LIPPI, RYANNonlinear and delayed impacts of climate on dengue risk in Barbados: A modelling study

Rachel Lowe, Antonio Gasparrini, Cédric J. Van Meerbeeck, Catherine A. Lippi, Roché Mahon, Adrian R. Trotman, Leslie Rollock, Avery Q. J. Hinds, Sadie J. Ryan, Anna M. Stewart-Ibarra

Article first published online: 17 JUL 2018 PLOS Medicine

DOI: 10.1371/journal.pmed.1002613


Over the last 5 years (2013–2017), the Caribbean region has faced an unprecedented crisis of co-occurring epidemics of febrile illness due to arboviruses transmitted by the Aedes sp. mosquito (dengue, chikungunya, and Zika). Since 2013, the Caribbean island of Barbados has experienced 3 dengue outbreaks, 1 chikungunya outbreak, and 1 Zika fever outbreak. Prior studies have demonstrated that climate variability influences arbovirus transmission and vector population dynamics in the region, indicating the potential to develop public health interventions using climate information. The aim of this study is to quantify the nonlinear and delayed effects of climate indicators, such as drought and extreme rainfall, on dengue risk in Barbados from 1999 to 2016.

Methods and findings
Distributed lag nonlinear models (DLNMs) coupled with a hierarchal mixed-model framework were used to understand the exposure–lag–response association between dengue relative risk and key climate indicators, including the standardised precipitation index (SPI) and minimum temperature (Tmin). The model parameters were estimated in a Bayesian framework to produce probabilistic predictions of exceeding an island-specific outbreak threshold. The ability of the model to successfully detect outbreaks was assessed and compared to a baseline model, representative of standard dengue surveillance practice. Drought conditions were found to positively influence dengue relative risk at long lead times of up to 5 months, while excess rainfall increased the risk at shorter lead times between 1 and 2 months. The SPI averaged over a 6-month period (SPI-6), designed to monitor drought and extreme rainfall, better explained variations in dengue risk than monthly precipitation data measured in millimetres. Tmin was found to be a better predictor than mean and maximum temperature. Furthermore, including bidimensional exposure–lag–response functions of these indicators—rather than linear effects for individual lags—more appropriately described the climate–disease associations than traditional modelling approaches. In prediction mode, the model was successfully able to distinguish outbreaks from nonoutbreaks for most years, with an overall proportion of correct predictions (hits and correct rejections) of 86% (81%:91%) compared with 64% (58%:71%) for the baseline model. The ability of the model to predict dengue outbreaks in recent years was complicated by the lack of data on the emergence of new arboviruses, including chikungunya and Zika.

We present a modelling approach to infer the risk of dengue outbreaks given the cumulative effect of climate variations in the months leading up to an outbreak. By combining the dengue prediction model with climate indicators, which are routinely monitored and forecasted by the Regional Climate Centre (RCC) at the Caribbean Institute for Meteorology and Hydrology (CIMH), probabilistic dengue outlooks could be included in the Caribbean Health-Climatic Bulletin, issued on a quarterly basis to provide climate-smart decision-making guidance for Caribbean health practitioners. This flexible modelling approach could be extended to model the risk of dengue and other arboviruses in the Caribbean region.

Read the full publication at PLOS Medicine






BUNTING, SOUTHWORTH, HERRERO, RYAN, WAYLENUnderstanding Long-Term Savanna Vegetation Persistence across Three Drainage Basins in Southern Africa

Erin L. Bunting , Jane Southworth, Hannah Herrero, Sadie J. Ryan, and Peter Waylen

Article first published online: 25 JUN 2018 Remote Sens. 2018, 10(7), 1013

DOI: 10.3390/rs10071013

ABSTRACT: Across savanna landscapes of southern Africa, people are strongly tied to the environment, meaning alterations to the landscape would impact livelihoods and socioecological development. Given the human–environment connection, it is essential to further our understanding of the drivers of savanna vegetation dynamics, and under increasing climate variability, to better understand the vegetation–climate relationship. Monthly time series of Advanced Very High-Resolution Radiometer (AVHRR)- and Moderate Resolution Imaging Spectroradiometer (MODIS) derived vegetation indices, available from as early as the 1980s, holds promise for the large-scale quantification of complex vegetation–climate dynamics and regional analyses of landscape change as related to global environmental changes. In this work, we employ time series based analyses to examine landscape-level vegetation greening patterns over time and across a significant precipitation gradient. In this study, we show that climate induced reductions in Normalized Difference Vegetation Index (NDVI; i.e., degradation or biomass decline) have had large spatial and temporal impacts across the Kwando, Okavango, and Zambezi catchments of southern Africa. We conclude that over time there have been alterations in the available soil moisture resulting from increases in temperature in every season. Such changes in the ecosystem dynamics of all three basins has led to system-wide changes in landscape greening patterns.

