Biodiversity and Conservation 11: 469–485, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.
Developing regional conservation priorities using red lists: a hypothetical example from the Swiss lowlands PETER B. PEARMAN Abteilung für Ökologie, Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland (e-mail:
[email protected]; fax: +41-1-635-6821) Received 7 September 2000; accepted in revised form 12 April 2001
Abstract. This paper investigates how different prioritizations of species for conservation can affect both the number of breeding individuals that receive protection and the distribution of conservation attention among different types of habitat. I use as a study example three red lists of the avifauna of Kanton Zürich in northern Switzerland. Species are weighted based on their placement in different red list categories to represent differences in species’ relative conservation value. I examine how these weightings affect the number of breeding pairs benefiting from increasing conservation effort. Conservation effort is defined as the number of ranked land parcels that receive conservation attention, be it through habitat enhancement, protection, or other measures. I rank parcels’ conservation value based on the number of weighted breeding pairs estimated for each parcel. Not surprisingly, the number of category-1, -2 and -3 breeding pairs that receive benefits varies greatly when different red lists are used. Changes in the relative conservation value of species in different categories influences both the number of breeding pairs and the number of parcels to receive conservation attention. The effect of increasing conservation effort on the number of breeding pairs and the proportion of each landscape type receiving attention also vary when different red lists and relative conservation values are used to determine conservation priorities. Use of the ‘official’ red list published by a governmental body (Bundesamt für Umwelt, Wald und Landschaft, Bern, Switzerland) results in more emphasis on conservation in agricultural landscape than did use of either of the other two lists. The process of prioritization of sites for conservation should evaluate the effects of variation in both the relative conservation value of species and species categorization that may arise due to incomplete data and variation in opinion. Key words: breeding habitat, census, conservation value, effort, endangered birds, extinction, priority, red list, Switzerland
Introduction The conservation of species in danger of regional extinction is pursued by governments and non-governmental organizations on two grounds. Firstly, endangered species are elements that contribute to a region’s biological diversity and whose regional extinction represents a measurable and potentially irretrievable loss. Secondly, many, if not most, species are endangered because of the loss of habitat critical to completion of one or more life history stages (e.g. Wilcove et al. 1998). Conservation efforts that preserve habitats for endangered species may also benefit other species of conservation concern that use a broader range of habitats or that have more modest habitat area requirements. Thus, focusing conservation efforts on species in great danger of
470 extinction can benefit both the targeted species and, to the degree that these serve as umbrella species, additional taxa that contribute to regional biodiversity (Simberloff 1998; Caro and O’Doherty 1999). Attempts to focus conservation efforts on the species in greatest danger of local or global extinction have been undertaken by the publication and dissemination of ‘red lists’. Global red lists are published by the International Union for the Conservation of Nature (IUCN 2000) and the development of national red lists is increasingly based on quantitative criteria (e.g. Avery et al. 1995; Warren et al. 1997). Red lists are ordered categories, providing a ranking of groups of species based on their risk of regional or global extinction, population trends, and endemism (e.g. Dunn et al. 1999). Red lists are thus statements of a perception of the conservation importance of species, based on a number of criteria, and are developed based on both objectively collected data and on expert opinion. The use of red lists as tools to focus and plan future conservation efforts has, however, received little scientific attention. In Switzerland, red lists are used to redirect development away from areas with listed species. Red lists can be used to estimate a prioritization of sites containing critical breeding habitat that would lead to maximum conservation benefit, but in reality red lists are seldom used as planning tools to prioritize sites for conservation attention (Mace and Kunin 1994). A list of ordered categories implies that sites with populations of highly ranked species should receive priority conservation attention, through reserve establishment, habitat improvement, conservation easement, or mitigation of development. But how much priority should be assigned to some sites over others? If species differ in conservation value, how does weighting species in different categories influence the distribution of conservation priority, both among populations of the species on the list and among the different types of habitat they occupy? This paper addresses the use of red lists as a planning tool to establish regional priorities for conservation. While a number of papers address the inclusion and ranking of species on red lists (Kirchhofer 1997; Mathew 1999), I begin with red lists as published assessments of the rank in which species merit regional conservation action based on an evaluation of their risk of extinction and other criteria. I identify how variation among species in conservation value (Pearman 2001), expressed by assigning weights to species in different categories, influences the conservation benefits received by species of secondary (but notable) conservation importance. This case study stands to benefit conservationists by demonstrating the impact of explicitly assigning relative conservation value to species, something that is implicitly done in assigning species to categories, but likely overlooked when red lists are used to divert or mitigate development. It provides a case study in how the categorization and valuation of species on red lists can influence the relative amount of different landscape types that receive conservation attention, providing conservationists with an example of the use of red lists as a regional planning tool. It also demonstates a potential use of regional censuses as a quantitative planning tool. The paper identifies how prioritization of sites for conservation is influenced by a number of red list
471 characteristics. Recognition of these characteristics may help increase the use of red lists as proactive planning tools for regional conservation by drawing attention to the implications that red list composition has for the conservation of species of secondary concern and the protection of different types of habitat.
