Olav Strand - Academia.edu (original) (raw)
Papers by Olav Strand
Journal of Mammalogy, 2000
Biological Conservation, 2003
We made monthly surveys of >2000 reindeer (Rangifer tarandus tarandus) from 1977 to 1987 before a... more We made monthly surveys of >2000 reindeer (Rangifer tarandus tarandus) from 1977 to 1987 before and after the construction of the Blue Lake hydroelectric reservoir in order to study the progressive impact of infrastructure development on wildlife. Following this development, reindeer densities within a 4-km radius declined gradually during winter to 8% of pre-development densities without significant changes in undeveloped control sites. During summer, reindeer gradually reduced use of areas within 4 km distance from roads and power lines to 36% of predevelopment density, with subsequent 217% increase in use of the few remaining sites located >4 km from infrastructure. Reindeer reproduction declined progressively as habitat was lost. Assessments of individual development projects seriously underestimate the long-term effects of the entire expanding infrastructure network. Piecemeal development has resulted in an estimated 70% loss of undisturbed reindeer habitat across the last century in Norway. During this time the reindeer population has become fragmented into 26 isolated sub-populations. Our results show that any further infrastructure development will put the remaining European population of wild mountain reindeer at great risk, as further habitat fragmentation will make the remaining undisturbed patches too small for holding viable populations. A general model of impacts of infrastructure on wildlife is presented. We discuss the importance of controlling piecemeal development in infrastructure for conservation of wildlife and argue that minimizing infrastructure development is likely one of the largest challenges in wildlife conservation ahead.
Biological Conservation, 2001
Southern Norway holds the last remaining population of wild reindeer (Rangifer tarandus tarandus)... more Southern Norway holds the last remaining population of wild reindeer (Rangifer tarandus tarandus) in Europe. Roads, railroads, and power lines have fragmented the original population into 26 separate herds. The reindeer populations are regulated directly according to availability of winter forage. These winter ranges, generally at lower elevations, are however, often subjected to development. Effects of infrastructure and associated human activity on the distribution of wild reindeer during winter were investigated in the Nordfjella mountain region of western Norway. Systematic aerial surveys of the distribution of ca. 2500 reindeer were conducted during late winter 1986–1998. Areas within 2.5 km from power lines were used less than available in 6 of the 8 sampling years, and areas beyond this zone more than expected. Density of reindeer was 79% lower within 2.5 km from power lines compared with background areas, and increased with increasing distance from infrastructure for comparable habitat. Available forage in terms of lichen cover declined 15–30-fold with distance, and was lowest in the undisturbed areas with the highest density of grazing animals. Areas within 5 km from resorts or from roads and power lines in combination were avoided in all years. Continued construction of roads, power lines and cabin resorts endanger these available winter ranges, and hence the long term survival of the population.
Journal of Animal Ecology, 1999
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1998
Canadian Journal of Zoology-revue Canadienne De Zoologie, 2003
Diversity and Distributions, 2000
Biological Conservation, 2001
Despite more than 69 years of protection populations of arctic fox (Alopex lagopus) in Scandinavi... more Despite more than 69 years of protection populations of arctic fox (Alopex lagopus) in Scandinavia has not recovered their former numbers or distribution following over-hunting at the turn of the century. We aimed to evaluate the possible fate of arctic fox populations using discrete-time models including both demographic and environmental variability. Because the reproduction of arctic fox in Scandinavia is dependent on the abundance of small rodents, which is cyclic, we included the temporal variability of reproductive performances in our viability analysis based on time series available for three Scandinavian populations. Whatever the modelling of the reproductive performances and the range of adult survival rates considered, the risks of extinction were high. They were very sensitive to adult survival rates and variability in reproductive performances. Populations with the longest duration between two successful reproductions were at the greatest risks of extinction. The time elapsed between two successful reproductions may depend on failure to respond to rodent peaks. The cyclicity of food availability for arctic fox may have been the main selective force for their large litter size, but may also be the cause of a fine-tuned, and fragile dynamic system.
Journal of Wildlife Management, 2004
... Jan Åge Riseth, Hans Tømmervik, Elina Helander-Renvall, Niklas Labba, Cecilia Johansson, Eiri... more ... Jan Åge Riseth, Hans Tømmervik, Elina Helander-Renvall, Niklas Labba, Cecilia Johansson, Eirik Malnes, Jarle W. Bjerke, Christer Jonsson ... Christian Nellemann, Ingunn Vistnes, Per Jordhøy, Ole-Gunnar Støen, Bjørn Petter Kaltenborn, Frank Hanssen, Rannveig Helgesen. ...