Read the full publication at Remote Sensing





MATYASTANGZICKUsing an Object-Based Approach to Quantify the Spatial Structure of Reflectivity Regions in Hurricane Isabel (2003). Part I: Comparisons between Radar Observations and Model Simulations

Corene J. Matyas, Stephanie E. Zick, Jingyin Tang

Article first published online: 25 APR 2018 Monthly Weather Review

DOI: 10.1175/MWR-D-17-0077.1

ABSTRACT: When a hurricane undergoes extratropical transition (ET), its rainbands evolve from a circular and compact shape to a more elongated, fragmented, and dispersed configuration with an exposed circulation center. This study calculates five metrics to measure these spatial changes in reflectivity regions as Hurricane Isabel (2003) underwent ET. A mosaic of observations from the Weather Surveillance Radar-1988 Doppler (WSR-88D) network is compared to reflectivity simulated by the Advanced Research Weather Research and Forecasting (WRF-ARW) Model. Six simulations are performed by varying the cumulus and microphysics parameterizations to produce a range of reflectivity configurations. A bias correction is applied to model-simulated reflectivity prior to the calculation of spatial metrics because lower reflectivity values are generally underrepresented, while higher values are generally overrepresented. However, the simulation with Kain–Fritsch cumulus and Morrison two-moment microphysics overpredicts reflectivity by 3–4 dBZ at all levels. We demonstrate that the spatial metrics effectively capture structural changes as reflectivity regions became more fragmented and dispersed and the center became more exposed. In this case study, the results were more sensitive to the choice of cumulus physics, compared with the choice of microphysics. The Kain–Fritsch simulations produce shapes that are too circular and solid when compared with WSR-88D observations, as the hurricanes lack distinct outer rainbands. Simulations with Tiedtke cumulus produce an elongated main reflectivity region as in WSR-88D, but with separate inner and outer rainbands that are too dispersed and fragmented. These results demonstrate the value in measuring spatial patterns rather than assessing model performance using visual inspection alone.

Read the full publication at Monthly Weather Review






Floating Fish Camp, Apalachicola River, Florida. Image courtesy The Florida Geographer.

CHEN, MOSSAFloating fish camps on the Apalachicola River, Florida: Increases and Implications

Joann Mossa, Yin-Hsuen Chen

Article first published online: 09 FEB 2018 The Florida Geographer


Peoples from various cultures and locations have been living on the edge or margin of water-land interfaces in floating houses of various types, either permanently or part-time. In some cases, people build these to access natural resources from both water and land environments. Through fieldwork on the Apalachicola River and branches, including the lower Chipola and Brothers Rivers in the Florida panhandle, a large variety of floating camps were observed. The purposes of this paper are to: 1) review historical information on the occurrence of floating dwellings and camps worldwide to give context to the study area; 2) map patterns and change since 1994 in different parts of the basin, including whether adjoining public or private lands to interpret potential areas of concern; and 3) examine the vernacular architecture of floating structures. Much of our discussion concerns current policy regarding floating structures in light of the need to maintain the ecological integrity of the river.

The earliest known references to floating homes or camps in the study area date back to the Great Depression of the 1930s, when society was in need of low-cost housing. Rather than being clustered in communities, the fish camps of the Apalachicola River and branches are spaced across this system. The number of floating camps along the Apalachicola River and some of its major branches, as measured using Google Earth and historical aerial photography, has increased from 63 in 1994 to 132 in 2004 to 177 in 2015. Since dredging associated with the Navigation Project stopped in 2002, 78% of the growth or 34 of 45 new floating structures has been on the main-stem Apalachicola River, compared to 54% or 37 of 69 from 1994 to 2004. Nearly half of the fish camps are located next to public lands, which in some cases are impacted by people residing within the camps. The rustic structures typically are built of reused building materials; amenities can include air conditioning and satellite dish television, and decorations include flags or name plaques. Studies of floating dwellings elsewhere, and communication with local officials, provides some guidance on the benefits and concerns for these increasingly numerous dwellings in terms of public safety, crime, and environment in relation to existing and potential policy.