Study area and methods In central Europe, opportunities to establish protected areas encompassing entire watersheds or ecosystems are limited (Wallis-De Vries 1995) and in contrast to regions with small human populations, conservation of critical habitat often depends on the concerted action of local authorities, community organizations, and individual landholders to protect small areas of critical habitat from development. On the national level, red lists published by governments are a legal basis for intervention in development activities and serve to focus and publicize conservation efforts. Regional conservation efforts in central Europe may be of substantial magnitude. For example, in the Kanton of Zürich, in north-central Switzerland, a minimum of 312 separate nature conservation areas (Naturschutzgebiete) each over 5 ha and averaging 23 ha, exist in an area of 1729 km2 . Study area Between 1986 and 1988 Kanton Zürich was surveyed for breeding pairs of birds by Weggler (1991). [In 1990 this heavily modified landscape consisted of approximately 28% managed forest, 44% agricultural land (most under intensive use), 17% settlement and the remaining 11% falling into lakes, dumps, nature preserves and sport fields.] Each 2 km by 2 km section of the Kanton, defined in accordance with the Swiss coordinate system, was divided into a variable number of irregularly shaped 40–60 ha parcels. Each of these parcels was categorized as to its principle land cover type: forest, wetland, settlement, or multiple-use agricultural land. Some parcels did not fall clearly into one of these types and were designated ‘mixed’. Each parcel was surveyed using transect searches to visually and auditorily detect males defending territories during the breeding season (Berthold 1976; Weggler 1991). Each parcel was visited at least five times between the end of March and the beginning of July. A different transect was used on each visit. The length of each transect in meters was at least 10 times the number of hectares in the parcel. Based on the number of individuals observed, an estimate of the number of breeding pairs of each species within the parcel was made using a factor to convert encounters along transects into densities within a particular habitat type. Conversion factors were determined for each species in each habitat in which it was encountered using data from a preliminary study. Weggler (1991) suggested that the number of breeding pairs in a parcel has a ± 30% error rate. Observations in the census database that fell outside the standardized sampling protocol,
472 including some wetlands and some linear habitats (hedges) were excluded in my analysis. A total of 588 483 breeding pairs, comprising 129 species, was estimated to inhabit the Kanton as of 1989. However, 53 of the reported species, contributing 583 487 pairs, or 99.15% of all pairs detected by the standard sampling protocol, were of no conservation interest on any red list and were excluded from study. Red lists Since 1989, no fewer than three separate red lists of the bird species in the Kanton have been published (Zbinden 1989, ‘1989 Vogelwarte’; Zbinden et al. 1994, ‘1994 BUWAL’; Weggler 1991, ‘Zürich Census’). Each of these lists divides species into three to four categories of endangered species (Table 1). None of the lists are the product of strict quantitative criteria in the assignment of species to category, but all report some weight being given to recent trends in abundance and distribution. I examined red list characteristics in relation to how site prioritization affected the number of breeding pairs in each category of each list. Lists were evaluated on the Table 1. Categories of red-listed species for three separate Swiss species red lists for birds. Study category
Published category
1989 Vogelwarte list (Zbinden 1989) 1 1 2 2 3 3
3
4
–
5
1991 Zürich Census list (Weggler 1991) 1 1.1 1 1.2 2 2 3
3.1
3 –
3.2 4
1994 BUWAL list (Zbinden et al. 1994) – 0 1 1 2 2 3 –
3 4
Description
Species with populations at a critical size Strong decline across region and local extinctions Vulnerable because of special habitat needs (such as large territories), many species with less than 200 pairs and some with less than 100 Restricted to Switzerland and vicinity, special conservation responsibility Not rare elsewhere but seldom occurring within Switzerland Extinct Threatened with extinction, less than 25 breeding pairs Strongly endangered, 25–100 breeding pairs, region-wide declines Endangered, usually 50–100 pairs, local declines and disappearances Scarce, 50–200 breeding pairs, no particular strong threat Scarce, regular breeding species and sporadic breeding populations Extinct Threatened with extinction in Switzerland Strongly endangered, region-wide decline and local extinctions Endangered, local declines and extinctions Unusual species not normally breeding in Switzerland
Note the similar definitions of categories among lists.
