2. Reference points and reference directions
Reference points are precise values of indicators used to provide context for the current status of an indicator. Establishing a reference point requires substantial understanding of an indicator’s properties, but it provides a rigorous way to assess ecosystem status. For some indicators, reference points will have already existed prior to the introduction of EBM. In the case of Puget Sound, the Washington Department of Health provides recommendations regarding human consumption of seafood subject to known levels of toxic contamination (Selecky et al. 2006). In the short-term, it may be challenging to develop actual point values for ecosystem reference levels (Pitcher 2001, Nichols 2003, Stallings 2009). However, a reference direction, which specifies how the trend in an indicator relates to the desired state of the ecosystem, can be informative as well (Figure 9; Jennings and Dulvy 2005, Failing and Gregory 2003). In comparison to reference points, the challenge of achieving consensus on reference directions is small and can be applied in data-poor situations (Tallis et al. 2010).
Figure 9. The relationship between target, benchmark, precautionary, and limit reference levels for an ecosystem indicator (adopted from Jennings and Dulvy 2005).
The concept of reference directions is familiar in the context of financial markets. For instance, the Dow Jones Industrial Average is an index representing the performance of 30 large, publicly owned U.S. corporations on the New York Stock Exchange. Though specific reference points are not widely agreed upon (Donaldson and Kim 1993) it is generally accepted that increases in the Dow Jones are economically favorable and reductions are unfavorable.
A second financial market example illustrates an alternative approach for establishing reference directions, based on relative performance. The S&P 500, a weighted index consisting of 500 companies traded on the New York Stock Exchange, American Stock Exchange, and NASDAQ stock market (National Bureau of Economic Research 2008), is commonly used to compare the direction of change of individual companies to the direction of change of the overall financial market (Elmer-DeWitt 2008; Figure 10). Companies that show greater percentage increases than the S&P 500 over the short-term (e.g., days, weeks, or months) and long-term (quarters or years) are considered to be leading the market, whereas companies that show lesser percentage increases than the S&P 500 over the short-term and long-term are considered to be lagging the market. Slipping companies are those that are behind the S&P 500 in the short-term but ahead in the long-term, and improving companies are those that are ahead of the S&P 500 in the short-term but behind in the long-term. This approach could be adopted for evaluating ecosystem indicators in Puget Sound relative to a summary index for each PSP goal, and would be useful for distinguishing indicators in need of management attention (lagging, slipping) from those on a desired trajectory (leading, improving).
Reference directions are already used widely in the management of natural systems. For instance, in San Francisco Bay and the North Sea increasing abundance of certain species of jellyfish is viewed as a sign of deteriorating ecosystem health (Purcell 2007), though no exact value corresponding to an undesired abundance level has been established. Similarly, a decline in disturbance-sensitive, specialist seabirds is viewed as indicative of strong anthropogenic influences (e.g., Chesapeake Bay; DeLuca et al. 2008) or worsening climatic conditions (e.g., central California coast; Parrish 2007), but a specific value for the rate or extent of decline marking an undesired state remains ambiguous. As a final example, in 2002 nearly 200 nations pledged to reduce the global rate of biodiversity loss by 2010 without establishing a target level for the amount of reduction that they desired (Walpole et al. 2009).
Figure 10. Use of reference directions based on relative performance of individual stocks (circles) and the S&P 500, a weighted index of overall market performance. Stocks that show greater percentage increases than the S&P 500 over the short-term (e.g., days, weeks, or months) and long-term (quarters or years) are considered to be leading the market, whereas stocks that show lesser percentage increases than the S&P 500 over the short-term and long-term are considered to be lagging the market. Slipping stocks are those that are behind the S&P 500 in the short-term but ahead in the long-term, and improving stocks are those that are ahead of the S&P 500 in the short-term but behind in the long-term. Adapted from www.nytimes.com
In Puget Sound, reference directions for indicators could serve as placeholders in order to allow time for the development of more precise reference points. Indeed, the Puget Sound Action Team (PSAT) has applied the reference direction approach previously (Puget Sound Action Team 2007b). Using a simple and easily-interpreted schematic, PSAT evaluated indicators based on whether their status was generally negative, fair, or positive and whether the trend in the indicator was negative, neutral, positive, or unknown compared to a desired status (Figure 11). In future versions of the PSSU, a similar approach could be applied productively to the indicator assessments presented in Chapters 2 and 3, provided that the direction of change that is considered desirable for each indicator is specified explicitly and its rationale explained.
Figure 11. Example of indicator report card from the 2007 State of the Sound document. This figure shows that the status of one indicator of the health of Puget Sound species, orcas, is generally negative because the dot is to the left of center, and its trend, indicated by the arrow, is also negative. Reproduced from Puget Sound Action Team 2007b.
