Road Ecology Center UC Davis

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1 Road Ecology Center UC Davis Title: Assessing the impact of roads on animal population viability Author: van der Grift, Edgar A., Wageningen University and Research Centre Verboom, Jana, Wageningen University and Research Centre Pouwels, Rogier, Wageningen University and Research Centre Publication Date: Series: Recent Work Permalink: Additional Info: van der Grift EA, Verboom J and Pouwels R Assessing the impact of roads on animal population viability. IN: Proceedings of the 2003 International Conference on Ecology and Transportation, Eds. Irwin CL, Garrett P, McDermott KP. Center for Transportation and the Environment, North Carolina State University, Raleigh, NC: pp Keywords: spatial, developments, roads, animal population, dynamic, species Abstract: Different tools have been developed to study the potential effects of spatial developments, such as the construction of roads, on the viability of animal populations. For instance, with dynamic (meta)population models the impacts of spatial developments can be accurately quantified. However, these models are often species specific and require detailed field research to validate the parameters used. If a multi-species analyses is needed, the use of such models is often impractical and expensive. In that case, an expert system, in which analyses of different species can be aggregated, may be a better tool to assess these kinds of impacts. Pros and cons of both types of tools are illustrated with (1) the ex-ante analyses of badger (Meles meles) population viability in central Limburg (The Netherlands) after the (proposed) construction of highway A73, and (2) the multi-species analyses of high priority locations to restore habitat connectivity across main roads in The Netherlands. Copyright Information: All rights reserved unless otherwise indicated. Contact the author or original publisher for any necessary permissions. escholarship is not the copyright owner for deposited works. Learn more at escholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.

2 Chapter 6...Habitat Connectivity Planning & Assessment ASSESSING THE IMPACT OF ROADS ON ANIMAL POPULATION VIABILITY Edgar A. van der Grift (Phone: , Jana Verboom and Rogier Pouwels, Alterra, Wageningen University and Research Centre, P.O. Box 47, NL-6700 AA Wageningen, The Netherlands Abstract: Different tools have been developed to study the potential effects of spatial developments, such as the construction of roads, on the viability of animal populations. For instance, with dynamic (meta)population models the impacts of spatial developments can be accurately quantified. However, these models are often species specific and require detailed field research to validate the parameters used. If a multi-species analyses is needed, the use of such models is often impractical and expensive. In that case, an expert system, in which analyses of different species can be aggregated, may be a better tool to assess these kinds of impacts. Pros and cons of both types of tools are illustrated with (1) the ex-ante analyses of badger (Meles meles) population viability in central Limburg (The Netherlands) after the (proposed) construction of highway A73, and (2) the multi-species analyses of high priority locations to restore habitat connectivity across main roads in The Netherlands. Introduction Ever expanding urban areas, and the continuous construction of new infrastructure in between, reduces both the quantity and quality of wildlife habitat (Reijnen et al. 2000). Formerly continuous habitat becomes highly fragmented, leaving small habitat patches scattered throughout the landscape. Populations in such small, isolated habitat patches have an increased risk to become extinct, while simultaneously the chance of (re)colonisation is reduced (Opdam 1991, Hanski 1999). Therefore, there is an increasing need to predict the environmental impact of spatial developments, such as the construction of roads, on animal population viability or even the survival of a species. Different tools have been developed to conduct population viability analyses (PVA) for a variety of species. Some of these PVA-tools are suitable to analyse the (potential) impacts of roads (Piepers et al. 2003). These PVA-tools can be divided into (meta)population models and expert systems. Metapopulation models simulate population dynamics using birth, death and migration dynamics in relation to habitat size, quality and connectivity. It is an advantage when the model is spatially explicit. Metapopulation models are usually speciesspecific. Expert systems are usually rule-based models, using thresholds to determine whether a population will be viable or not. Generally, these types of PVA-tools are based on thematic landscape databases (e.g., habitat map, land use map, road barrier map), and are suitable to analyse population viability for different species. In this paper two PVA-tools are presented, which have been successfully used in solving road-related fragmentation issues: (1) the metapopulation model DASSIM, and (2) the expert system LARCH. Pros and cons of both types of tools will be illustrated with two cases. Case 1 is the analysis of badger population viability in central Limburg (The Netherlands), using DASSIM, after the (proposed) construction of highway 73. Case 2 describes the multi-species analysis with LARCH of high-priority locations to restore habitat connectivity across main roads in the Netherlands. Similar