We investigate the decision rules adopted by individuals in local communities, whose livelihoods depend on common pool resource stocks and who face the cooperation dilemma in their everyday life. For ...this purpose, field experiments are modeled and the model structure and output are confronted with experimental data and with the relevant theory of collective action proposed by
Ostrom (1998) Ostrom, E., 1998. A behavioral approach to the rational choice theory of collective action.
American Political Science Review 92 (1), 1–22.. The field experiments analyze the cooperative action among coastal communities in Providence Island (Colombian Caribbean Sea). The simulation model is built according to the principles and methods of
System Dynamics. The model formalizes the feedback causality among
reputation,
trust and
reciprocity
Ostrom (1998) Ostrom, E., 1998. A behavioral approach to the rational choice theory of collective action.
American Political Science Review 92 (1), 1–22.. Moreover, based on the payoff structure and treatments used in the experiments, it considers other behavioral factors such as
temptation to free ride,
profit maximization,
awareness and
risk perception of the individuals in feedback perspective. Model behavior replicates the patterns in the experimental data and is highly sensitive to reciprocity and free-riding behavior. It reveals path-dependent characteristic to the initial
trust of the individuals in the group. The variables and decision rules built into the model structure provide the basis for a dialogue between the theories of collective action and future experimental designs to test and improve such theories.
A dynamic simulation model of salt accumulation on irrigated lands is presented. The original version of the model is part of a large-scale socio-economic model of irrigation-based regional ...development. The model introduced in this paper is a systemic one in the sense that it integrates four major sub-processes of rootzone salinization: irrigation, drainage, groundwater discharge and groundwater intrusion. It provides a comprehensive and general description of the long-term process of salt accumulation in lowlands under continuous irrigation practice, where irrigated lands are annually increased. Analysis of the model and simulation results reveal, under what conditions the salinity reaches alarming levels and with what strategies it can be controlled. For instance, in situations where the mixing of drainage water into irrigation water supplies is high, rootzone salinity quickly reaches alarming levels. More importantly, in this setting, the typical strategy of increasing the drainage in order to control the salinity level yields unprecedented exponentially growing salinity levels, a catastrophic result for the agriculture. The model structure can represent the basin wide salinization process on different geographical settings in agricultural development. In general, the model provides an experimental simulation platform, which can be used by the policy makers in the long term strategic management of large scale irrigation development projects. The model can also be of interest to the students and learners in teaching and research, in the related fields of environmental sciences.
The deleterious effects of sodium-induced secondary alkalinization on soil structure and hydraulic properties of calcareous soils can vary widely. This study aims to evaluate the impact of sodicity ...and leaching velocity on the physical and hydraulic properties of a calcareous clay-rich soil. Two application rates of tap water (TW) and sodic water (SW) are considered: fast leaching, equal to the saturated hydraulic conductivity, Ks, and slow leaching conditions, equal to have 1/2 Ks. For the TW and SW experiments, up to 14 and 26 leaching cycles were performed in duplicates, respectively. After the leaching applications, the PVC columns were cut horizontally, and undisturbed samples were removed from the different depths. It was observed that neither water quality nor water flow rate significantly affected water stable aggregate percentages. TW did not affect soil total porosity and bulk density except at the bottom of the column. On the other hand, there were remarkable reductions in soil porosity and bulk density in the SW leaching experiments ranging from 8.8 to 12.5% and 7.4–13.8%, respectively. High Na concentrations in leaching water caused aggregate swelling and dispersion, leading to reduced Na+ and enhanced Ca2+ transport to the lower portions of the soil column. In the lower layers, the severity of sodium-induced dispersion was restricted by calcium, which was exchanged by the excess amount of Na from the upper layers, maintaining soil particles flocculated. Ca2+, which tightens the soil particles and aggregates together, limited Na-induced disruption of the soil aggregation. Nonetheless, particles that broke away from aggregate did influence the hydraulic properties of the soils. Overall, the experiments revealed that although the physical and hydraulic properties of the soil are affected by the sodic waters and the flow rates, this effect is reduced in calcareous soils due to their strong bonding feature.
•Deleterious effect of Na on aggregation is less evident in calcareous clay-rich soil.•Sodium-induced degradation is more pronounced in the upper layers of calcareous soil.•Aggregates of well-structured calcareous soils resist compaction caused by Na.•Increased flow rates of sodic water accelerate soil degradation.•The higher the limestone and clay content, the more stable the soil structure.
