Invasion biologists – including those dealing with invasive plants – can learn something from the highly disturbed habitats that aquatic
Researcher Rocky Smiley Conducting Research in Drainage Ditch
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., 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.
j3w3lw33d said
Great article. It looks that these agricultural drainage ditches are the place to go to monitor habitat health in the midwest. It would be interesting to watch a drainage ditch in a vacant field as a test site in comparison to an active field.
buckeyebret1 said
No doubt they have value, but this oversimplifies the issues. The concerns about nutrient loads are not just for stream fishes in the small streams. Nutrient loads impact the dead zone in Lake Erie, harmful algal blooms in public waters, and keystone species like gizzard shad in reservoirs and large rivers. Wouldn’t want to abandon filter strips, etc. but this does have implications in designing restoration plans.
Pamela Zevit said
The challenge has always been getting these anthropogenically altered
habitats recognized for being habitat (even though many were former wetlands or stream channels). Here in BC they also can provide
critical habitat for at risk fish and amphibian species (as well as a
lot of other important critters). however with recent federal changes
to some of the overarching legislation that used to protect those
habitats now gone it is now even more challenging to ensure they
remain protected or appropriate best practices employed in management.
Add invasive species (like introduced Phalaris spp) and the pressure
from agricultural sectors to maintain field drainage and do ongoing
and highly invasive dredging and ‘cleaning’. Yet we also undertake
these same invasive practices to restore many waterways and wetlands – with demonstrable success. Then you have species like Oregon Spotted Frog, of which southwest BC has the only handful of Canadian
populations which will actually use these more disturbed and somewhat
marginal habitats (including reed canary grass) though not as a preferred habitat. Talk about a situation of trying to balance all these issues!
Pamela
Pamela Zevit, R.P. Bio
Adamah Consultants
Coquitlam BC Canada
604-939-0523
Re-connecting People & Nature