GOPHER SNAKE WILDLIFE HABITAT AREA ROUTINE EFFECTIVENESS EVALUATION

Transcription

1 GOPHER SNAKE WILDLIFE HABITAT AREA ROUTINE EFFECTIVENESS EVALUATION DRAFT March 2005 Prepared by: A. Haney and M. Sarell Ophiuchus Consulting Prepared for: Biodiversity Branch Ministry of Water, Land and Air Protection i

2 Executive Summary Wildlife habitat areas (WHAs) are established for areas containing important habitat or habitat features for Identified Wildlife under the Identified Wildlife Management Strategy, which is enabled under the Forest and Range Practices Act (FRPA). The importance of monitoring to evaluate the success of standards developed under FRPA has been recognized, and an effectiveness evaluation program, referred to as the FRPA Resource Evaluation Program (FREP), was initiated to assess the effectiveness of resource values managed for under FRPA, including wildlife. FREP implements a three-tiered approach to conducting effectiveness evaluations, referred to as routine, extensive and intensive evaluations. Routine evaluations are low intensity overview evaluations that use indicators that can be obtained at most sites (relatively simple qualitative measures, such as visual estimates and yes/no answers). Ovaska and Sopuck (2004) identified indicators and methods for monitoring the effectiveness of Gopher Snake WHAs. Spatial analysis of routine indicators was conducted using ArcView 3.2a geographic information system (GIS). Five routine indicators were analysed (Ovaska and Sopuck 2004): road density, land status, land use, fire potential and fire history. We conducted analyses for each indicator at both local and regional scales. Local scale includes the six approved WHAs at the time of the contract being awarded, and varying buffers from identified den sites at each WHA as well as at three selected benchmark sites. Regional scale includes the entire range of the BC metapopulation, comprised of the Fraser; Thompson-Nicola; Okanagan-Similkameen; and Kettle populations. The results presented in this report should be used with caution, due to the lack of confidence in the accuracy or applicability of most of the GIS spatial coverages, and the lack of field-proven information on the degree of impact each indicator has on Gopher Snake populations. It was found that road density is generally higher at WHA sites than benchmark sites, and within suitable habitat (excludes urban and agriculture) throughout the entire range. The land status analysis indicates a lower proportion of protected land at WHA sites than benchmarks, but a higher proportion than for the BC range. Land use at WHAs includes less rangeland (the most suitable habitat of the land use categories) than benchmarks but more than the metapopulation s range. No urban land use occurs at either WHAs or benchmarks, but WHA sites contain more agriculture than either benchmarks or the range. The potential for catastrophic or stand-replacing wildfire is greater at WHAs than at benchmarks, although it is lower than that for the BC range. Fire history during the 1900 s is considerably lower throughout the Southern Interior than expected based on historic fire regimes. The proportion of area burned during this time period is higher at WHAs than for the range, but is lower than at benchmarks. Although spatial analysis of routine indicators may be an efficient tool for determining the effectiveness of WHAs, especially when compared to benchmark populations, this approach was hampered by the following factors: no population estimates or viability analysis have been conducted at either WHAs or benchmarks, and it is only supposition that benchmarks are effective; no firm values have been determined for the degree of impact each indicator has on gophersnakes; and spatial coverages are often fraught with inaccuracies and/or lack of detail. Regardless, thresholds for each indicator have been suggested, although there are many site-specific factors that must be considered when assessing the effectiveness of each WHA. All of the WHA sites assessed were deemed to be effective for at least one of the indicators. However, only one site was judged effective for all of the indicators considered. ii

3 We recommend incorporating field-proven information from extensive evaluations into the spatial analysis, as well as obtaining or developing more accurate and detailed spatial coverages (particularly land status, fire potential and intensity of historic fire activity). Mitigation recommendations at WHA sites include: determining the specific impacts of roads on local snake populations and reduce threats where necessary; conduct stewardship at sites with high proportions of private land; and reduce wildfire threat and restore habitat suitability through thinning/burning of densely forested areas. iii

4 Table of Contents Executive Summary...ii Introduction...1 Methods...2 Results...3 Road Density...3 Land Status...6 Land Use...9 Fire Potential...12 Fire History...15 Discussion...18 Indicators...18 Effectiveness of WHAs...19 Recommendations...21 Literature Cited...22 Appendix I: Source coverages used in GIS spatial analysis...23 List of Tables Table 1: Local scale road densities and relative threat values for road type and proximity...4 Table 2: Regional scale road densities and relative threat values for road type...5 Table 3: Comparison of local and regional road densities...6 Table 4: Local scale land status....7 Table 5: Regional scale land status...9 Table 6: Comparison of local and regional land status...9 Table 7: Local scale land use...10 Table 8: Regional scale land use...11 Table 9: Comparison of local and regional land use...12 Table 10: Local fire potential...13 Table 11: Regional fire potential Table 12: Comparison of local and regional fire potential Table 13: Local scale fire history ( )...16 Table 14: Regional scale fire history ( ) Table 15: Comparison of local and regional fire history ( ) List of Figures Figure 1: Paved and gravel roads on suitable habitat within the known range of gophersnakes....5 Figure 2: Regional land status of suitable habitat in the potential range of gophersnakes...8 Figure 3: Regional land use in the known range of gophersnakes Figure 4: Regional fire potential in the known range of gophersnakes Figure 5: Regional fire history in the known range of gophersnakes...17 i