473 basis of their own criteria, identifying characteristics of the species categorizations that influenced the number of breeding pairs in each category and affected the prioritization of sites for conservation. Two of the red lists were slightly modified for purposes of the present analysis. In using the red list of Zbinden (1989), the third and fourth categories were pooled to form one category of sensitive species. Both this red list and the list of Weggler (1991) treated the entire Kanton Zürich as a single biogeographical unit in assigning species to categories. Zbinden (1989) addressed priority species for all of Switzerland while Weggler (1991) focused only on Kanton Zürich. In contrast, Zbinden et al. (1994) divided the Kanton in two as part of a greater subdivision of the entire country into ecological regions. When a species fell into two red list categories in different parts of the Kanton, I used the more endangered rating that the species received. This rating was consistent with the countrywide rating these species exhibited. Clearly the component species varied between categories (Table 1) of different lists (Table 2). Nonetheless, the published description of the categories and the criteria for inclusion were similar in that they decreased in level of endangerment with increasing category rank. Therefore, the red lists were strictly comparable as ordered lists indicating the rank of priority that groups of species shared in their need for conservation intervention, based on various authors’ work. Minor differences among lists in the criteria for category definition thus should not have affected the analysis presented here, nor the conclusions. I also excluded one red list species from the analysis, the sand martin Riparia riparia, a colony-breeding bird dependent on specialized breeding habitat, because the large numbers of breeding pairs at a small number of sites obscured trends displayed by other species. To express the relative conservation value of species in different categories, each species was weighted according to its categorization by multiplying the number of breeding pairs detected at a site by an integer that depended on the red list category. I focused my analysis on species of primary conservation interest, which I defined as being species in categories 1–3 of each red list. This eliminated all category-4 species from consideration, and made comparisons across the lists possible because no category-4 species on the 1994 BUWAL red list were found in the Kanton. Eliminating category-4 species was equivalent to suggesting that while category-4 species may be generally scarcer than category-5 (abundant) species, they were unlikely to receive much attention in the prioritization of sites for conservation. Of the species included in the study, 61 species were listed in categories 1–3 on the BUWAL red list for Kanton Zürich (Zbinden et al. 1994), 35 species on the Zürich Census list (Weggler 1991), and 43 species on the 1989 red list (Zbinden 1989). The assignation of species to the first three categories varied among the lists. Lists by Zbinden et al. (1994) and Zbinden (1989) had proportionately more category-3 species than the Zürich census list (Weggler 1991), which had relatively more category-1 species (Figure 1).
