Over the centuries, local communities have shaped atypical rules to deal with the uncertainty of their environment. They have developed complex prototypes for flexible overlapping institutions and ...arrangements to adapt their rules and uses to their uncertain environment. Today, this indigenous way of flexibly institutionalizing access rules could provide blueprints for dealing with uncertainty issues resulting from global change as well as designing practical guidelines for implementing resilient management. However, transforming indigenous skills for developing institutional flexibility into operational management rules that are appropriate in the current environmental and socioeconomic context is a huge challenge. However, communities could easily succeed in this reframing because the structuring principles of institutional flexibility are embedded in their mind frame. In this perspective, a participatory modeling process was applied in Senegal to explore, first, how to design a methodological platform to enable local people to shape different forms of environmental management and policies they consider appropriate in the new context of environmental uncertainty by drawing on their own attitudes to environmental management. Second, to increase the value of such “self-designed” outputs in improving knowledge about, and improving, the practical management of uncertainty, especially in drylands.
The participatory modelling method described here focuses on how to enable stakeholders to incorporate their own perception of environmental uncertainty and how to deal with it to design innovative ...environmental policies. This “self-design” approach uses role playing games and agent based modelling to let participants design their own conceptual framework, and so modelling supports, of issues. The method has a multi-scale focus I order to enable the whole multi-scale Sahelian logic to be expressed and on the other hand to encourage the players to deal with possible region-wide changes implied by their “local” policy objectives.
This multi-level participatory design of land use policies has been under experimentation in Senegal since 2008 in different local and national arenas. The process has resulted in the “self-design” of a qualitative and relatively simple model of Sahelian uncertainty, which can be played like a role playing game as well a computerized model. Results are shown in perceptible autonomous organisational learning at the local level. Participants were also able to incorporate their own ideas for new rules for access to resources. They designed innovative collective rules, organised follow up and monitoring of these new land uses. Moreover, meaningful ideas for environmental policies are beginning to take shape.
This work raises the epistemological question of what is meant by the term “indigenous knowledge” in environmental management, ranging from knowledge based on practical experience being included in the scholar's framing of knowledge, to a legitimate local ability to contextualize and re-arrange scientific expertise, to profoundly different worldviews which do not match ours.
•A participatory modelling lets people design their own model using their own knowledge.•An inclusionary method involves and interlinks stakeholders at local to national levels.•Participants create a qualitative model that nevertheless reflects the complexity of drylands environmental uncertainty.•Participants use the model to shape unusual uncertainty management principles for policy design.
Optimal foraging is one of the capital topics nowadays in Sahelian region. The vast majority of feed consumed by ruminants in Sahelian region is still formed by natural pastures. Pastoral constraints ...are the high variability of available forage and drinking water in space and especially in time (highly seasonal, interannual variability) and the scarcity of water resources. The mobility is the main functional and opportunistic adaptation to these constraints. Our goal in this paper is to formalize two dynamical models for interactions between a herd of domesticate animals, forage resources, and water resources inside a given Sahelian area, in order to confirm, explain, and predict by mathematical models some observations about pastoralism in Sahelian region. These models in some contexts can be similar to predator-prey models as forage and water resources can be considered as preys and herd’s animals as predators. These models exhibit very rich dynamics, since it predicts abrupt changes in consumer behaviour and disponibility of forage or water resources. The dynamics exhibits a possible coexistence between herd, resources, and water with alternative peaks in their trajectories.
•Simulation of a spatially explicit individual-based model to study the collective behaviour for motile phytoplankton.•The light attenuation and its impact on the creation of aggregation-break up ...rhythm regarding the groups.•The role of the active diel migration on groups’ formation and on the population dynamic.•The impact of social interactions (competition and cooperation) on the aggregation of motile phytoplankton cells.
In this article, we investigate the question of the impact of the diel vertical migration (DVM) and the light attenuation by the cells on both spatial pattern and population dynamics of phytoflagellates. For these purposes, we performed a simulation study by using a spatially explicit individual-based model (IBM). The designed IBM includes 2 global mechanisms: cellular motion which is modelled through a stochastic differential equation and demographic process that is density and light intensity dependent. We showed that under no-DVM, for competitive environment, increasing the light absorption helps the creation of a strong oscillatory behaviour, that breeds aggregation-break up rhythm, which is beneficial. However, when we pass to DVM regime, it will be more advantageous for the cells to reduce their light absorption. In regards of DVM effect, we showed that it has other benefits, apart from the acquisition of resources, such as enhancing the attraction mechanism that promotes cooperation and also helping the creation of spatial voids that permit the penetration of the light. Also, we showed that the DVM reduces the predation rate, so we prove quantitatively that the DVM reduces, in general, the grazing losses. Also, we found that the DVM strategy depends on the impact of the competition and cooperation between the cells on the division and death rates. So, probably for the motile species, the local competition is not high in order to let the cells gain advantages from the DVM regarding their survivability that is explained by an annual cyclic behaviour under seasonal environment.