5 Introduction The Great Basin Gophersnake is a large snake that inhabits the valleys of the southern interior of BC. There is a strong habitat correlation with grassland ecosystems, although other habitats are used as well. The gophersnake is a constrictor, preying primarily on small mammals and spending much of the active season in mammal burrows. Eggs are laid in small mammal burrows on warm aspect slopes and adult females may only be able to reproduce every two or three years. Over-wintering can occur in communal dens in deep bedrock fractures or talus, or individually deep within burrows in deep-soiled grasslands. The restricted range in BC, low reproductive capacity and extensive threats within their range have placed this snake on the province s Blue-list (CDC 2005) and it is federally-listed as Threatened (COSEWIC 2004). A federal recovery strategy has been drafted (Sarell et al. 2004) that identifies conservation of important gophersnake habitat on Crown land as a priority for the recovery of the species. This was verified in a conservation assessment that looked at the distribution and abundance of Crown lands within their suspected range (Haney and Sarell 2005). Wildlife habitat areas (WHAs) are established for areas containing important habitat or critical habitat features for Identified Wildlife under the Identified Wildlife Management Strategy, which is enabled under the Forest and Range Practices Act (FRPA). Identified Wildlife are species or plant communities that have been determined to require special management under FRPA. Wildlife habitat areas are managed through implementation of general wildlife measures (GWMs). The Forest and Range Practices Act and Regulations apply a more results based approach than the former prescriptive Forest Practices Code, and the importance of monitoring to evaluate the success of standards developed under FRPA has been recognized. An effectiveness evaluation program, referred to as the Forest and Range Resource Evaluation Program (FREP), was initiated to assess the effectiveness of 11 resource values managed for under FRPA, including wildlife. Wildlife habitat areas are one of several management tools and standards implemented under FRPA to address wildlife. The Forest and Range Resource Evaluation Program implements a three-tiered approach to conducting effectiveness evaluations. The three levels of assessment are referred to as routine, extensive and intensive evaluations. Routine evaluations are defined as: Low intensity overview evaluations that use indicators that can be obtained at most sites (relatively simple qualitative measures, such as visual estimates and yes/no answers). The identification of indicators and the methods for monitoring the effectiveness of Gophersnake WHAs has been developed (Ovaska and Sopuck 2004). 1

6 Methods Routine evaluation of the effectiveness of Great Basin Gophersnake Wildlife Habitat Areas used spatial analysis in comparing each WHA site with benchmarks and population ranges. The spatial analysis was conducted using ArcView 3.2a geographic information system (GIS), with resulting tables exported into Microsoft Excel Five routine indicators were analysed (Ovaska and Sopuck 2004): road density, land status, land use, fire potential and fire history. See Appendix I for a description of source coverages. Past fire intensity was recommended as an indicator for the historic fire analysis (Ovaska and Sopuck 2004), but this information is not available and the existing fire history coverage/analysis gives no indication of how severe fires were. The Biodiversity Branch of WLAP had previously conducted much of the spatial analysis for the first four indicators, including clipping indicator coverages to WHAs, buffers and range, and compiling the resulting areas or lengths into tables. We conducted analyses for each indicator at both local and regional scales. Local scale includes the six approved WHAs at the time of the contract being awarded, and varying buffers (0-200m, 200m-1km and 1km-2km) from identified den sites at each WHA and three selected benchmark sites. Two WHAs (3-008 and 3-009) were treated as a single site, as the WHAs were adjacent and the two outer buffers overlapped significantly. One pre-selected benchmark site was not used, as it was not a confirmed gophersnake den. A nearby, known gophersnake den was used instead. Regional scale includes the entire range of the BC metapopulation, including each of the four populations: Fraser; Thompson-Nicola (referred to as Thompson in tables); Okanagan- Similkameen (referred to as Okanagan in tables); and Kettle. Recent revisions have been made to the range of gophersnakes in BC (Haney and Sarell 2005). However, many of the base GIS coverages were already clipped to the previously known range, so this extent, and the term known range, were used for this project. With the exception of a small portion of one WHA buffer, all local sites fell within this range extent. Suitable habitat within the potential (as opposed to known) range of gophersnakes was available from a recent gophersnake conservation analysis (Haney and Sarell 2005). For some regional analyses we used only this suitable habitat instead of the entire area within the range. The larger potential range was sometimes used, rather than the known range, as well. Road density analysis incorporated only two general road types: gravel and paved. Distinction was not made between primary and secondary, or divided and undivided, paved roads, as many of the busiest highways in close proximity to dens are undivided (e.g. much of Hwy 97 in the south Okanagan is classified as a two-lane undivided paved road). Unimproved roads were not included, due to very limited traffic volume, and less likelihood of snakes basking on roads. See Appendix I for a list of TRIM categories excluded from the analysis. The TRIM road coverage contained many duplicate roads. This was dealt with by selecting each road category into separate shapefiles. Road segments that were completely contained in the shapefile of a higher category (more lanes or pavement) were selected and deleted from the lower category shapefile to reduce duplication. However, in many cases roads did not completely overlap (i.e. only a portion of a road segment overlapped with a higher category), or duplicate roads of the same category occurred. These were dealt with only at the local scale, by manually inspecting each road segment for duplicates and deleting those road segments that did overlap, which often involving splitting the road segment. Therefore, regional scale still contains some duplicate roads. 2