Germana (Swiss)
Hänfling Habicht Sperber Drosselrohrsänger Schwanzmeise Feldlerche Eisvogel Knäkente Baumpieper Bergpieper Alpensegler Graureiher Waldohreule Tafelente Reiherente Haselhuhn Uhu Flussregenpfeifer Weissstorch Wasseramsel Hohltaube Kolkrabe Rabenkrähe Dohle Wachtel Kuckuck Mittelspecht Kleinspecht
Index
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Linnet Goshawk Sparrowhawk Great Reed Warbler Long-tailed Tit Skylark Kingfisher Garganey Meadow Pipit Water Pipit Alpine Swift Grey Heron Long-eared Owl Pochard Tufted Duck Hazel Grouse Eagle Owl Little Ringed Plover White Stork Dipper Stock Dove Raven Carrion Crow Jackdaw Quail Cuckoo Middle Spotted Woodpecker Lesser Spotted Woodpecker
Englishb Acanthis (Carduelis) cannabina Accipter gentilis A. nisus Acrocephalus arundinaceus Aegithalos caudatus Alauda arvensis Alcedo atthis Anas querquedula Anthus trivialis An. spinoletta Apus melba Ardea cinerea Asio otus Aythya ferina Ay. fuligula Bonasa bonasia Bubo bubo Charadrius dubius Ciconia ciconia Cinclus cinclus Columba oenas Corvus corax C. corone corone C. monedula Coturnix coturnix Cuculus canorus Dendrocopos medius D. minor
Latin 264 36 72 19 113 2878 6 1 369 2 94 81 29 11 6 2 1 20 3 114 66 19 5311 114 14 346 133 98
Observed breeding pairs 3 3 3 1 5 2 3 3 2 3 3 5 3 3 3 3 3 3 1 5 2 3 5 2 2 2 3 3
1994
Red lists
Table 2. Species names, total breeding pairs from Zürich census transects and red list category for each species, as analysed in this study.
3 4 4 1 4 5 1 4 3 4 4 4 4 4 4 1 1 1 1 4 2 4 5 2 1 3 4 3
Zürich census 5 5 5 2 5 5 3 4 2 3 3 5 2 4 3 3 3 3 1 5 2 5 5 2 3 2 3 5
1989
474
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Schwarzspecht Zaunammer Baumfalke Turmfalke Bekassine Teichhuhn Gelbspötter Zwergreiher Wendehals Neuntöter Rotkopfwürger Lachmöwe Rohrschwirl Feldschwirl Nachtigall Grauammer Schwarzmilan Rotmilan Bergstelze Schafstelze Kolbenente Tannenhäher Steinschmätzer Pirol Mönchsmeise Wespenbussard Fasan Gartenrotschwanz Berglaubsänger Grauspecht Grünspecht Haubentaucher
Black Woodpecker Cirl Bunting Hobby Kestrel Snipe Moorhen Icterine Warbler Little Bittern Wryneck Red-backed Shrike Woodchat Shrike Black-headed Gull Savi’s Warbler Grasshopper Warbler Nightingale Corn Bunting Black Kite Red Kite Grey Wagtail Yellow Wagtail Red-crested Pochard Nutcracker Northern Wheatear Golden Oriole Willow Tit Honey Buzzard Pheasant Redstart Bonelli’s Warbler Grey-headed Woodpecker Green Woodpecker Great Crested Grebe
Dryocopus martius Emberiza cirlus Falco subbuteo F. tinnunculus Gallinago gallinago Gallinula chloropus Hippolais icterina Ixobrychus minutus Jynx torquilla Lanius collurio L. senator Larus ridibundus Locustella luscinioides Lo. naevia Luscinia megarhynchos Milaria calendra Milvus migrans Mi. milvus Motacilla cinerea Mo. flava Netta rufina Nucifraga caryocatactes Oenanthe oenanthe Oriolus oriolus Parus montanus Pernis apivorus Phasianus colchicus Phoenicurus phoenicurus Phylloscopus bonelli Picus canus P. viridis Podiceps cristatus
140 23 34 195 25 80 42 7 17 215 2 169 13 81 52 46 141 97 179 52 1 39 1 153 20 13 80 483 50 68 168 120
5 2 3 3 1 5 2 1 1 3 1 5 3 3 5 2 5 5 5 3 3 3 5 3 2 3 3 2 3 2 2 3
4 2 3 3 1 4 2 1 1 3 1 4 4 4 4 2 5 4 4 4 4 4 4 3 4 1 5 3 4 4 3 4
5 3 3 2 1 5 2 1 2 2 1 5 3 3 5 3 3 3 5 3 4 5 5 5 5 3 5 2 5 2 2 5
475
Kleines Sumpfhuhn Tüpfelsumpfhuhn Zwergsumpfhuhn Wasserralle Braunkehlchen Waldschnepfe Erlenzeisig Turteltaube Dorngrasmücke Klappergrasmücke Zwergtaucher Ringamsel Schleiereule Wiedehopf Kiebitz
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75
Little Crake Spotted Crake Baillon’s Crake Water Rail Stonechat Woodcock Siskin Turtle Dove Whitethroat Lesser Whitethroat Little Grebe Ring Ouzel Barn Owl Hoopoe Lapwing
Englishb Porzana parva Po. porzana Po. pusilla Rallus aquaticus Saxicola torquata Scolopax rusticola Spinus (Carduelis) spinus Streptopelia turtur Sylvia communis S. curruca Tachybaptus ruficolis Turdus torquatus Tyto alba Upupa epops Vanellus vanellus
Latin 1 7 2 58 16 8 6 156 75 24 44 6 21 5 116
Observed breeding pairs 3 3 3 3 1 3 5 3 1 3 3 3 5 1 2
1994
Red lists
4 4 4 2 1 1 4 4 2 3 4 4 2 1 2
Zürich census
4 3 4 5 2 5 5 3 2 5 3 3 5 1 2
1989
Red list categories for each species are shown. Observed number of breeding pairs is approximately ± 30% and only includes estimates originating from standardized transect samples. Special habitats, samples, and ad hoc observations were not considered. Fifty species without conservation interest on at least one red list are omitted (see text). a German names generally correspond to Heinzel et al. (1988). b English names correspond to Jonsson (1993).