Regional agricultural projects based on water resource development have many potential impacts on social and natural environments. In this research, potential long-term environmental problems of the ...Southeastern Anatolian Project (GAP) related to water resources, land use, land degradation, agricultural pollution and demography are analysed from a systems perspective. The analysis focuses on the totality of environmental, social and economic issues. For this purpose, a system dynamics simulation model (GAPSIM) has been developed as an experimental platform for policy analysis. GAPSIM was validated, first ‘structurally’, using the tests suggested by the literature and then the model ‘behaviour’ was tested and calibrated with respect to available data. The reference behaviour of GAPSIM reveals that, as the irrigated lands are developed, GAP faces significant water scarcity because of the increased intensity of cotton, the crop with the highest demands for water. Simulation results also indicate that two key environmental factors, pesticide and fertilizer consumption may reach undesirable levels. Alternative irrigation water release strategies, development rates of irrigated fields and farm rotation practices appear as important policy tools in achieving long-term environmental sustainability. GAPSIM promises to be not only a useful laboratory for policy makers of GAP, but also a useful generic structure applicable to other similar regional development projects.
•A coupled land use dynamics and surface/subsurface hydrologic model is developed.•Coupling of the two models is through the Leaf Area Index and Root Depth parameters.•The coupled model was used to ...assess the impact of different land use scenarios.•Conversion between agriculture and forest was more significant than forest stand type.•Incorporating seasonal land use variations in hydrologic models is emphasized.
Land use dynamics can have a significant impact on watershed hydrology. In this study, we develop a land use dynamics model coupled with a spatially distributed three-dimensional surface–subsurface hydrologic model. The coupled model is applied to the Bartin spring watershed, a rural watershed located in the northwestern Turkey. The land use dynamics model considers natural and anthropogenic transformations between land use categories classified as coniferous forests, deciduous forests, agriculture and settlement. The processes considered in the hydrodynamic model are evapotranspiration, overland flow, river channel flow, and saturated/unsaturated subsurface flow. The link between the land use model and the hydrodynamic model is through the vegetation parameters: leaf area index (LAI) and root depth (RD). The land use and hydrologic models were calibrated using satellite maps and daily flow and meteorological data, respectively. The correlation coefficient between the simulated and observed daily discharges for the considered watershed was about 0.72, indicating good agreement with observed data. The coupled model was used to simulate the water budget based on alternative land use and forest management scenarios. Results show that the water budget is most sensitive to variations in precipitation and conversion between forest and agricultural lands but is less sensitive to the type of forest stands. Overall, it is shown that the coupled model is a useful tool for assessing the impact of land use change on the watershed hydrological processes.
Humanity is on a deeply unsustainable trajectory. We are exceeding planetary boundaries and unlikely to meet many international sustainable development goals and global environmental targets. Until ...recently, there was no broadly accepted framework of interventions that could ignite the transformations needed to achieve these desired targets and goals.
As a component of the IPBES Global Assessment, we conducted an iterative expert deliberation process with an extensive review of scenarios and pathways to sustainability, including the broader literature on indirect drivers, social change and sustainability transformation. We asked, what are the most important elements of pathways to sustainability?
Applying a social–ecological systems lens, we identified eight priority points for intervention (leverage points) and five overarching strategic actions and priority interventions (levers), which appear to be key to societal transformation. The eight leverage points are: (1) Visions of a good life, (2) Total consumption and waste, (3) Latent values of responsibility, (4) Inequalities, (5) Justice and inclusion in conservation, (6) Externalities from trade and other telecouplings, (7) Responsible technology, innovation and investment, and (8) Education and knowledge generation and sharing. The five intertwined levers can be applied across the eight leverage points and more broadly. These include: (A) Incentives and capacity building, (B) Coordination across sectors and jurisdictions, (C) Pre‐emptive action, (D) Adaptive decision‐making and (E) Environmental law and implementation. The levers and leverage points are all non‐substitutable, and each enables others, likely leading to synergistic benefits.
Transformative change towards sustainable pathways requires more than a simple scaling‐up of sustainability initiatives—it entails addressing these levers and leverage points to change the fabric of legal, political, economic and other social systems. These levers and leverage points build upon those approved within the Global Assessment's Summary for Policymakers, with the aim of enabling leaders in government, business, civil society and academia to spark transformative changes towards a more just and sustainable world.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
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