Nina Hewitt | The University of British Columbia (original) (raw)
Papers by Nina Hewitt
Sustainability
Xanthium strumarium L. is a globally successful invasive herb that has had significant negative e... more Xanthium strumarium L. is a globally successful invasive herb that has had significant negative ecological, economic and social impacts in many world regions. The present study was therefore conducted to evaluate the invasive potential and spatial distribution patterns of X. strumarium in heavily invaded plant communities of the semiarid regions of northern Pakistan. Investigations were based on data from 20 plants grown in the Herbarium at the University of Malakand, and from observations in 450 plots distributed across 45 stands representing habitats across Northern Province including open fields, hillocks and abandoned areas in both urban and rural areas. Multivariate analysis identified elevation, organic matter and organic carbon as the environmental variables most associated with communities invaded by X. strumarium. Increased soil silt was positively associated and available water was negatively associated with X. strumarium–invaded communities. These key environmental charac...
Sustainability
Xanthium strumarium L. is a globally successful invasive herb that has had significant negative e... more Xanthium strumarium L. is a globally successful invasive herb that has had significant negative ecological, economic and social impacts in many world regions. The present study was therefore conducted to evaluate the invasive potential and spatial distribution patterns of X. strumarium in heavily invaded plant communities of the semiarid regions of northern Pakistan. Investigations were based on data from 20 plants grown in the Herbarium at the University of Malakand, and from observations in 450 plots distributed across 45 stands representing habitats across Northern Province including open fields, hillocks and abandoned areas in both urban and rural areas. Multivariate analysis identified elevation, organic matter and organic carbon as the environmental variables most associated with communities invaded by X. strumarium. Increased soil silt was positively associated and available water was negatively associated with X. strumarium–invaded communities. These key environmental charac...
Sustainability, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY)
Écoscience, 2018
ABSTRACT We developed a model of hardwood tree colonization in forest patches. We began with a ba... more ABSTRACT We developed a model of hardwood tree colonization in forest patches. We began with a basic model of species' recruitment density calculated as a function of seed production and juvenile survivorship. Survivorship probability was expressed as a function of seed size, using seed-sowing data for a wide variety of species. To account for dispersal, we used an exponential distancedecay function based on empirical colonization data for species classified by dispersal mechanism and seed mass. The basic model reasonably predicted observed recruitment densities at or near forest edges, except for small seeded, wind-dispersed species with strong establishment constraints, for which it over-predicts. Our dispersal term yielded predictions that were not statistically different from observed colonization. However, species with large seeds and unspecialized dispersal mechanism appear to have distinct thresholds beyond which no dispersal occurs. Further research should better account for establishment constraints among small-seeded species, dispersal constraints among large-seeded species and unspecialized dispersers, and improve the dispersal functions to better reflect vectors such as birds. Nevertheless, the present model is adequate for the prediction of colonization probabilities in fragmented forests, requiring only an estimate of the abundance of source trees of a species and the mean inter-fragment distances.
Landscape and Urban Planning
Natural Areas Journal, 2015
Encyclopedia of Geography, 2010
Renewable and Sustainable Energy Reviews, 2013
Environmental Reviews, 2012
The interactive effects of climate change and invasive alien species (IAS) pose serious threats t... more The interactive effects of climate change and invasive alien species (IAS) pose serious threats to biodiversity, ecosystems and human well-being worldwide. In particular, IAS are predicted to experience widespread changes in distribution in response to climate change, with many expanding their ranges into new areas. However, the two drivers of global change are seldom considered together in policy and management. We conducted a knowledge synthesis to assess the state of research on IAS range shifts under climate change in Canada. We found that the study of IAS distribution changes caused by climate change is a relatively new field of inquiry that integrates research in the areas of ecology, conservation biology, and environmental sciences. The multidisciplinary dimensions of the issue are largely overlooked in the scholarly literature, with most studies having a purely natural science perspective. Very little original research has occurred in the field to date; instead literature re...