analyses have been done for railroads and main waterways, but these will not be addressed in this paper (Van der Grift et al. 2003). The aim of presenting these tools and cases is to illustrate how population viability assessments can play a key role in careful spatial planning and are vital in prioritizing defragmentation initiatives. The cases emphasize the differences in both the approach and application of the two described PVA-tools. The Model Dassim DASSIM is a dynamic (meta)population model for the Eurasian badger (Meles meles) (Lankester 1989, Lankester et al. 1991). The model is able to simulate population dynamics for this species in both space and time. It has the ability to distinguish individual badgers, badger clans, local populations (i.e., clusters of badger clans, in which random mating occurs) and metapopulations (i.e., clusters of local populations, connected by dispersal) (Levins 1970, Andrewartha and Birch 1984). Local populations are spatially explicit, which is expressed in differences in the exchange probability between local populations, i.e., the likeliness that a badger from local population A will reach local population B. In addition, differences in mortality probability between local populations due to high or low road densities or differences in traffic volume can be applied. Other characteristics of DASSIM are the inclusion of demographic stochasticity, the ability to distinguish male and ICOET 2003 Proceedings 173 Making Connections

3 female badgers in two age classes (juvenile and adult), and the ability to include knowledge about the social structure of badger populations, i.e., badgers living in social groups (clans) in which not all individuals take part in reproduction. For further reading about the model DASSIM we refer to Verboom (1996) and Van Apeldoorn et al. (1997). Case 1: Simulating Badger Survival After Highway Construction The model DASSIM was used for the assessment of badger population viability after the proposed construction of the southern stretch of highway 73 in central Limburg, The Netherlands (Van der Grift and Verboom 2001). Initiator of the project was the Division Limburg of the Directorate-General of Public Works and Water Management, part of the Dutch Ministry of Transport, Public Works and Water Management. After completing the Environmental Impact Assessment (Heidemij 1993), the Division Limburg worked out a plan for mitigating and compensating the negative impacts of the construction of highway 73 that could not be avoided (Van der Molen et al. 1999, De Beijer and Van der Molen 1999). One of the problems is that the new road will intersect core badger habitat. Badgers are known to be sensitive to habitat fragmentation by roads (Van Apeldoorn and Kalkhoven 1991, Van der Zee et al. 1992). Annually almost a quarter of the whole badger population in the Netherlands is killed on roads (Broekhuizen et al. 1994, Anonymous 2002, Anonymous 2003). Furthermore, road construction will destroy setts and feeding areas, and if no measures are taken the highway may be a considerable barrier to badger movements (Clarke et al. 1998). All these impacts will affect population viability and may result in local extinction of the species. The mitigation and compensation plan included the construction of wildlife passages (mostly badger pipes; see figure 1) and fences to keep the animals from entering the road. Furthermore, the plan contained proposals for habitat restoration and the development of small-scale linear landscape elements (e.g., hedges, strips of woodland). The aim of the latter was to improve connectivity between foraging areas and sett sites, and to guide the animals to the wildlife passages. The question that remained was: Will the proposed set of mitigating and compensating measures be sufficient to ensure the survival of badgers in the area? We used the simulation model DASSIM to conduct a PVA in order to answer this question. Fig. 1. Badger pipes have proven to be effective road crossing structures for badgers. Photograph: Edgar van der Grift. The PVA focused on three scenarios for highway construction, which differ in the amount of mitigation and compensation measures taken, and the expected effectiveness of these measures (100 percent versus 50 percent effectiveness, i.e., half the wildlife tunnels cannot be used and half the fences are defective). These scenarios were compared with the situation that no highway is constructed. Basic information about the configuration of the badger population (position and size of local populations and network populations) was derived from recent sett and habitat surveys, and knowledge about the ecology and dispersal capacity of badgers. The simulation with DASSIM is schematically summarised in figure 2. ICOET 2003 Proceedings 174 Making Connections

