The term Leitbild was introduced in the first weeks of the term. Leitbild is a German word. Its most general meaning is: ”Leit-Bild – ein Bild, das leitet”: a guiding image. There are two components of leitbild, guidance or goal or orientation and the image or action or change. A leitbild creates a shared overall goal, offers orientation toward one long-term overall goal, and provides a basis for different professions and disciplines to work in the same direction. Leitbild refers not only to a common vision of actors. It relates also to the concept of autopoesis (from the Greek: self-organization) functioning as an interpersonal stabilizer. Developing the leitbild is a consensus-building process of is multidisciplinary and uses inputs from scientists, agency managers, and the community stakeholders. A desirable process would use historical information, such as aerial photographs, maps, interviews, dendochronology, hydrologic records, and biological surveys, as well as study of undisturbed reference rivers. Rogers (2006 River Research & Applications 22:269-280) labeled this activity as the “real river management challenge.”
So I offer the Leitbild as a critically important concept of Stream Habitat Management. As we build this activity we need to build on our knowledge structure and develop paradigms and principles. Boulton et al. (2008) in River Futures offer ten very broad tenets of successful integrative river science and management. Bunn and Arthington (2002) develop four principles related to altered flow. Firstly, flow is a major determinant of physical habitat in streams, which in turn is a major determinant of biotic composition; Secondly, aquatic species have evolved life history strategies primarily in direct response to the natural flow regimes; Thirdly, maintenance of natural patterns of longitudinal and lateral connectivity is essential to the viability of populations of many riverine species; Finally, the invasion and success of exotic and introduced species in rivers is facilitated by the alteration of flow regimes.
Concepts include such stalwarts as longitudinally ordered zones, river continuum, hydrogeomorphic patches, hydraulic habitat units, hydrologic stream types, hierarchical habitat templates, population regulation, trophic complexity, nutrient spiraling, floodplain connectivity, natural flow regimes, hydraulic geometry, microbial loop, fluvial channel evolution, and others. From these concepts the goal of stream science is to develop hypotheses, theories, postulates, and principles with the ultimate goal of setting up a system of laws of stream science. Principles may be borrowed from other disciplines, such as application of Bernouli’s principle for fluid flow. We have used this principle to approximate velocities and depths in river channels. The conservation of energy, which states that the for stead flow the sum of all forms of mechanical energy in a fluid along a streamline is the same at all points on that streamline. This requires that the sum of kinetic and potential energy remains constant.
But at this point in our course of study it is time to describe the principles that are specific to stream habitat management, a cross-disciplinary endeavor. Management requires technical skills, human skills, and conceptual skills to function in planning, organizing, directing, and controlling activities. The best stream habitat managers will be those with great technical and human skills and the ability to adopt innovative concepts and ideas that are appropriate to the Leitbild.
Please post a comment here describing your top 1, 2, or 3 key principles of stream habitat management. Comment on suggestions of others and try to keep this effort up until we break for Thanksgiving.
1 comment:
I'll give this a shot. One principle I would suggest is:
1. Acknowledge your assumptions and challenge them.
Thus far in the semester we have seen how assumptions led to disastrous management outcomes. Case in point would be the example of the Trinity River presented by Trush et al. (2000). When the Trinity was impounded, managers established a minimum flow release to create what they assumed was good salmonid habitat. Based on their assumptions they theoretically provided ample habitat; however, they failed to understand the importance of flows from snow melt that created and refreshed habitats. These flows were muted by the impoundment. They also failed to understand the role of variability in the flow regime. They assumed variability was not ecologically important and thus created a homogenous flow regime that allowed riparian vegetation to expand and grow to the point that it influenced channel morphology.
In the discussion I led we also addressed assumptions. One assumption we addressed was that streams are linear conduits of nutrients from terrestrial ecosystems to the ocean. Merz and Moyle (2006) demonstrated that nutrients can also travel in the opposite direction, from ocean to terrestrial ecosystems 100s of miles upstream, using salmon as biological vector. In agricultural management of California’s central valley, supplying anthropogenic fertilizers is common. However, it may be more cost-effective to remove barriers to salmon migration.
On what assumptions are we basing our current management? I think that at every point in management and at the beginning of every study we should clearly state our assumptions and then do our best to challenge them.
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