<strong>How</strong> <strong>to</strong> Evaluate Vulnerability <strong>in</strong> Chang<strong>in</strong>g Environmental Conditions? Edited by Roger A. Pielke, Sr. and Lelys Bravo de Guenni
Introduction Roger A. Pielke, Sr. The prevail<strong>in</strong>g paradigm has been that climate varia- exist<strong>in</strong>g paradigm for predict<strong>in</strong>g the future starts from bility and change can be projected decades or even a the global scale and then attempts <strong>to</strong> downscale <strong>to</strong> the century or more <strong>in</strong><strong>to</strong> the future (e.g. IPCC 1996, 2001). regional and local scales; it focuses on averages, is long- <strong>How</strong>ever, for several reasons -e.g. imperfect representerm, and depends on skilful prediction of the future. It tation of the full complexity of the Earth system, non- is therefore much less useful <strong>to</strong> policy-makers (Sarewitz l<strong>in</strong>ear spatial and temporal feedbacks, and imperfect et al. 2000). The <strong>in</strong>-depth discussion of why we need a foresight of human behaviour, it may not be possible <strong>to</strong> <strong>vulnerability</strong> approach that then follows will be illus- assess the range of potential future climate change actrated us<strong>in</strong>g water as an example. curately. Water is an essential component of life both <strong>in</strong> terms Therefore, a newer paradigm requires that our vul- of its quality and quantity; however, this resource is nerability <strong>to</strong> the entire spectrum of <strong>environmental</strong> threats threatened. For example, as reported <strong>in</strong> the Economist be assessed, <strong>in</strong>clud<strong>in</strong>g the rank<strong>in</strong>g of their seriousness. (May 29, 1999, p. 102), while 90% of the world's popula- Once vulnerabilities have been so <strong>evaluate</strong>d, whether or tion have enough water at present, it is estimated that not they can be quantitatively predicted for the future by 2050 more than 40% of the population will face some can then be tested. This part of the BAHC synthesis dis- water shortage (see also Sect. E.6.1). The lack of access cusses this perspective <strong>to</strong> assess risk associated with en- <strong>to</strong> safe water is even more serious. Accord<strong>in</strong>g <strong>to</strong> the same vironmental variability and change. In particular, we article <strong>in</strong> the Economist, develop<strong>in</strong>g countries often have should start the analysis by first assess<strong>in</strong>g <strong>vulnerability</strong>, very limited access <strong>to</strong> safe water supplies. Only about <strong>in</strong>stead of project<strong>in</strong>g possible climate change scenarios, 30% of the residents <strong>in</strong> rural Brazil, for example, cur- and then assess<strong>in</strong>g vulnerabilities based on that subset rently have access <strong>to</strong> safe water. of possible future climates. There is <strong>in</strong>creas<strong>in</strong>g recognition that threats <strong>to</strong> future This is a broader def<strong>in</strong>ition of <strong>vulnerability</strong> than that water quality and quantity are <strong>in</strong>fluenced by a wide va- used by the impacts community. As discussed later, this riety of <strong>environmental</strong> concerns. These concerns <strong>in</strong>volve approach <strong>in</strong>volves first assess<strong>in</strong>g all of the vulnerabilities effects both from natural and human orig<strong>in</strong>. Stahle et al. of an <strong>environmental</strong> (or other) resource <strong>to</strong> environmen- (2000), for example, document a 16th century megatal variability and change. Once these vulnerabilities are drought <strong>in</strong> western North America that dwarfs any determ<strong>in</strong>ed, estimates (with probabilities, if they can be drought s<strong>in</strong>ce then. Wilhite (2000) presents a series of quantified) of what scenarios would cause a vulnerabil- articles that demonstrates the extensive effect of drought ity threshold <strong>to</strong> be exceeded are specified. Also, unlike on human society. Kunkel et al. (1999) describe the im- the more narrowly def<strong>in</strong>ed concept of vUlnerability, nonportance of <strong>vulnerability</strong> <strong>to</strong> weather and climate exl<strong>in</strong>ear feedbacks between the resource be<strong>in</strong>g affected and tremes, and how this <strong>vulnerability</strong> changes <strong>in</strong> response the forc<strong>in</strong>gs are <strong>in</strong>cluded. <strong>to</strong> <strong>in</strong>creases <strong>in</strong> human exposure, even when extreme We will discuss first the relationship between pre- weather statistics rema<strong>in</strong> unchanged. Non-weather rediction and <strong>vulnerability</strong> <strong>in</strong> Chapt. E.2 and E.3. The scelated <strong>in</strong>fluences <strong>in</strong>clude land-use change effects on runnario approach will be reviewed later <strong>in</strong> Chapt. E.4 and off and stream flow, and deliberate eng<strong>in</strong>eer<strong>in</strong>g of wa- its shortcom<strong>in</strong>gs illustrated. The reasons why a vulnerter flow whereas human activities change the distribuability approach as presented <strong>in</strong> Chapt. E.5 is more aption and availability of water through eng<strong>in</strong>eer<strong>in</strong>g works. propriate for <strong>environmental</strong> assessments is because it is Examples of this k<strong>in</strong>d of human activity <strong>in</strong>clude rerout- regional and local <strong>in</strong> scale; it <strong>in</strong>volves the evaluation of <strong>in</strong>g of rivers, creat<strong>in</strong>g artificial surfaces (reservoirs), thresholds and the threat associated with extreme con- chang<strong>in</strong>g surface water content through irrigation of ditions; it can <strong>in</strong>clude a spectrum of threats, and can drylands or dra<strong>in</strong>age of wetlands, and through lift<strong>in</strong>g consider the effect of abrupt changes. In contrast, the groundwater <strong>to</strong> the surface.