4 start year 1 year male 2 female reproduction mortality n male juv n female juv n male n female etc (100 runs) migration: within / between local populations Fig. 2. Schematic overview of the simulation of Fig. 2. Schematic badger overview population of the simulation dynamics of badger with population DASSIM. dynamics with DASSIM. The study showed that highway construction is not necessarily bad for the viability of badger The study showed that highway populations construction in the region. That is is, not if all necessarily proposed wildlife bad passages for the and viability fences are of constructed badger populations in the region; that is, if all and proposed all these measures wildlife remain passages functional, and i.e. fences all wildlife are tunnels constructed can be used and year-round all these and measures remain functional, i.e. all wildlife fences tunnels show no can failures. be used Proper year-round management of and measures fences appears show to be no of decisive failures. Proper management importance to the survival of the species in the region: if only half of the measures is effective of measures appears to be of decisive importance to the survival of the species in the region: if only half of the badger population is likely to disappear (fig. 3). If no construction of the highway takes the measures is effective place, the and badger consequently population no mitigation is likely measures to are disappear installed, expected (fig. 3). autonomous If no construction increase of the highway takes place, and consequently in traffic volume no mitigation local and measures regional roads are would installed, result high expected badger mortality. autonomous That is increases in traffic volume at local and regional why badger roads population would viability result is in expected high badger to be lower mortality. for this scenario That than is why in case badger the population viability highway, including all wildlife measures, is constructed. is expected to be lower for this scenario than in the case where the highway, including all wildlife measures, is constructed. 160 Number aantal of badgers dassen Years tijd (jaar) Mitigation measures 100% effective au ton oom m et, alle m itig atie Mitigation au ton oom m et, 50% measures effectiviteit 50% effective Fig. 3. With DASSIM simulated trends in badger numbers after highway construction in central Limburg (The Netherlands) for two scenarios: (1) all mitigation measures function well, (2) only half of the proposed mitigation measures function well. Expert System Larch LARCH (Landscape ecological Analysis and Rules for the Configuration of Habitat) is an expert system that assesses the sustainability of habitat networks for a variety of species (Pouwels et al. 2002a). Input for the assessment is a habitat map. For each habitat patch the carrying capacity for the species concerned is calculated, based on size and habitat quality of the patch. Then LARCH analyses the configuration of the population, i.e., what habitat patches are occupied by individuals of the same local population and which local populations belong to the same metapopulation, using rules for maximum distances between local populations and metapopulations. Total carrying capacity of a metapopulation is compared with thresholds for a minimum viable metapopulation (MVMP) in order to determine whether a metapopulation is expected to be viable or not. Thresholds differ, dependent on the configuration of the metapopulation. When the metapopulation includes a key population, i.e., a relative large local population which is viable under the condition of one immigrant per generation, the threshold for a MVP can be considerably lower than in the case where no key population is present (Verboom et al. 2001). LARCH is able to include the barrier effect of roads in the analyses. The presence of roads may result in a decreased probability that an animal reaches a neighboring local population, and consequently to the split up ICOET 2003 Proceedings 175 Making Connections 4

5 of (meta)populations. The extent to which the road is a barrier is species-specific and can be gradually adjusted in the model, differing from no barrier at all to an absolute barrier. For a more comprehensive explanation of LARCH and the argumentation behind the rules and thresholds used in this expert system, we refer to Verboom et al. (2001), Pouwels et al. (2002a), Opdam et al. (2003) and Verboom & Pouwels (in press). Case 2: Assessing Priority Locations for Defragmentation In the Netherlands, high human population densities result in high road densities. Population density is on average 470 people/km 2. Paved road density is 3.4km/km 2, which is one of the highest in the world (fig. 4). Consequently habitat fragmentation is a widespread problem. Both core natural areas and ecological corridors are frequently intersected by roads. In addition planned habitat restoration areas or ecological linkages, such as the Robust Ecological Corridors, are crossed by roads as well, which may affect proper functioning of these measures to improve wildlife viability (Anonymous 2000). Fig. 4. Road network in the Netherlands. In the last decade many bottleneck analyses have been carried out to assess the locations where roads impact ecological networks within the Netherlands. The methods used in these assessments often differed, as well as the method to set priorities in solving the fragmentation problems. Some studies determined bottleneck locations by means of comparing the road network with existing or proposed ecological networks (Duel et al. 1992). Others used data on wildlife mortality due to collisions with cars to assess defragmentation locations, or mitigation sites were based on the ecology (e.g., migration routes) of certain species, such as otter (Lutra lutra), badger, roe deer (Capreolus capreolus) or red deer (Cervus elaphus) (Creemer et al. 1991, Bekker et al. 1995, Winter and Smit 1997). In other studies a combination of methods was used (e.g., Reitsma and Smit 1994, Den Held and Van Rij 1994, Krekels 1996). This resulted in a variety of maps with bottleneck locations and proposed mitigation sites, which partly overlap and partly are complementary