Peter Janssen

Long-term dynamic modeling of global population and built-up area in a spatially explicit way: HYDE 3.1

This paper describes a tool for long-term global change studies; it is an update of the History Database of the Global Environment (HYDE) with estimates of some of the underlying demographic driving factors of global change. We estimate total and urban/rural population numbers, densities and fractions (including built-up area) for the Holocene, roughly the period 10 000 BC to AD 2000 with a spatial resolution of 5 min longitude/latitude. With a total global population increase from 2 to 6145 million people over that time span, resulting in a global population density increase of < 0.1 cap/km2 to almost 46 cap/km 2 and a urban built-up area evolving from almost zero to 0.5 million km2 (still only <0.5% of the total global land surface, but with a huge impact in terms of demands of food, services, building materials, etc.), it is clear that this must have had, and will continue to have, a profound influence on the Earth’s environment and its associated (climate) change. We hope that this data base can contribute to the Earth System Modelers community to gain better insight into long-term global change research.

A new method for analysing socio-ecological patterns of vulnerability

This paper presents a method for the analysis of socio-ecological patterns of vulnerability of people being at risk of losing their livelihoods as a consequence of global environmental change. This method fills a gap in methodologies for vulnerability analysis by providing generalizations of the factors that shape vulnerability in specific socio-ecological systems and showing their spatial occurrence. The proposed method consists of four steps that include both quantitative and qualitative analyses. To start, the socio-ecological system exposed to global environmental changes that will be studied needs to be determined. This could, for example, be farmers in drylands, urban populations in coastal areas and forest-dependent people in the tropics. Next, the core dimensions that shape vulnerability in the socio-ecological system of interest need to be defined. Subsequently, a set of spatially explicit indicators that reflect these core dimensions is selected. Cluster analysis is used for grouping the indicator data. The clusters found, referred to as vulnerability profiles, describe different typical groupings of conditions and processes that create vulnerability in the socio-ecological system under study, and their spatial distribution is provided. Interpretation and verification of these profiles is the last step in the analysis. We illustrate the application of this method by analysing the patterns of vulnerability of (smallholder) farmers in drylands. We identify eight distinct vulnerability profiles in drylands that together provide a global overview of different processes taking place and sub-national detail of their distribution. By overlaying the spatial distribution of these profiles with specific outcome indicators such as conflict occurrence or migration, the method can also be used to understand these phenomena better. Analysis of vulnerability profiles will in a next step be used as a basis for identifying responses to reduce vulnerability, for example, to facilitate the transfer of best practices to reduce vulnerability between different places.

Issues of replicability in Monte Carlo modeling: a case study with a pesticide leaching model.

Sensitivity and uncertainty analyses based on Monte Carlo sampling were undertaken for various numbers of runs of the pesticide leaching model (PELMO). Analyses were repeated 10 times with different seed numbers. The ranking of PELMO input parameters according to their influence on predictions for leaching was stable for the most influential parameters. For less influential parameters, the sensitivity ranking was severely influenced by the seed number used. For uncertainty analyses, probabilities of exceeding a particular concentration were significantly influenced by the seed number used in the random sampling of values for the two parameters considered, even for those cases in which 5,000 model runs were undertaken (coefficient of variation of 10 replicated analyses, 5%). A decrease in the variability of exceedance probabilities could be achieved by further increasing the number of model runs. However, this may prove to be impractical when complex deterministic models with a relatively long running time are used. Attention should be paid to replicability aspects by modelers when devising their approach to assessing the uncertainty associated with the modeling and by decision makers when examining the results of probabilistic approaches.

Formalizing knowledge on international environmental regimes: A first step towards integrating political science in integrated assessments of global environmental change

International environmental regimes are considered key factors in dealing with global environmental change problems. It is important to understand if and how regimes are effective in tackling these problems, which requires knowledge on their potential impact on these problems as well as on their political feasibility. Integrated assessments of global environmental change, which are mainly bio-physical and technology-economic oriented, barely address knowledge on environmental regimes, due to problems in drawing general and policy relevant lessons on regime effectiveness and inherent difficulties in modelling human and social dimensions. This paper presents an innovative approach to formalize knowledge on the effectiveness of environmental regimes, so that scientists from both the political science and integrated assessment domain can understand it, discuss it and contribute to it. We constructed a conceptual framework for the systematic analysis of conditions that influence regime effectiveness and implemented it in a computer model using fuzzy logic methodology. We evaluated the fuzzy model in an ex post case study on four existing international environmental regimes. The model can be used as an aid in analysing the effectiveness of existing or future regimes, highlighting which determinants contribute to success or failure, and it enables systematic and meaningful comparisons between regimes and policy measures. We discovered that formalizing knowledge on environmental regimes in a framework and model enhanced its transparency and deductive power as it forced us to be explicit about our choices and assumptions. Developing and using the framework and model also revealed the lacunae in knowledge in environmental regime theory which may inform regime researchers to further structure and increase their knowledge. By making knowledge on environmental regimes explicit and understandable we have taken an important step towards a better integration of political science in integrated assessments. We believe, however, that this integration is still in its early days and requires further attention in the future.

