Papers by guillermo deferrari
Ondatra zibethicus (L), comúnmente conocida como "rata almizclera" o “muskrat” en su re... more Ondatra zibethicus (L), comúnmente conocida como "rata almizclera" o “muskrat” en su región de origen, es un roedor semiacuático que fue introducido en la Isla Grande de Tierra del Fuego en la década del 40 para el aprovechamiento de su piel considerada valiosa en el mercado comercial de pilíferos. En líneas generales, las especies introducidas son en su mayoría especies generalistas y oportunistas que se adaptan más fácilmente y llegan a incrementar rápidamente su población y uso de hábitats. La introducción de Ondatra zibethicus en Tierra del Fuego plantea el desarrollo de un estudio poblacional informativo, no sólo desde el punto de vista ecológico como especie invasora, sino también porque permite analizar la estructura genética de poblaciones pequeñas y aisladas. Se analizaron caracteres morfológicos de Ondatra que permiten caracterizar a la población desde su morfología corporal y craneana, como así también su constitución genética y parámetros ecológicos a fin de ex...
Over 20 years of stratospheric NO 2 vertical column density (VCD) data from ground-based zenith D... more Over 20 years of stratospheric NO 2 vertical column density (VCD) data from ground-based zenith DOAS spectrometers were used for trend analysis, specifically, via multiple linear regression. Spectrometers from the Network for the Detection of Atmospheric Composition Change (NDACC) cover the subtropical latitudes in the Northern Hemisphere (Izaña, 28 • N), the southern Subantarctic (Ushuaia, 55 • S) and Antarctica (Marambio, 64 • S, and Belgrano, 78 • S). The results show that for the period 1993-2014, a mean positive decadal trend of +8.7 % was found in the subtropical Northern Hemisphere stations, and negative decadal trends of −8.7 and −13.8 % were found in the Southern Hemisphere at Ushuaia and Marambio, respectively; all trends are statistically significant at 95 %. Belgrano only shows a significant decadal trend of −11.3 % in the summer/autumn period. Most of the trends result from variations after 2005. The trend in the diurnal build-up per hour (DBU) was used to estimate the change in the rate of N 2 O 5 conversion to NO 2 during the day. With minor differences, the results reproduce those obtained for NO 2. The trends computed for individual months show large monthto-month variability. At Izaña, the maximum occurs in December (+13.1 %), dropping abruptly to lower values in the first part of the year. In the Southern Hemisphere, the polar vortex dominates the monthly distributions of the trends. At Marambio, the maximum occurs in midwinter (−21 %), whereas at the same time, the Ushuaia trend is close to its annual minimum (−7 %). The large difference in the trends at these two relatively close stations suggests a vortex shift towards the Atlantic/South American area over the past few years. Finally, the hemispheric asymmetry obtained in this work is discussed in the framework of the results obtained by previous works that considered tracer analysis and Brewer-Dobson circulation. The results obtained here provide evidence that the NO 2 produced by N 2 O decomposition is not the only cause of the observed trend in the stratosphere and support recent publications pointing to a dynamical redistribution starting in the past decade.
![Research paper thumbnail of UV measurements at Marambio and Ushuaia during 2000–2010 [Discussion paper]](https://attachments.academia-assets.com/106720159/thumbnails/1.jpg)
Solar ultraviolet (UV) irradiances were measured with NILU-UV multichannel radiometers at Ushuaia... more Solar ultraviolet (UV) irradiances were measured with NILU-UV multichannel radiometers at Ushuaia (54 • S) and Marambio (64 • S) between 2000 and 2013. The measurements were part of the Antarctic NILU-UV network, which was started in cooperation between Spain, Argentina and Finland. The erythemally weighted UV irradiance time series of both stations were analyzed for the first time in this study. The quality assurance procedures included a traveling refence instrument to transfer the irradiance scale to the stations. The time series were homogenized and high quality measurements were available for the period 2000-2010. During this period UV indices of 11 or more were measured on 5 and 35 days at Marambio and Ushuaia, correspondingly. At Marambio, the peak daily maximum UV index of 12 and dailydoses of around 7 kJ/m 2 were measured in November 2007. Typically the highest UV daily doses were at both stations around 6 kJ/m 2 , and they occurred on time periods, when the station was inside the polar vortex with very low total ozone amount. At both stations, dailydoses of late November could even exceed those of summer. At Marambio, in some years, also dailydoses in October can be as high as those during the summer. At Ushuaia, the peak daily maximum UV index of 13 was measured twice: in November 2003 and 2009. Also during those days, the station of Ushuaia was inside the polar vortex. Copyright statement. TEXT 1 Introduction The NILU-UV Antarctic network was established in 1999/2000 in scientific cooperation between the Spanish Agencia Estatal de Meteorología (AEMET), the Finnish Meteorological Institute (FMI) and the Argentinian Dirección Nacional del Antártico-Instituto Antártico Argentino (DNA-IAA) and Centro Austral de Investigaciones Cientificas (CADIC). The goal was to promote