7 Land status information for much of the BC range of gophersnakes originated from broad-scale provincial coverages. More detailed and accurate ownership information was available for the South Okanagan (Appendix I). Protected lands include Provincial Parks and Protected Areas, and WHAs at a regional scale (kept separate at local scale). In the South Okanagan, protected includes all federal, provincial and private conservation land. Some land use designations were lumped for the land use analyses. The forest category includes a variety of designations, including old forest, young forest, recently logged, selectively logged, and recently burned. Agriculture includes agriculture/residential mixes, and fresh water and wetland designations have been combined into the water/wetland category. The other land use category includes recreational activities (e.g. golf courses), barren surfaces, and very minor amounts of shrub and avalanche chute designations. All indicators except road density are presented as percentiles of the land area. Results Tables and maps for each analysis are presented in the following sections for local and regional scales, as well as a comparison between the two scales. Maps of local sites are intentionally devoid of identifying features to protect the location of snake dens, many of which also host rattlesnakes that have been prone to persecution. Results are presented for expanding buffers from the den, although it is recognized that gophersnakes may not evenly use habitats throughout these buffers. Interpretation of results focuses on the area within 1km of dens, as this is where the majority of gophersnake activity has been known to occur (Shewchuk 1996). Road Density Road traffic has been identified as a significant threat to many wide-ranging snakes (Ovaska and Sopuck 2004). The amount and proximity of roads, combined with the frequency of traffic, influence the degree of threat to populations. Table 1 presents road density in m/ha at a local scale, as well as relative threat values based on road type and proximity to dens. The table also contains maps depicting the amount and type of roads at each local site. All benchmarks occur in the Okanagan-Similkameen population, as do all WHA sites except one (3-008 and 3-009), which occurs in the Thompson-Nicola. None of the WHA or benchmark sites have roads within 200m of the den. The average relative threat value, based on road density and road type, within 1 km of WHA dens is 19, with a range of 4 to 35. Average road threat value within 1km of benchmark dens is 7, with a range of 0 to 16. The benchmark with the highest road density, however, has a lake and river between the den and the majority of roads within 1km. In this instance, the area used by gophersnakes within 1km of the den would actually have no paved road and very little gravel road. Most benchmarks have much higher road density and threat values in the 1-2km buffer. 3

8 Table 1: Local scale road densities and relative threat values for road type and proximity. Local Road Density WHA 0-200m 200m-1km 1-2km Total 1km Total 2km Map WHA: Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat WHA: Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat WHA: Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat WHA: Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat WHA: & Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat Benchmark: Barcello Gravel (m/ha) na Paved (m/ha) na Total (m/ha) na Roadtype Threat 1 na Benchmark: Darcus Gravel (m/ha) na Paved (m/ha) na Total (m/ha) na Roadtype Threat 1 na Benchmark: Ski Skree Gravel (m/ha) na Paved (m/ha) na Total (m/ha) na Roadtype Threat 1 na Roadtype Threat factors: gravel = 1; paved = 3 4

9 Road density and relative threat value for road type at a regional scale are presented in Table 2. These values are given for suitable habitat (excludes urban, agriculture and waterbodies), from a recent provincial conservation analysis (Haney and Sarell 2005), within the known range of gophersnakes. Values for suitable habitat occurring on Crown land within this same range are given in the table as well. Regional scale roads are portrayed in Figure 1. Table 2: Regional scale road densities and relative threat values for road type. Regional Road Density Fraser Thompson Okanagan Kettle BC Range Suitable Habitat Gravel (m/ha) Paved (m/ha) Paved (m/ha) Total (m/ha) Total (m/ha) Roadtype Threat 1 Suitable Crown Gravel (m/ha) Roadtype Threat 1 1 Roadtype Threat factors: gravel = 1; paved = 3 Figure 1: Paved and gravel roads on suitable habitat within the known range of gophersnakes. 5

10 The Okanagan-Similkameen ( Okanagan ) population has the highest road density (gravel and paved) and threat value within suitable habitat. The Fraser population has the lowest but is followed closely by the Thompson-Nicola ( Thompson ). Road densities are approximately 25% less on suitable Crown land than the entire range, despite suitable habitat excluding urban areas. Table 3 provides a comparison of road density at local and regional scales for the BC range (metapopulation) and each of the populations that contain WHAs. Averages for WHA and benchmark buffers are given for the total area within 1km and within 2km of dens. The benchmark and WHA average roadtype threats listed in Table 3 are based on average road densities multiplied by the applicable threat factor, and not based on average threat value. Benchmarks occur only in the Okanagan, so average values for the BC range are the same as for the Okanagan population. Table 3: Comparison of local and regional road densities. Local/Regional Road Density BC Range Benchmark Avg. WHA Avg. 1 km 2 km 1 km 2 km Suitable Habitat Suitable Crown Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat Okanagan Gravel (m/ha) Paved (m/ha) Total (m/ha) Roadtype Threat Thompson Gravel (m/ha) na na Paved (m/ha) na na Total (m/ha) na na Roadtype Threat 1 na na Roadtype Threat factors: gravel = 1; paved = 3 Average road density for WHAs is consistently higher than benchmarks and suitable habitat within population and metapopulation ranges. This suggests that either roadways and dens have an affinity for occurring in proximity to each other, versus dens being evenly distributed throughout their range, or most known dens happen to be located near roads, resulting from a sampling bias. Land Status The ownership status of lands originated from two sources, and the coverage available for the south Okanagan was more detailed and accurate than that obtained for the rest of the range of gophersnakes (Appendix I). Table 4 provides land status at a local scale. The GIS coverage was modified to ensure that WHAs had a land status of WHA, so a column listing the land status of WHAs is not included in the table (they are 100% WHA). 6

