Tara Martin | University of British Columbia (original) (raw)
Papers by Tara Martin
WIREs Climate Change, 2018
Assessing species' vulnerability to climate change is a prerequisite for developing effective... more Assessing species' vulnerability to climate change is a prerequisite for developing effective strategies to conserve them. The last three decades have seen exponential growth in the number of studies evaluating how, how much, why, when, and where species will be impacted by climate change. We provide an overview of the rapidly developing field of climate change vulnerability assessment (CCVA) and describe key concepts, terms, steps and considerations. We stress the importance of identifying the full range of pressures, impacts and their associated mechanisms that species face and using this as a basis for selecting the appropriate assessment approaches for quantifying vulnerability. We outline four CCVA assessment approaches, namely trait‐based, correlative, mechanistic and combined approaches and discuss their use. Since any assessment can deliver unreliable or even misleading results when incorrect data and parameters are applied, we discuss finding, selecting, and applying in...
With many conservation issues requiring urgent action, determining how much data are needed to in... more With many conservation issues requiring urgent action, determining how much data are needed to inform good decisions is a common problem. We examine this problem in relation to the protection of critical habitat, the habitat required for species' recovery and persistence. The protection of critical habitat is an essential step in the threatened species recovery process. It is also one of the most contentious and protracted decisions faced by environmental agencies. Uncertainty about what constitutes critical habitat, and the challenges of balancing competing societal objectives and of protecting critical habitat once identified are stalling the recovery process. We offer insight into this challenge by investigating how long we can afford to spend identifying critical habitat before opportunities to recover a species are lost. We illustrate our decision model using Canada's threatened northern abalone (Haliotis kamtschatkana). Our method delivers the stopping time at which habitat protection must begin , despite uncertainty, in order to avoid an unacceptable risk of extinction.
Biological Conservation, 2013
Abstract: In the northwest corner of Australia lies a landscape of extraordinary character. Known... more Abstract: In the northwest corner of Australia lies a landscape of extraordinary character. Known as the Kimberley, its ancient landforms have been shaped by wind and water over millions of years. The Kimberley is vast tracts of savanna, dotted by boab trees and dissected by mountain ranges, gorges and valleys hiding pockets of rainforest. The region was nam more
Journal of Applied Ecology, 2015
Background/Question/Methods Species’ habitats should be identified as accurately as possible to m... more Background/Question/Methods Species’ habitats should be identified as accurately as possible to maximize the benefit to conservation and minimize the opportunity costs of habitat protection. However, delaying habitat protection in favor of improving accuracy could result in additional habitat loss in the interim. Determining how much time to invest on learning about species’ habitat use and requirements is therefore important to maximize the accuracy of habitat identification while still allowing for timely protection. To address this question, we developed a general approach to determining the optimal amount of time to spend on learning before protecting habitats. We assumed that the accuracy of habitat identification improves over time as learning occurs, resulting in a greater proportion of habitats correctly identified and protected. We also assumed that habitat loss is ongoing, resulting in a decrease in the area of available habitats that can be protected over time. We then ex...
Climate change is a major threat to global biodiversity and its impacts can act synergistically t... more Climate change is a major threat to global biodiversity and its impacts can act synergistically to heighten the severity of other threats. Most research on projecting species range shifts under climate change has not been translated to informing priority management strategies on the ground. We develop a prioritization framework to assess strategies for managing threats to biodiversity under climate change and apply it to the management of invasive animal species across one sixth of the Australian continent, the Lake Eyre Basin. We collected information from key stakeholders and experts on the impacts of invasive animals on 148 of the region's most threatened species and 11 potential strategies. Assisted by models of current distributions of threatened species and their projected distributions, experts estimated the cost, feasibility and potential benefits of each strategy for improving the persistence of threatened species with and without climate change. We discover that the relative cost-effectiveness of invasive animal control strategies is robust to climate change, with the management of feral pigs being the highest priority for conserving threatened species overall. Complementary sets of strategies to protect as many threatened species as possible under limited budgets change when climate change is considered, with additional strategies required to avoid impending extinctions from the region. Overall we find that the ranking of strategies by cost-effectiveness was relatively unaffected by including climate change into decision-making, even though the benefits of the strategies were lower. Future climate conditions and impacts on range shifts become most important to consider when designing comprehensive management plans for the control of invasive animals under limited budgets to maximize the number of threatened species that can be protected.