Read the full publication at The Florida Geographer





DOWHANIUK, GOLDMANRYAN – Park isolation in anthropogenic landscapes: land change and livelihoods at park boundaries in the African Albertine Rift

Jonathan Salerno, Colin A. Chapman, Jeremy E. Diem, Nicholas Dowhaniuk, Abraham Goldman, Catrina A. MacKenzie, Patrick Aria Omeja, Michael W. Palace, Rafael Reyna-Hurtado, Sadie J. Ryan, Joel Hartter

Article first published online: 14 NOV 2017 Regional Environmental Change

DOI: 10.1007/s10113-017-1250-1

ABSTRACT: Landscapes are changing rapidly in regions where rural people live adjacent to protected parks and reserves. This is the case in highland East Africa, where many parks are increasingly isolated in a matrix of small farms and settlements. In this review, we synthesize published findings and extant data sources to assess the processes and outcomes of park isolation, with a regional focus on people’s livelihoods at park boundaries in the Ugandan Albertine Rift. The region maintains exceptionally high rural population density and growth and is classified as a global biodiversity hotspot. In addition to the impacts of increasing numbers of people, our synthesis highlights compounding factors—changing climate, increasing land value and variable tenure, and declining farm yields—that accelerate effects of population growth on park isolation and widespread landscape change. Unpacking these processes at the regional scale identifies outcomes of isolation in the unprotected landscape—high frequency of human-wildlife conflict, potential for zoonotic disease transmission, land and resource competition, and declining wildlife populations in forest fragments. We recommend a strategy for the management of isolated parks that includes augmenting outreach by park authorities and supporting community needs in the human landscape, for example through healthcare services, while also maintaining hard park boundaries through traditional protectionism. Even in cases where conservation refers to biodiversity in isolated parks, landscape strategies must include an understanding of the local livelihood context in order to ensure long-term sustainable biodiversity protection.

Read the full publication at Regional Environmental Change






MEHEDYMonitoring land use/land cover change, urban growth dynamics and landscape pattern analysis in five fastest urbanized cities in Bangladesh

Mohammad Mehedy Hassan

Article first published online: 08 JUL 2017 Remote Sensing Applications: Society and Environment

DOI: 10.1016/j.rsase.2017.07.001

ABSTRACT: With little known and explored urban morphology in the fastest growing countries like Bangladesh in South Asia, this study aims at exploring urban spatial signature and explaining spatiotemporal land use and land cover patterns in the five cities (Rajshahi, Rangpur, Sylhet, Khulna, and Barisal) in Bangladesh. Using time series Landsat imagery, socioeconomic data and, other geospatial information with ecological analysis tools, this study quantifies and characterize the spatial-temporal landscape patterns and urban growth trajectory across the five selected sites. The spatial representation of these five sites demonstrates a continuous increase in urban/built-up areas replacing arable agricultural land, waterbodies, vegetation cover and wetlands, which thereby substantially altering the structure and function of the ecosystem surrounding the cities. Built up areas, representing impervious surface as observed from land cover maps in these five cities, are expanding quickly. The total built-up cover within the five cities grew from 2356 ha in 1973 to 13,435 ha in 2014 with a net increase of approximately 468%, while vegetation cover and crops field within same time period declined at 27.77% and 61.91%, respectively. This dramatic urban/built-up expansion has resulted in an increasingly faster alteration in the landscape composition causing to structural complexity at both class level and landscape level. Such rapid and unplanned urban expansion further has brought an overwhelming challenge to planners and policy makers, and has put a strain on local authorities to properly manage and utilize its limited land-based resources due to lack of time series geospatial information. The resulting thematic map and spatial information from this study is, therefore, to facilitate an understanding of urban growth dynamics and land cover change pattern in the five cities in Bangladesh. The result further can aid planners, stakeholders, and other interested groups to make the best possible choices regarding limited land-based resources to achieve an economically prosperous and environmentally sustainable future.

