December 2012 Number 1 - Utah Native Plant Society

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Utah Native Plant Society Prioritizing Plant Species for Conservation in Utah: Developing the UNPS Rare Plant List Walter Fertig, Chair, Utah Native Plant Society Rare Plant Committee Abstract. Rare plant lists are an important tool for identifying and prioritizing species for conservation attention. Over a dozen systems have been derived for ranking the rarity and conservation priority of plant and animal species, each differing in emphasis, methods, and biological and anthropogenic criteria. In 2007 I developed a new ranking protocol for the flora of Wyoming that combines aspects of the NatureServe, International Union for Conservation of Nature (IUCN), and US Fish and Wildlife Service systems and the classic paper “Seven forms of Rarity” by Deborah Rabinowitz. The so-called “Wyoming protocol” was adopted by the Utah Native Plant Society’s Rare Plant Committee to develop an updated rare plant list for Utah. In this protocol, species or varieties are assessed using seven qualitative criteria: Utah’s contribution to global distribution, number of populations in the state, number of individuals, habitat specificity, intrinsic rarity, magnitude of threats, and population trend. Individual criteria are rated on a binary scale (0 for unthreatened, 1 for at risk) based on expert opinion. Species for which no data are available are scored “unknown”. The values for each criterion are summed to derive a minimum and maximum potential score for each taxon. The minimum score is calculated by summing each individual score and treating any unknown criteria as 0. The maximum score is derived in the same way, except that unknown criteria are given a value of 1. The two summary scores are averaged to determine a conservation priority rank. Those taxa that are at risk for a large number of criteria have higher conservation priority ranks than those species that are at risk for only a few criteria. This simple method allows practitioners to rapidly identify the relatively small subset of species of high or extremely high conservation priority (those with limited ranges, few populations, low numbers, high habitat specificity, high intrinsic rarity, high threats, and downward trends) and those species with significant data gaps in need of additional study. Being able to differentiate among species based on their priority score enables conservationists and managers to better allocate limited resources to those taxa most in need. The UNPS Utah rare plant list developed by the Rare Plant Committee and attendees of a breakout ranking session at the Fifth Southwestern Rare Plant Conference is presented in Appendices 1-4, with modifications adopted at subsequent Utah Rare Plant meetings from 2010-2012. Experts predict that one-fifth to one-third of all vascular plant species in the United States are threatened with local or range-wide extinction (Center for Plant Conservation 2000). This number is only likely to increase as plant habitat becomes increasingly fragmented and disturbed by development, climate change, or invasion by non-native weeds. Not all plant species, however, are equally imperiled. Some species are naturally rare due to their limited range, high habitat specificity, or low population size (Rabinowitz 1981), but may not be in imminent danger because their population trends are stable or threats are presently low. Because so many species are potentially vulnerable and conservation resources (time, funding, and personnel) are nearly always inadequate, conservation biologists have a dilemma determining which species should be the highest priority for attention (Noss and Cooperrider 1994; Regan 2005). Rare species lists can be an important tool for identifying and prioritizing those taxa (species, subspecies, and varieties) most vulnerable to extinction. Over the past 40 years conservation biologists have proposed more than a dozen ranking systems for creating state or national rare species lists (Andelman et al. 2004). Ranking schemes often differ widely in their emphasis on inherent rarity, degree of threat, vulnerability of extinction as well as their scoring methods and overall complexity and transparency (Akcakaya et al. 2000; Faber-Langendoen et al. 2009; IUCN 2001; O’Grady et al. 2004; Rabinowitz 1981; Regan et al. 2004; Spence 2012, US Fish and Wildlife Service 1983). These systems also utilize different criteria for ranking, including abundance, number of populations, geographic range, area of occupancy, population trend, intrinsic rarity, taxonomic distinctiveness, ecological significance, population viability, habitat condition or degree of fragmentation, magnitude and imminence of threats, and number of protected populations (Andelmann et al. 2004; Beissinger et al. 2000; Breininger et al. 1998; Holsinger 1992; IUCN 2001; Keith 1998; Mace et al. 2008; Millsap et al. 1990; Panjabi et al. 2005; Rabinowitz 1981; Regan et al. 2004; Spence 2012; US Fish and Wildlife Service 1983). Ideally, a ranking system should have a strong biological basis, recognize the significance of threats and trends, be easy to apply and update with available information (while recognizing the importance of data gaps), and be transparent (Fertig 2011). Each ranking system has its merits, but none meet all of these criteria. For 196