Royal Society Open Science, 2015
Diversity and Distributions, 2014
ABSTRACT AimTrophic cascades are a common consequence of herbivore outbreak and in the absence of... more ABSTRACT AimTrophic cascades are a common consequence of herbivore outbreak and in the absence of hunting can cause the local extinction of native plant species and communities. We compared plant communities at 66 island and mainland sites to test the hypothesis that deer (Cervidae) determine species cover, richness and diversity and that palatable species become rare at high deer density. We validate a region-wide index of deer density and impact on plant communities in a region where culturally significant food plants maintained by aboriginal people prior to European contact helped to define baseline plant communities.LocationGulf and San Juan Island archipelagos and North American mainland.Methods We conducted surveys of 49 native, 10 exotic and 15 culturally significant plant species and deer sign at 66 sites on 35 islands and mainland to determine deer abundance and plant species cover, richness and diversity. We identified culturally significant food plants facilitated by aboriginal people using ethnobotanical knowledge, quantified plant palatability via cafeteria trials and characterized shrub architecture.ResultsNative and culturally significant shrub cover, richness and diversity were 52–85% lower at sites with abundant deer (0.9–2.8 ha−1) versus no deer. However, these values were also 38–82% lower at sites in the lowest deer density class (< 0.08 ha−1) versus sites with no deer present. Palatable cover was 92% lower where deer were abundant versus absent and 28% lower in low-density versus deer-free sites. Shrub architecture provided an easily applied index of native and culturally significant plant cover and deer density.Main conclusionsWe provide comparative examples of endangered plant communities to demonstrate that, contrary to the intermediate disturbance hypothesis, any positive effect of deer on plant diversity on islands in the Pacific north-west of North America occurs at densities < 0.08 ha−1, if at all. This detailed example of trophic downgrading highlights the need and provides the methods to identify herbivore densities compatible with the persistence of all native species in conserved landscapes.
Biological Conservation, 2015
Pacific Conservation Biology
WIREs Climate Change, 2018
Assessing species' vulnerability to climate change is a prerequisite for developing effective... more Assessing species' vulnerability to climate change is a prerequisite for developing effective strategies to conserve them. The last three decades have seen exponential growth in the number of studies evaluating how, how much, why, when, and where species will be impacted by climate change. We provide an overview of the rapidly developing field of climate change vulnerability assessment (CCVA) and describe key concepts, terms, steps and considerations. We stress the importance of identifying the full range of pressures, impacts and their associated mechanisms that species face and using this as a basis for selecting the appropriate assessment approaches for quantifying vulnerability. We outline four CCVA assessment approaches, namely trait‐based, correlative, mechanistic and combined approaches and discuss their use. Since any assessment can deliver unreliable or even misleading results when incorrect data and parameters are applied, we discuss finding, selecting, and applying in...
With many conservation issues requiring urgent action, determining how much data are needed to in... more With many conservation issues requiring urgent action, determining how much data are needed to inform good decisions is a common problem. We examine this problem in relation to the protection of critical habitat, the habitat required for species' recovery and persistence. The protection of critical habitat is an essential step in the threatened species recovery process. It is also one of the most contentious and protracted decisions faced by environmental agencies. Uncertainty about what constitutes critical habitat, and the challenges of balancing competing societal objectives and of protecting critical habitat once identified are stalling the recovery process. We offer insight into this challenge by investigating how long we can afford to spend identifying critical habitat before opportunities to recover a species are lost. We illustrate our decision model using Canada's threatened northern abalone (Haliotis kamtschatkana). Our method delivers the stopping time at which habitat protection must begin , despite uncertainty, in order to avoid an unacceptable risk of extinction.