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1997
Molecular Ecology, 2006
The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after havin... more The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after having gone through a severe decline in population size in the beginning of the 20th century, from which it has failed to recover despite more than 65 years of protection. Arctic foxes have a high dispersal rate and often disperse over long distances, suggesting that there was probably little population differentiation within Scandinavia prior to the bottleneck. It is, however, possible that the recent decline in population size has led to a decrease in dispersal and an increase in population fragmentation. To examine this, we used 10 microsatellite loci to analyse genetic variation in 150 arctic foxes from Scandinavia and Russia. The results showed that the arctic fox in Scandinavia presently is subdivided into four populations, and that the Kola Peninsula and northwest Russia together form a large fifth population. Current dispersal between the populations seemed to be very low, but genetic variation within them was relatively high. This and the relative FST values among the populations are consistent with a model of recent fragmentation within Scandinavia. Since the amount of genetic variation is high within the populations, but the populations are small and isolated, demographic stochasticity seems to pose a higher threat to the populations’ persistence than inbreeding depression and low genetic variation.
Polar Biology, 2001
We investigated the distribution of wild reindeer (Rangifer tarandus tarandus) from aerial survey... more We investigated the distribution of wild reindeer (Rangifer tarandus tarandus) from aerial surveys in 1986–1998 in 622 contiguous 4-km2 grid squares in relation to density of power lines, roads and ski trails in the Nordfjella region, south-central Norway. Density of reindeer was significantly lower in developed quadrats compared to undeveloped quadrats and decreased with increasing density of development. No reindeer were observed in areas exceeding 1.3 km/km2 of linear structures and only 1.1% of the reindeer were observed in areas exceeding 0.8 km/km2 of linear structures, an area constituting 17% of the study area. The results imply that development, and also the degree of development, affect the availability of range for wild reindeer. Furthermore, the results suggest that reindeer may abandon areas once disturbance exceeds a critical level. We conclude that there is a need for cumulative impact assessments of the overall development in Norwegian mountain regions, to preserve the last remaining wild reindeer populations in Europe.
Ecography, 2010
Anthropogenic fragmentation of habitat and populations is recognized as one of the most important... more Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub-populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within-fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine-scale Allee or Allee-like effects, as well as environmental influences related to increased competition and exclusion by red foxes.
Journal of Mammalogy, 2000
Biological Conservation, 2003
We made monthly surveys of >2000 reindeer (Rangifer tarandus tarandus) from 1977 to 1987 before a... more We made monthly surveys of >2000 reindeer (Rangifer tarandus tarandus) from 1977 to 1987 before and after the construction of the Blue Lake hydroelectric reservoir in order to study the progressive impact of infrastructure development on wildlife. Following this development, reindeer densities within a 4-km radius declined gradually during winter to 8% of pre-development densities without significant changes in undeveloped control sites. During summer, reindeer gradually reduced use of areas within 4 km distance from roads and power lines to 36% of predevelopment density, with subsequent 217% increase in use of the few remaining sites located >4 km from infrastructure. Reindeer reproduction declined progressively as habitat was lost. Assessments of individual development projects seriously underestimate the long-term effects of the entire expanding infrastructure network. Piecemeal development has resulted in an estimated 70% loss of undisturbed reindeer habitat across the last century in Norway. During this time the reindeer population has become fragmented into 26 isolated sub-populations. Our results show that any further infrastructure development will put the remaining European population of wild mountain reindeer at great risk, as further habitat fragmentation will make the remaining undisturbed patches too small for holding viable populations. A general model of impacts of infrastructure on wildlife is presented. We discuss the importance of controlling piecemeal development in infrastructure for conservation of wildlife and argue that minimizing infrastructure development is likely one of the largest challenges in wildlife conservation ahead.
Biological Conservation, 2001
Southern Norway holds the last remaining population of wild reindeer (Rangifer tarandus tarandus)... more Southern Norway holds the last remaining population of wild reindeer (Rangifer tarandus tarandus) in Europe. Roads, railroads, and power lines have fragmented the original population into 26 separate herds. The reindeer populations are regulated directly according to availability of winter forage. These winter ranges, generally at lower elevations, are however, often subjected to development. Effects of infrastructure and associated human activity on the distribution of wild reindeer during winter were investigated in the Nordfjella mountain region of western Norway. Systematic aerial surveys of the distribution of ca. 2500 reindeer were conducted during late winter 1986–1998. Areas within 2.5 km from power lines were used less than available in 6 of the 8 sampling years, and areas beyond this zone more than expected. Density of reindeer was 79% lower within 2.5 km from power lines compared with background areas, and increased with increasing distance from infrastructure for comparable habitat. Available forage in terms of lichen cover declined 15–30-fold with distance, and was lowest in the undisturbed areas with the highest density of grazing animals. Areas within 5 km from resorts or from roads and power lines in combination were avoided in all years. Continued construction of roads, power lines and cabin resorts endanger these available winter ranges, and hence the long term survival of the population.
