Francesco Tonini

Mapping return levels of absolute NDVI variations for the assessment of drought risk in Ethiopia

Abstract The analysis and forecasting of extreme climatic events has become increasingly relevant to plan effective financial and food-related interventions in third-world countries. Natural disasters and climate change, both large and small scale, have a great impact on non-industrialized populations who rely exclusively on activities such as crop production, fishing, and similar livelihood activities. It is important to identify the extent of the areas prone to severe drought conditions in order to study the possible consequences of the drought on annual crop production. In this paper, we aim to identify such areas within the South Tigray zone, Ethiopia, using a transformation of the Normalized Difference Vegetation Index (NDVI) called Absolute Difference NDVI (ADVI). Negative NDVI shifts from the historical average can generally be linked to a reduction in the vigor of local vegetation. Drought is more likely to increase in areas where negative shifts occur more frequently and with high magnitude, making it possible to spot critical situations. We propose a new methodology for the assessment of drought risk in areas where crop production represents a primary source of livelihood for its inhabitants. We estimate ADVI return levels pixel per pixel by fitting extreme value models to independent monthly minima. The study is conducted using SPOT-Vegetation (VGT) ten-day composite (S10) images from April 1998 to March 2009. In all short-term and long-term predictions, we found that central and southern areas of the South Tigray zone are prone to a higher drought risk compared to other areas.

Simulating the Spread of an Invasive Termite in an Urban Environment Using a Stochastic Individual-Based Model

ABSTRACT Invasive termites are destructive insect pests that cause billions of dollars in property damage every year. Termite species can be transported overseas by maritime vessels. However, only if the climatic conditions are suitable will the introduced species flourish. Models predicting the areas of infestation following initial introduction of an invasive species could help regulatory agencies develop successful early detection, quarantine, or eradication efforts. At present, no model has been developed to estimate the geographic spread of a termite infestation from a set of surveyed locations. In the current study, we used actual field data as a starting point, and relevant information on termite species to develop a spatially-explicit stochastic individual-based simulation to predict areas potentially infested by an invasive termite, Nasutitermes corniger (Motschulsky), in Dania Beach, FL. The Monte Carlo technique is used to assess outcome uncertainty. A set of model realizations describing potential areas of infestation were considered in a sensitivity analysis, which showed that the model results had greatest sensitivity to number of alates released from nest, alate survival, maximum pheromone attraction distance between heterosexual pairs, and mean flight distance. Results showed that the areas predicted as infested in all simulation runs of a baseline model cover the spatial extent of all locations recently discovered. The model presented in this study could be applied to any invasive termite species after proper calibration of parameters. The simulation herein can be used by regulatory authorities to define most probable quarantine and survey zones.

Telecoupling Toolbox: spatially explicit tools for studying telecoupled human and natural systems

Telecoupling is a novel interdisciplinary umbrella concept that enables natural and social scientists to understand and generate information for managing how humans and nature can sustainably coexist worldwide. The telecoupling framework gains its distinction by enabling researchers to dive deeply into systemic complexities, even if systems are far away from each other. It is also ambitious in its aim to meet challenges unencumbered by disciplines. To understand the forces affecting sustainability across local to global scales, it is essential to build a comprehensive set of spatially explicit tools for describing and quantifying multiple reciprocal socioeconomic and environmental interactions over distances. We introduce the Telecoupling Toolbox, the first set of tools developed to map and identify the five major interrelated components of the telecoupling framework: systems, flows, agents, causes, and effects. The modular design of the toolbox allows the integration of existing tools and software to assess synergies and trade-offs associated with policies and other local to global interventions. We show applications of the toolbox by using two representative telecoupling case studies that address a variety of socioeconomic and environmental issues. The results suggest that the toolbox can systematically map and quantify multiple telecouplings under various contexts while providing users with an easy-to-use interface. It is our hope that the innovative, free, and open-source toolbox can provide a useful platform to address globally important issues, such as land use and land cover change, species invasion, migration, flows of ecosystem services, and trade of goods and products.

Dispersal Flights of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae)

ABSTRACT The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a pest of major economic concern. This termite is particularly known for its tendency to establish populations in nonendemic areas via maritime vessels as well as human-aided transport of infested materials. The natural spread of this species after new introductions occurs in part by dispersal flights originating from mature colonies. Dispersal flight activity is also the primary variable for the evaluation of area-wide management programs. Few studies exist describing the dynamics and distribution of a typical dispersal flight for this species. The present study used data collected by mark—recapture of C. formosanus alates over 12 individual evenings of dispersal flights in the New Orleans French Quarter. In this study, we found that for one selected flight dispersal location, which was not affected by a high density of trap locations nearby, alates flew on average 621m from their parent colony. A new record of a 1,300-m dispersal flight was recorded. Spatial analysis showed that neither wind nor light affected the direction of flight, which may, however, be attributed to scarce light and wind measurements in the study region.