Armed conflict distribution in global drylands through the lens of a typology of socio-ecological vulnerability

Motivated by an inconclusive debate over implications of resource scarcity for violent conflict, and common reliance on national data and linear models, we investigate the relationship between socio-ecological vulnerability and armed conflict in global drylands on a subnational level. Our study emanates from a global typology of smallholder farmers’ vulnerability to environmental and socioeconomic stresses in drylands. This typology is composed of eight typical value combinations of variables indicating environmental scarcities, resource overuse, and poverty-related factors in a widely subnational spatial resolution. We investigate the relationships between the spatial distribution of these combinations, or vulnerability profiles, and geocoded armed conflicts, and find that conflicts are heterogeneously distributed according to these profiles. Four profiles distributed across low- and middle-income countries comprise all drylands conflicts. Comparing models for conflict incidence using logit regression and receiver operator characteristic analysis based on (1) the set of all seven indicators as independent variables and (2) a single, only vulnerability profile-based variable proves that the nonlinear typology-based variable is the better explanans for conflict incidence. Inspection of the profiles’ value combinations makes this understandable: A systematic explanation of conflict incidence and absence across all degrees of natural resource endowments is only reached through varying importance of poverty and resource overuse depending on the level of endowment. These are nonlinear interactions between the explaining variables. Conflict does not generally increase with resource scarcity or overuse. Comparison with conflict case studies showed both good agreement with our results and promise in expanding the set of indicators. Based on our findings and supporting literature, we argue that part of the debate over implications of resource scarcity for violent conflict in drylands may be resolved by acknowledging and accounting for nonlinear processes.

A checklist for model credibility, salience, and legitimacy to improve information transfer in environmental policy assessments

Modelers involved in environmental policy assessments are commonly confronted with the lack of uptake of model output by policy actors. Actors have different expectations of models, condensed into three quality criteria: credibility, salience, and legitimacy. The fulfilment of quality criteria is also dynamic as expectations vary, change, and possibly counteract each other. We present a checklist for modelers involved in model-based assessments that is aimed at the identification and monitoring of issues, limitations and trade-offs regarding model quality criteria. It draws upon the literature of integrated assessments as well as case study analysis of environmental policy assessments for the Dutch government, based on expert interviews and embedded experience. The checklist is intended to be consulted during assessments; its application may result in greater awareness among modelers involved in assessments regarding model quality criteria, and may positively affect the uptake of model-based knowledge from environmental policy assessments by policy actors. Model credibility, salience and legitimacy are affected by various factors.Factors are summarized based on interviews, literature and a case study.A model evaluation checklist for modelers is presented to help detect such factors.The checklist may improve the uptake of model-based output by decision makers.

Innovating the IPCC review process—the potential of young talent

There is significant potential in young talent for enhancing the credibility of the scientific assessments such as the IPCC’s by contributing to quality assurance and quality control. In this essay, we reflect on an experiment that was done by the Dutch government as part of its government review of a contribution to the IPCC’s Fifth Assessment Report (AR5). In an effort to review the entire Working Group II contribution to the AR5 within the official review period for the Second Order Draft (SOD), the PBL Netherlands Environmental Assessment Agency turned to PhD students. This article shows that a systematic review focusing on transparency and errors of a large scientific assessment document using young talented scientists can be successful if certain conditions are met. The reviewers need to have intrinsic motivation to conduct the review. There needs to be a communication plan that fosters engagement and a clear methodology to guide the reviewers through their task. Based on this experiment in review, we reflect on the wider potential for openness and crowdsourcing in scientific assessment processes such as the IPCC’s.

Établir la qualité des preuves pour les situations de décision complexes et controversées

Les decisions politiques sur les risques environnementaux complexes font frequemment intervenir des elements scientifiques contestes. Il n’y a generalement pas de « faits » qui conduisent a une politique correcte unique. Les elements de preuve qui sont integres dans les avis scientifiques destines a une decision politique necessitent une evaluation de leur qualite. En 2003, l’Agence neerlandaise d’evaluation environnementale a adopte une methode standardisee, designee sous le nom de « guide », dans le cadre de laquelle les principaux aspects de la production et de l’utilisation des connaissances sont presentes grâce a une liste de controle visant a l’evaluation et a la communication des incertitudes. Dans cet article, nous presentons des resultats de l’application de ce guide a la controverse sur les risques des particules en suspension. La deliberation active sur l’incertitude dans un contexte d’expertise entraine un processus d’apprentissage commun entre les experts et les decideurs politiques, ce qui conduit a une meilleure prise de conscience du phenomene d’incertitude et de ses implications politiques.