January 2008, Vol. 20, No.1

Research Notes

Genetically Engineered Corn May Harm Stream Ecosystems

Biofuels are getting the spotlight for producing fewer greenhouse gas emissions when compared to traditional fossil fuels. But the genetically engineered corn produced to create biofuels is itself raising questions on just how ecologically friendly biofuels are.

Ecological impacts of genetically engineered corn are particularly important because of increased corn demand created by biofuels production, according to a U.S. National Academy of Sciences news release.

A new study indicates that a popular type of genetically engineered corn — known as Bt corn — may damage the ecology of streams draining Bt cornfields in ways that have not been previously considered by regulators. The study, which was funded by the National Science Foundation (NSF), is reported in the Oct. 8 Proceedings of the National Academy of Sciences.

This study, according to NSF, provides the first evidence that toxins from Bt corn may travel long distances in streams and may harm stream insects that serve as food for fish. These results compound concerns about the ecological impacts of Bt corn raised by previous studies showing that corn-grown toxins harm beneficial insects living in the soil.

Licensed for use in 1996, Bt corn is engineered to produce a toxin that protects against pests, particularly the European corn borer, the news release notes. Bt corn now accounts for approximately 35% of corn acreage in the United States, and its use is increasing.

“Overall, our study points to the potential for unintended and unexpected consequences from the widespread planting of genetically engineered crops,” said Jennifer Tank, Galla Associate Professor at the University of Notre Dame (Ind.) and a member of the team studying Bt corn.

“The exact extent to which aquatic ecosystems are, or will be, impacted is still unknown and likely will depend on a variety of factors, such as current ecological conditions, agricultural practices, and climate [and] weather patterns,” Tank said.

James Raich, an NSF program director, added that “increased use of corn for ethanol is leading to increased demand for corn and increased acreage in corn production. Previous concerns about the nutrient enrichment of streams that accompany mechanized row-crop agriculture are now compounded by toxic corn byproducts that enter our streams and fisheries, and do additional harm.”

For more information, contact Raich at jraich@nsf.gov or Tank at tank.1@nd.edu 

Australia’s Rainfall Offers Glimpse of Future

The ongoing reductions in southern Australia’s rainfall in winter and spring have been magnified by increased temperatures. Wenju Cai of the Commonwealth Scientific and Industrial Research Organisation (CSIRO; Campbell, Australian Capital Territory, Australia) said the latest modeling by the Intergovernmental Panel on Climate Change (IPCC) predicts a 5% to 15% rainfall decrease by 2070.

“There is no longer any doubt that climate change caused by increases in greenhouse gases is influencing seasonal shifts in rainfall patterns,” Cai said. “Our results provide strong evidence that rising temperatures, hence increasing evaporation due to the enhanced greenhouse effect, impact on Australia’s water resources, in addition to any reduction in rainfall.”

What could partially offset this is an increase in summer rainfall in southeastern Australia, as simulated by some IPCC models, according to a CSIRO news release. This increase is consistent with a large Tasman Sea warming where the ocean warming rate is the fastest in the Southern Hemisphere.

Cai said climate models also indicate that about half of the rainfall decline in southwest Western Australia can be directly linked to increases in atmospheric greenhouse gas levels. He said there are also likely to be further declines in rainfall in northwest Western Australia in the future.

Rainfall shifts and seasonal variability in the Australian region had three engines, according to Cai: the El Niño–Southern Oscillation phenomenon in the Pacific Ocean; a similar feature in the Indian Ocean known as the Indian Ocean Dipole; and the Southern Annular Mode, a pattern in the Southern Ocean that promotes air flows towards southeast Australia.

“I see two important challenges for Australian scientists in this research field, the first being the realistic simulation of the drivers linking ocean and atmospheric conditions and seasonal rainfall,” Cai said. “The second is the development of more powerful models that will narrow the uncertainties of climate modeling and develop more specific projections for separate regions and [centers] within Australia.”

For more information on CSIRO’s research on climate change, see www.csiro.au/csiro/channel/pchbm.html.  

Researchers To Study Effect of Floods on Estuaries

The sediment discharge in northwestern U.S. rivers appears to be increasing, scientists say, and researchers at Oregon State University (OSU; Corvallis) are wondering how this might effect coastal estuaries during winter flood events.

A team of OSU researchers will use a $620,000 grant from the U.S. Environmental Protection Agency to study the sediment deposits and the effects, and to document the recovery of the benthic communities — communities of organisms that live in and on the bottom of the ocean floor.

The increase in sediment discharge, according to an OSU news release, is due to an increasing number of intense precipitation events; changes in the landscape through logging, agriculture, and development; the evolution of complex river systems into channels; and the drainage of tidal marshes through diking and other human influences that reduce the buffering capacity of natural systems to absorb sediment load.

The researchers will study the impact of increasing sediment loads on worms, clams, and small crustaceans — estuarine species that represent important prey for Dungeness crab, fish, and seabirds, according to Anthony D’Andrea, an assistant professor in the OSU College of Oceanic and Atmospheric Sciences and a co-principal investigator on the study.

“This is the first step in assessing the risks to estuaries posed by extreme rain events in the region,” D’Andrea said. “Muddy, rain-swollen rivers are a signature characteristic of the Pacific Northwest, yet the impact of flood sedimentation events on benthic communities is poorly understood.”

The OSU researchers also will track the response of native and nonindigenous species to sedimentation events to see if this type of disturbance allows non-native species to gain a foothold and thrive at the expense of native species, the news release notes.

D’Andrea and co-principal investigator Rob Wheatcroft will stage their experiment at Netarts Bay near Tillamook, Ore., because it has no river system, and the organisms in the tidal flats have not previously been exposed to constant flooding.

“Studying benthic communities in established flood plains is tricky,” D’Andrea noted, “because the resident organisms may already be adapted to flood events and have a quicker recovery. Starting from scratch will give us better baseline data and lead to a more accurate predictive model.”

At press time, the researchers were planning to add a layer of fine sediment from local watersheds onto study plots in Netarts Bay in December and compare them with nearby control plots. A subset of those plots will be subjected to a second simulated sedimentation event 40 or 50 days later to see if multiple events have different impacts. December and January are peak rainfall months for Tillamook County, which has seen increasing precipitation problems in recent years.

Between 1910 and 1950, the Wilson River entering Tillamook Bay experienced three total peak runoff events. Since 1960, the Wilson has seen 17 peak events, including six in the 1990s. Damage from these floods during a 6-year period alone topped $60 million.

Likewise, major sedimentation events have been increasing in Pacific estuaries, and sediment deposits of up to 12 cm thick have been documented.

For more information, contact D’Andrea at dandrea@coas.oregonstate.edu