Biological Conservation, 2013
Abstract: In the northwest corner of Australia lies a landscape of extraordinary character. Known... more Abstract: In the northwest corner of Australia lies a landscape of extraordinary character. Known as the Kimberley, its ancient landforms have been shaped by wind and water over millions of years. The Kimberley is vast tracts of savanna, dotted by boab trees and dissected by mountain ranges, gorges and valleys hiding pockets of rainforest. The region was nam more
Journal of Applied Ecology, 2015
Background/Question/Methods Species’ habitats should be identified as accurately as possible to m... more Background/Question/Methods Species’ habitats should be identified as accurately as possible to maximize the benefit to conservation and minimize the opportunity costs of habitat protection. However, delaying habitat protection in favor of improving accuracy could result in additional habitat loss in the interim. Determining how much time to invest on learning about species’ habitat use and requirements is therefore important to maximize the accuracy of habitat identification while still allowing for timely protection. To address this question, we developed a general approach to determining the optimal amount of time to spend on learning before protecting habitats. We assumed that the accuracy of habitat identification improves over time as learning occurs, resulting in a greater proportion of habitats correctly identified and protected. We also assumed that habitat loss is ongoing, resulting in a decrease in the area of available habitats that can be protected over time. We then ex...
Climate change is a major threat to global biodiversity and its impacts can act synergistically t... more Climate change is a major threat to global biodiversity and its impacts can act synergistically to heighten the severity of other threats. Most research on projecting species range shifts under climate change has not been translated to informing priority management strategies on the ground. We develop a prioritization framework to assess strategies for managing threats to biodiversity under climate change and apply it to the management of invasive animal species across one sixth of the Australian continent, the Lake Eyre Basin. We collected information from key stakeholders and experts on the impacts of invasive animals on 148 of the region's most threatened species and 11 potential strategies. Assisted by models of current distributions of threatened species and their projected distributions, experts estimated the cost, feasibility and potential benefits of each strategy for improving the persistence of threatened species with and without climate change. We discover that the relative cost-effectiveness of invasive animal control strategies is robust to climate change, with the management of feral pigs being the highest priority for conserving threatened species overall. Complementary sets of strategies to protect as many threatened species as possible under limited budgets change when climate change is considered, with additional strategies required to avoid impending extinctions from the region. Overall we find that the ranking of strategies by cost-effectiveness was relatively unaffected by including climate change into decision-making, even though the benefits of the strategies were lower. Future climate conditions and impacts on range shifts become most important to consider when designing comprehensive management plans for the control of invasive animals under limited budgets to maximize the number of threatened species that can be protected.
Royal Society Open Science, 2015
Diversity and Distributions, 2014
ABSTRACT AimTrophic cascades are a common consequence of herbivore outbreak and in the absence of... more ABSTRACT AimTrophic cascades are a common consequence of herbivore outbreak and in the absence of hunting can cause the local extinction of native plant species and communities. We compared plant communities at 66 island and mainland sites to test the hypothesis that deer (Cervidae) determine species cover, richness and diversity and that palatable species become rare at high deer density. We validate a region-wide index of deer density and impact on plant communities in a region where culturally significant food plants maintained by aboriginal people prior to European contact helped to define baseline plant communities.LocationGulf and San Juan Island archipelagos and North American mainland.Methods We conducted surveys of 49 native, 10 exotic and 15 culturally significant plant species and deer sign at 66 sites on 35 islands and mainland to determine deer abundance and plant species cover, richness and diversity. We identified culturally significant food plants facilitated by aboriginal people using ethnobotanical knowledge, quantified plant palatability via cafeteria trials and characterized shrub architecture.ResultsNative and culturally significant shrub cover, richness and diversity were 52–85% lower at sites with abundant deer (0.9–2.8 ha−1) versus no deer. However, these values were also 38–82% lower at sites in the lowest deer density class (< 0.08 ha−1) versus sites with no deer present. Palatable cover was 92% lower where deer were abundant versus absent and 28% lower in low-density versus deer-free sites. Shrub architecture provided an easily applied index of native and culturally significant plant cover and deer density.Main conclusionsWe provide comparative examples of endangered plant communities to demonstrate that, contrary to the intermediate disturbance hypothesis, any positive effect of deer on plant diversity on islands in the Pacific north-west of North America occurs at densities < 0.08 ha−1, if at all. This detailed example of trophic downgrading highlights the need and provides the methods to identify herbivore densities compatible with the persistence of all native species in conserved landscapes.
