week, he writes about emerging trends
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Each year in April and May as farmers in the central US fertilize their crops, nearly 450 thousand metric tons of nitrates and phosphates pour down the Mississippi River. When these chemicals reach the Gulf of Mexico, they cause a feeding frenzy as photosynthetic algae absorb the nutrients. It’s a boom-and-bust cycle of epic proportions: The algae populations grow explosively, then die and decompose. This process depletes the water of oxygen on a vast scale, creating a suffocating “dead zone” the size of Massachusetts where few, if any, animals can survive.
The EPA has been working to reduce the size of the dead zone, with a goal of shrinking it to about 5,000 square kilometers—a quarter of its current size—by 2015. But a new study in Environmental Science & Technology shows that other efforts to preserve the environment may be exacerbating the dead zone. Kristopher Hite, a graduate student in biochemistry at Colorado State University, explains the implications of the study on his blog, Tom Paine’s Ghost.
The study examined the implications of a 2007 law that requires the US to annually produce 36 billion gallons of biofuels by 2022. Barring major biofuel production breakthroughs from sources like algae or microbes, most of this fuel will come from crops grown in the central US; the fertilizers and other agricultural waste they produce will flow straight down the Mississippi and feed the dead zone. Hite says the study, led by Christine Costello, found that meeting this goal will make it impossible for the EPA to reach its target reduction in the size of the dead zone. Even if fertilizer-intensive corn is replaced with more eco-friendly crops like switchgrass, the vast increase in agricultural production will cause the dead zone to grow unless preventive measures are taken.
So what can be done about it? The Society for Conservation Biology suggests that increasing the size of wetlands or other buffer zones around the source of the pollution—the farms themselves—could help.
Unfortunately, artificial wetlands have their own negative ecological side effects. As this post at Conservation Maven shows, some created wetlands are dominated by invasive species. Apparently, the heavy equipment used to build the sites also compacts the soil in a way that makes it more difficult for native species to flourish.
But not all human-made wetlands are bad. Conservation Maven also points to a Swedish study which found that less-diverse wetlands dominated by tall plants are actually more efficient at removing nitrogen from runoff than many other sites. So creating wetlands can be a very effective means of removing pollutants from water, even if local biodiversity suffers. The current pace of biofuel development, however, exceeds the capacity of available wetlands.
More on ecology at Researchblogging.org:
* The dangers of rhododendrons: A beautiful mountain shrub may contribute to landslides.
* What are the limits to growth? A 2008 study revisits a 1972 book that made dire predictions about the impact of human civilization on the planet.
* The water footprint of coffee: How much water does it take to make a cup of coffee? It depends on where (and how) the coffee is grown.
Hite remains an optimist, pointing to new technology that uses fungi to convert the cellulose in wood chips, corn stalks, and other agricultural “waste” into biofuels. If this can be done efficiently, we could eventually harvest several times more energy from the same amount of cropland. Even while acknowledging that we may still face problems like the Gulf’s dead zone, Hite believes that ultimately technology can help us prevent greater ecological disasters like global warming.
But should Hite even be making this case? How do we decide whether it’s ecologically sensible to produce biofuels or build wetlands? Some have argued that the advocacy of scientists like Hite and websites like Conservation Maven is misplaced. Shouldn’t scientists just be interested in giving us the facts, staying removed from policy decisions and letting the general public and politicians decide how to act? Doesn’t becoming an advocate introduce bias into the scientific process, potentially tarnishing results?
James Hrynyshyn is a freelance journalist and unapologetic environmental advocate who says that many of the best scientists, from Albert Einstein, to Carl Sagan, to NASA’s James Hansen, have also been important policy advocates. On his blog, The Island of Doubt, Hrynyshyn cites a May paper in Conservation Biology by Michael Nelson and John Vucetich, who argue that scientists’ advocacy positions can easily be separated from scientific truths. For instance, late in his life the great chemist Linus Pauling damaged his reputation by peddling vitamin C as a cure-all, but that didn’t take away from his earlier scientific contributions, for which he won two Nobel prizes.
More importantly, Hrynyshyn says, it’s unfair and unwise to restrict individuals—who are interested citizens as well as working scientists—from participating in the political process, especially when those individuals have knowledge and expertise that applies directly to important problems. Conservation biologists can both alert us to potential ecological disasters and offer insight into how to solve them. Why not tap their expertise to help form policy decisions?
There’s much more discussion of ecology—and ecologists’ role in creating environmental policy—at ResearchBlogging.org.
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Monday, October 5, 2009
"My commitment is to revitalize ecosystems while providing pleasure and raising awareness that the vitality of any community and the continuity of its cultural heritage depends upon the health of the natural world that embraces it.
HUMBLE: [< L. humilis low, small, slight, akin to humus, soil, earth (see HUMUS)]
HUMUS: [L. earth, ground, soil < IE. * ghom-: see HOMAGE]
HOMAGE: [< L. homo, a man , IE. *ghom-, < base *gtheim-, earth, ground, whence L. humus, Gr. chthon, earth, OE. guma man]
More than many environmental artists, the work of Brandon Ballengée bridges the gap between research biology and art. He combines a fascination with fish and amphibians with the techniques of commercial art photography.
In 1996 Ballengée began collaborating with scientists to create hybrid environmental art/ ecological research projects. Since then he has had numerous exhibitions nationally and internationally in which he presents photographs and biological samples of the creatures he collects. He is involved directly with field research and uses the visual impact of science to engage the public in a discussion of broader environmental issues.
Originally from Alabama, Jane Ingram Allen has specialized in decomposable indoor and outdoor mixed media installations using handmade paper, found natural materials and native seeds. Her multi-part structures invite participation from visitors, schoolchildren, wildlife and the weather and are designed for museums, parks and unconventional sites throughout the USA, Japan, Philippines and Taiwan.
Jane Ingram Allen often works with artists, her son Chris Allen - a jazz composer and trombonist, and volunteers of all ages to create her site-specific installations. She often combines these with workshops to teach participants how to make handmade paper using locally available plant materials. Public projects have involved placing colorful bird sculptures representing a wide variety of species made from handmade paper pulp for temporary art installations along buildings in downtown Schenectady, NY and other locations.
Other projects such as "Disappearing Boundary" (1996) consisted of a fence made of fallen branches and handmade paper with wildflower seeds in it. The paper components were designed to dissolve in the rain over time, dropping seeds along a plowed line of earth beneath the fence structure. "The line of wildflowers that emerges will also gradually disappear as theyHow does art inform technology to progress?
How does technology inform art?
What resinates with artist when creating art about nature?
Why are artists drawn to environmental issues?
What experience do artist need in order to have a connection to nature?
Will science alone be able to solve the issues of the environment?
How will art assist in the aid of the environment?