Germana (Swiss)
Index
Table 2. Continued.
476
477
Figure 1. Percent of all species detected in the Kanton Zürich bird survey that fall into different red list categories. See text and Table 1 for category descriptions.
Conservation priority and effort Parcels were ranked according to the total number of weighted breeding pairs, the highest ranking parcel holding the largest sum of weighted breeding pairs over all species. I examined how red list identity and category weighting affected (a) the prioritization of parcels and (b) the number of breeding pairs of species in each category that would potentially receive conservation benefit. The ranking of parcels thus represented their conservation value based on the number of (weighted) breeding pairs of birds of conservation interest. I analysed variation in the accumulation of breeding pairs in different red list categories, in most cases over 25–160 highest ranked parcels (approximately 1000–9000 ha total). The summation of breeding pairs over parcels of decreasing rank represented the number of pairs affected by increasing conservation effort. Results and discussion Red list characteristics The number of breeding pairs of species in categories 1–3 is a minute fraction of all breeding pairs estimated to occur in Kanton Zürich, less than 3% on all three lists. Thus all three lists implicitly suggest that relatively few individuals merit priority
478
Figure 2. Number of breeding pairs estimated to fall into species listed on the first three red list categories. The average number of breeding pairs per species in each category is shown at the base of each column.
conservation action in the Kanton. However, the average number of breeding pairs represented by species in categories 1–3, each varies between the lists (Figure 2). On the 1989 red list, only 42 breeding pairs are contributed by all category-1 species. In addition to the small number of category-1 species, breeding pairs of species in category-2 outnumber the number of species in category-3 by more than a factor of 2. The 1994 list differs from the 1989 list by suggesting that twice as many breeding pairs fall into the first three categories (7068 pairs vs. 3371 for the 1994 and 1989 lists, respectively). The Zürich Census list differs from the other two lists in two respects: first, a relatively large number of breeding pairs are contributed by category-1 species. Second, slightly more than three quarters of all breeding pairs fall into the third category (Figure 2). Thus, in this list the numerical rank of the category is the same as the rank order of number of breeding pairs contributed by species in that category. These differences among lists are relevant to variation in the prioritization of land parcels based on the lists and to understanding the accumulation of breeding pairs as parcels of decreasing priority are included for conservation. Accumulation of breeding pairs The accumulation of breeding pairs in ‘protected’ parcels as one considers additional parcels of decreasing rank depends both on the weighting given to species in the red list categories and on the red list that was used to prioritize sites for conservation.
479
Figure 3. Cumulative breeding pairs, by category, vs. cumulative number of parcels under conservation consideration. Rank order of parcels is determined from number of weighted-pairs in each parcel. Weightings for each category are shown. Variation in line length and the distance between points occurs because of variation in the number of parcels with tied rankings.