11 Table 4: Local scale land status. Local Land Status 0-200m 200m-1km 1-2km Total 1km Total 2km Map WHA: WHA 100% 22% 2% 25% 8% Protected 1 0% 6% 8% 6% 8% Crown (unprotected) 0% 0% 21% 0% 16% IR 0% 72% 68% 69% 69% Private 0% 0% 0% 0% 0% WHA: WHA 88% 16% 20% 19% 14% Protected 1 0% 16% 13% 16% 19% Crown (unprotected) 0% 3% 25% 3% 19% IR 0% 0% 0% 0% 0% Private 12% 65% 42% 63% 47% WHA: WHA 100% 52% 5% 54% 17% Protected 1 0% 30% 31% 29% 30% Crown (unprotected) 0% 3% 45% 3% 34% IR 0% 0% 0% 0% 0% Private 0% 15% 20% 14% 18% WHA: WHA 48% 13% 9% 15% 10% Protected 1 0% 0% 0% 0% 0% Crown (unprotected) 0% 2% 9% 2% 7% IR 27% 36% 36% 35% 36% Private 25% 49% 46% 48% 47% WHA: and WHA 71% 43% 1% 45% 15% Protected 0% 0% 0% 0% 0% Crown (unprotected) 29% 23% 50% 24% 42% IR 0% 31% 41% 29% 37% Private 0% 3% 8% 3% 6% Benchmark: Barcello Protected 1 0% 0% 0% 0% 0% Crown (unprotected) 98% 81% 54% 82% 61% IR 0% 0% 0% 0% 0% Private 2% 19% 46% 18% 39% Benchmark: Darcus Protected 1 91% 51% 53% 53% 53% Crown (unprotected) 9% 37% 15% 36% 20% IR 0% 0% 0% 0% 0% Private 0% 12% 32% 12% 27% Benchmark: Ski Skree Protected 1 100% 99% 83% 99% 87% Crown (unprotected) 0% 0% 1% 0% 1% IR 0% 0% 0% 0% 0% Private 0% 1% 15% 1% 12% 1 Includes private, provincial and federal conservation lands 7

12 The amount of protected land, which includes WHA status, within 1km of WHA dens ranges from 15 to 83%. Protected/WHA within 2km of dens ranges from 10 to 47%. Understandably, relatively little unprotected Crown land occurs within 1km of most WHA dens, as the available Crown land was incorporated into the WHA. However, WHA site & has a substantial amount of unprotected Crown for some reason, and WHA has a small amount. It is possible that the land status coverage is inaccurate. Three of the five WHA sites have Indian Reserve constituting a fairly high proportion of the area within both 1km and 2km of dens. Private land is significant at three of the five WHA sites as well. Benchmarks do not contain any WHA, and range from 0 to 99% protected land within 1km of dens. Unprotected Crown land varies from 0 to 83% within 1km of benchmark dens. No Indian Reserve occurs within two kilometres of any benchmark den. A fair amount of private land exists at two of the benchmarks. Land status analysis at a regional scale includes suitable habitat within the potential range (Table 5 and Figure 2). Figure 2: Regional land status of suitable habitat in the potential range of gophersnakes. 8

13 Table 5: Regional scale land status. Regional Land Status Fraser Thompson Okanagan Kettle Total Protected 1 16% 6% 12% 0% 10% Crown (unprotected) 55% 49% 49% 47% 50% IR 9% 11% 16% 0% 12% Private 20% 34% 24% 53% 28% 1 Includes WHA, and in the south Okanagan private, provincial and federal conservation lands The Fraser population contains the highest proportion of protected land and unprotected Crown land, while the Okanagan has the most Indian Reserve and the Kettle the most private land. Overall, 50% of the BC range is unprotected Crown, and almost 30% is private, while only 10% is protected. Table 6 provides a comparison of land status at local and regional scales, for both the BC range and the range of the Okanagan and Thompson populations. At a metapopulation level, the average amount of protected lands at WHAs is less than at benchmarks, but much higher than on suitable habitat in the provincial range. The amount of private land is similar among the three, except is lower within 1km of benchmark dens. Table 6: Comparison of local and regional land status. Local/Regional Land Status Benchmark Avg. WHA Avg. Suitable 1 km 2 km 1 km 2 km Habitat BC Range WHA 0% 0% 31% 13% Protected 51% 47% 10% 12% 10% Crown (unprotected) 39% 27% 6% 24% 50% IR 0% 0% 27% 28% 12% Private 10% 26% 26% 24% 28% Okanagan WHA 0% 0% 28% 12% Protected 51% 47% 13% 14% 12% Crown (unprotected) 39% 27% 2% 19% 49% IR 0% 0% 26% 26% 16% Private 10% 26% 31% 28% 24% Thompson WHA na na 45% 15% Protected na na 0% 0% 6% Crown (unprotected) na na 24% 42% 49% IR na na 29% 37% 11% Private na na 3% 6% 34% Land Use Local-scale land use is listed in Table 7. All WHA and benchmark sites are almost entirely rangeland and/or forestry use within 200m of dens. A large amount of agricultural activity occurs within 1km at two WHAs and one benchmark. One WHA has mining activity less than one km from the den. 9