to each other. It was the desire of both the Ministry of Agriculture, Nature Management and Fisheries, the Ministry of Transport, Public Works and Water Management and the Ministry of Spatial Planning, Housing and the Environment to produce a complete overview of mitigation sites, determined by means of an assessment of changes in population viability due to the presence of roads. Furthermore, setting priorities was needed, based on the ecological profit of defragmentation measures. We used the model LARCH to assess potential habitat configuration and network population viability for ten focal species in the situation with and without roads (Van der Grift et al. 2003). The latter can be interpreted as the situation in which all fragmentation effects by roads are mitigated. Each focal species represents a ICOET 2003 Proceedings 176 Making Connections

6 group of species, sensitive to roads as barriers, with similar habitat requirements and dispersal capacity. The selected focal species represent the different main habitat types in the Netherlands: forests, heartland and dunes, wetlands, and lowland creek tributaries. By comparing the two population viability analyses (with and without roads) defragmentation locations were identified for each species group. Defragmentation locations were distinguished at road transects where network population viability shifted either from non-viable (extinction probability >5% in 100 years) towards viable (extinction probability 1-5% in 100 years) or highly viable (extinction probability <1% in 100 years), or from viable to highly viable, solely due to the removal of road barriers. Priorities were set by calculating the increase in population viability as a result of defragmentation. High-priority locations were defined as locations where the increase in carrying capacity exceed the threshold for a sustainable habitat network with a key patch, i.e., a habitat network that sustains a minimum viable metapopulation in configurations with a key population. For main roads a total of 840 defragmentation locations were identified and mapped. At about 75 percent of the locations mitigation measures will result in an immediate increase in population viability. At the other locations similar results may be achieved, but only if other bottleneck locations are addressed first. In 23 percent of the cases the location is a bottleneck for two or more species groups at the same time. The maximum number of species groups for which one location is identified as bottleneck is five. About 24 percent of the identified defragmentation locations were labeled high-priority for the construction of wildlife passages and restoring habitat connectivity. Comparison of PVA-Tools With dynamic (meta)population models such as DASSIM impacts of spatial developments can be accurately quantified. Hence such models are powerful tools to predict trends in population development. However, these models are often species specific and require detailed field research to validate the parameters used. If a multi-species analysis is needed, the use of such models is often impractical and expensive. In that case, an expert system, such as LARCH, may be a better tool to assess ecological impacts of changes in land use. While dynamic (meta)population models focus on changes over time, e.g., population growth, expert systems usually focus on spatial patterns at a certain moment in time. Consequently, the number of necessary parameters in an expert system is more limited. Furthermore, the parameter values in expert systems may be based on estimations by experts, especially in early development stages of such an expert system, hence are not always based on empirical research. Both the limited number of parameters and the less underpinned estimations of parameter values simplifies the implementation of a multitude of species in expert systems. Expert systems are usually more suitable to aggregate analyses of different species due to the more simple model design. The downside of expert systems is that they are static and hence evaluate the viability of populations for only a certain moment in time. The use of thresholds in expert systems also results in discrete classifications as viable or not viable; trends in population viability cannot be visualized. Both tools facilitate the comparison of different scenarios and thus support decision-making. Application of PVA-Tools DASSIM has been applied in three studies: the description of management perspectives for badger populations in fragmented landscapes (Lankester et al. 1991), the comparison of scenarios for spatial development in the central regions of the Netherlands (Van Apeldoorn et al. 1998), and the above-described simulation of badger population dynamics in relation to highway construction scenarios (Van der Grift and Verboom 2001). LARCH has been used in a large number of studies, such as environmental impact assessments (Wieman et al. 2000), the development of national and regional plans for spatial development (Broekmeyer et al. 2000), the design of ecological networks or corridors (Reijnen and Koolstra 1998, Foppen et al. 1999, Reijnen et al. 2001, Groot Bruinderink et al. 2003, Van der Sluis et al. 2003), mitigation and compensation projects in relation to habitat fragmentation by transportation corridors (Van der Grift and Koolstra 2001, Van der Grift et al. 2003), plans for habitat development and habitat restoration (Groot Bruinderink et al. 2000), demarcation proposals for protected nature areas or