For all lists, the accumulation of breeding pairs of category-1 species is most rapid when these species receive a weighting of one (1) and species in other categories are weighted by a factor of zero (Figures 3a–c). Both linear weighting (3, 2, 1) and equal weighting (1, 1, 1) of species in the three classes lead to similar reduced rates of accumulation of breeding pairs of category-1 species. The small number of breeding pairs of category-1 species listed under the 1989 list leads to very few breeding pairs being accumulated under the corresponding prioritization of standard-sample parcels. This is because all category-1 species on the 1989 list occurred in just over 20 parcels and once all these are included, no further pairs remain to be considered under the 1,0,0-weighting scheme. Very few breeding pairs in categories 2 and 3 occur in these parcels (Figures 3d–i), although additional pairs in non-standard samples were not considered. The effects of heavily weighting relatively few species, comprising a small number of breeding pairs, are twofold: First, conservation activities become focused on relatively fewer sites, decreasing expense and logistics. Second, few other species of concern may benefit from these efforts. Overall, it may be difficult to justify allocating overwhelming conservation value and resources to regionally endangered species with particularly narrow habitat requirements and small population sizes. This is in contrast to situations where rare species serve as umbrella species for large scale conservation planning. Greater conservation benefit (i.e., more weighted-pairs in conserved parcels) might be obtained by decreasing conservation priority for rare species and/or by including additional species (and breeding pairs) in the category of highest
480 endangerment. Rare species may not deserve overwhelming regional conservation attention when they do not act as umbrella species, as illustrated by the distinct scenarios for the protection of pairs between the 1989 and 1994 red lists. Of course when breeding site limitation or nest disturbance can be linked as a cause of the rarity of globally endangered species, the focus on breeding site protection is highly justified. In the case analysed here, focus of conservation effort on a small number of sites would be an efficient use of resources in an effort to prevent regional extinction of particular species, but populations of other species of concern may be neglected. Such decisions, when global extinction is not an issue, may depend on the conservation value of the species involved (as expressed here by weightings, Pearman 2001). The means to assign relative conservation value of species on regional red lists is an area ripe for environmental and social research, and would contribute to the use of red lists as a planning tool. Accumulation of breeding pairs of category-2 species in protected parcels is most pronounced under the 1994 red list. Breeding pairs of category-2 species accumulate most rapidly under a linear weighting scheme (3, 2, 1) and their accumulation is nearly as rapid when pairs in each category are weighted equally (Figure 3d). The 1994 red list includes a large number of species in category-2 with large populations, relative to the other two red lists. When category-2 species on the 1994 red list receive either of the two non-zero weightings, a site prioritization results where the accumulation of category-2 breeding pairs far outstrips the accumulation of category-1 breeding pairs. When conservation holdings (i.e., parcels) are prioritized based on the number of weighted breeding pairs, the abundance of species in lower categories (category-2 in this example) may work against the accumulation of breeding pairs in higher categories. This may happen even when weighting (value) favours species in higher categories. Large numbers of breeding pairs of category-2 species in a small number of breeding sites may raise the priority of these sites when the number of weighted breeding pairs is used to determine the conservation priority of sites. This can occur when red lists consist of categories that express divergent bases for high conservation priority. A number of species may be listed because a region may be responsible for a large proportion of the species’ population globally (i.e., endemism), though the species may not be scarce within the region itself. This, and listing for other reasons unrelated to the number of breeding pairs of a species within the region, may result in the listing of species with relatively large local populations, as with the category-2 species in the 1994 red list (e.g., Alauda arvensis, Phoenicurus phoenicurus). This may result in high priorities for sites with few or no category-1 species. If category-2 species are not extreme habitat specialists, a number of these species may co-occur in a parcel and contribute to the site’s conservation value. This suggests that the diversity of rare breeding birds may contribute to raising the conservation value of sites when weighted breeding pairs are used to develop conservation priorities on a site by site basis, as is done here.
