The need for a volume dealing with the concept of indicator organisms became evident during a symposium on the subject, organized by the present editors for the Southern California Academy of Sciences. Ques tions were posed about the appropriate uses of indicator organisms and the "rules" governing the application of the indicator concept to particular problems. For example, how does one distinguish true indicators from biological anomalies? What kinds of organisms can appropriately be associated with conditions and events at various scales in time and space? To what extent does one species represent other species in the same environmental setting? Can the indicator concept be applied to the context of modern sampling and analytical technology? How can anthropogenic perturbations be distinguished from natural phenomena? How can unlike matrices from differing data bases with differing scales best be matched? Such questions are especially pertinent in today's research environment. The use of indicator organisms, while certainly not new, is the corner stone for much scientific research. In the past two decades, indicator organisms have played increasingly important roles in the development and implementation of public policy. In particular, indicator organisms are being used to describe local environments and natural or anthropogenic perturbations to them, although there are pitfalls and problems associated with those usages. A growing number of nonbiologists, including physical oceanographers, find indicator organisms helpful, and sometimes essential, to their re search.

The Chang Tang, the vast, remote Tibetan steppe, is one of the most forbidding places on earth. Yet this harsh land is home to a unique assemblage of large mammals, including Tibetan antelope, gazelle, argali sheep, wild ass, wild yak, wolves, snow leopards, and others. Since 1985, George B. Schaller and his Chinese and Tibetan co-workers have surveyed the flora and fauna of the Chang Tang. Their research provides the first detailed look at the natural history of one of the world's least known ecosystems.

This book is unique in providing a global overview of alpine (high mountain) habitats that occur above the natural (cold-limited) tree line, describing the factors that have shaped them over both ecological and evolutionary timescales. The broad geographic coverage helps synthesise common features whilst revealing differences in the world's major alpine systems from the Arctic to the Tropics. The words "barren" and "wasteland" have often been applied to describe landscapes beyond the treeline. However, a closer look reveals a large diversity of habitats, assemblages and individual taxa, largely connected to topographic diversity within individual alpine regions. The book considers habitat-forming factors (landforms, energy and climate, hydrology, soils, and vegetation) individually, as well as their composite impacts on habitat characteristics. Evolution and population processes are examined in the context of the responsiveness / resilience of alpine habitats to global change. Finally, a critical assessment of the potential impacts of climate change, atmospheric pollutants and land use is made and related to the management and conservation options available for these unique habitats.