4.1.1 Demographic significance Confined populations grow more rapidly than populations from which dispersal is permitted (Lidicker, 1975; Krebs, 1979; Tamarin et at., 1984), and demography in island populations where dispersal is restricted differs greatly from nearby mainland populations (Lidicker, 1973; Tamarin, 1977, 1978; Gliwicz, 1980), clearly demonstrating the demographic signi ficance of dispersal. The prevalence of dispersal in rapidly expanding populations is held to be the best evidence for presaturation dispersal. Because dispersal reduces the growth rate of source populations, it is generally believed that emigration is not balanced by immigration, and that mortality of emigrants occurs as a result of movement into a 'sink' of unfavourable habitat. If such dispersal is age- or sex-biased, the demo graphy of the population is markedly affected, as a consequence of differ ences in mortality in the dispersive sex or age class. Habitat heterogeneity consequently underlies this interpretation of dispersal and its demographic consequences, although the spatial variability of environments is rarely assessed in dispersal studies.

Reviews the quantitative tools used in the study of subjects such as biodiversity, resource management and endangered species preservation. Topics covered include population viability analysis, population dynamics, metapopulation models, estimating timing of extinctions, quasi-extinction and more.

A guidebook for hikers, bikers, and equestrians, Hiking from Portland to the Coast explores the many trails and logging roads that crisscross the northern portion of Oregon's Coast Range. Designed to showcase convenient "looped" routes, it also describes complete throughways connecting Portland to the coastal communities of Seaside and Tillamook. Each of the 30 trails described includes a backstory to help users appreciate the history and significance of the places through which they are traveling.