An Agent-based Model of the South African Offshore Hake Trawl Industry: Part II Drivers and Trade-offs in Profit and Risk

2017 ◽  
Vol 142 ◽  
pp. 257-267 ◽  
Author(s):  
Rachel Cooper ◽  
Astrid Jarre
2021 ◽  
Author(s):  
Rose A. Marks ◽  
Mpho Mbobe ◽  
Marilize Greyling ◽  
Jennie Pretorius ◽  
D. Nicholas McLetchie ◽  
...  

ABSTRACTResilience to abiotic stress is associated with a suite of functional traits related to defense and longevity. Stress tolerant plants are generally slow growing with extended leave lifespans and reduced allocation to reproduction. Resurrection plants are ideal systems to test for trade-offs associated with stress tolerance due to their extreme resiliency. While, growth defense trade-offs are well-characterized, few studies have tested for natural variation associated with tolerating the harshest environments. Here, we surveyed a suite of functional traits related to stress tolerance, leaf economics, and reproductive allocation in natural populations of the South African resurrection plant Myrothamnus flabellifolia. We selected three distinct field sites in South Africa ranging from mesic to xeric. Despite considerable environmental variation across the study area, M. flabellifolia plants were extremely and similarly stress tolerant at all sites. However, we detected notable variation in other life history and morphological traits. Plants in more mesic sites were larger, faster growing, and had more inflorescences. In contrast, plants from the most xeric sites appeared to invest more in persistence and defense, with lower growth rates and less reproductive allocation. Together, this suggests that desiccation tolerance is a binary trait in M. flabellifolia with little natural variation, but that other phenotypes are more labile. The trait syndromes exhibited by plants at the different study sites align with general expectations about growth defense tradeoffs associated with the colonization of extreme environments. We show that plants from the least stressful sites are more reproductive and faster growing, whereas plants from the most stressful sites were slower growing and less reproductive. These findings suggest that M. flabellifolia plants are finely tuned to their environment.


2017 ◽  
Vol 132 ◽  
pp. 91-103 ◽  
Author(s):  
Christian Grovermann ◽  
Pepijn Schreinemachers ◽  
Suthathip Riwthong ◽  
Thomas Berger

PLoS ONE ◽  
2021 ◽  
Vol 16 (2) ◽  
pp. e0246788
Author(s):  
Simon J. Lloyd ◽  
Zaid Chalabi

Undernutrition is a major contributor to the global-burden of disease, and global-level health impact models suggest that climate change-mediated reductions in food quantity and quality will negatively affect it. These models, however, capture just some of the processes that will shape future nutrition. We adopt an alternative standpoint, developing an agent-based model in which producer-consumer smallholders practice different ‘styles of farming’ in the global food system. The model represents a hypothetical rural community in which ‘orphan’ (subsistence) farmers may develop by adopting an ‘entrepreneurial’ style (highly market-dependent) or by maintaining a ‘peasant’ style (agroecology). We take a first look at the question: how might patterns of farming styles—under various style preference, climate, policy, and price transmission scenarios—impact on hunger and health-supporting conditions (incomes, work, inequality, ‘real land productivity’) in rural areas? imulations without climate change or agricultural policy found that style preference patterns influence production, food price, and incomes, and there were trade-offs between them. For instance, entrepreneurial-oriented futures had the highest production and lowest prices but were simultaneously those in which farms tended towards crisis. Simulations with climate change and agricultural policy found that peasant-orientated agroecology futures had the highest production, prices equal to or lower than those under entrepreneurial-oriented futures, and better supported rural health. There were, however, contradictory effects on nutrition, with benefits and harms for different groups. Collectively the findings suggest that when attempting to understand how climate change may impact on future nutrition and health, patterns of farming styles—along with the fates of the households that practice them—matter. These issues, including the potential role of peasant farming, have been neglected in previous global-level climate-nutrition modelling but go to the heart of current debates on the future of farming: thus, they should be given more prominence in future work.


PLoS ONE ◽  
2018 ◽  
Vol 13 (1) ◽  
pp. e0190506 ◽  
Author(s):  
Claudia Dislich ◽  
Elisabeth Hettig ◽  
Jan Salecker ◽  
Johannes Heinonen ◽  
Jann Lay ◽  
...  

