Systems theorists have been divided by a common language. Disparate definitions of terms for key concepts relating to dynamic systems have historically impeded communication about the attributes of those systems. Resilience, for example, has sometimes been quantified as inversely proportional to the time required for a system to return to its former state after perturbation. Brian Walker and David Salt, along with their colleagues in the Resilience Alliance ( www.resalliance.org), prefer to think of resiliency more in terms of “getting back, rather than bouncing back.” And what exactly does that mean? After an industry colleague implored, “Just give me five good case studies, then I'll know what you mean,” Walker and Salt responded with Resilience Thinking, an excellent book that will very likely influence the way many of us perceive and cope with change.

Brian Walker, born and raised in Zimbabwe, was for many years the chief of Australia's Commonwealth Scientific and Industrial Research Organisation's Division of Wildlife and Ecology. He is now the science program director of the Resilience Alliance, a small group of eminent international ecologists, economists, and ecosystem scientists. Inspired by C. S. “Buzz” Holling, these scientists have worked together since 1999 to increase the resiliency, and thus the sustainability, of social-ecological systems, and to communicate that science to the public. Walker said he felt “the specter of colleagues peering over his shoulder and pointing at unsubstantiated statements and loose definitions” (p. xiii) while he was writing this book, which prompted him to partner with experienced science writer David Salt “to remove jargon and boring qualification” (p. xiii). The result is vivid, comprehensible, persuasive, and plainly written, though not compromised by oversimplification.

The purpose of Resilience Thinking is captured on page 14: “Resiliency thinking is about understanding and engaging with a changing world. By understanding why the system as a whole is changing, we are better placed to build a capacity to work with change, as opposed to being a victim of it.” In other words, the goal of this book is to present a framework for understanding the world that increases the likelihood of sustaining Earth's life-support systems through the coming decades of accelerating global and regional change.

Drawing from their work and collaborations with the Resiliency Alliance, the authors explain resiliency thinking with carefully stated definitions, with effective visual metaphors (e.g., the ball-in-the-basin metaphor represents domains of attraction and the thresholds that separate them with a double-looped figure 8 diagramming system evolution and devolution through time), and, most vividly, with five diverse case histories of humans confronting significant change in their environments under very different economic and ecological circumstances.

The case of the drought-stricken farmers of the Goulburn-Broken basin of southeastern Australia is particularly powerful. The farmers pray for rain, but not for so much as to raise saline ground-water up to root level, where it would kill orchard trees or pasture grasses. The problematic salinity of the soil is a result of a history of flood irrigation and removal of native trees. The thinning soil stratum that separates drought disaster from flood disaster mirrors the thinning divide between ecosystem states (here, sustainable farms and irreversible desertification) in the ball-in-the-basin metaphor.

Three other case histories also demonstrate how land use or resource extraction can, with little warning, make the social–ecological system brittle—less capable of absorbing change without shattering into a degraded system. The everglades sawgrass meadows and the sea-grass beds in adjacent coastal waters “self-organized for 5000 years around low levels of nutrients” and were resilient to hurricanes and fire. Now, however, both are threatened by eutrophication caused by agricultural pollution and water diversion. When Caribbean corals are stressed by nutrient loading, hurricanes, warming sea surface temperatures, pollution, or disease, they are not protected from overgrowth by fleshy algae, because grazing fishes and invertebrates have been overfished or have succumbed to disease. Increasing human densities and globalized businesses and recreational activities threaten natural values of the Northern Highland Lake District of northern Wisconsin. In this case history, the authors illustrate how constructing future alternative scenarios can prod native tribes, local businessmen, recreational fishermen, and others invested in the region to share their hopes, concerns, and ideas for sustaining the region's important natural values.

The final case history, of the Kristianstads Vattenrike marshlands in southern Sweden, is an interesting contrast to the other four. Here, human land use, rather than potentially tipping the system into a degraded state, is required for maintaining the favored state. Historical grazing and haymaking are the only ways to prevent the valued marshland from reverting to forest through natural succession.

Each case history is presented with enough historical background to explain how past land-use decisions inadvertently led to the present situation, in which worried or desperate human beings attempt to sustain their livelihoods in damaged and increasingly brittle ecosystems buffeted by disturbances that have ever more unpredictable consequences. The case studies reinforce the generalization that social (human) and ecological systems are inextricably linked: “We are all part of the system.” The authors touch lightly, yet effectively, on three human conditions that underlie our degradation of natural systems: desperation (no choice), greed (willful heedlessness of future consequences), or misunderstanding. This book focuses on ameliorating the third problem.

Another point made forcefully throughout the book is that business as usual, in particular the management goal of optimizing production or extraction of one or a few resources, is not sustainable. Our thinking must expand to see enough of the whole system, including the links across scales, to recognize what drives change and when to embrace natural change, not resist it.

To describe natural change in social–ecological systems, the authors introduce a temporal succession metaphor that was more obscure than the ball-in-the-basin metaphor. The argument, again from the Resilience Alliance, is that systems cycle between four phases: rapid growth, conservation of “capital,” release (“creative destruction”), and reorganization. All possible transitions between ecosystem states occur except for that from release back to conservation. Although the reader can begin to glimpse how this cycle might describe the rise and fall of empires or other social–ecological systems, another book of case histories may be necessary to elucidate these ideas for the general public. Walker and Salt simply introduce the notion that if we are aware of the current phase of our social–ecological system, we may be able to recognize windows of opportunity, or manage relatively graceful transitions from the creative destruction to the reorganization phase.

Walker and Salt have interwoven the five case histories requested by their industry colleague with clear definitions of challenging concepts, and geometric or other, more playful metaphors (e.g., “bugworld” versus “cogworld”). The resulting book should make resiliency thinking come alive, and hopefully, become part of the lives of a broad, diverse audience, including many whose future actions will either rebuild or erode Earth's resiliency. This short, highly effective book may tip us toward the more constructive path.