Introduction

Let's step back for a moment and think about general lessons from our analysis of northern spotted owl population dynamics.

1. Even with the huge effort that has been expended it is difficult to be sure that current forest management plants are sufficient to ensure persistence.

2. Long-lived animals are buffered from immediate extinction because of the long life span, but that also means that our understanding of the population dynamics is very limited.

3. Understanding something about population dynamics is critical to making intelligent management choices.
   1. Focus management efforts on policies that will increase juvenile survivorship and fledging success.

   2. Protection of unoccupied, suitable habitat is critical to population persistence.

   3. Population/metapopulation is the appropriate unit of management.

This overview of the northern spotted owl has also introduced you to one of the most detailed population viability analyses available for any species, plant or animal. In fact, most population viability analyses have focused on ``charismatic megavertebrates,''¹ e.g., the grizzly bear, the northern spotted owl, and the red-cockaded woodpecker.

The focus on these species is often justified by arguing that they are ``umbrella species,'' whose protection will enhance the protection of many other species less immediately attractive to the general public. There are, however, several reasons protecting ``umbrella species'' may fail to protect other species of concern:

• Protection of large expanses of habitat will not necessarily ensure that all plant or animal species in that area will persist. Successional change or the invasion of exotics may lead to exclusion of other components of the community without endangering the charismatic megavertebrates that were the original target. Plants and invertebrates (and small mammals and small cold-blooded vertebrates for that matter) may require management even within a large ecosystem that is being protected for use of a charismatic megavertebrate.

• Many plant and invertebrate species are found in highly localized populations in the absence of any association with these species, e.g., Texas wild rice (Zizania texana), caliente farewell-to-spring (Clarkia tembloriensis subsp. calientensis).

  Bay checkerspot Euphydryas editha bayensis is restricted to serpentine outcrops in the San Francisco Bay area, which lost all its large vertebrates by the turn of the century.

• Plants and invertebrates (and small mammals and small cold-blooded vertebrates for that matter) share few of the life-history characteristics that put large vertebrates at risk of extinction. They can exist in much smaller areas than large vertebrates, e.g., urban and suburban corridors. Techniques for management of charismatic megavertebrates may or may not apply to them.

• Areas that are important for protection of diversity in one group of organisms are not necessarily the same as those that are important for protection of diversity in another group, unless very large areas are protected. We'll discuss the problem of identifying ``hotspots'' later in the course.