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Fransson, P., Franklin, O., Lindroos, O., Nilsson, U. & Brännström, Å. (2020). A simulation-based approach to a near optimal thinning strategy: allowing for individual harvesting times for individual trees. Canadian Journal of Forest Research, 50(3), 320-331
Open this publication in new window or tab >>A simulation-based approach to a near optimal thinning strategy: allowing for individual harvesting times for individual trees
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2020 (English)In: Canadian Journal of Forest Research, ISSN 0045-5067, E-ISSN 1208-6037, Vol. 50, no 3, p. 320-331Article in journal (Refereed) Published
Abstract [en]

As various methods for precision inventories, such as LiDAR, are becoming increasingly common in forestry, individual-tree level planning is becoming more viable. Here, we present a method for finding the optimal thinning times for individual trees from an economic perspective. The method utilizes an individual tree-based forest growth model that has been fitted to Norway spruce (Picea abies (L.) Karst.) stands in northern Sweden. We find that the optimal management strategy is to thin from above, i.e. harvesting trees that are larger than average. We compare our optimal strategy with a conventional management strategy and find that it results in approximately 20% higher land expectation value. Furthermore, we find that increasing the discount rate will, for the optimal strategy, reduce the final harvest age and increase the basal area reduction. Decreasing the cost to initiate a thinning (e.g., machinery-related transportation costs) increases the number of thinnings and delays the first thinning.

National Category
Forest Science
Identifiers
urn:nbn:se:umu:diva-156740 (URN)10.1139/cjfr-2019-0053 (DOI)000516761900008 ()
Funder
Swedish Research Council Formas, 2012-1008
Note

Originally included in thesis in manuscript form 

Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2020-03-19Bibliographically approved
Joshi, J., Brännström, Å. & Dieckmann, U. (2020). Emergence of social inequality in the spatial harvesting of renewable public goods. PloS Computational Biology, 16(1), Article ID e1007483.
Open this publication in new window or tab >>Emergence of social inequality in the spatial harvesting of renewable public goods
2020 (English)In: PloS Computational Biology, ISSN 1553-734X, E-ISSN 1553-7358, Vol. 16, no 1, article id e1007483Article in journal (Refereed) Published
Abstract [en]

Spatially extended ecological public goods, such as forests, grasslands, and fish stocks, are at risk of being overexploited by selfish consumers-a phenomenon widely recognized as the 'tragedy of the commons.' The interplay of spatial and ecological dimensions introduces new features absent in non-spatial ecological contexts, such as consumer mobility, local information availability, and strategy evolution through social learning in neighborhoods. It is unclear how these features interact to influence the harvesting and dispersal strategies of consumers. To answer these questions, we develop and analyze an individual-based, spatially structured, eco-evolutionary model with explicit resource dynamics. We report the following findings. (1) When harvesting efficiency is low, consumers evolve a sedentary consumption strategy, through which the resource is harvested sustainably, but with harvesting rates far below their maximum sustainable value. (2) As harvesting efficiency increases, consumers adopt a mobile 'consume-and-disperse' strategy, which is sustainable, equitable, and gives maximum sustainable yield. (3) A further increase in harvesting efficiency leads to large-scale overexploitation. (4) If costs of dispersal are significant, increased harvesting efficiency also leads to social inequality between frugal sedentary consumers and overexploitative mobile consumers. Whereas overexploitation can occur without social inequality, social inequality always leads to overexploitation. Thus, we identify four conditions that-while being characteristic of technological progress in modern societies-risk social inequality and overexploitation: high harvesting efficiency, moderately low costs of dispersal, high consumer density, and the tendency of consumers to adopt new strategies rapidly. We also show how access to global information-another feature widespread in modern societies-helps mitigate these risks.

Author summary: Throughout history, humans have shaped ecological landscapes, which in turn have influenced human behavior. This mutual dependence is epitomized when human consumers harvest a spatially extended renewable resource. Simple models predict that, when multiple consumers harvest a shared resource, each is tempted to harvest faster than his/her peers, putting the resource at risk of overexploitation. It is unclear, however, how the interplay among resource productivity, consumer mobility, and social learning in spatial ecological public goods games influences evolved consumer behavior. Here, using an individual-based, spatially structured, eco-evolutionary model of consumers and a resource, we find that increasing resource productivity initially promotes efficient resource use by enabling mobile consumption strategies, but eventually leads to inequality and overexploitation, as overexploitative mobile consumers coexist with frugal sedentary consumers. When consumers are impatient (i.e., eager to imitate successful strategies) or myopic (i.e., unaware of conditions outside of their neighborhoods), inequality and overexploitation tend to aggravate.