Biological Conservation, 2015
Pacific Conservation Biology
Journal of Animal Ecology, Jun 2014
Threats to migratory animals can occur at multiple periods of the annual cycle that are separated... more Threats to migratory animals can occur at multiple periods of the annual cycle that are separated by thousands of kilometers and span international borders. Populations of the iconic monarch butterfly (Danaus plexippus) of eastern North America have declined over the last 21 years. Three hypotheses have been posed to explain the decline: habitat loss on the overwintering grounds in Mexico, habitat loss on the breeding grounds in the United States and Canada, and extreme weather events.
Our objectives were to assess population viability, determine which life-stage, season and geographic region are contributing the most to population dynamics and test the three hypotheses that explain the observed population decline.
We developed a spatially-structured, stochastic and density-dependent periodic projection matrix model that integrates patterns of migratory connectivity and demographic vital rates across the annual cycle. We used perturbation analysis to determine the sensitivity of population abundance to changes in vital rate among life-stages, seasons, and geographic regions. Next, we compared the singular effects of each threat to the full model where all factors operate concurrently. Finally, we generated predictions to assess the risk of host plant loss as a result of genetically modified crops on current and future monarch butterfly population size and extinction probability.
Our year-round population model predicted population declines of 14% and a quasi-extinction probability (<1000 individuals) greater than 5% within a century. Monarch abundance was more than four times more sensitive to perturbations of vital rates on the breeding grounds than on the wintering grounds. Simulations that considered only forest loss or climate change in Mexico predicted higher population sizes compared to milkweed declines on the breeding grounds. Our model predictions also suggest that mitigating the negative effects of genetically modified crops results in higher population size and lower extinction risk.
Recent population declines stem from reduction in milkweed host plants in the United States that arise from increasing adoption of genetically modified crops and land-use change, not from climate change or degradation of forest habitats in Mexico. Therefore, reducing the negative effects of host plant loss on the breeding grounds is the top conservation priority to slow or halt future population declines of monarch butterflies in North America.
Journal of Applied …, Jan 1, 2012
1. Designing practical rules for controlling invasive species is a challenging task for managers,... more 1. Designing practical rules for controlling invasive species is a challenging task for managers, particularly when species are long-lived, have complex life cycles and high dispersal capacities. Previous findings derived from plant matrix population analyses suggest that effective control of long-lived invaders may be achieved by focusing on killing adult plants. However, the cost-effectiveness of managing different life stages has not been evaluated.
2. We illustrate the benefits of integrating matrix population models with decision theory to undertake this evaluation, using empirical data from the largest infestation of mesquite (Leguminosae: Prosopis spp) within Australia. We include in our model the mesquite life cycle, different dispersal rates and control actions that target individuals at different life stages with varying costs, depending on the intensity of control effort. We then use stochastic dynamic programming to derive cost-effective control strategies that minimize the cost of controlling the core infestation locally below a density threshold and the future cost of control arising from infestation of adjacent areas via seed dispersal.
3. Through sensitivity analysis, we show that four robust management rules guide the allocation of resources between mesquite life stages for this infestation: (i) When there is no seed dispersal, no action is required until density of adults exceeds the control threshold and then only control of adults is needed; (ii) when there is seed dispersal, control strategy is dependent on knowledge of the density of adults and large juveniles (LJ) and broad categories of dispersal rates only; (iii) if density of adults is higher than density of LJ, controlling adults is most cost-effective; (iv) alternatively, if density of LJ is equal or higher than density of adults, management efforts should be spread between adults, large and to a lesser extent small juveniles, but never saplings.
4. Synthesis and applications. In this study, we show that simple rules can be found for managing invasive plants with complex life cycles and high dispersal rates when population models are combined with decision theory. In the case of our mesquite population, focussing effort on controlling adults is not always the most cost-effective way to meet our management objective.