Zachary Christman

Modelling dry season deciduousness in Mexican Yucatán forest using MODIS EVI data (2000–2011)

This study maps interannual variation in the spatial extent of deciduousness in the dry tropical forests of the southern Yucatán (Mexico) from 2000 to 2011 using seasonal variability thresholds based on Moderate Resolution Imaging Spectroradiometer (MODIS) Enhanced Vegetation Index (EVI) data and relates deciduousness to precipitation- and temperature-derived climate variables using linear regressions. The annual occurrence of deciduousness is most frequently observed in forests located in a regional rain shadow at moderate elevations. Regression results suggest that deciduousness is more strongly associated with atypically hot conditions (–2°C; R 2 = 0.44) than with atypically dry conditions (R 2 = 0.19), in contrast to other phenological processes (e.g. leaf growth, peak productivity) driven primarily by precipitation.

Vulnerable, but why? Post-traumatic stress symptoms in older adults exposed to Hurricane Sandy

OBJECTIVE Drawing on pre-disaster, peri-disaster, and post-disaster data, this study examined factors associated with the development of post-traumatic stress disorder (PTSD) symptoms in older adults exposed to Hurricane Sandy. METHODS We used a sample of older participants matched by gender, exposure, and geographic region (N=88, mean age=59.83 years) in which one group reported clinically significant levels of PTSD symptoms and the other did not. We conducted t-tests, chi-square tests, and exact logistic regressions to examine differences in pre-disaster characteristics and peri-disaster experiences. RESULTS Older adults who experienced PTSD symptoms reported lower levels of income, positive affect, subjective health, and social support and were less likely to be working 4 to 6 years before Hurricane Sandy than were people not experiencing PTSD symptoms. Those developing PTSD symptoms reported more depressive symptoms, negative affect, functional disability, chronic health conditions, and pain before Sandy and greater distress and feelings of danger during Hurricane Sandy. Exact logistic regression revealed independent effects of preexisting chronic health conditions and feelings of distress during Hurricane Sandy in predicting PTSD group status. CONCLUSIONS Our findings indicated that because vulnerable adults can be identified before disaster strikes, the opportunity to mitigate disaster-related PTSD exists through identification and resource programs that target population subgroups. (Disaster Med Public Health Preparedness. 2016;10:362-370).

Deforestation and fragmentation of seasonal tropical forests in the southern Yucatán, Mexico (1990–2006)

The southern Yucatán (SY) has been recognized as a hotspot of biodiversity with great risk of deforestation. Land change analysis, based on classified Landsat TM and ETM + satellite imagery (1990, 2000 and 2006), was used to estimate the annual deforestation rates of 141 land management units of the SY, and spatial patterns of forest fragmentation around and within the Calakmul Biosphere Reserve (CBR), which comprises approximately one-third of the region. Results indicate a decrease in annual deforestation rates over 1990–2006, from 0.15% year−1 to 0.06% year−1, but with significant sub-regional variations in the quantity and rate of forest loss. Despite a decline in deforestation during this period, there was considerable fragmentation both inside and outside the CBR. While population pressures and the expansion of pasture have caused deforestation across the region, agricultural intensification, diversified income strategies and reserve conservation may have contributed to reduced forest loss during the study period.

Diversification and Adaptive Capacity across Scales in an Emerging Post-Frontier Landscape of the Usumacinta Valley, Chiapas, Mexico

SUMMARY This study investigates impacts and implications of recent landscape change in rural Mexico, through a case study in the Usumacinta Valley of eastern Chiapas. It addresses types of livelihood diversification strategies associated with changing land cover from 1984–2013, and the processes and roles that vary by actors and their scales of influence. After widespread forest loss and the expansion of extensive cattle ranching during the twentieth century, the region has exhibited several new economic and livelihood strategies in recent decades. Results from a combination of satellite imagery analysis and individual interviews from a wide range of land use decision makers demonstrate the dynamism of this landscape. The introduction of new crops, including teak, rubber and oil palm, as well as off-farm work, continue to shape the social and physical landscape and differentially impact the adaptive capacities of residents. Results indicate that small landholders often need to incorporate more crops into their agricultural portfolio and increase off-farm activities, leading to an atomization of livelihood strategies. By contrast, large landholders are able to pursue more specialized and lucrative agricultural opportunities.

Smallholders' adaptations to droughts and climatic variability in southeastern Mexico

This study explores the temporal and spatial variability and change in rainfall across southeastern Mexico and the mechanisms by which smallholder farmers adapt to this variability, especially droughts. Members of 150 households in 10 communities were interviewed to investigate adaptation strategies among swidden maize smallholders, linked to their perceptions of climate changes. Precipitation data from seven weather stations were analyzed for the 1973–2012 period. Precipitation anomalies were estimated to evaluate the annual and seasonal stability, deficit, or surplus; and linear regressions were used to evaluate trends. Then, these anomalies were linked to variation in reported agricultural practices. Weather station data show a considerable decline in precipitation in most of the study area, coupled with increased drought frequency and an increase in negative anomalies in recent years. Surveys revealed several mechanisms of adaptation, including adjustment of the agricultural calendar (e.g. delaying planting, combined with planting a greater number of varieties of maize), water storage, and livelihood diversification both within and outside of agriculture. These adaptive mechanisms are responsive to demonstrated climatic change over the past 40 years, though globalization affects Mexicos agrarian economy, and farmers likely respond to a combination of economic and climatic factors. Understanding how resource- and climate-dependent swidden farmers respond to co-occurring climatic and economic changes is essential for effective adaptation policy design.