Proceedings of SPIE, Jan 22, 2002
ABSTRACT The presence of clouds is responsible for an important variation in the UV and visible r... more ABSTRACT The presence of clouds is responsible for an important variation in the UV and visible radiation at the Earth&#39;s surface. Although for practical purposes cloud transmittance is often considered plane in the UV and visible, a wavelength dependence is observed. In this paper we performed a statistical study of cloud transmittance at Ushuaia for wavelengths between 295 and 600 nm, following different procedures. A decrease of the transmittance for increasing wavelengths in the UVA and the visible was observed (0 to 50% decrease at 600 nm regarding to 340 nm) in good agreement with the observations made by other authors. Nevertheless, for wavelengths below 320 nm our results show discrepancy with other papers. Since Ushuaia is a small town n a fairly unpolluted area, a possible reason for this differences is that, as a consequence of low ozone amounts in the troposphere, Rayleigh scatter is more important than ozone absorption, even in this part of the spectrum.
Proceedings of SPIE, Sep 9, 2002
ABSTRACT When a multi-channel radiometer is calibrated using the sun as calibration source, the e... more ABSTRACT When a multi-channel radiometer is calibrated using the sun as calibration source, the error in the calculated calibration constants may be large when solar zenith angles increase. A multi-regression model has proved to be suitable to derive narrowband irradiance from broadband irradiance, ozone column and solar zenith angles (SZA). In this paper, a modification of this model is being proposed to improved the multi-channel instrument sun calibration against spectroradiometers, considering a channel of a multi-channel radiometers as a broadband instrument. The errors in the GUV irradiance, compared to the spectroradiometer irradiance, diminished considerably at all channels for SZA larger than 50a, then, this technique could be particularly beneficial to calibrate radiometers installed at high latitudes, where SZA during winter, even at noon, are larger than 50a.
Proceedings of SPIE, Jun 26, 2003
The IAI Network for the measurement of ultraviolet radiation in Chile, Argentina and Puerto Rico ... more The IAI Network for the measurement of ultraviolet radiation in Chile, Argentina and Puerto Rico is composed of ten multi-channel radiometers (GUV 511, Bisopherical Instruments Inc.), which are periodically sun calibrated with a traveling reference GUV (RGUV). The RGUV is ...
Proceedings of SPIE, Aug 5, 2013
ABSTRACT
1) feasibility of eradication in pilot areas; 2) assessment of vital and dispersion rates and bui... more 1) feasibility of eradication in pilot areas; 2) assessment of vital and dispersion rates and building predictive models of the spread of the invasion, and 3) determination of objective criteria to declare beaver eradication in areas under management. Capacity building is critical for this complex process. Assembling the social capital needed to manage the problem requires a continuous dialogue and agreed agendas among various stakeholders. The scientific sector can assist in this process without imposing unilateral agendas, but identifying the right questions and understanding the particularities of other sectors, the culture of organizations and the time frames needed for practical responses to achieve science-based conservation.
Proceedings of SPIE, Sep 29, 2006
abstract An Antarctic UV-monitoring network established in 1999 as a Spanish-Finnish-Argentinian ... more abstract An Antarctic UV-monitoring network established in 1999 as a Spanish-Finnish-Argentinian co-operation consists of multiband filter radiometers located at Belgrano, Marambio, and Ushuaia. To provide with quality controlled and assured calibrated groundbased Antarctic UV data, bi-weekly lamp tests were used on every site and visits of travelling reference instruments on two of the sites. Along the six years of operation, the sensitivity in some of the instrument channels was found to drift up to 61%. In both stations ...