14 Table 7: Local scale land use. Local Land Use WHA 0-200m 200m-1km 1-2km Total 1km Total 2km Map WHA: Rangelands 0% 0% 5% 46% 5% 36% Forest 100% 100% 95% 54% 95% 64% Agriculture 0% 0% 0% 0% 0% 0% WHA: Rangelands 22% 94% 39% 42% 41% 42% Forest 77% 6% 17% 39% 16% 34% Agriculture 1% 0% 44% 19% 43% 25% WHA: Rangelands 66% 98% 63% 38% 64% 44% Forest 34% 0% 15% 50% 14% 41% Agriculture 0% 2% 23% 12% 22% 15% WHA: Rangelands 2% 71% 34% 14% 36% 20% Forest 98% 29% 53% 61% 52% 59% Agriculture 0% 0% 5% 18% 5% 15% Mining 0% 0% 8% 6% 7% 6% WHA: & Rangelands 21% 26% 48% 35% 47% 39% Forest 79% 74% 51% 59% 52% 57% Agriculture 0% 0% 2% 5% 1% 4% Benchmark: Barcello Rangelands na 57% 62% 47% 62% 51% Forest na 43% 38% 43% 38% 42% Agriculture na 0% 0% 10% 0% 7% Benchmark: Darcus Rangelands na 100% 40% 33% 42% 36% Forest na 0% 34% 39% 33% 37% Agriculture na 0% 3% 18% 3% 14% Fresh water na 0% 22% 10% 22% 13% Benchmark: Ski Skree Rangelands na 95% 84% 49% 84% 58% Forest na 5% 16% 50% 16% 42% Agriculture na 0% 0% 0% 0% 0% 10

15 Regional land use analysis includes the entire area within the known range of gophersnakes (Table 8 and Figure 3). Forest is the dominant land use overall, and within each population, at approximately 50%. Rangeland is the next highest land use, and the population having the lowest amount of this land use if the Okanagan. Agriculture (including residential/agriculture mixes) comes in third, but is lower in the Fraser than the other populations. The water/wetland category forms a significant portion of regional land use in the Okanagan. The other land use category includes recreational activities (e.g. golf courses), barren surfaces, and a very small amount of avalanche chute and shrub. Table 8: Regional scale land use. Regional Land Use Fraser Thompson Okanagan Kettle Rangelands 40% 37% 23% 34% Forest Total 30% 50% 47% 47% 46% 48% Agriculture 4% 9% 12% 14% 10% Urban 0% 2% 5% 3% 3% Mining 0% 0% 0% 0% 0% Water/wetland 3% 5% 12% 1% 8% Other 3% 1% 0% 1% 1% Figure 3: Regional land use in the known range of gophersnakes. 11

16 Table 9 presents a comparison of land use proportions at local and regional scales, for the BC metapopulation range, and within the range of each population. The Okanagan contains all the benchmarks sites and the majority of the WHA sites. Benchmarks have a much higher amount of rangeland than WHA sites, although WHAs are still higher than the total range. In the Okanagan population and the BC metapopulation, agricultural land use is slightly higher at WHA sites than in the total range. Table 9: Comparison of local and regional land use. Local/Regional Land Use BC Range Benchmark Avg. WHA Avg. 1 km 2 km 1 km 2 km Total Range Rangeland 62% 51% 40% 37% 30% Forest 38% 42% 47% 52% 48% Agriculture 0% 7% 12% 11% 10% Urban 0% 0% 0% 0% 3% Mining 0% 0% 1% 1% 0% Water / wetland 0% 0% 0% 0% 8% Other 0% 0% 0% 0% 1% Okanagan Rangeland 62% 51% 36% 35% 23% Forest 38% 42% 44% 49% 47% Agriculture 0% 7% 17% 14% 12% Urban 0% 0% 0% 0% 5% Mining 0% 0% 2% 2% 0% Water / wetland 0% 0% 0% 0% 12% Other 0% 0% 0% 0% 0% Thompson Rangeland na na 47% 39% 37% Forest na na 52% 57% 47% Agriculture na na 1% 4% 9% Urban na na 0% 0% 2% Mining na na 0% 0% 0% Water / wetland na na 0% 0% 5% Other na na 0% 0% 1% Fire Potential Fire is considered a habitat maintaining function but can become a threat when intense, hot fires occur. The GIS coverage depicting potential for catastrophic wildlife appears to use only natural disturbance type and stand age to determine the likelihood of fire. Low potential is assigned to stands less than 150 years, high potential to stands over 250 years, and moderate to those in between. This does not take into account site-specific factors such as previous stand-maintaining fire activity, tree density and ingrowth, or prevalence of dry weed species like cheatgrass and knapweed. The coverage, therefore, seems to underestimate the actual chance of high intensity wildfire, particularly in younger stands. Fire potential at a local scale is provided in Table 10, including maps of each site. Note that data is missing for a small portion of the 2km buffer for WHA & 3-00, as the supplied coverage was clipped to the known range, and the buffer extends beyond this range. 12

