ateam - Potsdam Institute for Climate Impact Research

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ATEAM final report Section 5 and 6 (2001-2004) 52 has a far lower biodiversity (1477 vascular plant species (van der Meijden et al. 1996)), but a very high grain yield (8.1 t ha -1 for 1998-2000 average (Ekboir 2002)). While providing useful information about the stock of resources at a European scale, absolute differences in species numbers or yield levels are not good measures for comparing regional impacts between these countries. Expressing a relative change would overcome this problem (e.g. -40% grain yield in Spain versus + 8% in The Netherlands), but also has a serious limitation: the same relative change can occur in very different situations. Table 14 illustrates how a relative change of –20 % can represent very different impacts, both between and within environments. Therefore comparisons of relative changes in single grid cells must be interpreted with great care and cannot easily be compared. We used the recently developed Environmental Classification of Europe (see next section) to put the results into their environmental context. The highest ecosystem service supply achieved within an Environmental Zone is used as a reference value (ESref, Table 14) to stratify potential impacts. Stratified potential impacts are calculated as the fraction of modelled ecosystem service value relative to the highest achieved ecosystem service value in that environmental zone, giving a value with a 0-1 range. Because the environmental context is altered by global change, consistent environmental strata are determined for each time slice, so that the ecosystem service reference value (ESref) changes over time. As shown in Figure 39, the stratified potential impact map shows more regional detail than the original potential impact map. This is the regional detail required to compare potential impacts across regions. In addition to comparing regions, the change of stratified sensitivity potential impact over time can be seen by looking at three time slices through the 21 st century, 2020, 2050 and 2080 relative to the 1990 baseline (Figure 39, third row of maps). The change in stratified potential impact compared to baseline conditions shows how changes in ecosystem services affect a given location. Regions where ecosystem service supply relative to the environment increases have a positive change in potential impact and vice versa. This change in potential impact is used to estimate vulnerability (see below). Our method to express changes in potential impacts leads to a small risk of ‘false’ zero or positive change. If relative to the previous time slice the reference value decreases more than the modelled ecosystem service supply value for a grid cell, the stratified potential impact may stay the same or even increase. This is the case when the potential of an environmental zone to provide an ecosystem service decreases as a whole, but in a specific grid cell the modelled supply does not change very much so that it remains high or unchanged relative to the reference. This is what happens in grid cell B of environment 1 in Table 14. The environmental potential (indicated by the reference value ESref) decreases by 0.3, but the modelled value in the grid cell decreases only by 0.2, resulting in a change in potential impact of zero. This means at t and t+1 the same fraction of the reference value is supplied by the grid cell, even though the absolute supply of ecosystem service goes down. When interpreting maps of changing potential impacts or vulnerability, one needs to keep this rare case in mind. This is one of several reasons (discussed later) to look also at the constituting indictors separately when interpreting vulnerability of a region.
ATEAM final report Section 5 and 6 (2001-2004) 53 Table 14 Example of changing ecosystem service (grain yield in t ha -1 a -1 ) supply in four grid cells and two different environments between two time slices (t and t+1). The potential to supply the ecosystem service decreases over time in environment 1 (green shading), and increases over time in environment 2 (blue shading). The “Value in a grid cell” is the ecosystem service supply under global change conditions as estimated by an ecosystem model. The relative change in ecosystem service may not form a good basis for analysing regional potential impacts, in this example it is always –20%. When changes are stratified by their environment, comparison of potential impacts in their specific environmental context is possible. The “Stratified potential impact” is the “Value in a grid cell” divided by the “Highest ecosystem service value” in a specific Environmental Zone at a specific time slice (see text). Note that there is a small risk of ‘false’ zero or positive change in potential impacts when the stratification is used (e.g. grid cell B, see text). Environmental Zone environment 1 environment 2 Grid cell grid cell A grid cell B grid cell C grid cell D Time slice t t+1 t t+1 t t+1 t t+1 Value in grid cell (t ha -1 a -1 ) 3.0 2.4 1.0 0.8 8.0 6.4 5.0 4.0 Absolute change (t ha -1 a -1 ) 0.6 0.2 1.6 1.0 Relative change (%) -20 -20 -20 -20 Highest ecosystem service value, ESref (t ha -1 a -1 ) 3.0 2.7 3.0 2.7 8.0 8.8 8.0 8.8 Stratified potential impact, PIstr 1.0 0.9 0.3 0.3 1.0 0.7 0.6 0.5 Change in potential impact, ∆PI -0.1 0.0 -0.3 -0.1 6.2.5.2 The Environmental Classification of Europe (EnC) A new Environmental Classification of Europe (EnC) is used to interpret ecosystem service changes in their environmental context. The EnC was developed in 2002 (Figure 40; Metzger et al. 2004a, in collaboration with the Wageningen research institute Alterra 36 ). This classification forms the spine of the Vulnerability Assessment framework for two reasons: • It allows us to stratify potential impacts (see previous section; Metzger and Schröter 2004); • It allows the Vulnerability Assessment framework to be applied in other studies at various scales (Metzger et al. 2004b). The distribution of environmental zones shift with shifting environments. A specific discriminant function for each EnC class based on variables available form the climate change scenarios was created to calculate the distribution of each zone for future scenarios. Figure 41 shows how the Environmental Zones shift for one of the scenarios. The UK Countryside survey (http://www.cs2000.org.uk/; Haines-Young et al., 2000) has shown how a statistically derived environmental classification can be used to integrate and summarize different forms of ecological data (e.g. field samples, satellite imagery, modelling results). Within ATEAM, climate and land use change scenarios were analysed using the EnC. Summarizing the scenarios per Environmental Zone makes differences in variability and trends in the scenarios across the European environment apparent, e.g. between Atlantic North and Mediterranean North (Figure 42). Similar 36 Alterra - Alterra is part of Wageningen University and Research Centre and closely co-operates with the department of Environmental Sciences from Wageningen University. http://www.alterra.wur.nl/UK/organisatie/
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