Place, publisher, year, edition, pages
Public Library Science, 2020
National Category
Computational Mathematics Social Sciences Interdisciplinary Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:umu:diva-168342 (URN)10.1371/journal.pcbi.1007483 (DOI)000510916500009 ()31914166 (PubMedID)
Available from: 2020-02-24 Created: 2020-02-24 Last updated: 2020-02-24Bibliographically approved
Zhang, L., Thibert-Plante, X., Ripe, J., Svanback, R. & Brännström, Å. (2019). Biodiversity loss through speciation collapse: Mechanisms, warning signals, and possible rescue. Evolution, 73(8), 1504-1516
Open this publication in new window or tab >>Biodiversity loss through speciation collapse: Mechanisms, warning signals, and possible rescue
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2019 (English)In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 73, no 8, p. 1504-1516Article in journal (Refereed) Published
Abstract [en]

Speciation is the process that generates biodiversity, but recent empirical findings show that it can also fail, leading to the collapse of two incipient species into one. Here, we elucidate the mechanisms behind speciation collapse using a stochastic individual-based model with explicit genetics. We investigate the impact of two types of environmental disturbance: deteriorated visual conditions, which reduce foraging ability and impede mate choice, and environmental homogenization, which restructures ecological niches. We find that: (1) Species pairs can collapse into a variety of forms including new species pairs, monomorphic or polymorphic generalists, or single specialists. Notably, polymorphic generalist forms may be a transient stage to a monomorphic population; (2) Environmental restoration enables species pairs to reemerge from single generalist forms, but not from single specialist forms; (3) Speciation collapse is up to four orders of magnitude faster than speciation, while the reemergence of species pairs can be as slow as de novo speciation; (4) Although speciation collapse can be predicted from either demographic, phenotypic, or genetic signals, observations of phenotypic changes allow the most general and robust warning signal of speciation collapse. We conclude that factors altering ecological niches can reduce biodiversity by reshaping the ecosystem's evolutionary attractors.

Keywords
Assortative mating, hybridization, speciation, species diversity, warning signals
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-163080 (URN)10.1111/evo.13736 (DOI)000482092600001 ()30980527 (PubMedID)
Available from: 2019-11-14 Created: 2019-11-14 Last updated: 2019-11-14Bibliographically approved
Liu-Helmersson, J., Rocklöv, J., Sewe, M. & Brännström, Å. (2019). Climate change may enable Aedes aegypti infestation in major European cities by 2100. Environmental Research, 172, 693-699
Open this publication in new window or tab >>Climate change may enable Aedes aegypti infestation in major European cities by 2100
2019 (English)In: Environmental Research, ISSN 0013-9351, E-ISSN 1096-0953, Vol. 172, p. 693-699Article in journal (Refereed) Published
Abstract [en]

Background: Climate change allows Aedes aegyptito infest new areas. Consequently, it enables the arboviruses the mosquito transmits - e.g., dengue, chikungunya, Zika and yellow fever – to emerge in previously uninfected areas. An example is the Portuguese island of Madeira during 2012–13.

Objective: We aim to understand how climate change will affect the future spread of this potent vector, as an aidin assessing the risk of disease outbreaks and effectively allocating resources for vector control.

Methods: We used an empirically-informed, process-based mathematical model to study the feasibility of Aedes aegypti infestation into continental Europe. Based on established global climate-change scenario data, we assess the potential of Aedes aegypti to establish in Europe over the 21st century by estimating the vector population growth rate for five climate models (GCM5).

Results: In a low carbon emission future (RCP2.6), we find minimal change to the current situation throughout the whole of the 21st century. In a high carbon future (RCP8.5), a large parts of southern Europe risks being invaded by Aedes aegypti.

Conclusion: Our results show that successfully enforcing the Paris Agreement by limiting global warming to below 2 °C significantly lowers the risk for infestation of Aedes aegypti and consequently of potential large-scale arboviral disease outbreaks in Europe within the 21st century.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Aedes aegypti, Vector invasion, Europe, Climate change
National Category
Public Health, Global Health, Social Medicine and Epidemiology Climate Research
Identifiers
urn:nbn:se:umu:diva-143763 (URN)10.1016/j.envres.2019.02.026 (DOI)000468377500079 ()30884421 (PubMedID)
Funder
Swedish Research Council, 2015-03917Swedish Research Council Formas, 2017-01300
Note