•Predator-induced aggregation in motile phytoplankton.•Modelling resource competition and anti-predator cooperation in phytoplankton.•Individual-based modelling for motile phytoplankton cells.•IBMs ...conception and numerical simulations.•Impact of competition and cooperation on the aggregation process.
The phytoplankton's spatial aggregation is a very important phenomenon that can give responses to many questions such as the passage from the unicellularity to the multicellularity. In this work, we are interested by predator-induced aggregations in motile phytoplankton. Our aim is to bring, through a simulation study, some explanations on how these groups form and analyze the simultaneous effect of both resource competition and anti-predation cooperation on the groups’ formation process. For this purpose, we developed a 3D individual-based model (IBM) that takes into account small-scale biological processes for the phytoplankton cells that are: (1) motion, described by a stochastic differential equation in which the drift term is density-dependent to take into account the attraction mechanism between cells due to their chemosensory abilities and the dispersal term representing the diffusion of cells in water, (2) a density-dependent birth–death process to describe the demographical process in phytoplankton cells. In the latter, division and death rates were considered density-dependent to include a local competition for resources that slows up the cell's division and a local cooperation in phytoplankton that reduces the cell's predation death. We implemented the IBM and considered several scenarios that combine three different levels of resource competition with three different intensities of cooperation. The different scenarios were tested using real parameter values for phytoplankton.
The simulation of the IBM showed that phytoplankton cells form aggregations via the “coming together” mechanism driven by the cell's motion process in which, the attraction mechanism is enhanced by the cooperation behavior (the latter is a response to the predation stress). After that, groups grow through the “remaining together” mechanism which is a consequence of the division–death process and also the attraction mechanism which prevents the daughter cells from leaving the group after division. Also, the simulation of the different scenarios highlights the role of cooperation in the formation of aggregates and shows that although resource competition impairs the aggregation process and the group size, cooperation plays an important role in sustaining the aggregating process and when it is strong, the induced aggregation process is so successful that it completely prevents cells being grazed; and both group and population sizes are maintained at a good level.
A two-patch model, SEi1,…,EinIiLi, i=1,2, is used to analyze the spread of tuberculosis, with an arbitrary number n of latently infected compartments in each patch. A fraction of infectious ...individuals that begun their treatment will not return to the hospital for the examination of sputum. This fact usually occurs in sub-Saharan Africa, due to many reasons. The model incorporates migrations from one patch to another. The existence and uniqueness of the associated equilibria are discussed. A Lyapunov function is used to show that when the basic reproduction ratio is less than one, the disease-free equilibrium is globally and asymptotically stable. When it is greater than one, there exists at least one endemic equilibrium. The local stability of endemic equilibria can be illustrated using numerical simulations. Numerical simulation results are provided to illustrate the theoretical results and analyze the influence of lost sight individuals.
In this paper, we are interested in the numerical treatment of a nonlinear model describing phytoplankton aggregation. The model consists in an integro-differential diffusion equation, with a ...chemotaxis term responsible for self-attraction of phytoplankton cells. We develop and implement a numerical scheme to solve this nonlinear PDE and present numerical solutions for parameters values corresponding to real conditions in nature. The numerical results emphasize the role of the nonlinear chemotaxis term in producing aggregating patterns and further, they are used to explore the asymptotic behavior of the model.
Abstract
Transhumants move their herds based on strategies simultaneously considering several environmental and socio-economic factors. There is no agreement on the influence of each factor in these ...strategies. In addition, there is a discussion about the social aspect of transhumance and how to manage pastoral space. In this context, agent-based modeling can analyze herd movements according to the strategy based on factors favored by the transhumant. This article presents a reductionist agent-based model that simulates herd movements based on a single factor. Model simulations based on algorithms to formalize the behavioral dynamics of transhumants through their strategies. The model results establish that vegetation, water outlets and the socio-economic network of transhumants have a significant temporal impact on transhumance. Water outlets and the socio-economic network have a significant spatial impact. The significant impact of the socio-economic factor demonstrates the social dimension of Sahelian transhumance. Veterinarians and markets have an insignificant spatio-temporal impact. To manage pastoral space, water outlets should be at least
$$15\ km$$
15
k
m
from each other. The construction of veterinary centers, markets and the securitization of transhumance should be carried out close to villages and rangelands.
Sahelian transhumance is a seasonal movement of herds based on strategies. These strategies are based on environmental and socio-economic factors. However, it is empirically difficult to establish ...the influence of each factor on the spatio-temporal distribution of herds. This paper presents a microsimulation software Sahelian transhumance simulator (STS). STS determines the spatio-temporal influence of each factor on herd movements. It also proposes scenarios for developing and securing the Sahelian pastoral space.
•Reductionist analysis of the movement factors of Sahelian transhumant herds.•Influence of each herd movement factor in the transhumant’s decision-making process.•Confirmation of transhumance’s social dimension using microsimulations and GPS data.•Scenarios for Sahel Pastoral land-use Plan and Securitization.•Hierarchization of herd movement factors to model Sahelian transhumance.
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