landscapes (Pelk et al. 1999), species protection plans (Foppen et al. 1998, Van Apeldoorn and Nieuwenhuizen 1998), nature management plans (Nieuwenhuizen et al. 2000, Nijhof and Van Apeldoorn 2001, Pouwels et al. 2002b), urban ecology plans (Snep et al. 2001), and evaluations of the efficacy of nature policy (Anonymous 2002). Conclusions Road planning more and more requires the assessment of impacts on nature and the environment. Although impacts on individual animals have to be addressed, e.g. expected road kill rates, more emphasis should be put on the impacts of road construction and road use on the viability of populations. Models and expert systems may be helpful tools to assess population viability. These tools give the possibility to predict changes in viability, or even threats to the (local) survival of a species, before road construction is started and thus may ICOET 2003 Proceedings 177 Making Connections

7 play a key role in comparing scenarios and in decision making. Impacts of roads can be best analysed with spatially explicit (meta)population models. However, these models require extended information about the biology and ecology of a species, which is often not available. Expert systems may be a practical alternative, facilitating rather easy, rule-based analyses of population viability for a variety of species. Acknowledgements: Many thanks to the Center for Transportation and the Environment (CTE) and the U.S. Department of Transportation, in particular for the invitation and financial support to present this paper at the International Conference on Ecology and Transportation in Lake Placid, New York, USA. Financial support for the study on badger viability was provided by the Division Limburg of the Directorate- General of Public Works and Water Management, part of the Dutch Ministry of Transport, Public Works and Water Management. The assessment of defragmentation locations in The Netherlands was funded by the Ministry of Agriculture, Nature Management and Fisheries, the Ministry of Spatial Planning, Housing and the Environment, and the Ministry of Transport, Public Works and Water Management. Thanks also to Beno Koolstra (Alterra), Vanya Simeonova (Alterra) and Marcel Huijser (Western Transportation Institute), who commented on an earlier draft of this manuscript. Biographical Sketches: Edgar A. van der Grift has been working in the field of road ecology for over ten years. As a research ecologist at Alterra, he was involved in a multitude of studies that focussed on the ecological impacts of roads and railroads, the effectiveness of mitigation measures such as wildlife crossing structures, and the implementation of ecological knowledge in national and regional transportation policy. Jana Verboom works as a senior-scientist in the field of landscape ecology at Alterra. She specialises in the design and development of (meta)population models and expert systems. She played a key role in the development of both DASSIM and LARCH. The modelling of fragmented populations, in relation to landscape planning, receives most of her attention and, consequently, was the subject of her Ph.D. dissertation. Rogier Pouwels is a landscape ecologist at Alterra. His work mainly focuses on the further development and application of the expert system LARCH. He was involved in a large number of studies in which this expert system was successfully used, including research on the impacts of habitat fragmentation by transportation corridors. References Andrewartha, H.G. & L.C. Birch (eds.) The ecological web: more on the distribution and abundance of animals. University of Chicago Press, Chicago, USA. Anonymous Natuur voor mensen, mensen voor natuur. Nota natuur, bos en landschap in de 21 e eeuw. Ministerie van Landbouw, Natuurbeheer en Visserij, Den Haag, The Netherlands. Anonymous Natuurbalans Milieu- en Natuurplanbureau, Bilthoven/Wageningen, The Netherlands. Anonymous Natuurcompendium Natuur in cijfers. Milieu- en Natuurplanbureau, Bilthoven/ Wageningen and Centraal Bureau voor de Statistiek, Heerlen, The Netherlands. Bekker, H., B. van den Hengel, H. van Bohemen and H. van der Sluijs Nature across motorways. Rijkswaterstaat, Dienst Weg- en Waterbouwkunde, Delft, The Netherlands. Broekhuizen, S., G.J.D.M. Müskens and K. Sandidorf Invloed van sterfte door verkeer op de voortplanting bij dassen. IBN-report 055. DLO-Instituut voor Bos- en Natuuronderzoek, Wageningen, The Netherlands. Broekmeyer, M., H. Dijkstra, H. Farjon, M. Goossen, R. Reijnen, J. Roos-Klein Lankhorst, S. de Vries, R. Alkemade and F. Bethe Effecten van ongewijzigd ruimtelijk beleid op natuur, landschap en recreatie : Achtergrond document methode VIJNO toets fase 1. Alterra-report 047. Alterra, Green World Research, Wageningen, The Netherlands. Clarke, G.P., P.C.L. White and S. Harris Effects of roads on badger (Meles meles) populations in southwest England. Biological Conservation 86: Creemer, M., R. Krekels and R. Hoeve Dassen in Overijssel. Voorstellen voor de bescherming van de das (Meles meles) en zijn leefomgeving in Overijssel. Dassenberaad Overijssel, Zwolle. De Beijer, R. and P. van der Molen Natuurcompensatieplan Rijksweg 73-Zuid (concept). Rapport 3. Dienst Landelijk gebied Limburg, Roermond, The Netherlands. Den Held, J.J. and K.C. van Rij Van snippen en snippers Ontsnipperingsmaatregelen voor de natuur langs rijkswegen in Gelderland. Heidemij Advies, Arnhem, The Netherlands. ICOET 2003 Proceedings 178 Making Connections

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