Veterinary Parasitology: Regional Studies and Reports, Jul 1, 2020
Wild and domestic dogs are important reservoir hosts of numerous intestinal parasites that repres... more Wild and domestic dogs are important reservoir hosts of numerous intestinal parasites that represent potential infection sources for both humans and wild or other domestic animals. The aim of this study was to determine the presence, diversity, and contamination potential of intestinal parasites in dog feces contaminating urban and recreational areas in Ushuaia (Tierra del Fuego province, Argentina). A total of 80 canine fecal samples were collected from urban (playgrounds, streets, sidewalks, squares and coastal walks) and recreational areas (winter centers for raising and training sled dogs) in 2018. Samples were preserved in 5% formalin and processed using formalin-ethyl acetate sedimentation and FLOTAC dual Pellet techniques. Data were analyzed using the R software. At least one parasite species was recovered in 32.5% of the total samples examined. Of the seven parasite species detected, infection by protozoan species was higher than helminth infections (28.8% versus 8.8%). Sarcocystis sp. (20.0%), Giardia sp. (8.8%) and Cystoisospora spp. (7.5%) were the most frequent species, followed by Toxocara canis (5.0%), Echinococcus spp./Taenia spp. (2.5%), Trichuris vulpis and Uncinaria sp. (1.3% for both). Single infections (69.2%) were more frequent than coinfections with two (19.2%) and three parasite species (11.5%). This study provides the first description of the diversity and frequency of intestinal parasite species in dog feces from Ushuaia, the southernmost city in the world. The unfavorable environment of Ushuaia, characterized by low temperatures and winter snowfall, is likely to reduce parasite survivability, decreasing contamination potential. Some parasite species found are potentially zoonotic and represent an important risk for the human population and a source of infection to free-roaming pets. The results of this study revealed the need to strengthen the prevention, surveillance and control of these infections in pets, as well as to implement programs for public health education, control measures for the free-roaming canine population, and responsible pet ownership in the study area.
International Journal of Remote Sensing, Aug 20, 2005
... 19973. Bird, JC, Pal, SR, Carswell, AI, Donovan, DP, Manney, GL, Harris, JM and Uchino, O. 19... more ... 19973. Bird, JC, Pal, SR, Carswell, AI, Donovan, DP, Manney, GL, Harris, JM and Uchino, O. 1997. ... Following the major warming, ozone depletion was stopped abruptly and streamers of low PV inside the vortex were observed in the output of the ECMWF analysis (Simmons et al ...
Atmospheric Chemistry and Physics, Nov 10, 2017
Over 20 years of stratospheric NO 2 vertical column density (VCD) data from ground-based zenith D... more Over 20 years of stratospheric NO 2 vertical column density (VCD) data from ground-based zenith DOAS spectrometers were used for trend analysis, specifically, via multiple linear regression. Spectrometers from the Network for the Detection of Atmospheric Composition Change (NDACC) cover the subtropical latitudes in the Northern Hemisphere (Izaña, 28 • N), the southern Subantarctic (Ushuaia, 55 • S) and Antarctica (Marambio, 64 • S, and Belgrano, 78 • S). The results show that for the period 1993-2014, a mean positive decadal trend of +8.7 % was found in the subtropical Northern Hemisphere stations, and negative decadal trends of −8.7 and −13.8 % were found in the Southern Hemisphere at Ushuaia and Marambio, respectively; all trends are statistically significant at 95 %. Belgrano only shows a significant decadal trend of −11.3 % in the summer/autumn period. Most of the trends result from variations after 2005. The trend in the diurnal build-up per hour (DBU) was used to estimate the change in the rate of N 2 O 5 conversion to NO 2 during the day. With minor differences, the results reproduce those obtained for NO 2. The trends computed for individual months show large monthto-month variability. At Izaña, the maximum occurs in December (+13.1 %), dropping abruptly to lower values in the first part of the year. In the Southern Hemisphere, the polar vortex dominates the monthly distributions of the trends. At Marambio, the maximum occurs in midwinter (−21 %), whereas at the same time, the Ushuaia trend is close to its annual minimum (−7 %). The large difference in the trends at these two relatively close stations suggests a vortex shift towards the Atlantic/South American area over the past few years. Finally, the hemispheric asymmetry obtained in this work is discussed in the framework of the results obtained by previous works that considered tracer analysis and Brewer-Dobson circulation. The results obtained here provide evidence that the NO 2 produced by N 2 O decomposition is not the only cause of the observed trend in the stratosphere and support recent publications pointing to a dynamical redistribution starting in the past decade.
