by Tim Harrigan
George Vellidis believes that healthy aquatic ecosystems are an important part of maintaining a sustainable animal production system — in Michigan or anywhere else.
Vellidis, a professor of biological and agricultural engineering at the University of Georgia, emphasizes several key points, including:
- healthy aquatic ecosystems are resilient,
- because management is so important, farm size alone is not a good indicator of risk to water quality,
- negative impacts on aquatic ecosystems are measurable, and
- farming systems can be designed and managed for low environmental impact.
"Healthy aquatic ecosystems rebound from seasonal water level fluctuations and flood plains and wetlands provide flood control benefits," he said. "They support a diversity of fish, wildlife and plant life."
Vellidis described a study of two streams on the same farm with similar characteristics: one had been fenced to restrict animal access while the other was degraded by cattle access. In his comparison of stream impacts and ecosystem integrity he measured the range and diversity in the streams of benthic macro invertebrates such as snails, worms and stoneflies. These organisms differ in their tolerance to amount and types of pollution. Streams that are degraded by stream bank erosion and sedimentation from animal access, oxygen depletion from runoff of manure pollutants or other stressors show clear differences. There were fewer indicator organisms—both in number and type—in the degraded stream.
Livestock farms that are expanding in size, or building larger facilities, have a greater potential for adverse impacts on the environment, but they are less likely to have a problem because of the intense management practices necessary on larger farms. Management appears to be more important than farm size or type of operation. Larger, modern farms generally confine livestock under a roof so there is little chance of runoff from animal holding areas. Similarly, well-managed pasture-based systems that maintain a dense, vegetative cover, observe setbacks and restrict animal access to streams and other environmentally sensitive areas can be a community asset with minimal adverse impacts. In his work in developing sustainable agroecosystems, Vellidis demonstrated the value of vegetative covers and riparian buffers in removing nitrates and other pollutants from agricultural runoff. This landscape approach to creating natural barriers to overland flow, and an emphasis on controlling nonpoint source pollution are key components in maintaining sustainable aquatic ecosystems.