2019 ◽  
Vol 16 (151) ◽  
pp. 20180733 ◽  
Author(s):  
Cameron J. Hosking ◽  
David Raubenheimer ◽  
Michael A. Charleston ◽  
Stephen J. Simpson ◽  
Alistair M. Senior

Lifespan and fecundity, the main components in evolutionary fitness, are both strongly affected by nutritional state. Geometric framework of nutrition (GFN) experiments has shown that lifespan and fecundity are separated in nutrient space leading to a functional trade-off between the two traits. Here we develop a spatially explicit agent-based model (ABM) using the GFN to explore how ecological factors may cause selection on macronutrient appetites to optimally balance these life-history traits. We show that increasing the risk of extrinsic mortality favours intake of a mixture of nutrients that is associated with maximal fecundity at the expense of reduced longevity and that this result is robust across spatial and nutritional environments. These model behaviours are consistent with what has been observed in studies that quantify changes in life history in response to environmental manipulations. Previous GFN-derived ABMs have treated fitness as a single value. This is the first such model to instead decompose fitness into its primary component traits, longevity and fecundity, allowing evolutionary fitness to be an emergent property of the two. Our model demonstrates that selection on macronutrient appetites may affect life-history trade-offs and makes predictions that can be directly tested in artificial selection experiments.


2020 ◽  
Vol 4 ◽  
Author(s):  
Hugo Fernandez-Mena ◽  
Graham K. MacDonald ◽  
Sylvain Pellerin ◽  
Thomas Nesme

2021 ◽  
Author(s):  
Amir Molajou ◽  
Abbas Afshar

Abstract The current study introduces a conceptual socio-hydrological based framework for water-energy-food (WEF) nexus. The proposed conceptual framework aims to investigate how farmers' dynamic agricultural activities under different socio-economic conditions affect the WEF systems. The WEF nexus model has been integrated with an Agent-Based Model, reflecting the farmers’ agricultural activities. Furthermore, the agent-based model benefits from Association Rule Mining to define farmer agents’ agricultural decision-making in various conditions. The processes within the WEF nexus are simultaneously physical, socio-economic, ecological, and political. Indeed, there are interrelated interactions among the mentioned processes in ways that have not yet properly delineated, mapped, or even perceived. Thus, for obtaining sustainable outcomes, the current study attempts to investigate trade-offs among natural resources and social systems in the WEF nexus approach. The proposed framework may provide more in-depth future insights for policy-makers through capturing bidirectional feedbacks among farmers and WEF systems. Furthermore, the proposed socio-hydrological WEF nexus framework can be adapted and applied to various societies and environments to provide more in-depth future insights for policy-makers through capturing bidirectional feedbacks among farmers and WEF systems.


2021 ◽  
Author(s):  
Hannah Gumble ◽  
Sarah Wise

New forms of mobility reshape the transportation landscape, changing movement for both their users and others in the environment. The transition period during which novel forms of travel are being explored can be a challenging time while the use of spaces must be renegotiated. E-scooters, which have recently been more widely introduced to the UK, are experiencing such a moment as riders, planners, and other users of the streetscape are determining what role this technology will play in communities. The data gaps surrounding e-scooters can make this an especially difficult question for planners because of the cost of gathering relevant observational data, much of which is held under private company ownership. In light of this, this work presents an agent-based model developed to examine the integration of e-scooters into existing streetscapes. Agent-based models explore phenomena through focusing on individual behaviour and rules which in turn gives rise to emergent large scale patterns. These patterns can be dissected and interrogated with a variety of tools, allowing us to tease out individual as well as group experiences of different scenarios. An agent-based approach allows us to capture the individual behaviours of e-scooter users and those of cyclists, drivers of variously sized vehicles, pedestrians, and others present in the environment. By focusing on the interactions of these various street users, we can explore how different approaches to e-scooter integration may fare relative to varying street configurations. Their decision frameworks are informed by observational studies of e-scooter users in order to augment the available data. We discuss the current state of understanding e-scooter behaviour and the potential modelling applications, present an initial behavioural framework of e-scooter decision making and inter-modal interactions, and highlight some preliminary results examining the differences between e-scooters operating on roads versus shared segregated cycle lanes. The work concludes with a case study comparing two modelled scenarios, one including a segregated cycle lane and one without. Drawing upon metrics such as the route segmentation/ cut-off rate and average travel comfort, we can more precisely explore how new forms of mobility will influence different kinds of street users in order to better understand the trade-offs associated with different paths forward.


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