Renewable and Sustainable Energy Reviews, 2013
The interactive effects of climate change and invasive alien species (IAS) pose serious threats t... more The interactive effects of climate change and invasive alien species (IAS) pose serious threats to biodiversity, ecosystems and human well-being worldwide. In particular, IAS are predicted to experience widespread changes in distribution in response to climate change, with many expanding their ranges into new areas. However, the two drivers of global change are seldom considered together in policy and management. We conducted a knowledge synthesis to assess the state of research on IAS range shifts under climate change in Canada. We found that the study of IAS distribution changes caused by climate change is a relatively new field of inquiry that integrates research in the areas of ecology, conservation biology, and environmental sciences. The multidisciplinary dimensions of the issue are largely overlooked in the scholarly literature, with most studies having a purely natural science perspective. Very little original research has occurred in the field to date; instead literature reviews are common. Research focuses on modeling range changes of current IAS threats, rather than predicting potential future IAS threats. The most commonly studied IAS already occur in Canada as native species that have spread beyond their range (e.g., lyme disease, mountain pine beetle, smallmouth bass) or as established invaders (e.g., gypsy moth). All of these IAS are expected to expand northward with climate change, resulting in widespread negative impacts on forest and freshwater biodiversity, carbon sequestration, and public health. Many barriers to predicting IAS range change under climate change are identified in the literature, including the complexity of the issue, lack of ecological data, and failure to integrate climate change -IAS interactions into research, policy, and management. Recommendations for increased research and monitoring, and the need for policy and management reform predominate in the literature.
Journal of Biosciences, Jan 1, 1999
Ecologists recognize that many species will not migrate rapidly enough to keep up with shifting e... more Ecologists recognize that many species will not migrate rapidly enough to keep up with shifting ecosystem conditions due to climate change. Assisted migration was proposed several decades ago as a strategy to help maintain populations of slow-moving species. However, many scientists see assisted migration as problematic, largely because its potential to preserve species stands in direct tension with its potential to produce invasion by the focal species, thereby threatening the recipient ecosystem. Scholarly debate on this topic has intensified during the last three years and threatens to produce a stalemate in policy and action on the issue. We take stock of the academic literature on this topic and identify possible avenues toward consensus in what might otherwise become an intractable ethical and policy problem. We tease apart the arguments in the debate, distinguishing among the direct risks and benefits to species, ecosystems and society on the one hand, and other arguments regarding scientific justification, evidence-base and feasibility on the other. We present a conceptual framework to help scientists and policy makers find common ground and work towards case-and context-specific solutions.
Biological Conservation, Jan 1, 2011
Assisted migration was proposed several decades ago as a means of addressing the impacts of clima... more Assisted migration was proposed several decades ago as a means of addressing the impacts of climate change on species populations. While its risks and benefits have been debated, and suggestions for planning and management given, there is little consensus within the academic literature over whether to adopt it as a policy. We evaluated the main features of the assisted migration literature including the study methods, taxonomic groups, geographic regions and disciplines involved. We further assessed the debate about the use of assisted migration, the main barriers to consensus, and the range of recommendations put forth in the literature for policy, planning or implementation. Commentaries and secondary literature reviews were as prevalent as first-hand scientific research and attention focussed on a global rather than regional level. There was little evidence of knowledge transfer outside of the natural sciences, despite the obvious policy relevance. Scholarly debate on this topic has intensified during the last 3 years. We present a conceptual framework for evaluating arguments in the debate, distinguishing among the direct risks and benefits to species, ecosystems and society on the one hand, and other arguments regarding scientific justification, evidence-base and feasibility on the other. We also identify recommendations with potential to advance the debate, including careful evaluation of risks, benefits and trade-offs, involvement of relevant stakeholders and consideration of the complementarity among assisted migration and less risk-tolerant strategies. We conclude, however, that none of these will solve the fundamental, often values-based, challenges in the debate. Solutions are likely to be complex, context-dependent and multi-faceted, emerging from further research, discussion and experience.► We review the literature on assisted migration (AM) as a climate change adaptation strategy. ► A majority of articles generally endorse AM, but opposition is intensifying. ► We present a conceptual framework for analyzing the debate. ► More original research is needed into processes and effects of assisted range extension. ► There are no simple solutions to the often value-based challenges in the debate.
Landscape and Urban Planning, Jan 1, 2008
We investigated tree species composition, diversity and size structure of eight privately owned h... more We investigated tree species composition, diversity and size structure of eight privately owned hardwood forest remnants and a 50 ha portion of semi-old-growth forest (Backus Woods) in the Long Point region, Southern Ontario. Our aim was to determine the degree to which fragmented forests in the region harbor and sustain tree species diversity and to provide a baseline for ongoing study of these forests. The eight woodlots collectively exhibited over 95% of regional tree species. Analysis of size structure within these woodlots suggested that many species were being replaced successfully. While Backus Woods was among the largest and most species-rich of the areas sampled, rates of species accumulation were often lower than in the woodlots, particularly in the understory. Selective cutting in the woodlots may explain this high understory diversity, which is marked by a greater importance of shade-intolerant tree species as compared to Backus Woods where minimum intervention management is practiced. We suggest that the privately owned, and largely unprotected, fragmented forests in this region be recognized for their high tree diversity and potential to sustain tree diversity into the future.