Calochortiana December 2012 Number 1 example, the US Fish and Wildlife Service (1983) system for listing species under the US Endangered Species Act is heavily weighted towards threats and taxonomic distinctiveness at the expense of other aspects of rarity (Master et al. 2000). The IUCN (2001) protocol focuses chiefly on population size, trends, and likelihood of extinction but is dependent on quantitative viability data that are not always available for vascular plants. One advantage of the IUCN protocol, however, is its recognition of “data deficient” species (Akçakaya et al. 2000). Rabinowitz (1981) introduced a simple, but elegant, binary ranking system using just three components of rarity: geographic range, abundance, and habitat specificity. But several additional biological and anthropogenic criteria (such as threat) were not incorporated, which limits the suitability of the Rabinowitz system for prioritizing among different kinds of rare species. The most widely used ranking protocol today is the natural heritage system, first developed by The Nature Conservancy in the 1970s (Master 1991) and now administered by NatureServe. In this system, full species or varieties are assigned a conservation rank on a scale of 1 (critically imperiled) to 5 (demonstrably secure) across their entire global range (G rank) and at a subregional scale (state/province, or S rank). Traditionally, G and S ranks were based on the number of occurrences (discrete biological populations), abundance, or risk of extinction as determined by expert opinion (Master et al. 2000). In the past decade, NatureServe protocols have become more quantitative and consider additional ranking criteria, including long and short-term trends, area of occupancy, condition of occurrences, intrinsic rarity, and threat (Faber-Langendoen et al. 2009; Regan et al. 2004). Unfortunately, the revised NatureServe ranking protocol has become more complex and less transparent. Individual ratings are weighted differently, some criteria are used only conditionally, and scores are tallied by a “black box” computer algorithim (Faber-Langendoen et al. 2009). As part of my doctoral dissertation on plant conservation in Wyoming (Fertig 2011), I developed a hybrid ranking protocol by borrowing components of each of the preceding systems. As a starting point, I adopted most of the rarity factors from NatureServe (Regan et al. 2004), added the uncertainty components of IUCN (2001), and included an emphasis on threats from the US Fish and Wildlife Service (1983). The ranking system itself is a modification of the qualitative, binary scoring employed by Rabinowitz (1981), expanded to include additional criteria. I added a simple scoring component to classify plant species into six different rarity classes reflecting each taxon’s overall conservation priority (Fertig 2009, 2011). In 2007, I beta-tested the “Wyoming protocol” at the annual Utah rare plant meeting sponsored by the Utah Native Plant Society (UNPS) and Red Butte Garden. Following the meeting, the UNPS state board voted to reestablish a rare plant committee and charged it with applying this ranking system to the entire Utah vascular plant flora in order to create a new, prioritized list of rare plant species for the state. A draft version of the list was presented at a special session of the Fifth Southwestern Rare and Endangered Plant Conference, held at the University of Utah in March 2009. Based on feedback from meeting participants and other experts, the list was revised and published in November 2009 (Fertig 2009). The list has since been updated twice (Fertig 2010a, 2012) based on additional input from the UNPS Rare Plant Committee, attendees of the Society’s annual rare plant meeting, and review of new literature. The purpose of this paper is to briefly describe the Wyoming ranking protocol and its application to the flora of Utah. Appendices 1-4 include the current lists of Utah plants on the Extremely High Priority, High Priority, Watch, and Need Data lists. The paper concludes with a comparison of the current list to previous rare plant lists for Utah and a discussion of additional applications and future directions. METHODS Ranking Criteria The Wyoming protocol is based on seven biological and anthropogenic factors that influence the conservation priority of a vascular plant species. These criteria are: 1. Geographic range. Geographic range takes into account the state’s contribution to the total global distribution of a species. Six geographic range categories are recognized (Table 1). Local and regional endemics have highly restricted global distributions, ranging from single populations covering a few acres to less than 250,000 km 2 (an area about the size of the state of Wyoming). Widespread species, defined as occupying a global range in excess of 250,000 km 2 , can still be considered rare if state populations are widely isolated from the core of the species’ range (disjunct) or are at its very edge (peripheral). A small number of plant species may occur widely but are limited to small, often scattered or discontinuous habitats and occupy less than 5% of the state (sparse). Species that are introduced to the state are not included in the rankings. 2. Number of Populations. This criterion is based on the number of extant populations of a species within Utah (occurrences outside the state are not considered). Populations are defined as aggregations of individual plants within a specific geographic area that are separated from other populations by a physical barrier, extensive area of unsuitable habitat, or sufficient distance to prevent gene flow (usually about 1-2 km). The num- 197
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December 2012 Number 1 - Utah Native Plant Society

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