Identifying Potential Indicators of Conservation Value Using Natural Heritage Occurrence Data
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Ecological Applications, 16(1), 2006, pp. 186±201 q 2006 by the Ecological Society of America IDENTIFYING POTENTIAL INDICATORS OF CONSERVATION VALUE USING NATURAL HERITAGE OCCURRENCE DATA PETER B. PEARMAN,1 MICHAEL R. PENSKAR,EDWARD H. SCHOOLS, AND HELEN D. ENANDER Michigan Natural Features Inventory, Michigan State University, P.O. Box 30444, Lansing, Michigan 48909-7944 USA Abstract. Conservation planning based on the occurrence of rare species has been criticized as being too limited in scope to conserve biodiversity as a whole. Conversely, planning based on indicator taxa may lack suf®cient focus to conserve those species in greatest need of conservation. An alternative approach is to identify a variety of species at risk that are associated with areas of conservation value, which is de®ned based on species-independent characteristics. We identi®ed potential indicators of conservation value using occurrence data on species at risk and independent information on conservation value that incorporated indices of ecosystem integrity. We propose a taxonomically diverse group of indicator species that are strongly associated with areas of exceptional ecosystem in- tegrity, to serve as a focus for further research and in planning for biodiversity conservation. We identify potential indicator species by de®ning a null model in which species at risk are equally associated with areas of high ecosystem integrity, then by conducting random- ization tests to identify noncompliant species in the state of Michigan, USA. Areas of high ecosystem integrity are selected using criteria to ¯ag (1) secure biotic communities with structural integrity and few exotic species, (2) natural areas subjected to expert review, (3) contiguous relict areas of forest interior, (4) contiguous areas of unmodi®ed wetland, and (5) all these areas combined. We determine the spatial occurrence of species at risk using data from Michigan's statewide Natural Heritage database. The potential indicators include plants, insects, and birds. Their species identity and distribution of occurrences varies with the ®ve scenarios, and together the species broadly cover the entire state. These species at risk, many of which occur throughout the Great Lakes region, may be used to identify additional areas potentially high in conservation value and to monitor their conservation. The ecological criteria and numerical methods we employ may be broadly applicable as Heritage Program databases in North America and parts of Latin America grow to become representative of species distributions. Key words: adaptive management; conservation planning; conservation priority; endangered species; heritage program; inventory; monitoring; null model; randomization test; rarity; reserve selection; surrogate species. INTRODUCTION 1993, 1994, Margules and Pressey 2000). These tasks The current rates of fragmentation and habitat loss, are complicated because the richness of species in a usurpation of primary productivity for human purpos- single taxon is often not indicative of richness in other es, and resulting loss of populations indicate a pressing taxa or larger groups (Prendergast et al. 1993, Flather need for establishment of reserve networks, restoration et al. 1997, Kerr 1997, Lawton et al. 1998, van Jaars- of ecosystems, and management of these areas for bio- veld et al. 1998, Vessby et al. 2002). Further, few pro- diversity conservation (Robinson et al. 1995, Dobson posed indicators may ful®ll multiple criteria that have et al. 1997, Hughes et al. 1997, Vitousek et al. 1997). been established for indicator species (Hilty and Mer- Evaluating all of biological diversity as a basis for enlender 2000, Lindenmayer et al. 2000), suggesting reserve selection would be a mammoth undertaking the importance of considering ecological function and (Raven and Wilson 1992). Thus, identi®cation of in- requirements of suites of species in selecting indicators dicators for systematically choosing locations with for conservation planning (Lambeck 1997, Simberloff high conservation value, then managing and monitor- 1998, Soule et al. 2003). Nonetheless, debate surrounds ing for biodiversity conservation are principal tasks for the relative importance of information on species dis- conservation biologists (Noss 1990, Kremen et al. tributions and environmental variation across land- scapes for conserving both biodiversity and the eco- Manuscript received 27 December 2004; revised 12 April system services it provides (Brooks et al. 2004a, b, 2005; accepted 18 April 2005; ®nal version received 13 June Higgins et al. 2004, Molnar et al. 2004, Pressey 2004). 