Sustainability
Xanthium strumarium L. is a globally successful invasive herb that has had significant negative e... more Xanthium strumarium L. is a globally successful invasive herb that has had significant negative ecological, economic and social impacts in many world regions. The present study was therefore conducted to evaluate the invasive potential and spatial distribution patterns of X. strumarium in heavily invaded plant communities of the semiarid regions of northern Pakistan. Investigations were based on data from 20 plants grown in the Herbarium at the University of Malakand, and from observations in 450 plots distributed across 45 stands representing habitats across Northern Province including open fields, hillocks and abandoned areas in both urban and rural areas. Multivariate analysis identified elevation, organic matter and organic carbon as the environmental variables most associated with communities invaded by X. strumarium. Increased soil silt was positively associated and available water was negatively associated with X. strumarium–invaded communities. These key environmental charac...
Sustainability
Xanthium strumarium L. is a globally successful invasive herb that has had significant negative e... more Xanthium strumarium L. is a globally successful invasive herb that has had significant negative ecological, economic and social impacts in many world regions. The present study was therefore conducted to evaluate the invasive potential and spatial distribution patterns of X. strumarium in heavily invaded plant communities of the semiarid regions of northern Pakistan. Investigations were based on data from 20 plants grown in the Herbarium at the University of Malakand, and from observations in 450 plots distributed across 45 stands representing habitats across Northern Province including open fields, hillocks and abandoned areas in both urban and rural areas. Multivariate analysis identified elevation, organic matter and organic carbon as the environmental variables most associated with communities invaded by X. strumarium. Increased soil silt was positively associated and available water was negatively associated with X. strumarium–invaded communities. These key environmental charac...
Sustainability, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY)
Écoscience, 2018
ABSTRACT We developed a model of hardwood tree colonization in forest patches. We began with a ba... more ABSTRACT We developed a model of hardwood tree colonization in forest patches. We began with a basic model of species' recruitment density calculated as a function of seed production and juvenile survivorship. Survivorship probability was expressed as a function of seed size, using seed-sowing data for a wide variety of species. To account for dispersal, we used an exponential distancedecay function based on empirical colonization data for species classified by dispersal mechanism and seed mass. The basic model reasonably predicted observed recruitment densities at or near forest edges, except for small seeded, wind-dispersed species with strong establishment constraints, for which it over-predicts. Our dispersal term yielded predictions that were not statistically different from observed colonization. However, species with large seeds and unspecialized dispersal mechanism appear to have distinct thresholds beyond which no dispersal occurs. Further research should better account for establishment constraints among small-seeded species, dispersal constraints among large-seeded species and unspecialized dispersers, and improve the dispersal functions to better reflect vectors such as birds. Nevertheless, the present model is adequate for the prediction of colonization probabilities in fragmented forests, requiring only an estimate of the abundance of source trees of a species and the mean inter-fragment distances.
Landscape and Urban Planning
Natural Areas Journal, 2015
Encyclopedia of Geography, 2010
Renewable and Sustainable Energy Reviews, 2013
Environmental Reviews, 2012
The interactive effects of climate change and invasive alien species (IAS) pose serious threats t... more The interactive effects of climate change and invasive alien species (IAS) pose serious threats to biodiversity, ecosystems and human well-being worldwide. In particular, IAS are predicted to experience widespread changes in distribution in response to climate change, with many expanding their ranges into new areas. However, the two drivers of global change are seldom considered together in policy and management. We conducted a knowledge synthesis to assess the state of research on IAS range shifts under climate change in Canada. We found that the study of IAS distribution changes caused by climate change is a relatively new field of inquiry that integrates research in the areas of ecology, conservation biology, and environmental sciences. The multidisciplinary dimensions of the issue are largely overlooked in the scholarly literature, with most studies having a purely natural science perspective. Very little original research has occurred in the field to date; instead literature re...