Journal of Animal Ecology, 1999
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1998
Canadian Journal of Zoology-revue Canadienne De Zoologie, 2003
Diversity and Distributions, 2000
Biological Conservation, 2001
Despite more than 69 years of protection populations of arctic fox (Alopex lagopus) in Scandinavi... more Despite more than 69 years of protection populations of arctic fox (Alopex lagopus) in Scandinavia has not recovered their former numbers or distribution following over-hunting at the turn of the century. We aimed to evaluate the possible fate of arctic fox populations using discrete-time models including both demographic and environmental variability. Because the reproduction of arctic fox in Scandinavia is dependent on the abundance of small rodents, which is cyclic, we included the temporal variability of reproductive performances in our viability analysis based on time series available for three Scandinavian populations. Whatever the modelling of the reproductive performances and the range of adult survival rates considered, the risks of extinction were high. They were very sensitive to adult survival rates and variability in reproductive performances. Populations with the longest duration between two successful reproductions were at the greatest risks of extinction. The time elapsed between two successful reproductions may depend on failure to respond to rodent peaks. The cyclicity of food availability for arctic fox may have been the main selective force for their large litter size, but may also be the cause of a fine-tuned, and fragile dynamic system.
Journal of Wildlife Management, 2004
... Jan Åge Riseth, Hans Tømmervik, Elina Helander-Renvall, Niklas Labba, Cecilia Johansson, Eiri... more ... Jan Åge Riseth, Hans Tømmervik, Elina Helander-Renvall, Niklas Labba, Cecilia Johansson, Eirik Malnes, Jarle W. Bjerke, Christer Jonsson ... Christian Nellemann, Ingunn Vistnes, Per Jordhøy, Ole-Gunnar Støen, Bjørn Petter Kaltenborn, Frank Hanssen, Rannveig Helgesen. ...
Canadian Journal of Zoology-revue Canadienne De Zoologie, 1997
Molecular Ecology, 2006
The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after havin... more The arctic fox (Alopex lagopus) in Scandinavia is classified as critically endangered after having gone through a severe decline in population size in the beginning of the 20th century, from which it has failed to recover despite more than 65 years of protection. Arctic foxes have a high dispersal rate and often disperse over long distances, suggesting that there was probably little population differentiation within Scandinavia prior to the bottleneck. It is, however, possible that the recent decline in population size has led to a decrease in dispersal and an increase in population fragmentation. To examine this, we used 10 microsatellite loci to analyse genetic variation in 150 arctic foxes from Scandinavia and Russia. The results showed that the arctic fox in Scandinavia presently is subdivided into four populations, and that the Kola Peninsula and northwest Russia together form a large fifth population. Current dispersal between the populations seemed to be very low, but genetic variation within them was relatively high. This and the relative FST values among the populations are consistent with a model of recent fragmentation within Scandinavia. Since the amount of genetic variation is high within the populations, but the populations are small and isolated, demographic stochasticity seems to pose a higher threat to the populations’ persistence than inbreeding depression and low genetic variation.
Polar Biology, 2001
We investigated the distribution of wild reindeer (Rangifer tarandus tarandus) from aerial survey... more We investigated the distribution of wild reindeer (Rangifer tarandus tarandus) from aerial surveys in 1986–1998 in 622 contiguous 4-km2 grid squares in relation to density of power lines, roads and ski trails in the Nordfjella region, south-central Norway. Density of reindeer was significantly lower in developed quadrats compared to undeveloped quadrats and decreased with increasing density of development. No reindeer were observed in areas exceeding 1.3 km/km2 of linear structures and only 1.1% of the reindeer were observed in areas exceeding 0.8 km/km2 of linear structures, an area constituting 17% of the study area. The results imply that development, and also the degree of development, affect the availability of range for wild reindeer. Furthermore, the results suggest that reindeer may abandon areas once disturbance exceeds a critical level. We conclude that there is a need for cumulative impact assessments of the overall development in Norwegian mountain regions, to preserve the last remaining wild reindeer populations in Europe.
Ecography, 2010
Anthropogenic fragmentation of habitat and populations is recognized as one of the most important... more Anthropogenic fragmentation of habitat and populations is recognized as one of the most important factors influencing loss of biodiversity. Since it is difficult to quantify demographic parameters in small populations, we need alternative methods to elucidate important factors affecting the viability of local populations. The Fennoscandian arctic fox inhabits a naturally fragmented alpine tundra environment, but historic anthropogenic impacts have further fragmented its distribution. After almost 80 yr of protection, the population remains critically endangered. Both intrinsic factors (related to the isolation and size of sub-populations) and extrinsic factors (related to environmental conditions influencing patch quality and interspecific competition) have been proposed as explanations for the lack of population growth. To distinguish between these hypotheses, we conducted a spatially explicit analysis that compares areas where the species has persisted with areas where it has become locally extinct. We used characteristics of the fragments of alpine tundra habitat and individual arctic fox breeding dens (including both currently active dens and historically active dens) within the fragments to evaluate the importance of habitat characteristics and connectivity in explaining variation in persistence within a fragment. The number of reproductive events in a fragment was related to the size of the fragment, but not more than expected following a 1:1 relationship, suggesting little effect of fragment size on the relative number of reproductions. The likelihood of a den being used for breeding was positively associated with factors minimising interspecific competition as well as increasing within-fragment connectivity. These results support the idea that the failure of Fennoscandian arctic fox to recover is caused by demographic factors that can be related to fine-scale Allee or Allee-like effects, as well as environmental influences related to increased competition and exclusion by red foxes.