Francesco Pizzitutti, William Pan, Alisson Barbieri, J Jaime Miranda, Beth Feingold, Gilvan R. Guedes, Javiera Alarcon-Valenzuela and Carlos F. Mena

Background:  The Amazon environment has been exposed in the last decades to radical changes that have been accompanied by a remarkable rise of both Plasmodium falciparum and Plasmodium vivax malaria.  The malaria transmission process is highly influenced by factors such as spatial and temporal heterogeneities of the environment and individual-based models.

Methods:  This paper presents a validated agent-based model of local-scale malaria transmission.  The model reproduces the environment of a typical riverine village in the northern Peruvian Amazon, where the malaria transmission is highly seasonal and apparently associated with flooding of large areas caused by the neighboring river.  Agents representing humans, mosquitoes and the two species of Plasmodium (P. falciparum and P. vivax) are simulate in a spatially explicit representation of the environment around the village.  The model environment includes: climate, people houses positions and elevation.  A representation of changes in the mosquito breeding areas extension caused by the river flooding is also included in the simulation environment.

Results:  A calibration process was carried out to reproduce the variations of the malaria monthly incidence over a period of 3 years.  The calibrated model is also able to reproduce the spatial heterogeneities of local scale malaria transmission.  A “what if” eradication strategy scenario is proposed; if the mosquito breeding sites are eliminated through  mosquito larva habitat management in a buffer area extended at least 200 m around the village, the malaria transmission is eradicated from the village.

Conclusions:  The use of agent-based models can reproduce effectively the spatiotemporal variations of the malaria transmission in a low endemicity environment dominated by river floodings like in the Amazon

Keywords:  Agent-based model, Malaria, Amazon, Low endemicity, Anopheles darling, Plasmodium vivax, Plasmodium falciparum.

View Full-Text  

Carolina Sampedro, Francesco Pizzitutti, Diego Quiroga, Stephen J. Walsh, Carlos F. Mena

The Galapagos Archipelago, as islands environment, have to deal with intrinsic disadvantages such as small size, remoteness, insularity, disaster proneness, and environmental fragility, which translate in limited access to natural and social resources (ONU, 1994) generating dependence on a narrow range of products and incrementing import reliance, which in turn compromise the Galapagos inhabitants´ food security.  In this context, this research applied an SD model approach in order to identify the driving forces and relationships that influence the food availability system through the analysis of its variables and interactions, to understand how population growth and food consumption in the Galapagos Islands are related to supply dynamics such as local agriculture production and food imports. It was observed that local production keeps a decreasing trend in the three scenarios, as well as an imports reliance increase. Also, agricultural areas in the Galápagos Islands are regulated mostly by cattle ranching activities, which present an increasing trend due to meat importation restrictions.  And, that while production keeps expanding into the agricultural area, a more effective control of invasive species is possible. In this regard, Galapagos food security depends on a decreasing local farming and an increasing dependence on food imports, what in turn increases the vulnerability of the islands food security. These three growth scenarios as well as production and consumption tendencies, further proves the difficulties and limitations of the Galapagos Island´s food security. Therefore, overcome the island disadvantages towards a self-reliance in local production is a goal to pursue.  

Fátima L. Benítez,  Carlos F. Mena, Leo Zurita-Arthos

The Galapagos Islands are a unique sanctuary for wildlife and have gone through a fluctuating process of urbanization in the three main inhabited islands. Despite being colonized since the 1800s, it is during the last 25 years that a dramatic increase in population has been observed. Analyzing impervious surface change over this period in an ecologically fragile environment is a challenging task, thus two methods that have been widely employed in studying urban environments were compared in this study: sub-pixel using spectral mixture analyses (SMA) and object-based classification. The SMA linear model, applied over moderate spatial resolution imagery, does not produce accurate results for urban composition mapping showing significant spectral confusion between classes. Instead, the object-based classification using spectral indices proved to be more effective for detecting impervious surfaces over heterogeneous urban environments in inhabited islands. The accuracy assessment showed a correlation between estimated and true impervious surface abundance fraction higher than first expected (R2 = 67.7%) for the object-based classification, considering the limitations of pixel size (Landsat imagery) in small heterogeneous urban landscapes. Hence, this methodology was applied to all three urban centers for further analysis. Through this assessment, the average annual growth rate in urban areas was calculated as 3.3% from 1992 to 2017. The foreseen applications and local implications for land planning and management are especially important for the Galapagos Islands. There is a need for planning systems and processes that involve all stakeholders, in order to support pre-existing conservation initiatives and sustainable development policies.

Keywords: inhabited islands; urbanization; SMA; object-based classification; Galapagos

View Full-Text

Stephen J. Walsh, Carlos F. Mena

Laura Brewington, Brian G. Frizzelle, Stephen J. Walsh, Carlos F. Mena, Carolina Sampedro

Analysis of marine and coastal systems is of fundamental importance to environmental scientists, engineers, and managers. Since the 1960s, remote sensing has played an important role in characterizing the marine environment, with particular emphasis on sea surface features, temperature, and salinity; mapping of shorelines, wetlands, and coral reefs; local fisheries and species movements; tracking hurricanes, earthquakes, and coastal flooding; and changes in coastal upwelling and marine productivity. This chapter reviews marine applications of remote sensing worldwide, exploring contemporary satellite systems, research themes, and analytical methods. In the Galapagos Islands of Ecuador, marine remote sensing has been limited to the use of large-scale daily image-gathering systems, such as CZCS, MODIS, SeaWiFS, and AVHRR, due to persistent cloud cover and constrained research budgets. Recent advances in satellite technology and availability, however, offer new opportunities for remote sensing in the Galapagos archipelago and beyond. Moderate-resolution sensors like SPOT and Landsat continue to be relevant for regional-scale evaluations of marine and coastal environments, identifying hotspots or focal areas for the use of more fine-grained imagery like QuickBird, WorldView-2, and aerial photographs. Radar systems like Aquarius and SAR show promise in new lines of oceanographic research, including sea surface salinity and the differentiation of mangrove subspecies. The use of ancillary or in situ data for calibration and validation of remotely-sensed image analysis can overcome the limitations of sensors used in bathymetric applications, while advances in cellular and GPS technology facilitate real-time reporting from citizen scientists for integrated monitoring of environmental and social change.

View Full-Text

Shifting Baselines in the Galapagos White Fin Fishery, Using Fisher’s Anecdotes to Reassess Fisheries Management: The Case of the Galapagos Grouper

Diana V. Burbano, Carlos F. Mena, Paulina Guarderas, Luis Vinueza, Gunther Reck

This study links social and ecological aspects of the white fin fishery in San Cristobal Island. This is a traditional fishery focused at first on the Galapagos grouper (Mycteroperca olfax), a top predator and an iconic species of the archipelago as part of a traditional dish to celebrate Easter on the continent. We used anecdotal information and perceptions provided by three generations of fisherman to understand the impacts of fishing on the dried and salted fishery. Significant differences were found among fishers’ groups surveyed and interviewed for this study. The oldest group indicated a greater past abundance of the Galapagos grouper than the other two younger age groups. The close relationship between fishers and their activity have generated certain knowledge about marine environments, its species, and the dynamics developed in their fishing areas, creating a perception of changes in this fishery.

View Full Text