Cada año entrada la primavera, cuando los días comienzan a alargarse, empiezan las consultas sobr... more Cada año entrada la primavera, cuando los días comienzan a alargarse, empiezan las consultas sobre el agujero de ozono y sobre los problemas que pueden surgir a la hora de exponernos al sol. Muchas de las consultas que recibimos desde hace años son mitos y otras verdades, y es la intención de esta nota poner algo de claridad sobre diferentes temas vinculados a la capa de ozono. Informaremos sobre la problemática regional, sus causas y consecuencias, analizando mitos y realidades del fenómeno.Fil: Deferrari, Guillermo Alejandro. Universidad Nacional de Tierra del Fuego; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Camilión, María Carolina. Universidad Nacional de Tierra del Fuego; Argentin
Journal of Zoology, Nov 10, 2022
The North American beaver (Castor canadensis) has been an invasive species in the Tierra del Fueg... more The North American beaver (Castor canadensis) has been an invasive species in the Tierra del Fuego archipelago since its intentional introduction in 1946. Its activities have led to such severe impacts on various environments that eradication has been tested as a management strategy. We assessed how vital rates (i.e., survivorship and reproduction) of the beavers were affected by time since invasion and population management history (such as lethal control). We constructed vertical life tables and compared survivorship, age‐specific survivorship, generation time, and life expectancy for different landscapes and management histories. As part of an eradication pilot program conducted between 2016–2018, 922 beavers were removed in seven pilot areas of the Isla Grande de Tierra del Fuego, Argentina. Areas in which beavers have resided longest since invasion, areas without hunting pressure, and areas previously cleared of beavers had higher survivorship and longer generation time and life expectancy. Areas where beaver management was historical (trapping performed by the provincial government) or focused (trapping by landowners) had shorter life expectancy and generation time and advanced age at first reproduction. Beavers showed demographic plasticity in relation to time since invasion (increasing survivorship, generation time, life expectancy, and cohort life expectancy consistent with populations close to carrying capacity in areas with low or null management). They also exhibited plasticity in response to management histories (advanced breeding onset, reduced survivorship, and life expectancy in managed areas—similar to managed populations in their native range). We present management implications from demographic perspective for a future eradication or control program of beavers. We also highlight the importance of landowners in shaping beaver demography for the future management of the species. Beaver demography reacts dynamically and rapidly to local removal, creating challenges for management based on the removal of beavers.
Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in ... more Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in South America. Ground UV irradiances were measured by multichannel radiometers as part of the Inter American Institute for Global Change Radiation network. The irradiance channels used for this study were centered at 305 nm (for UV-B measurements) and 340 nm (for UV-A measurements). Results were presented as daily maximum irradiances, as monthly averaged, daily integrated irradiances and as the ratio of 305 nm to 340 nm. These findings are the first to be based on a long time series of semispectral data from the southern region of South America. As expected, the UV-B channel and total column ozone varied with latitude. The pattern of the UV-A channel was more complex because of local atmospheric conditions. Total column ozone levels of <220 Dobson Units were observed at all sites. Analysis of autocorrelations showed a larger persistence of total column ozone level than irradiance. A decreasing cross-correlation coefficient between 305 and 340 nm and an increasing cross-correlation coefficient between 305 nm and ozone were observed at higher latitudes, indicating that factors such as cloud cover tend to dominate at northern sites and that ozone levels tend to dominate at southern sites. These results highlight the value of long-term monitoring of radiation with multichannel radio-meters to determine climatological data and evaluate the combination of factors affecting ground UV radiation.
Ecología austral, Dec 1, 1996
Alterations induced by beaver (Castor canadensis) provide a striking example of how the animals i... more Alterations induced by beaver (Castor canadensis) provide a striking example of how the animals influence forest ecosystems. Beavers modify stream morphology and hydrology by removing trees, building dams and retaining sediment and organic material in the stream channel. We studied the effect of beaver impoundments on nutrient dynamics of the native forest (Nothofagus sp.) of Isla Grande of Tierra del Fuego (Argentina), by comparing sediments and pond waters of beaver altered and unaltered sites (controls) over a 3 year period. Concentration of organic carbon, nitrogen, phosphorous, and inorganic nitrogen (nitrate-N and nitrite-N) were significantly greater in sediments of beaver sites. Also nitrites and nitrates were higher in beaver pond waters. Resumen. Las alteraciones provocadas por las actividades del castor (Castor canadensis) resultan un ejemplo claro de cómo los animales influencian el ecosistema forestal. Los castores modifican la morfología e hidrología de las cursos de agua por la remoción de árboles, construcción de diques y retención de sedimento y materia orgánica en la cuenca. Nosotros estudiamos el efecto de los endicamientos producidos por el castor sobre la dinámica de nutrientes del bosque de Nothofagus de Tierra del Fuego (Argentina) comparando sedimentos y agua de estanques de sitios alterados por castor y no alterados (controles) durante un periodo de 3 años. Las concentraciones de carbono, nitrógeno orgánico e inorgánico (N-nitrato y N-nitrito) y fósforo fueron significativamente mayores en los sedimentos de sitios alterados. Tambien las concentraciones de nitratos y nitritos fueron significativamente más altas en aguas de estanques de castor.