Read the full publication at Remote Sensing Applications: Society and Environment






HERRERO, SOUTHWORTH, BUNTING, CHILD – Using Repeat Photography to Observe Vegetation Change Over Time in Gorongosa National Park


Article first published online: JUN 2017 African Studies Quarterly

ABSTRACT: Protected areas are important conservation tools, as they can be managed to preserve baseline ecosystem health, including that of vegetation dynamics. Understanding long-term ecosystem dynamics within a protected area enables one to understand how this static park landscape responds to outside pressure and changing drivers. In this study, a repeat photography analysis was used to analyze changes in the vegetation pattern and abundance at Gorongosa National Park in Mozambique across seventy-two years of the parks history. Archival photographs dating as far back as 1940 were selected for sites that could be relocated in a subsequent field visit in 2012. Qualitative and quantitative analysis on vegetation abundance by structural group was undertaken using Edwards’ Tabular Key. Results when comparing the photographic pairs show that, in general, tree cover has increased on average from 25 percent to 40 percent over the last seventy-two years. This 15 percent increase may be in response to environmental drivers such as human management, herbivory, fire, and precipitation. Contrary to many recent studies on shrub encroachment in southern Africa, this study finds an increase in tree cover. Such analysis and results are valuable in that they demonstrate long-term ecological change within a managed protected area.

Read the full publication at African Studies Quarterly


CHEN, MOSSA, WUAnthropogenic landforms and sediments from dredging and disposing sand along the Apalachicola River and its floodplain

Joann Mossa, Yin-Hsuen Chen, Scott P. Walls, G. Mathias Kondolf, Chia-Yu Wu

Article first published online: 12 MAR 2017 Geomorphology

DOI: 10.1016/j.geomorph.2017.03.010

ABSTRACT: The Apalachicola River, which begins at the confluence of the Chattahoochee and Flint rivers near the Georgia-Florida State line, has multiple human impacts. Water inputs declined due to upstream irrigation and urbanization in Georgia. Sediment trapped by numerous small to large dams, including construction of Jim Woodruff Dam in 1954 near the Apalachicola-Chattahoochee-Flint (ACF) confluence has increased degradation. Shortly thereafter, the river was modified for a navigation project, with 29.6 × 106 m3 dredged between 1957 and 2002 from the Apalachicola alone. This study investigates how historic dredging coincides with the modern morphology of the channel and how historic dredging, disposal, and other activities have modified the floodplain landforms and sediments. This analysis of the navigation impacts in the middle Apalachicola River (River Miles 40 to 65) ties spatial and temporal variations of dredging, field-derived bathymetry, historic maps, patterns of floodplain disposal of dredge spoil from LiDAR imagery, and modern point bar channel change of the Apalachicola River. Floodplain mounds of coarse material, built from out-of-bank disposal constitute > 800,000 m3 in the study area. Approximately 7.7 × 106 m3 of sediment was dredged within the study reach, roughly 11% of the volume dredged remains on the floodplain. Sand bars were disposal sites thus their increased area of 263% is partly tied to this practice. Thus, the legacy of dredging affects the modern sedimentology and morphology of the floodplain and channel. Findings show that a failed navigation project could have been pre-empted with better geomorphic, geologic and hydrologic study and suggest that vegetative restoration of point bars would help in narrowing and stabilizing this dynamic system.

Read the full publication at Geomorphology






Image courtesy PLoS Neglected Tropical Diseases
Image courtesy PLoS Neglected Tropical Diseases

KRACALIK, MORRIS, BLACKBURN – Cholera in Cameroon, 2000-2012: Spatial and Temporal Analysis at the Operational (Health District) and Sub Climate Levels

Moise C. Ngwa, Song Liang, Ian T. Kracalik, Lillian Morris, Jason K. Blackburn, Leonard M. Mbam, Simon Franky Baonga Ba Pouth, Andrew Teboh, Yang Yang, Mouhaman Arabi, Jonathan D. Sugimoto, John Glenn Morris Jr.

Article first published online: 17 NOV 2016 PLoS Neglected Tropical Diseases

DOI: 10.1371/journal.pntd.0005105


Cholera was first reported in Cameroon in 1971. From 2000–2012, Cameroon reported on average 3,344.2 cases per year. When we divided the country into its four climate subzones (Sudano-Sahelian, Tropical Humid, Guinea Equatorial, and Equatorial Monsoon), there were very different patterns of spatial clustering of health districts with elevated attack rates, as well as differing sets of ecological determinants of cases counts. In the northern Sudano-Sahelian climate subzone, reported cases tended to occur between July and September, during the rainy season; whereas, the southern Equatorial Monsoon subzone reported cases year-round, with the lowest burden during the same rainy season. As cholera displays different epidemiological patterns by subzone, a single approach to controlling cholera for the whole nation does not appear to be viable. Additional prospective epidemiological studies are needed to further elucidate subzone-specific determinants of cholera burden, in order to provide sufficient evidence-based guidance for the formulation and assessment of regionally tailored intervention strategies.

Read the full publication at PLoS Neglected Tropical Diseases