Originally included in thesis in manuscript form with title "Climate change may enable Aedes aegypti mosquitoes infestation in major European cities by 2100"

Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2019-06-20Bibliographically approved
Liu-Helmersson, J., Brännström, Å., Sewe, M. & Rocklöv, J. (2019). Estimating past, present and future trends in the global distribution and abundance of the arbovirus vector Aedes aegypti. Frontiers In Public Health, 7, Article ID 148.
Open this publication in new window or tab >>Estimating past, present and future trends in the global distribution and abundance of the arbovirus vector Aedes aegypti
2019 (English)In: Frontiers In Public Health, ISSN 2296-2565, Vol. 7, article id 148Article in journal (Refereed) Published
Abstract [en]

Background: Aedes aegypti is the principal vector for several important arbovirus diseases, including dengue, chikungunya, yellow fever, and Zika. While recent empirical research has attempted to identify the current global distribution of the vector, the seasonal, and longer-term dynamics of the mosquito in response to trends in climate, population, and economic development over the twentieth and the twenty-first century remains to be elucidated.

Methods: In this study, we use a process-based mathematical model to estimate global vector distribution and abundance. The model is based on the lifecycle of the vector and its dependence on climate, and the model sensitivity to socio-economic development is tested. Model parameters were generally empirically based, and the model was calibrated to global databases and time series of occurrence and abundance records. Climate data on temperature and rainfall were taken from CRU TS3.25 (1901–2015) and five global circulation models (CMIP5; 2006–2099) forced by a high-end (RCP8.5) and a low-end (RCP2.6) emission scenario. Socio-economic data on global GDP and human population density were from ISIMIP (1950–2099).

Findings: The change in the potential of global abundance in A. aegypti over the last century up to today is estimated to be an increase of 9.5% globally and a further increase of 20 or 30% by the end of this century under a low compared to a high carbon emission future, respectively. The largest increase has occurred in the last two decades, indicating a tipping point in climate-driven global abundance which will be stabilized at the earliest in the mid-twenty-first century. The realized abundance is estimated to be sensitive to socioeconomic development.

Interpretation: Our data indicate that climate change mitigation, i.e., following the Paris Agreement, could considerably help in suppressing risks of increased abundance and emergence of A. aegypti globally in the second half of the twenty-first century.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
Aedes aegypti, mathematical model, vector abundance, temperature, precipitation, climate change, socioeconomic factors, global vector abundance
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-143762 (URN)10.3389/fpubh.2019.00148 (DOI)000472667800001 ()31249824 (PubMedID)
Funder
EU, Horizon 2020, 734584Swedish Research Council, 2015-03917Swedish Research Council Formas, 2017-01300
Note

Originally included in thesis in manuscript form.

Available from: 2018-01-09 Created: 2018-01-09 Last updated: 2020-05-06Bibliographically approved
Wickman, J., Diehl, S. & Brännström, Å. (2019). Evolution of resource specialisation in competitive metacommunities [Letter to the editor]. Ecology Letters, 22(11), 1746-1756
Open this publication in new window or tab >>Evolution of resource specialisation in competitive metacommunities
2019 (English)In: Ecology Letters, ISSN 1461-023X, E-ISSN 1461-0248, Vol. 22, no 11, p. 1746-1756Article in journal, Letter (Refereed) Published
Abstract [en]

Spatial environmental heterogeneity coupled with dispersal can promote ecological persistence of diverse metacommunities. Does this premise hold when metacommunities evolve? Using a two-resource competition model, we studied the evolution of resource-uptake specialisation as a function of resource type (substitutable to essential) and shape of the trade-off between resource uptake affinities (generalist- to specialist-favouring). In spatially homogeneous environments, evolutionarily stable coexistence of consumers is only possible for sufficiently substitutable resources and specialist-favouring trade-offs. Remarkably, these same conditions yield comparatively low diversity in heterogeneous environments, because they promote sympatric evolution of two opposite resource specialists that, together, monopolise the two resources everywhere. Consumer diversity is instead maximised for intermediate trade-offs and clearly substitutable or clearly essential resources, where evolved metacommunities are characterised by contrasting selection regimes. Taken together, our results present new insights into resource-competition-mediated evolutionarily stable diversity in homogeneous and heterogeneous environments, which should be applicable to a wide range of systems.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
Adaptive dynamics, coexistence, consumer-resource interactions, ESS, spatial models
National Category
Ecology
Identifiers
urn:nbn:se:umu:diva-162861 (URN)10.1111/ele.13338 (DOI)000480204800001 ()31389134 (PubMedID)2-s2.0-85070487188 (Scopus ID)
Available from: 2019-09-06 Created: 2019-09-06 Last updated: 2020-01-09Bibliographically approved
Pontarp, M., Brännström, Å. & Petchey, O. L. (2019). Inferring community assembly processes from macroscopic patterns using dynamic eco-evolutionary models and Approximate Bayesian Computation (ABC). Methods in Ecology and Evolution, 10(4), 450-460
Open this publication in new window or tab >>Inferring community assembly processes from macroscopic patterns using dynamic eco-evolutionary models and Approximate Bayesian Computation (ABC)
2019 (English)In: Methods in Ecology and Evolution, ISSN 2041-210X, E-ISSN 2041-210X, Vol. 10, no 4, p. 450-460Article, review/survey (Refereed) Published
Abstract [en]