17 Table 10: Local fire potential. Local Fire Potential WHA 200m 1km 2km Total 1km Total 2km Map WHA: High 11% 0% 3% 0% 3% 1% Moderate 11% 33% 4% 14% 5% 12% Low 78% 67% 86% 37% 85% 49% Total 100% 100% 93% 51% 93% 61% Non-forest 0% 0% 7% 49% 7% 39% WHA: High 0% 0% 0% 0% 0% 0% Moderate 8% 2% 4% 15% 4% 12% Low 71% 9% 15% 44% 15% 37% Total 79% 11% 20% 59% 19% 49% Non-forest 21% 89% 80% 41% 81% 51% WHA: High 0% 0% 0% 0% 0% 0% Moderate 31% 0% 15% 39% 14% 33% Low 1% 1% 6% 14% 6% 12% Total 31% 1% 21% 53% 20% 45% Non-forest 69% 99% 79% 47% 80% 55% WHA: High 0% 0% 0% 0% 0% 0% Moderate 71% 30% 37% 23% 37% 26% Low 24% 31% 33% 42% 33% 40% Total 95% 60% 70% 65% 70% 66% Non-forest 5% 40% 30% 35% 30% 34% WHA: & High 0% 0% 0% 0% 0% 0% Moderate 70% 46% 44% 38% 44% 40% Low 19% 48% 17% 23% 18% 21% Total 89% 94% 60% 61% 62% 61% Non-forest 11% 6% 40% 39% 38% 39% Benchmark: Barcello High na 0% 0% 0% 0% 0% Moderate na 42% 31% 31% 31% 31% Low na 3% 8% 13% 7% 11% Total na 45% 39% 44% 39% 42% Non-forest na 55% 61% 56% 61% 58% Benchmark: Darcus High na 0% 0% 0% 0% 0% Moderate na 1% 11% 6% 10% 7% Low na 0% 19% 41% 19% 35% Total na 1% 30% 47% 29% 42% Non-forest na 99% 70% 53% 71% 58% Benchmark: Ski Skree High na 0% 0% 0% 0% 0% Moderate na 0% 3% 15% 3% 12% Low na 1% 15% 38% 14% 32% Total na 1% 18% 53% 17% 44% Non-forest na 99% 82% 47% 83% 56% 13

18 The high fire potential category occurs at only one local site, WHA However, due to the lack of confidence in the categories, the information should be interpreted using the total fire potential values (equivalent to forested area). WHA sites 8-023, and 3-008&3-009 have a substantial amount of forested area potentially prone to stand-replacing fire events. Regional scale fire potential is presented in Table 11 and Figure 4. Information is missing for the northern tip of the Fraser population. High fire potential is very minor throughout the range, according to the GIS coverage, although the total fire potential area is quite large. The Thompson population has the largest fire threat, and the Fraser the lowest. Table 11: Regional fire potential. Regional Fire Potential Thompson Okanagan 1% 2% 0% 0% 1% Moderate 22% 33% 27% 1% 27% Low 32% 54% 47% 67% 48% High Fraser Kettle Total Total 55% 89% 74% 67% 76% Non-forest 45% 11% 26% 33% 24% Figure 4: Regional fire potential in the known range of gophersnakes. 14

19 A summary of both local and regional fire potential is provided in Table 12. Both benchmarks and WHA sites have lower threat of fire than the overall range, for the metapopulation and each applicable population. The average WHA fire potential is greater than the average for benchmark sites. Table 12: Comparison of local and regional fire potential. Local/Regional Fire Benchmark Avg. WHA Avg. Total Potential 1 km 2 km 1 km 2 km Range BC Range High 0% 0% 0% 0% 1% Moderate 15% 17% 25% 26% 27% Low 13% 26% 29% 30% 48% Total 28% 43% 55% 57% 76% Non-forest 72% 57% 46% 43% 24% Okanagan High 0% 0% 0% 0% 0% Moderate 15% 17% 15% 21% 27% Low 13% 26% 35% 34% 47% Total 28% 43% 51% 55% 74% Non-forest 72% 57% 50% 45% 26% Thompson High na na 0% 0% 2% Moderate na na 44% 40% 33% Low na na 18% 21% 54% Total na na 62% 61% 89% Non-forest na na 38% 39% 11% Fire History A GIS coverage of historic fire activity from 1919 to 2000 was obtained, but does not include information on fire intensity. Fire history at local sites is presented in Table 13, including maps of each site. It should be noted that the proportion of area burned is not relative to 100%, as areas may have burned more than once during this time period. Given a mean fire return interval of 5-50 years for stand-maintaining fire events in NDT4 subzones (Wong et al. 2003), the expected proportion of area burned should be at least 180%. Table 13 indicates that actual fire activity is drastically lower than expected under natural fire regimes. The proportion of area previously burned within WHAs varies from 2% to 83%, and within 2km of WHA dens ranges from 22% to 76%. Burned area within 2km of benchmark dens varies from 2% to 106%. 15

20 Table 13: Local scale fire history ( ). Local Fire History WHA 200m 1km 2km Total 1km Total 2km Map WHA: Number of Fires/1000ha Area Burned 15% 0% 37% 23% 36% 26% WHA: Number of Fires/1000ha Area Burned 62% 61% 79% 75% 78% 76% WHA: Number of Fires/1000ha Area Burned 83% 100% 59% 58% 60% 59% WHA: Number of Fires/1000ha Area Burned 2% 32% 38% 17% 38% 22% WHA: & Number of Fires/1000ha Area Burned 57% 203% 73% 20% 78% 34% Benchmark: Barcello Number of Fires/1000ha na Area Burned na 0% 0% 2% 0% 2% Benchmark: Darcus Number of Fires/1000ha na Area Burned na 138% 84% 113% 86% 106% Benchmark: Ski Skree Number of Fires/1000ha na Area Burned na 101% 128% 83% 127% 94% 16

21 Fire history at a regional scale (Table 14, Figure 5) indicates that the area burned during the 91 year time period is even more dramatically lower than expected. The Okanagan population has the highest proportion of burned area, but is still only 33%. Table 14: Regional scale fire history ( ). Regional Fire History Fraser Thompson Okanagan Kettle Total Number of Fires/1000ha Area Burned 14% 10% 33% 22% 21% Figure 5: Regional fire history in the known range of gophersnakes. Table 15 presents a comparison of local and regional fire history. The proportion of area burned from 1919 to 2000 is much higher at benchmark sites than at WHA sites, which are in turn higher than the total range. Although the Thompson range has been subjected to less fire activity than the BC or Okanagan range, the Thompson WHA site has previously burned to a higher degree than both metapopulation and Okanagan population WHA sites on average. 17