A Spatial Analysis of Body Mass Index and Neighborhood Factors in Community-Dwelling Older Men and Women.

The spatial distribution of obesity among the older population can yield insights into the influence of contextual factors associated with this public health problem. We tested the relationship between neighborhood-level characteristics and body mass index (BMI) using global and local spatial statistics of geographic clustering, using data derived from a random-digit-dial sample of 5,319 community-dwelling adults aged 50 to 74 residing in 1,313 census tracts in New Jersey. Geographically weighted regression modeled associations between BMI clusters and neighborhood characteristics, including metrics of structure, safety, demographics, and amenities. Across the sample panel, average BMI was 28.62 kg/m2 for women and 28.25 kg/m2 for men. There was significant spatial clustering of obesity by census tract, varying by gender across the state. Neighborhood characteristics were more strongly related to BMI for women than men. This research illuminates the role of neighborhood contextual factors and will assist community planners, officials, and public health practitioners as they address the rise in obesity.

Precipitation Variability and Adaptation Strategies in the Southern Yucatan Peninsula, Mexico: Integrating Local Knowledge with Quantitative Analysis

Climatic variability, including droughts, has long affected the Mayan Lowlands. Therefore, farmers have developed coping strategies to mitigate these impacts. In the past, however, records of these effects and responses were largely anecdotal. In modern times, the perceptions of farmers, especially those practicing rain-fed agriculture, combined with the increased availability of accurate historical climatic records and forecasts, can provide useful information regarding periods of decreased precipitation and strategies employed to resist and respond to drought effects. As part of the multidisciplinary and inter-institutional project, New Knowledge about Ecosystem Level Response to Increased Frequency of Large-Scale Natural Disturbance Driven by Climate Change, this chapter outlines the spatial and temporal variability of precipitation across the Southern Yucatan Peninsula, Mexico, and examines Mayan farmers’ adaptations to droughts and other climate perturbations. The authors analyzed precipitation trends and anomalies from 1953 to 2007, using linear regressions and the quintile method to classify meteorological droughts. Authors also conducted 150 household interviews across 10 communities to investigate Mayan farmers’ adaptations to climate perturbations. Results demonstrate a significant decrease in annual and rainy season precipitation across much of the study area, coupled with an increased occurrence of droughts, especially since 1980. Interviewed subsistence maize farmers have adapted to decreasing and irregular precipitation by adjusting agricultural calendars, planting more maize varieties, increasing water storage, and diversifying their practices both within the agricultural system and beyond it. Through this research, the authors demonstrate the importance of incorporating farmers’ local and traditional knowledge into prevention and mitigation policies of governmental and non-governmental institutions in the region.

Distinguishing land change from natural variability and uncertainty in central Mexico with MODIS EVI, TRMM precipitation, and MODIS LST data

Precipitation and temperature enact variable influences on vegetation, impacting the type and condition of land cover, as well as the assessment of change over broad landscapes. Separating the influence of vegetative variability independent and discrete land cover change remains a major challenge to landscape change assessments. The heterogeneous Lerma-Chapala-Santiago watershed of central Mexico exemplifies both natural and anthropogenic forces enacting variability and change on the landscape. This study employed a time series of Enhanced Vegetation Index (EVI) composites from the Moderate Resolution Imaging Spectoradiometer (MODIS) for 2001–2007 and per-pixel multiple linear regressions in order to model changes in EVI as a function of precipitation, temperature, and elevation. Over the seven-year period, 59.1% of the variability in EVI was explained by variability in the independent variables, with highest model performance among changing and heterogeneous land cover types, while intact forest cover demonstrated the greatest resistance to changes in temperature and precipitation. Model results were compared to an independent change uncertainty assessment, and selected regional samples of change confusion and natural variability give insight to common problems afflicting land change analyses.

Comparison between buprenorphine provider availability and opioid deaths among US counties

BACKGROUND Buprenorphine is an effective medication for the treatment of opioid addiction, but current barriers to buprenorphine access limit treatment availability for many patients. We identify and characterize regions within the United States (US) with poor buprenorphine access relative to the observed burden of overdose deaths. METHODS This cross sectional study includes US county-level data on the number of available buprenorphine providers (Substance Abuse and Mental Health Services Administration Buprenorphine Treatment Practitioner Locator) and the number of opioid-related overdose deaths between 2013 and 2015 (Centers for Disease Control and Prevention WONDER Database). Counties with fewer than 10 deaths during this time period were excluded to maintain patient privacy. Population-adjusted county death rates and provider availability were compared to identify locations with high disease burdens and limited buprenorphine access. The presence of significant clustering across the dataset was evaluated using Global Morans I and zones of significant spatial clusters and anomalies were identified using Local Indicator of Spatial Autocorrelation. RESULTS County data were available for 846 counties from 49 states and the District of Columbia, comprising 83% of the US population. The median number of opioid overdose deaths per county was 20.0 deaths per 100,000 residents (interquartile range 13.4-29.9, range 2.9 to 108.8). The number of buprenorphine providers per 100,000 county residents ranged from 0 to 45, with a median of 5.9 (interquartile range 3.2 to 9.5). Global Morans I analysis yielded significant clustering in the distribution of both providers and deaths, with notable significant clusters of higher than average providers and deaths in the Northeast, and scattered mismatched regions of lower-than-average providers and higher-than-average deaths across the Southern, Midwestern, and Western US. Graphical analysis of buprenorphine provider availability and overdose burden reveals limited treatment access relative to overdose deaths throughout much of the Midwestern and Southern US. CONCLUSIONS Substantial county-level imbalances between the availability of buprenorphine providers and the burden of opioid overdose deaths are present within the US.