481 Site prioritization and habitat type The prioritization of parcels using different red lists results in different distributions of affected habitat types in the parcels under consideration. These differences become more apparent with increasing conservation effort. This is clearly demonstrated when a linear ranking (3, 2, 1) is applied to breeding pairs in the different categories. At an effort of 25 parcels under conservation consideration, wetland sites comprised about one-third of the parcels (Figure 4) compared to their representation among all landscape parcels (Figure 5). This reflects the fact that little wetland breeding habitat remains in Kanton Zürich and several red-listed species are wetland breeders, e.g., Acrocephalus arundinaceus, lxobrychus minutus, and Gallinago gallinago. Use of the 1989 red list results in relatively more consideration given to forested sites, while the 1994 red list afforded more consideration to agricultural parcels, with the Zürich Census red list intermediate (Figures 4a–c). With increasing effort, the consideration given to agricultural land increases considerably relative to other land types when parcels are prioritized under the 1994 list, and to a lesser degree under the Zürich Census list as well (Figures 4d, e, g, h). The proportional distribution among landscape types is most even when parcels are prioritized under the 1989 red list (Figures 4c, f, i). Zbinden et al. (1994) recognize that the intensification of agriculture has
Figure 4. Proportion of parcels of each type, for three levels of conservation effort (rows). Parcels were prioritized using weightings of the species on three different red lists (columns). For each red list, parcels were ranked based on a 3, 2, 1-weighting of the breeding pairs in the parcel in the first three red list categories.
482
Figure 5. Proportion of parcels of each landscape type, throughout the Kanton of Zürich. A total of 3283 parcels is represented.
negatively affected a number of species that breed in fallow agricultural fields and hedge rows. Study of population trends in species with various breeding habitat requirements suggests that this is a trend across Europe (e.g., Böhning-Gaese and Bauer 1996). Ad hoc data and non-standard samples that existed in the database were not considered here in order to make comparisons of the amounts of affected parcels of habitat. While outside the scope of this paper, a more detailed analysis with specific conservation goals could employ the omitted data, and the methodology described here, to generate a ranking of the conservation priority for all surveyed sites in Kanton Zürich. Such an analysis could examine separately the conservation priority of areas not sampled under the standard methodology. The results demonstrate the variation that various red lists may produce in the distribution of habitat receiving conservation attention. The political implications of these differences may obviously be substantial. Differences among red list categories in species number and composition, and the differing relative conservation value of species, may result in different sectors of the public being affected by conservation activity. In this example from the Swiss lowlands, increase in conservation effort primarily affects agricultural lands under the 1994 list presented in a federal publication (Zbinden et al. 1994). In contrast, conservation prioritization under either of the other two lists would potentially have more impact on forest management practices
483 in Kanton Zürich, where current forest practice leaves few standing snags and little course woody debris to support forest insect diversity (Schiegg 2000 a, b).
Conclusions Over less than a decade, three red lists applicable to the avifauna of Kanton Zürich have been published. As ordered lists, these publications are explicit statements of the rank need for conservation attention merited by species. I suggest the use of red lists for regional conservation planning, in addition to their usual role in mitigation and project impact assessment in Switzerland. The census of the entire Kanton in the late 1980s allows a comparison of the prioritization of parcels for conservation consideration under different scenarios of conservation effort and relative value of species. While each red list was the product of expert opinion, the lists varied in gross ways including both the number of species in the categories and the number of breeding pairs those species contributed. The use of lists that vary in these ways may generate substantial differences in the priority assigned to sites for conservation attention. This suggests that when red lists are used to establish regional conservation priorities, an evaluation should be made of how variation in species categorization and relative conservation value affect the distribution of conservation effort among areas with differing land use. The pro-active use of red lists for planning (cf. Avery et al. 1995) has the potential to integrate conservation activities beyond the ad hoc use of red lists for the diversion and remediation of development. Analyses of the sensitivity of the implications of regional red lists for habitat conservation, like the one presented here, may provide an idea of how the conservation priority of land parcels changes with changes in the categorization of red list species or their relative conservation value. Variation in categorization may result from incomplete knowledge of species (Master 1991) and differences in expert opinion. Increasingly, quantitative criteria for red list categorization (e.g. Daniels et al. 1991; Master 1991; Mace and Lande 1991) may reduce variation among draft red lists, and among alternate prioritizations of sites for conservation, that arise from differences in expert opinion. Nonetheless expert opinion will remain important in assigning species to red list categories due to the incompleteness of demographic and other relevant data for determining extinction risk. Expert opinion and other subjective information will be important for determining the relative conservation value of species (Pearman 2001). Variation in the number of species and breeding pairs among red list categories should alert conservationists. Such variation obviously may cause different assessments of conservation value to effect the number of individuals in each category that benefit from conservation attention. Red lists are a conservation tool, regardless of how they are used or the criteria used to develop them. The impact on regional habitat- and species-conservation priorities of variation
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