2005. Corresponding Editor: J. B. Zedler. These issues suggest the collective importance of data 1 Present address: Department of Ecology and Evolution, University of Lausanne-Biophore, CH-1015 Lausanne, Swit- on species distributions, species environmental depen- zerland. E-mail: [email protected] dencies, and the spatial distribution of land types for 186 February 2006 INDICATORS OF CONSERVATION VALUE 187 guiding the conservation of biodiversity (Cowling et monitoring is unclear (Andelman and Fagan 2000, Pos- al. 2004). singham et al. 2002), quantitative analysis of Heritage Species with pressing conservation needs can fall Program data has seen little exploration. outside hotspots of species richness of well-studied Efforts to identify indicator species for biodiversity taxa (Prendergast et al. 1993, Panzer and Schwartz conservation and management have previously taken 1998, Chase et al. 2000), and protecting conservation- two approaches. Taxonomic groups, functional groups, dependent species may involve large investment com- or individual species may be identi®ed a priori as part pared to that needed for protecting biodiversity of an indicator scheme for studying potential reserve (Kintsch and Urban 2002). While protection of rare networks. The scheme is then tested for correspondence species may provide substantial bene®ts for other spe- and correlation between the indicator group and a cies (Mikusinski et al. 2001, Lawler et al. 2003), some broader group of species using incidence and distri- studies suggest that few species bene®t from efforts bution data (Ryti 1992, Prendergast et al. 1993, An- directed at rare species because of their restricted dis- delman and Fagan 2000). Alternatively, indicator tribution and idiosyncratic habitat needs (Andelman groups may be inferred from empirical patterns in data and Fagan 2000, Chase et al. 2000, Fleishman et al. obtained from statistically valid ®eld sampling (Kre- 2000, Possingham et al. 2002). Nonetheless, rare and men 1992, Dufrene and Legendre 1997). Statistical listed species may be useful as indicators of forest con- analysis of Heritage Program databases is complicated servation value (Thor 1998, Gustafsson 2000, Sillett because information is unavailable on unsurveyed ar- et al. 2000, Uliczka and Angelstam 2000). Identi®ca- eas and locations where tracked species were not ob- tion of additional rare species to serve as indicators served. Statistically valid sampling designs are gen- could broaden accessory bene®ts obtained by directing erally lacking. Natural Heritage and other species da- limited resources toward their conservation. To facil- tabases are often biased geographically due to differ- itate this we identify potential indicators of conser- ential access to private and public lands, and by focus vation value in pools of species at risk (listed species on vertebrates and vascular plants (Margules et al. and additional watch-list species) by investigating their 1994). Natural Heritage Program occurrence data are, relationship with ecosystem integrity (Karr 1991, thus, not well suited for the ordination, classi®cation, Woodley et al. 1993). The potential positive relation- and correlation approaches used with data from ran- ships between ecosystem integrity, ecosystem services, domly sampled units. and the occurrence of species at risk (Costanza et al. An alternative approach would be to de®ne a null 1997, Rapport et al. 1998, Balmford et al. 2002) sug- model for association of species at risk with areas of gest focusing on ecosystem integrity to evaluate con- high ecosystem integrity that are recognized by em- servation value. We employ data on current and his- ploying species-independent criteria, then to test for torical land cover and occurrence of species at risk to deviations from the model using a randomization test evaluate the conservation value of all 1900 93.2-km2 (Rebelo and Siegfried 1992, Gotelli and Graves 1996). townships in Michigan, USA. We develop this approach, clarifying assumptions and providing caveats that must be considered when em- Natural Heritage Program dataÐa source for ploying these methods using Natural Heritage data or identifying rare species indicators? similar information. The existence of Heritage Program Species needing conservation attention are identi®ed databases in North America and much of Latin America by nongovernmental organizations and governmental (Deblinger and Jenkins 1991, Groves et al. 1995) sug- bodies to help prioritize conservation efforts (Master gests that as these databases become increasingly rep- 1991). Occurrence data on these species in North resentative of regional species occurrence, the methods America and elsewhere are available from Natural Her- developed here may be useful for identifying potential itage Program databases, a set of resources with im- indicators for locating and managing areas with high mense geographic