Browsing by Author "Evans, Tom"

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Cognitive Biases about Climate Variability in Smallholder Farming Systems in Zambia
(Weather, Climate, and Society, 2019-04) Attari, Shahzeen; Caylor, Kelly; Estes, Lyndon; Evans, Tom; Sheffield, Justin; Vergopolan, Noemi; Waldman, Kurt
Given the varying manifestations of climate change over time and the influence of climate perceptions on adaptation, it is important to understand whether farmer perceptions match patterns of environmental change from observational data. We use a combination of social and environmental data to understand farmer perceptions related to rainy season onset. Household surveys were conducted with 1171 farmers across Zambia at the end of the 2015/16 growing season eliciting their perceptions of historic changes in rainy season onset and their heuristics about when rain onset occurs. We compare farmers’ perceptions with satellite-gauge-derived rainfall data from the Climate Hazards Group Infrared Precipitation with Station dataset and hyper-resolution soil moisture estimates from the HydroBlocks land surface model. We find evidence of a cognitive bias, where farmers perceive the rains to be arriving later, although the physical data do not wholly support this. We also find that farmers’ heuristics about rainy season onset influence maize planting dates, a key determinant of maize yield and food security in sub-Saharan Africa. Our findings suggest that policy makers should focus more on current climate variability than future climate change.
Dependency Provenance in Agent Based Modeling
(2013-08) Chen, Peng; Plale, Beth; Evans, Tom
Researchers who use agent-based models (ABM) to model social patterns often focus on the model's aggregate phenomena. However, aggregation of individuals complicates the understanding of agent interactions and the uniqueness of individuals. We develop a method for tracing and capturing the provenance of individuals and their interactions in the NetLogo ABM, and from this create a "dependency provenance slice", which combines a data slice and a program slice to yield insights into the cause-effect relations among system behaviors. To cope with the large volume of fine-grained provenance traces, we propose use-inspired filters to reduce the amount of provenance, and a provenance slicing technique called "non-preprocessing provenance slicing" that directly queries over provenance traces without recovering all provenance entities and dependencies beforehand. We evaluate performance and utility using a well known ecological NetLogo model called "wolf-sheep-predation".
Formal/Informal Employment and Urban Food Security in Sub-Saharan Africa
(Applied Geography, 2020-01) Blekking, Jordan; Waldman, Kurt; Tuholske, Cascade; Evans, Tom
Sub-Saharan Africa (SSA) is expected to add nearly 800 million urban residents by 2050. Due to this rapid urban population increase there is an urgent need to understand the drivers of urban food security across the region. Understanding food security in an urban environment is difficult due to the complexity of the relationships between urban consumers and food suppliers. Unlike rural communities, urban residents produce little of their own food, and are largely reliant on food suppliers to meet their dietary needs. Identifying urban food insecure households is further complicated by the lack of food security metrics specifically designed for the urban context. We use household-level data from 718 low-income households in Lusaka, Zambia, to assess urban food security through two measures, the Food Consumption Score (FCS) and the Coping Strategies Index (CSI). Our assessment investigates the association between food security and different employment types across the city, with particular attention paid to spatial variance of outcomes and statistical differences between households with majority formal or informal employment. Our study reveals three substantial findings. First, we find statistically significant differences in FCS and CSI of households predominantly engaged with formal employment over households engaged in informal employment. Secondly, we find significant associations between purchasing food from informal and formal food suppliers and the use of coping strategies and consumption of higher calorie foods. Lastly, we identify substantial challenges in using FCS and CSI to evaluate urban food security. Both metrics are predicated on underlying assumptions that may not accurately represent household food consumption and coping strategies in urban areas of SSA.
A Hybrid Approach to Population Construction For Agricultural Agent-Based Simulation
(2016) Chen, Peng; Evans, Tom; Frisby, Michael; Izquierdo, Eduardo; Plale, Beth
An Agent Based Model (ABM) is a powerful tool for its ability to represent heterogeneous agents which through their interactions can reveal emergent phenomena. For this to occur though, the set of agents in an ABM has to accurately model a real world population to reflect its heterogeneity. But when studying human behavior in less well developed settings, the availability of the real population data can be limited, making it impossible to create agents directly from the real population. In this paper, we propose a hybrid method to deal with this data scarcity: we first use the available real population data as the baseline to preserve the true heterogeneity, and fill in the missing characteristics based on survey and remote sensing datasets; then for the remaining undetermined agent characteristics, we use the Microbial Genetic Algorithm to search for a set of values that can optimize the replicative validity of the model to match data observed from real world. We apply our method to the creation of a synthetic population of household agents for the simulation of agricultural decision making processes in rural Zambia. The result shows that the synthetic population created from the farmer register can correctly reflect the marginal distributions and the randomness of survey data; and can minimize the difference between the distribution of simulated yield and that of the observed yield in Post Harvest Survey (PHS).
Hybrid-maize seed certification and smallholder adoption in Zambia
(Journal of Environmental Planning and Management, 2020-07) Blekking, Jordan; Waldman, Kurt; Evans, Tom
During the 1990s many Southern African governments liberalized their seed markets. This move initiated an influx of hybrid-maize seeds onto markets through greater involvement of private seed developers. Since then the number of varieties of hybrid seeds has grown considerably. Using an institutional analysis framework, we illustrate the complex system of actors and feedbacks that govern the seed certification process in Zambia. We also examine how small holder hybrid-seed use has changed over the last decade. We find the Zambian seed certification system allows for frequent certification of new varieties each year without much scrutiny of seed use and performance by smallholders. Smallholders face a complex challenge in selecting seeds due to inconsistencies between the potential yields cited during the seed certification process and the reported yields of smallholders. This inconsistency jeopardizes the goal of food security sought after by both smallholders and policymakers.
Introduction to GIS and Spatial Data Analysis
(Indiana University Workshop in Methods, 2014-04-04) Evans, Tom
This course teaches what a GIS is and what you can do with it. Participants will be introduced to spatial data structures and issues of spatial data representation. Brief exercises will be used to emphasize particular dimensions of spatial data analysis. Applications will address census data analysis (and import), fundamentals of map design, and data integration. The workshop will use ArcGIS, although the principles discussed will be broadly applicable to any GIS toolkit. The workshop will conclude with a presentation of next steps to gain additional training in GIS and spatial data analysis.