Interciencia, Jul 1, 2004
Photochemistry and Photobiology, 2006
Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in ... more Ozone and UV radiation were analyzed at eight stations from tropical to sub-Antarctic regions in South America. Ground UV irradiances were measured by multichannel radiometers as part of the Inter American Institute for Global Change Radiation network. The irradiance channels used for this study were centered at 305 nm (for UV-B measurements) and 340 nm (for UV-A measurements). Results were presented as daily maximum irradiances, as monthly averaged, daily integrated irradiances and as the ratio of 305 nm to 340 nm. These findings are the first to be based on a long time series of semispectral data from the southern region of South America. As expected, the UV-B channel and total column ozone varied with latitude. The pattern of the UV-A channel was more complex because of local atmospheric conditions. Total column ozone levels of <220 Dobson Units were observed at all sites. Analysis of autocorrelations showed a larger persistence of total column ozone level than irradiance. A decreasing cross-correlation coefficient between 305 and 340 nm and an increasing cross-correlation coefficient between 305 nm and ozone were observed at higher latitudes, indicating that factors such as cloud cover tend to dominate at northern sites and that ozone levels tend to dominate at southern sites. These results highlight the value of long-term monitoring of radiation with multichannel radio-meters to determine climatological data and evaluate the combination of factors affecting ground UV radiation.
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Papers by guillermo deferrari
El objetivo de este trabajo es evaluar en base a las primeras experiencias la potencialidad del uso de VANTs para la generación de información factible de obtener en su empleo, como así también la interpretación de dicha información y la aplicabilidad de la misma.
Las primeras imágenes cenitales fueron obtenidas mediante un VANT marca DJI modelo phantom 4 en un área actualmente libre de castores y bajo estudio de recuperación. Las imágenes obtenidas permiten mediante el uso de softwares especializados obtener ortofotomosaicos, modelos digitales de elevación del terreno (MDT) y mapas topográficos de alta resolución espacial (importante en la interpretación de los cursos de agua utilizados) para detectar los diferentes signos de actividad de la especie. La presencia de diques, madrigueras activas, comederos, áreas de renovales, zonas de corte son algunos de los datos obtenidos desde las imágenes.
La utilización de esta herramienta reduce el tiempo de recorrido en zonas de difícil acceso muy comunes en la Provincia, generando a su vez información de suma utilidad para el manejo de la especie en diferentes áreas. No obstante la interpretación de las imágenes requiere de un conocimiento previo de la Biología de la especie y su interacción con el medioambiente.
Se recolectaron 62 muestras de materia fecal de perros de espacios públicos de diferentes barrios de la ciudad de Ushuaia (zona urbana) y de tres estaciones de trineo ubicadas en los alrededores de la ciudad (zona no urbana). Las muestras se fijaron en formol 5% y se procesaron mediante la técnica Ritchie y FLOTAC Pellet en el CEPAVE.
Como resultado del análisis, el 33,9% de las muestras (21/62) resultaron positivas para al menos una especie parásita. Se identificaron un total de 7 especies parásitas y entre ellas, las más prevalentes fueron Sarcocystis sp. (19,4%), Giardia lamblia (9,7%) e Isospora spp. (9,7%), seguidos de Toxocara sp. (4,8%), Taeniidae Echinococcus spp./Taenia spp. (3,2%), Trichuris sp. (1,6%) y Uncinaria sp. (1,6%). El 66,7% de las muestras fecales positivas presentaron una sola especie parásita. Sin embargo, se hallaron muestras fecales con dos (19,0%) y hasta con tres especies parásitas (14,3%). Al diferenciar los sitios analizados, la zona no urbana mostró un mayor porcentaje de parasitosis respecto de la zona urbana (53,3% versus 27,7%). Asimismo la zona no urbana presentó una mayor cantidad de especies parásitas respecto de la zona urbana (6 versus 4 especies parásitas).
Los resultados obtenidos dan cuenta del nivel de contaminación fecal del ambiente, el cuidado insuficiente de las mascotas y la consecuente infección parasitaria que tienen los perros en la ciudad más austral del mundo. El hallazgo de parásitos de importancia zoonótica en Ushuaia sugiere la necesidad de profundizar el control sanitario en el área y promover actividades de prevención.