Statistical techniques exist for inferring community assembly processes from community patterns. Habitat filtering, competition, and biogeographical effects have, for example, been inferred from signals in phenotypic and phylogenetic data. The usefulness of current inference techniques is, however, debated as a mechanistic and causal link between process and pattern is often lacking, and evolutionary processes and trophic interactions are ignored.

Here, we revisit the current knowledge on community assembly across scales and, in line with several reviews that have outlined challenges associated with current inference techniques, we identify a discrepancy between the current paradigm of eco-evolutionary community assembly and current inference techniques that focus mainly on competition and habitat filtering. We argue that trait-based dynamic eco-evolutionary models in combination with recently developed model fitting and model evaluation techniques can provide avenues for more accurate, reliable, and inclusive inference. To exemplify, we implement a trait-based, spatially explicit eco-evolutionary model and discuss steps of model modification, fitting, and evaluation as an iterative approach enabling inference from diverse data sources.

Through a case study on inference of prey and predator niche width in an eco-evolutionary context, we demonstrate how inclusive and mechanistic approaches-eco-evolutionary modelling and Approximate Bayesian Computation (ABC)-can enable inference of assembly processes that have been largely neglected by traditional techniques despite the ubiquity of such processes.

Much literature points to the limitations of current inference techniques, but concrete solutions to such limitations are few. Many of the challenges associated with novel inference techniques are, however, already to some extent resolved in other fields and thus ready to be put into action in a more formal way for inferring processes of community assembly from signals in various data sources.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
biogeography, community assembly, community structure, ecology, evolution, process inference
National Category
Bioinformatics (Computational Biology) Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-158737 (URN)10.1111/2041-210X.13129 (DOI)000463036400001 ()
Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-05-21Bibliographically approved
Hochrainer-Stigler, S., Colon, C., Boza, G., Brännström, Å., Linnerooth-Bayer, J., Pflug, G., . . . Dieckmann, U. (2019). Measuring, modeling, and managing systemic risk: the missing aspect of human agency. Journal of Risk Research
Open this publication in new window or tab >>Measuring, modeling, and managing systemic risk: the missing aspect of human agency
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2019 (English)In: Journal of Risk Research, ISSN 1366-9877, E-ISSN 1466-4461Article in journal (Refereed) Epub ahead of print
Abstract [en]

It is problematic to treat systemic risk as a merely technical problem that can be solved by natural-science methods and through biological and ecological analogies. There appears to be a discrepancy between understanding systemic risk from a natural-science perspective and the unresolved challenges that arise when humans with their initiatives and interactions are included in systemic-risk considerations. It is therefore necessary to investigate possible fundamental differences and similarities of systemic risk with and without accounting for human involvement. Focusing on applied and implementation aspects of measuring, modeling, and managing systemic risks, we identify three important and distinct features characterizing such fundamental differences: indetermination, indecision, and responsibility. We contend that, first, including human initiatives and interactions in systemic-risk considerations must emphasize a type of variability that is especially relevant in this context, namely the role of free will as a fundamental source of essential indetermination in human agency. Second, we postulate that collective indecision generated by mutual uncertainty often leads to the suspension or alteration of rules, procedures, scripts, and norms. Consequently, the associated systemic risks cannot be incorporated into explanatory models, as the new causal rules cannot be predicted and accounted for. Third, analogies from biology and ecology, especially the idea of ‘contagion,’ downplay human agency, and therefore human responsibility, promoting the false belief that systemic risk is a merely technical problem. For each of these three features, we provide recommendations for future directions and suggest how measuring, modeling, and managing approaches from the natural-science domain can best be applied in light of human agency.

