|Shields Jr, Fletcher|
Submitted to: Ecological Restoration
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2004
Publication Date: 6/1/2005
Citation: Shields Jr., F. D., Knight, S. S., Cooper, C. M. 2005. Stream ecosystem restoration: Is watershed treatment effective without instream habitat rehabilitation? Ecological Restoration. 23(2):103-109. Interpretive Summary: Stream ecosystems in agricultural watersheds are often severely degraded by erosion and sedimentation. Scientists differ about the relative importance of treatments that are applied to local stream reaches and those applied across entire watersheds, and thus there is uncertainty regarding design of effective restoration strategies. Three severely damaged stream reaches in northern Mississippi watersheds were sampled over 11 years. All three experienced improved water quality and physical habitat due to watershed-level treatments, but one of the three was also treated using structures and vegetation applied specifically to the studied reach. These reach-scale treatments were produced by slightly modifying traditional channel erosion controls. Watershed-scale treatments alone had negligible effects on stream fish communities, but when combined with instream treatments, produced major shifts toward lightly-degraded stream conditions. These findings show that modifying traditional stream channel erosion control practices to include environmental criteria can be effective over the long term.
Technical Abstract: Opinions differ on the relative importance of watershed-scale and local, instream measures for restoring stream ecosystems. Presented are observations over an 11-year period of two severely incised, warmwater streams in northwestern Mississippi. Both streams were channelized and experienced rapid channel erosion between 1963 and 1985. More than $20 million were expended on erosion control measures throughout the watersheds between 1985 and 2000, and sediment yields declined by factors of about three to six. Instream habitat rehabilitation structures were constructed and willows were planted along a one-km reach near the mouth of one of the watersheds in 1992. Fish and physical aquatic habitat data were collected within this treated reach and in untreated reaches in both watersheds. Effects of rehabilitation on habitat and fish communities were found to be positive in both the short and long term. After 10 years, mean water depth in the reach subjected to rehabilitation was more than twice as great as for the untreated reaches. Eleven years after rehabilitation, the treated reach supported 60% more species and an order of magnitude more fish biomass per unit area than the untreated reaches. Watershed measures and improvements in water quality must be coupled with instream and riparian zone measures in order to achieve recovery of habitat-limited warmwater stream fish populations.