Working backwards to move forwards: Graph-based connectivity metrics for reserve network selection

In this paper we apply graph theory in a reserve selection exercise to explore the tradeoffs between maintaining connectivity and minimizing the total area of a protected area network. Rather than focus on a single organism, we used a multi-species approach and looked at the tradeoff curves for organisms with varying dispersal abilities. We first generated the tradeoff curves using a graph-based metric to determine the importance of individual patches for maintaining connectivity. We then performed an analogous set of analyses using patch size as a surrogate measure of importance.     

MAKING SMARTER ENVIRONMENTAL MANAGEMENT DECISIONS1

ABSTRACT: This paper outlines a sound, practical approach for making more informed decisions about environmental policy choices. It emphasizes the importance of using a structured decision process to specify and organize values, use these values to create alternatives, and assess tradeoffs to help achieve a desired balance across key objectives. Although these decision making steps are based on common sense, they are often neglected or poorly carried out as part of the complex evaluations of natural resource options. We discuss several reasons for this frequent neglect of decision making principles and provide examples from recent water use planning projects to demonstrate some of the benefits of using a structured, decision focused approach: new and better solutions, increased and more productive participation by stakeholders, and greater defensibility and acceptance of the resource management evaluation process and its conclusions.     

The moral residue of conservation

Should conservationists use lethal management to control introduced wildlife populations? Should they kill individual animals to protect endangered species? Are trade-offs that prioritize some values at the expense of others morally appropriate? These sorts of ethical questions are common in conservation. In debating such questions, conservationists often seem to presume 1 of 2 possible answers: the act in question is right or it is wrong. But morality in conservation is considerably more complex than this simple binary suggests. A robust conservation ethic requires a vocabulary that gives voice to the uncertainty and unease that arise when what seems to be the best available course of action also seems to involve a measure of wrongdoing. The philosophical literature on moral residue and moral dilemmas supplies this vocabulary. Moral dilemmas arise when one must neglect certain moral requirements to fulfill others. Under such circumstances, even the best possible decision leaves a moral residue, which is experienced emotionally as some form of grief. Examples of conservation scenarios that leave a moral residue include management of introduced rabbits in Australia, trophy hunting in Africa, and forest management trade-offs in the Pacific Northwest. Moral residue is integral to the moral experience of conservationists today, and grief is an appropriate response to many decisions conservationists must make. Article impact statement: Defensible conservation decisions may neglect moral requirements, leaving a moral residue; conservationists should respond with grief.     

Exploring community assembly through an individual-based model for trophic interactions

Traditionally, the dynamics of community assembly has been analyzed by means of deterministic models of differential equations. Despite the theoretical advances provided by such models, they are restricted to questions about community-wide features. The individual-based modeling offers an opportunity to link bionomic features to patterns at the community scale, allowing us to understand how trait-based assembly rules can arise by dynamical processes. The present paper introduces an individual-based model of community assembly, and discusses some of the major advantages and drawbacks of this approach. The model was framed to deal with predation among size-structured populations, incorporating allometric constraints to energetic requirements, movement, life-history features and interaction relationships among individuals. A protocol of assembly procedure is proposed, in which a period of intense species introductions is followed by a period without introductions. The resultant communities did not present any pattern of trait over-dispersion, meaning that the multivariate distances of bionomic features among co-occurring species were neither larger nor more regular than expected in a random collection of species. It suggests a weak influence of interspecific interactions in the model environment and individualistic rules of coexistence, driven mainly by the spatial structure. This highlights that trait over-dispersion and resource partitioning should not be considered a necessary condition for coexistence, even in communities entirely structured by internal processes like predation and competition.     

SPACE-TIME TRADEOFFS ACROSS THE HYDROLOGIC DATA SETS OF COMPETING RAINFALL-RUNOFF MODELS: A PRELIMINARY ANALYSIS1

ABSTRACT: The concept of a space-time tradeoff is extended to the hydrologic data sets of competing rainfall-runoff modeling techniques. Examples are given by comparing the performance of a regression model and a quasi-physically based model using data from an experimental catchment and data synthetically generated. Space-time tradeoffs are demonstrated within the data sets of the two modeling techniques, but not across the competing hydrologic data sets.     

