Defining A Healthy Riparian Area Dr. Karl Wood, Director Water Resources Research Institute Dr. Terrell Baker, Riparian Ecologist New Mexico State University Las Cruces, NM
Webster’s Definition of “Health” 1. Physical and mental well-being; 2. Soundness; 3. Freedom from defect, pain, or disease; 4. Normality of mental and physical functions How does this definition apply to riparian areas?
What are some other terms or phrases used to describe watersheds? Functioning and Non-Functioning Proper Functioning Condition Impaired At Risk Upward Trend Downward Trend Stable Sustainable
Some Related Definitions Rangeland Health (Natural Research Council 1994) “The degree to which the integrity of the soil and ecological processes of rangeland ecosystems are maintained” Forest Health (U.S. Forest Service) “A condition wherein a forest has the capacity across the landscape for renewal, for recovery from a wide range of disturbances, and for retention of ecological resiliency, while meeting current and future needs of people for desired levels of values, uses, products, and services” Riparian Health (Need Citation) “” Feds have some 70 plus definitions
Compare to Wetlands • Lots of science • Tight definition (at least comparatively) • Regulatory authority
Why this vision of everything being black or white, and why are these definitions bothersome? 1. They convey that everything is either right or wrong. 2. They infer that nature gives values to society. 3. They also infer that society’s values are mutual across all lands, both public and private
Most people have an intuitive idea of what constitutes a healthy riparian area; at least, they believe they can recognize an unhealthy one when they see it. Using “health” to describe watersheds is probably inappropriate.
Riparian Conditions Fall Along A Continuum! How can we express that continuum? Ecosystem Succession or the Sere is a good start!
Concept of the Sere Example developed in North America by H.C. Cowles and F.E. Clements about 100 years ago Climax Conifers Deciduous trees Shrubs Perennial grasses and forbs Climate Annuals Mosses Lichens Bare Rock Soil depth and richness Time
Conifer invasion of a meadow
Insects and disease spread in a crowded forest
Concept of the Sere Climax Shrubs Perennial grasses and forbs Climate Annuals Mosses Lichens Bare Rock Soil depth and richness Time
Concept of the Sere Perennial grasses and forbs Climax Climate Annuals Mosses Lichens Bare Rock Soil depth and richness Time
Concept of the Sere Climate Lichens Climax Bare Rock Soil depth and richness Time
Would A Society Ever Want To Maintain Bare Rock Or a Very Low Seral Stage Riparian Area? Example: Irrigation Ditches
General Comments On Ecosystem Succession • Movement towards climax is called succession • Movement away from climax is called retrogression (e.g. Desertification) • The kinds of animals different in each seral stage. • The climax seral stage usually does not represent the greatest species diversity of plants and animals. • Subclimax seral stages may be maintained by continuous or discontinuous perturbations such as fire, grazing, hurricanes, etc. • Multiple equilibrium communities and complex successional pathways may be possible within a sere.
Explanations of “ecosystem succession” have been modified and expanded by: Gleason 1926 – recognized individual species differences Tansley 1935 – proposed more than one climax for a site Watt 1947 - identified the importance of patches and disturbance cycles Egler 1954 – noted that species did not always invade but were present and increased Pickett 1976 – recognized importance of natural selection and disturbance Connell and Slatyer 1977 – proposed facilitation, tolerance, and inhibition Grime 1979 – proposed ruderal, competitive, and stress-tolerant stages Huston and Smith 1987 – demonstrate 5 successional patterns: sequential succession, divergence, total suppression, convergence, and pseudo- cyclic replacement Shugart 1984 – claimed mechanistic rather than deterministic processes Westoby 1989 – explained state-and-transition models or thresholds Oliver and Larson 1990 – allowed for chaotic or non-equilibrium cycles
Tomanage a riparian area, managers need to know: 1. What is the potential or climax seral stage of the riparian area? 2. What is the present seral stage of the riparian area? • Is it all the same or are there different seral stages in different parts of the riparian area? 3. Are there several acceptable seral stages and a preferred seral stage of the riparian area and/or its parts? • 4. Can the preferred seral stage be achieved with the present technology, time, legal, political, and economic constraints?
Concept of the Sere Conifers Most choices are here! Deciduous trees Shrubs Perennial grasses and forbs Climate Annuals Mosses Lichens Bare Rock Soil depth and richness Time
“If the prime objective is wood products, we may continue to overgraze, letting in the woodland and sacrificing watershed values. If on the other hand the prime objective is watersheds, we should restore grass, which all the evidence indicates is a better watershed cover than either brush or woodland.” Aldo Leopold
Steps for Watershed Management Preliminary Assessment and Surveillance
Preliminary Assessments and Surveillance “Nothing in nature is isolated. Nothing is without reference to something else. Nothing achieves meaning apart from that which neighbors it.” Johann Wolfgang von Goethe “There is something fascinating about studies of science. One gets such wholesale returns of conjecture out of such trifling investment of fact.” Mark Twain
Steps for Watershed Management Preliminary Assessment and Surveillance Goal Setting Prioritization and Targeting Watershed Planning – develop document with roles and implementation strategy Implementation Performance evaluation
For any given response variable such as: Erosion, Runoff, Evaporation, Stream Temperature, Sediment Load, Arsenic Content, Plant Growth, Insect Populations, etc. Questions should be asked: 1. What are the natural levels with variations between hours, days, months, and years? 2. What are maximum potential levels? 3. What are the tolerable levels to sustain the preferred seral stage? 4. What are the desirable levels? • Are the desirable levels achievable with present technology, time, legal, political, and economic constraints?
Conclusions Nature abhors a void Nature abhors topographical prominence Nature abhors a crowd Natural changes are often dynamic and catastrophic with unpleasant consequences for humans Human changes of nature may be dynamic and catastrophic, or static, controlled, predictable, and beneficial to humans, wildlife, and watersheds Human influence is most probable for avoiding catastrophes and assuring ecological, social, and economic stability.
Conclusions A Healthy Watershed = preferred seral state is attained Sustainability = preferred seral stage is maintained against the processes of succession and retrogression, including invasions, especially by exotics
Thank you! Thank you!