Glen Canyon Dam Adaptive Management Program Administrative History

Even unmanaged ecosystems are characterized by combinations of stability and instability and by unexpected shifts in behavior from both internal and external causes. That is even more true of ecosystems managed for the production of food or fiber. Data are sparse, knowledge of processes limited, and the act of management changes the system being managed. Surprise and change is inevitable. Here we review methods to develop, screen, and evaluate alternatives in a process where management itself becomes partner with the science by designing probes that produce updated understanding as well as eco- nomic product.

Renewable natural resources provide important contributions to food, fiber, and recreation in many parts of the world. The economies of some regions a r e heavily dependent on fisheries and forestry, and consumptive use of wildlife (hunting) is a traditional recreational pastime across Europe and North America. The management of renewable resources usually involves public agencies that are responsible for harvest regulation, and often production enhancement, so as to provide sustainable yields into the long-term future (resource husbandry). The track record of such agencies has been spotty: many resources have been mined to low levels before effective harvest regulation could be developed, while others have been managed so conservatively as to miss major harvesting opportunities.

Three key features of renewable resources have made them difficult to manage. First, sustainable production depends on leaving behind a "capital" stock after each harvesting, and there are definite limits to the production rates that this stock can maintain. Second, harvesting is normally undertaken by a community or industry of harvesters whose activities (investment, searching, etc.) are not completely monitored or regulated, so that dynamic responses, such as overcapitalization of fishing fleets, are common. Third, the biological relationships between managed stock size and production rates arises through a complex interplay between the organisms and their surrounding ecosystem; for any particular population, this relationship cannot be predicted in advance from ecological principles and must, instead, be learned through actual management experience.

This book is on the various methods of environmental impact assessment as a guide to design of new environmental development and management projects. This approach surveys the features of the environment likely to be affected by the developments under consideration, analyses the information collected, tries to predict the impact of these developments and lays down guidelines or rules for their management.

This book is concerned with practical problems, e.g. development in Canada, the management of fisheries, pest control, etc. It is devoted to a general understanding of environmental systems through methods that have worked in the real world with its many uncertainties. It does not reject the concept of environmental impact analysis but rather stresses the need for fundamental understanding of the structure and dynamics of ecosystems.

An ecological survey of the riparian zone of the Colorado River from Lees Ferry to the Grand Wash Cliffs, Arizona, was initiated between 1 June 1974 and 30 June 1976. The purposes of this study were:

First, to describe vegetational changes as a result of the controlled water release from Glen Canyon Dam, second, preparation of a vegetation map from river level up to the 500 foot contour level, third, to describe population densities, home ranges, and demography of important vertebrates, fourth, to inventory insects of the riparian zone, fifth, to describe the distribution and impact caused by feral burros, and sixth, to describe the interrelationships of humans with the biota.

The major findings include the following: (1)The construction of Glen Canyon Dam has permitted the development of a new riparian community. This community is characterized by salt cedar, arrowweed, coyote willow, desert broom, and seep willow. (2) Botanical investigations in the riparian and adjacent habitats discerned the presence of 807 species of vascular plants representing 92 families. Also, two species, previously undescribed, Flaveria mcdougallii and Euphorbia rossii, are presented. (3) An accessment of important vertebrates and insects revealed: a) rodent communities on beaches tend to be less productive and less stable than those rodent communities of the terrace areas, b) Peromyscus eremicus appears to be the most successful small mammal in the riparian zone, c) rodent survivorship is very low and suggests a nearly annual population turnover, d) 178 species of birds utilize the riparian zone, of these 41 breed there, e) the most common bird species is the Lucy's Warbler, f) over 12,000 insect specimens in 20 orders and 247 families were collected and prepared, g) insect production on the exotic salt cedar fluctuate dramatically in comparison to insect production on dominant native plants. (4) Feral ass distribution was found to be greater than previously believed. It has been determined that the expanding feral ass populations are systematically destroying riparian and desert habitats within the study area and their immediate removal is suggested. (5) Human impact seems to be a function of visitor activities and the specific biotic sensitivity of the use area rather than a function of the total number of users. (6) In 1974, 395 different campsites were reported between Lees Ferry and Pierce's Ferry. In 1975, 350 different campsites were used. (7) Establishment and maintenance of an inner canyon trail system, the removal of all future human fecal waste material and education of river users may be the means to minimize habitat destruction rather than just setting a user-day limit.