22 Table 15: Comparison of local and regional fire history ( ). Local/Regional Fire Benchmark Avg. WHA Avg. History 1 km 2 km 1 km 2 km BC Range Total Range Number of Fires/1000ha Area Burned 71% 68% 47% 38% 21% Okanagan Number of Fires/1000ha Area Burned 71% 68% 53% 46% 33% Thompson Number of Fires/1000ha na na Area Burned na na 78% 34% 10% Discussion The effectiveness of WHAs can be measured by how well conservation is applied to the site and how well threats are avoided. A series of routine indicators were suggested (Ovaska and Sopuck 2004) as a means of evaluating the effectiveness of WHAs at regional and local scales. In theory, analyzing routine indicators proximal to dens is an efficient tool for determining the effectiveness of a WHA, especially when compared to benchmark populations. This approach, however, was hampered by the following factors: There are no firm population estimates or viability analyses for benchmark or WHA populations, so it is only supposition that benchmarks are effective and not at risk, and comparisons to WHAs are approximate. There are no firm values for the impacts that threats (indicators) may have on a population. Indicator information derived from existing spatial coverages is subject to numerous inaccuracies, may be at an inappropriate scale, and/or measure attributes that do not accurately interpret the desired indicator. A comparison of the average values for each indicator between benchmarks and WHAs provides rough thresholds between effective and effective but at risk. The following sections discuss the results of examining the five indicators, including the potential implications of each indicator and then how each WHA rates. Indicators Roads The impacts from paved roads were presumed to be three times that of gravel roads, due to higher traffic volumes and the increased thermoregulatory attraction of paved roads. Appropriate effectiveness thresholds for roadtype threat values (sum of density times threat factor of each road type) within 1km of dens may be up to approximately 15 for effective, and 30 for functioning but at risk. Although it does not apply to any of the WHA analysed, thresholds for road threat within 200m of dens would be much lower, perhaps 5 for effective and 10 for functioning but at risk. Besides the proximity of roads and amount of use, there are a number of other factors that need to be considered as well. The spatial pattern of roads (e.g. all on one side of den vs. den surrounded) should be assessed. The amount and quality of habitat between den 18

23 and roads (enticing the snakes to stay in that area), as well as barriers between den and roads (e.g. lakes preventing the snakes travelling to the roads) also need to be taken into consideration. Land Status To be effective, we estimate that approximately half of the area within 1km of dens should be protected (including WHA), with almost all of the area within 200m protected. Functioning but at risk thresholds may be about one-third of the 1km area protected, with at least 75% of the area within 200m of dens 1. The type of land status in surrounding areas also needs to be considered. Generally, Crown land, and to some extent Indian Reserves, are less likely to impact snake populations than private land. Not effective or marginal WHAs may need stewardship programs on surrounding lands. Land Use Rangeland would be the most suitable habitat for gophersnakes of the land use categories. A suggested threshold for effectiveness is that rangeland comprise at least a third of the area within 1km of dens. Functioning but at risk WHAs may have rangeland proportions of about 20% or more. The types of other land uses occurring must be taken into account, as forest may be suitable habitat depending on the density and logging activity/history. WHAs with a large amount of densely forested area may need enhancement initiatives undertaken, such as thinning and burning. Existing land uses that pose threats to gophersnakes (e.g. urban, agriculture, mining) must be weighed heavily as well. Fire Potential Catastrophic or stand-replacing forest fires are presumably more likely to kill gophersnakes than low intensity stand-maintaining fires in grasslands and open forests, where snakes may be able to take shelter in rodent burrows. Appropriate WHA thresholds for total fire potential within 1km of dens may be: under about one-third of the area are effective; and over one-third of the area are functioning but at risk. However, stand conditions other than age must be considered, including tree density. Old but very open stands are at much lower risk of catastrophic fire than young, dense stands. Ingrowth of Douglas-fir into ponderosa pine forests will increase the likelihood of intense fire as well. Topography and location of surrounding dense stands relative to the 1km area should also be assessed. Fire History Fire history can be used as an indication of ecosystem health in NDT4 subzones, which were historically maintained by frequent low-intensity fires. Threshold values are not applicable, however, as the entire range of gophersnakes has been subjected to fire suppression for many decades and is not functioning under natural fire regimes. Effectiveness of WHAs WHA Road density: effective very low density, and only gravel roads occur within both 1km and 2km. 1 It should be noted that one benchmark site has no protected land within 2km of the den a WHA should be established on the available crown land. 19

