Invasion biologists – including those dealing with invasive plants – can learn something from the highly disturbed habitats that aquatic
ecologist Rocky Smiley studies. Rocky works for the United States Department of Agriculture – Agricultural Research Service. Over the past 19 years he has studied fishes, amphibians, and reptiles of channelized agricultural streams in the South and Midwest. His current research evaluates ecological impacts of agricultural conservation practices and restoration designs for these degraded streams.
In recent work in Ohio, Rocky had to trudge through stagnant, silted agricultural drainage ditches with chest waders in the summer heat accompanied by deer flies and mosquitos. Can any work be worth that kind of misery? As it turns out, yes, it can be.
Over the past 200 years, the agricultural practices of stream channelization and habitat modification have damaged or destroyed more than 80% of the riparian corridors in North America. There is a worldwide decline in fish, amphibian, and reptile populations. Relating the two phenomena is not a stretch.
These kinds of changes raise huge questions for environmental scientists, the biggest question being: How do we deal with the imperfect world of massively altered ecosystems? Do we focus on protecting high-quality habitat? Or can we salvage something from ecosystems that many have given up for nearly dead?
Research by Rocky and his colleagues offers hope that even highly degraded ecosystems have something to offer. And, according to their research, even modest changes could markedly improve the quality of aquatic habitat in degraded agricultural streams.
For example, Rocky and his colleagues examined agricultural drainage ditches in Ohio and Indiana – looking at riparian habitat, geomorphology, instream habitat, water chemistry, and fishes. Initial results indicated fish communities in these degraded streams are more strongly influenced by instream habitat (i.e., water depth, velocity, substrate types) than riparian habitat or water chemistry. Follow-up assessments of relationships between fishes and water chemistry found that fish communities were weakly influenced by water chemistry. These results suggest that the current conservation focus on reducing nutrient, pesticide, and sediment loads in agricultural drainage ditches will not benefit the fishes within these streams.
Indeed, Rocky’s ecological assessments of filter strips and pesticide reduction practices have confirmed that these practices have little to no influence on the habitat and fishes in drainage ditches. (That bears repeating in capital letters: FILTER STRIPS AND PESTICIDE REDUCTION PRACTICES APPEAR TO HAVE NO INFLUENCE ON THE HABITAT AND FISHES IN DRAINAGE DITCHES.) Instead conservation and restoration plans need to incorporate practices capable of improving instream habitat.
Rocky notes “I have been surprised by the numbers and different types of fishes that I have captured in agricultural drainage ditches. My study sites are small streams and many dry up in the summer. Yet many fishes found in agricultural drainage ditches are those typically found in headwater streams in the Midwest.”
What does this mean for agriculture and the management of agricultural ditches? It means “these small streams should not be considered ecological sacrifice areas for agriculture.” Instead, as Rocky notes, “drainage ditch management needs to shift from a singular focus on agricultural drainage to a more holistic focus that recognizes ditches as streams capable of providing fish habitat, drainage, and other ecosystem services.”
Additional details can be obtained from the following articles:
Smiley, P. C. Jr., K.W., King, R.B. Gillespie, and N.R. Fausey. 2012. Influence of watershed scale atrazine reduction practices on pesticides and fishes within channelized agricultural headwater streams. Journal of Sustainable Watershed Science and Management 1: 61–75. (Click on link to free access article.)
Smiley, P. C. Jr., K. W. King, and N.R. Fausey. 2011. Influence of herbaceous riparian buffers on physical habitat, water chemistry, and stream communities within channelized agricultural headwater streams. Ecological Engineering 37: 1314-1323.
Smiley, P. C. Jr., R. B., Gillespie, K. W., King, and C. Huang. 2009. Management implications of the relationships between water chemistry and fishes within channelized headwater streams in the midwestern United States. Ecohydrology 2: 294-302.
Smiley, P. C. Jr., F. D. Shields Jr., and S. S. Knight. 2009. Designing impact assessments for evaluating the ecological effects of conservation practices on streams in agricultural landscapes. Journal of the American Water Resources Association 45: 867-878.
Smiley, P. C. Jr., R. B., Gillespie, K. W., King, and C. Huang. 2008. Relative contributions of habitat and water quality to the integrity of fish communities in agricultural drainage ditches. Journal of Soil and Water Conservation 63: 218A-219A.