FARM INCOME AND GROUND WATER QUALITY IMPLICATIONS FROM REDUCING SURFACE WATER SEDIMENT DELWERIES1

ABSTRACT: The potential surface water and ground water quality tradeoff implications from the nonpoint source provisions of the 1987 Water Quality Act are investigated in this paper using a national linear programming model developed at Iowa State University and modified by the Economic Research Service and the Leaching Evaluation of Agricultural Chemicals (LEACH) Handbook developed by the U.S. Environmental Protection Agency. The linear programming model is used to maximize net farm revenue using optimal combinations of crop rotations and tillage practices for each region of the United States given natural resource constraints. The LEACH handbook is used to determine the relative potential for pesticides to leach below the root zone for different soil types, hydrologic conditions, pesticides used, and tillage practices. The results indicate that imposing a surface water quality erosion constraint aimed at reducing sediment concentrations results in a larger decrease in farm income than imposing a uniform 5 ton per acre per year erosion constraint. Both constraints could result in regional improvement in ground water quality in some regions of the country while decreasing ground water quality in other regions.     

Quantifying Tradeoffs Associated with Hydrologic Environmental Flow Methods

Freshwater management requires balancing and tradingoff multiple objectives, many of which may be competing. Ecological needs for freshwater are often described in terms of environmental flow recommendations (e.g., minimum flows), and there are many techniques for developing these recommendations, which range from hydrologic rules to multidisciplinary analyses supported by large teams of subject matter experts. Although hydrologic rules are well acknowledged as overly simplified, these techniques remain the state‐of‐the‐practice in many locations. This article seeks to add complexity to the application of these techniques by studying the emergent properties of hydrologic environmental flow methodologies. Two hydrologic rules are applied: minimum flow criteria and sustainability boundaries. Objectives and metrics associated with withdrawal rate and similarity to natural flow regimes are used to tradeoff economic and environmental needs, respectively, over a range of flow thresholds and value judgments. A case study of hypothetical water withdrawals on the Middle Oconee River near Athens, Georgia is applied to demonstrate these techniques. For this case study, sustainability boundaries emerge as preferable relative to both environmental and economic outcomes. Methods applied here provide a mechanism for examining the role of stakeholder values and tradeoffs in application of hydrologic rules for environmental flows.     

黄河中游地区生态系统服务的时空演变及权衡与协同关系研究

明晰黄河中游地区生态系统服务的权衡协同关系,是保证生态系统服务长期有效供应,实现黄河流域生态保护与高质量发展的重要前提。本文利用InVEST模型、ArcGIS和Matlab等工具对2000—2020年黄河中游地区的土壤保持、水源涵养、固碳以及生境质量服务的时空特征及其协同权衡关系进行分析。结果表明：（1）黄河中游地区土壤保持、水源涵养和生境质量服务总体呈上升趋势,而固碳服务呈波动下降趋势;（2）2000—2020年,土壤保持、水源涵养服务总体表现为“南高北低”,其高、低值区有所变动;固碳服务整体呈“东南高、西北低”,高、低值区变化不明显;生境质量服务高、低值区相间分布,高值区稍有扩散;（3）黄河中游地区固碳与生境质量服务、生境质量与水源涵养服务、水源涵养与土壤保持服务为协同关系,固碳与土壤保持服务、生境质量与土壤保持服务为权衡关系,而固碳与水源涵养服务整体上表现为不相关;（4）生境质量与水源涵养、土壤保持服务的权衡区面积比例呈上升趋势,而水源涵养和土壤保持服务的协同区面积比例呈上升趋势,固碳与其他服务在大部分区域表现为不相关关系。     

山西省“三生”功能协同/权衡关系分析

为探究生产—生活—生态（“三生”）功能协调情况,基于综合评价模型和力学平衡模型,选用2005年、2010年和2018年土地利用类型和统计数据,测度山西省“三生”功能时空演变及协同/权衡关系特征。结果表明:（1）2005—2018年“三生”功能时空分异特征明显,生产功能为下降态势,呈现出“平原高,山区低”的分布格局;生活功能持续上升,空间分布与生产功能相似;生态功能呈上升状态,但需注意恶化倾向,空间格局稳定。（2）研究期间,“三生”功能协同性显著提升且趋势合理,空间分布与生产、生活功能趋同。（3）依据“三生”功能协调度偏离情况,划分功能主导区和提升区,明确各县域功能特征。研究结果可为国土空间规划提供依据。     

Promoting Large,Compact Mature Forest Patches in Harvest Scheduling Models

Spatially explicit harvest scheduling models that can promote the development of dynamic mature forest patches have been proposed in the past. This paper introduces a formulation that extends these models by allowing the total perimeter of the patches to be constrained or minimized. Test run results suggest that the proposed model can produce solutions with fewer, larger, and more compact patches. In addition, patches are more likely to be temporally connected with this formulation. Methods for identifying the tradeoffs between the net present value of the forest and the size and perimeter of the evolving patches are demonstrated for a hypothetical forest.