24 Land status: functioning but at risk all of the 200m buffer area, but only 31% of the 1km area, is protected; other surrounding land is all IR and Crown. Land Use: functioning but at risk (although not functioning according to threshold) only 5% is rangeland, but the remainder is forest that is mostly moderately open and rugged (pers.obs.). Fire Potential: functioning but possibly at risk total fire potential is 93% of the 1km area, but the forest is fairly open. WHA Road Density: not functioning high density of both gravel and paved roads; most roads are located to the east of the den within 1km, but there is one gravel road to the south. Land Status: functioning but at risk only 88% of the 200m area, and 35% of the 1km area, is protected. Land Use: effective fairly high proportion of rangeland, although a large amount of agriculture occurs; the agricultural activities in the area are mostly pasture, though, and not cultivated or hayed (pers.obs.) Fire Potential: effective low amount of fire potential within 1km of den, and forest is very open (pers.obs.). WHA Road Density: effective, but marginal paved road density is high within 1km, but roads are all located to the west of the den, with abundant suitable habitat east of the road. Land Status: effective all of the 200m area, and over half of the 1km area, is protected. There appears to be a small amount of unprotected Crown land just outside the 200m buffer, which should be incorporated into the WHA. Land Use: effective high proportion of rangeland, but a large amount of agricultural activity occurs within 1km of the den; agricultural land at this site includes hayfields (pers.obs.). Fire Potential: effective low amount of fire potential, and forest is open and on the uphill side of the 1km area. WHA Road Density: effective only gravel roads occur within 1km of the den, but a large amount of paved road occurs within 2km. Land Status: not functioning less than half of the area within 200m of the den, and only 15% within 1km, is protected. Land Use: functioning but at risk, but marginal just over a third of the 1km area is rangeland, although the fire potential coverage indicates a significant portion of this area is forested; both agriculture and mining activities occur within 1km of the den. Fire Potential: functioning but at risk 70% of the area within 1km of the den has fire potential, and the forest is moderately closed to dense. WHA & Road Density: functioning but at risk high density of paved road in close proximity to dens. 20

25 Land Status: functioning but at risk almost half of the area within 1km of dens, but only 71% of the area within 200m, is protected; very little land protected beyond 1km. WHA should be expanded to incorporate as much of the unprotected Crown land as possible. Land Use: effective high proportion of rangeland, but also a high amount of forest that may need thinning. Fire Potential: functioning but at risk high amount of fire potential within 1km of dens; forest conditions unknown. Recommendations Spatial analysis: Incorporate information on the degree of impact each indicator has on gophersnake populations, based on field-proven results (extensive and possibly intensive evaluations). Indicators can then be ranked according to their significance. Obtain a more accurate land status coverage for the entire BC range. Include range use (grazing tenure and plans) information in the land use analysis. Obtain a more precise fire potential coverage, which includes site-specific factors. WHA mitigation: Determine gophersnake patterns of dispersal at WHAs to establish whether existing roads cause significant impacts, and where these do occur, implement mitigation measures to reduce threats (e.g. drift fencing and underpasses). Implement stewardship programs where WHAs have a high proportion of private land in surrounding areas. Reduce fire threat and enhance gophersnake habitat through thinning/burning of forested areas. Utilize WHA indicator thresholds as a guide to determine whether the establishment of each new WHA is appropriate. 21

26 Literature Cited COSEWIC (Committee on the Status of Wildlife in Canada) Canadian Species at Risk, November Haney, A. and M. Sarell Conservation analysis for the Great Basin Gophersnake (Pituophis catenifer) in British Columbia. Prepared for Biodiversity Branch, Ministry of Water, Land and Air Protection, Victoria, BC. Hobbs, J Gopher snakes (and cohorts): An assessment of selected den sites in the Thompson/Fraser and Okanagan snake populations. Ministry of Water, Land and Air Protection, Habitat Branch. Victoria, BC. Ovaska, K. and L. Sopuck Indicators and Methods for Monitoring the Effectiveness of Gopher Snake Wildlife Habitat Areas. Report prepared for BC Ministry of Water, Land and Air Protection, Biodiversity Branch. Victoria, B.C. Sarell, M.J., D. Nield, and the BC Southern Interior Reptile and Amphibian Recovery Team Recovery Strategy for the Great Basin Gopher Snake (Pituophis catenifer deserticola) in Canada. Prepared for the National Recovery Program (RENEW) under the Accord for the Protection of Species at Risk, Environment Canada, Ottawa. Shewchuk, C.H The natural history of reproduction and movement patterns in the Gopher Snake (Pituophis melanoleucus) in Southern British Columbia. M.Sc. Thesis, Department of Biology, University of Victoria. Victoria, BC. Wong, C., B. Dorner and H. Sandmann Estimating historic variability of natural disturbances in British Columbia. Ministry of Forest, Forest Science Program, and Ministry of Sustainable Resource Management, Resource Planning Branch. 22

27 Appendix I: Source coverages used in GIS spatial analysis. Gophersnake known range From Hobbs Supplied by WLAP Biodiversity Branch. Suitable habitat within potential range of Gophersnakes From Haney and Sarell Gophersnake Wildlife Habitat Areas Six approved WHAs as of September Supplied by WLAP Biodiversity Branch. Road Density Analysis TRIM II (Terrain and Resource Information Management) transportation layer. Supplied by WLAP Biodiversity Branch already clipped to known range of gophersnakes. Modified to remove entirely overlapping segments of different road categories (FCODE descriptions). Further modified within local (WHA and benchmark) buffers to remove all overlapping roads. TRIM transportation categories excluded from final road coverage: airfield; airport; airportabandoned; airstrip; bridge; bridge-foot; bridge-trestle; cut (roadway); embankment/fill (roadway); ferry route; rail line-abandoned; rail line (double track); rail line (multiple track); rail line (single track); road-overgrown; road-unimproved; skid trail; snowshed (railway); spur; trail; tunnel (rail). Land Status Analysis From Haney and Sarell 2005, which includes provincial IR, PA and private land coverages, and SOCS (South Okanagan Conservation Strategy) land ownership coverage. Clipped Tantalis coverage supplied by WLAP Biodiversity Branch, but not used in analysis. Land Use Analysis BTM (Baseline Thematic Mapping) 1:250,000 scale land use mapping. Supplied by WLAP Biodiversity Branch already clipped to known range. Fire Potential Analysis Original source unknown. Supplied by WLAP Biodiversity Branch already clipped to known range. Fire History Analysis British Columbia natural disturbance database, Canadian Forest Service ( 23