Stochastic spread models: A comparison between an individual-based and a lattice-based model for assessing the expansion of invasive termites over a landscape

Abstract Spatially-explicit simulation models can help state and local regulatory agencies to predict both the rate and direction of the spread of an invasive species from a set of surveyed locations. Such models can be used to develop successful early detection, quarantine, or eradication plans based on the predicted areas of infestation. Individual-based models (IBMs) are often used to replicate the dynamics of complex systems and are both able to incorporate individual differences and local interactions among organisms, as well as spatial details. In this work, we introduce a new stochastic lattice-based model for simulating the spread of invasive termites over a landscape and compare it to a recently published stochastic individual-based approach, based on the same ecological parameters, with the goal of improving its computational efficiency. The two modeling frameworks were tested over a homogeneous landscape with randomly located sources of infestation. Further, the setting of a case-study of an invasive termite, Nasutitermes corniger (Motschulsky), was used to simulate the spread of the species in Dania Beach, Florida, U.S.A., and the results of the proposed model were compared with an earlier application of the IBM over the same area. The results show that the extent of the infested areas predicted by the new lattice-based model is similar, thus comparable, to the individual-based model while improving the computation time significantly. The simulation presented in this work could be used by the regulatory authorities to draw one or more areas of intervention instead of wasting resources by randomly surveying unknown perimeters.

The Role of Geographic Information Systems for Analyzing Infestations and Spread Of Invasive Termites (Isoptera: Rhinotermitidae And Termitidae) in Urban South Florida§

ABSTRACT The ability to manage geospatial data has made Geographic Information Systems (GIS) an important tool for a wide range of applications over the past decades, including management of natural resources, analysis of wildlife movement, ecological niche modeling, or land records management. This paper illustrates, using invasive termite species as examples, how GIS can assist in identifying their potential sources of infestations and model their spread in urban South Florida. The first case study shows that the Formosan subterranean termite, Coptotermes formosanus Shiraki, and the Asian subterranean termite, Coptotermes gestroi (Wasmann) (Isoptera: Rhinotermitidae), were introduced into and dispersed across South Florida by sailboats and yachts. The second case study shows an agent-based model to simulate the natural spread of Nasutitermes corniger (Motschulsky) (Isoptera: Termitidae) in Dania Beach, Florida. This paper provides an overview of basic functionalities in GIS and demonstrates how they can be customized for advanced modeling and simulation.

Disjunctitermes insularis, a new soldierless termite genus and species (Isoptera, Termitidae, Apicotermitinae) from Guadeloupe and Peru

Abstract Disjunctitermes insularis gen. n. & sp. n. is described from workers collected on Guadeloupe and in Peru and is the first soldierless termite found on a deep-water island. As with many soldierless and soil-feeding termite species, the enteric valve morphology is an essential diagnostic character of D. insularis. The D. insularis sequence cluster, derived from a barcode analysis with twelve other described genera of New World Apicotermitinae, is well resolved. Results of a stochastic dynamic spread model suggest that the occurrence of D. insularis on Guadeloupe may be the result of a pre-Colombian overwater dispersal event from mainland South America.

Proliferation of the invasive termite Coptotermes gestroi (Isoptera: Rhinotermitidae) on Grand Cayman and overall termite diversity on the Cayman Islands

Abstract The Asian subterranean termite, Coptotermes gestroi (Wasmann) (Isoptera: Rhinotermitidae), was discovered on Grand Cayman Island in 2000 and, by 2014, had been recorded from 102 land-based localities. These data were used in a hierarchical cluster analysis to identify homogeneous clusters of sites to estimate separate introduction points on the island. Results suggest 4 separate introductions of C. gestroi to Grand Cayman by boat and 1 by land transport from other previously infested parts of the island. The infestations by boat could be either primary introductions (originating from another island) or secondary introductions (originating from other previously infested parts of Grand Cayman). An individual-based model was used to simulate non-anthropogenic spread of C. gestroi over Grand Cayman from 2014 to 2050. The model predicts that by 2050, most of the western part of Grand Cayman will likely be heavily infested by C. gestroi, whereas patches of unsuitable habitat restrict the expansion of the species over the central and eastern parts of the island. In the absence of further human introductions, it will likely take a century for C. gestroi to saturate the island by natural dispersal only. Based on detailed termite diversity surveys, we provide updated records for 14 termite species, collectively, on Grand Cayman, Little Cayman, and Cayman Brac.