Renewable and Sustainable Energy Reviews, 2013
The interactive effects of climate change and invasive alien species (IAS) pose serious threats t... more The interactive effects of climate change and invasive alien species (IAS) pose serious threats to biodiversity, ecosystems and human well-being worldwide. In particular, IAS are predicted to experience widespread changes in distribution in response to climate change, with many expanding their ranges into new areas. However, the two drivers of global change are seldom considered together in policy and management. We conducted a knowledge synthesis to assess the state of research on IAS range shifts under climate change in Canada. We found that the study of IAS distribution changes caused by climate change is a relatively new field of inquiry that integrates research in the areas of ecology, conservation biology, and environmental sciences. The multidisciplinary dimensions of the issue are largely overlooked in the scholarly literature, with most studies having a purely natural science perspective. Very little original research has occurred in the field to date; instead literature reviews are common. Research focuses on modeling range changes of current IAS threats, rather than predicting potential future IAS threats. The most commonly studied IAS already occur in Canada as native species that have spread beyond their range (e.g., lyme disease, mountain pine beetle, smallmouth bass) or as established invaders (e.g., gypsy moth). All of these IAS are expected to expand northward with climate change, resulting in widespread negative impacts on forest and freshwater biodiversity, carbon sequestration, and public health. Many barriers to predicting IAS range change under climate change are identified in the literature, including the complexity of the issue, lack of ecological data, and failure to integrate climate change -IAS interactions into research, policy, and management. Recommendations for increased research and monitoring, and the need for policy and management reform predominate in the literature.
Journal of Biosciences, Jan 1, 1999
Ecologists recognize that many species will not migrate rapidly enough to keep up with shifting e... more Ecologists recognize that many species will not migrate rapidly enough to keep up with shifting ecosystem conditions due to climate change. Assisted migration was proposed several decades ago as a strategy to help maintain populations of slow-moving species. However, many scientists see assisted migration as problematic, largely because its potential to preserve species stands in direct tension with its potential to produce invasion by the focal species, thereby threatening the recipient ecosystem. Scholarly debate on this topic has intensified during the last three years and threatens to produce a stalemate in policy and action on the issue. We take stock of the academic literature on this topic and identify possible avenues toward consensus in what might otherwise become an intractable ethical and policy problem. We tease apart the arguments in the debate, distinguishing among the direct risks and benefits to species, ecosystems and society on the one hand, and other arguments regarding scientific justification, evidence-base and feasibility on the other. We present a conceptual framework to help scientists and policy makers find common ground and work towards case-and context-specific solutions.
Biological Conservation, Jan 1, 2011
Assisted migration was proposed several decades ago as a means of addressing the impacts of clima... more Assisted migration was proposed several decades ago as a means of addressing the impacts of climate change on species populations. While its risks and benefits have been debated, and suggestions for planning and management given, there is little consensus within the academic literature over whether to adopt it as a policy. We evaluated the main features of the assisted migration literature including the study methods, taxonomic groups, geographic regions and disciplines involved. We further assessed the debate about the use of assisted migration, the main barriers to consensus, and the range of recommendations put forth in the literature for policy, planning or implementation. Commentaries and secondary literature reviews were as prevalent as first-hand scientific research and attention focussed on a global rather than regional level. There was little evidence of knowledge transfer outside of the natural sciences, despite the obvious policy relevance. Scholarly debate on this topic has intensified during the last 3 years. We present a conceptual framework for evaluating arguments in the debate, distinguishing among the direct risks and benefits to species, ecosystems and society on the one hand, and other arguments regarding scientific justification, evidence-base and feasibility on the other. We also identify recommendations with potential to advance the debate, including careful evaluation of risks, benefits and trade-offs, involvement of relevant stakeholders and consideration of the complementarity among assisted migration and less risk-tolerant strategies. We conclude, however, that none of these will solve the fundamental, often values-based, challenges in the debate. Solutions are likely to be complex, context-dependent and multi-faceted, emerging from further research, discussion and experience.► We review the literature on assisted migration (AM) as a climate change adaptation strategy. ► A majority of articles generally endorse AM, but opposition is intensifying. ► We present a conceptual framework for analyzing the debate. ► More original research is needed into processes and effects of assisted range extension. ► There are no simple solutions to the often value-based challenges in the debate.
Landscape and Urban Planning, Jan 1, 2008
We investigated tree species composition, diversity and size structure of eight privately owned h... more We investigated tree species composition, diversity and size structure of eight privately owned hardwood forest remnants and a 50 ha portion of semi-old-growth forest (Backus Woods) in the Long Point region, Southern Ontario. Our aim was to determine the degree to which fragmented forests in the region harbor and sustain tree species diversity and to provide a baseline for ongoing study of these forests. The eight woodlots collectively exhibited over 95% of regional tree species. Analysis of size structure within these woodlots suggested that many species were being replaced successfully. While Backus Woods was among the largest and most species-rich of the areas sampled, rates of species accumulation were often lower than in the woodlots, particularly in the understory. Selective cutting in the woodlots may explain this high understory diversity, which is marked by a greater importance of shade-intolerant tree species as compared to Backus Woods where minimum intervention management is practiced. We suggest that the privately owned, and largely unprotected, fragmented forests in this region be recognized for their high tree diversity and potential to sustain tree diversity into the future.