Place, publisher, year, edition, pages
Routledge, 2019
Keywords
Systemic risk, human agency, measuring systemic risk, managing systemic risk, modelling systemic risk
National Category
Social Sciences Interdisciplinary
Identifiers
urn:nbn:se:umu:diva-164627 (URN)10.1080/13669877.2019.1646312 (DOI)000485129600001 ()2-s2.0-85071978306 (Scopus ID)
Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2019-11-08
Lundström, N. L. P., Loeuille, N., Meng, X., Bodin, M. & Brännström, Å. (2019). Meeting yield and conservation objectives by harvesting both juveniles and adults. American Naturalist, 193(3), 373-390
Open this publication in new window or tab >>Meeting yield and conservation objectives by harvesting both juveniles and adults
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2019 (English)In: American Naturalist, ISSN 0003-0147, E-ISSN 1537-5323, Vol. 193, no 3, p. 373-390Article in journal (Refereed) Published
Abstract [en]

Sustainable yields that are at least 80% of the maximum sustainable yield are sometimes referred to as "pretty good yields" (PGY). The range of PGY harvesting strategies is generally broad and thus leaves room to account for additional objectives besides high yield. Here, we analyze stage-dependent harvesting strategies that realize PGY with conservation as a second objective. We show that (1) PGY harvesting strategies can give large conservation benefits and (2) equal harvesting rates of juveniles and adults is often a good strategy. These conclusions are based on trade-off curves between yield and four measures of conservation that form in two established population models, one age-structured model and one stage-structured model, when considering different harvesting rates of juveniles and adults. These conclusions hold for a broad range of parameter settings, although our investigation of robustness also reveals that (3) predictions of the age-structured model are more sensitive to variations in parameter values than those of the stage-structured model. Finally, we find that (4) measures of stability that are often quite difficult to assess in the field (e.g., basic reproduction ratio and resilience) are systematically negatively correlated with impacts on biomass and size structure, so that these later quantities can provide integrative signals to detect possible collapses.

Place, publisher, year, edition, pages
University of Chicago Press, 2019
Keywords
fisheries management, maximum sustainable yield, pretty good yield, Pareto front, resilience, size structure
National Category
Ecology Evolutionary Biology
Identifiers
urn:nbn:se:umu:diva-155571 (URN)10.1086/701631 (DOI)000459624900007 ()30794450 (PubMedID)
Available from: 2019-01-22 Created: 2019-01-22 Last updated: 2019-04-01Bibliographically approved
Fransson, P., Nilsson, U., Lindroos, O., Franklin, O. & Brännström, Å. (2019). Model-based investigation on the effects of spatial evenness, and size selection in thinning of Picea abies stands. Scandinavian Journal of Forest Research, 34(3), 189-199
Open this publication in new window or tab >>Model-based investigation on the effects of spatial evenness, and size selection in thinning of Picea abies stands
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2019 (English)In: Scandinavian Journal of Forest Research, ISSN 0282-7581, E-ISSN 1651-1891, Vol. 34, no 3, p. 189-199Article in journal (Refereed) Published
Abstract [en]

Size and spatial distribution of trees are important for forest stand growth, but the extent to which itmatters in thinning operations, in terms of wood production and stand economy, has rarely beendocumented. Here we investigate how the choice of spatial evenness and tree-size distribution ofresidual trees impacts wood production and stand economy. A spatially explicit individual-basedgrowth model was used, in conjunction with empirical cost functions for harvesting andforwarding, to calculate net production and net present value for different thinning operations inNorway spruce stands in Northern Sweden. The in silico thinning operations were defined by threevariables: (1) spatial evenness after thinning, (2) tree size preference for harvesting, and (3) basalarea reduction. We found that thinning that increases spatial evenness increases net productionand net present value by around 2.0%, compared to the worst case. When changing the spatialevenness in conjunction with size preference we could observe an improvement of the netproduction and net present value up to 8.0%. The magnitude of impact differed greatly betweenthe stands (from 1.7% to 8.0%) and was highest in the stand with the lowest stem density.

Place, publisher, year, edition, pages
Taylor & Francis, 2019
Keywords
thinning, individual-based model, spatial distribution, forest management, simulation
National Category
Forest Science
Identifiers
urn:nbn:se:umu:diva-156738 (URN)10.1080/02827581.2019.1577914 (DOI)000459142200003 ()
Funder
Swedish Research Council Formas, 2012-1008
Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2019-04-16Bibliographically approved
Projects
Precision forestry for the future: enhanced forest management by optimized tree selection in thinning operations [2012-1008_Formas]; Umeå UniversityEvolution in spatially-structured populations [2015-03917_VR]; Umeå University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9862-816x

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