Instituto de Geografía
Permanent URI for this community
Browse
Browsing Instituto de Geografía by Subject "14 Vida submarina"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- ItemHacia una Ley de costas para Chile bajo lineamientos de una gestión integral y gobernanza: estudio de casos de California-EE.UU. y Nueva Zelanda(2022) Schneider Schiehl, Bárbara Macarena; Handke, Michael; Martínez Reyes, Carolina del Pilar; Pontificia Universidad Católica de Chile. Instituto de GeografíaEsta investigación exploratoria pretendió dar respuesta a la pregunta de investigación: ¿Cómo los Principios de Ostrom pueden ser directrices para la construcción de una ley de costas para Chile bajo un enfoque de Gestión Integral de Áreas Litorales?. Se planteó como objetivo general: analizar las leyes de costas de Nueva Zelanda y California- EE.UU., para identificar directrices de gobernanza que guíen una ley de costas para Chile, bajo un criterio de Gestión Integral de Áreas Litorales (GIAL) de Barragán. El diseño metodológico consistió: 1) definición y obtención de siete ejes temáticos coincidentes con los elementos del Decálogo (Barragán, 2014) y los Principios de Ostrom (2000; 2015b), que permitieron analizar los cuerpos normativos, organizados en siete matrices de contenido; 2) diseño de una codificación por temas, que posibilitó sub-organizar la información; 3) identificación de nuevos códigos como sub-temas que proporcionó una escala analítica adecuada, determinando con ello el grado de cumplimiento de los Principios de Ostrom (2000; 2015b). Con los resultados obtenidos se observó un alto grado de cumplimiento, deduciendo que ambos referentes teóricos se complementan. Se concluye que los Principios de Gobernanza de Ostrom pueden ser directrices para una ley de costas bajo el enfoque de GIAL.
- ItemReconstrucción climática del holoceno en Patagonia Noroeste mediante diatomeas(2023) Sepúlveda Zúñiga, Einer Alexander; Sagredo T., Esteban; Pontificia Universidad Católica de Chile. Instituto de GeografíaEl sector Pacífico de Patagonia Noroeste (PNO; 40°-44°S) se ha establecido como una región clave para descifrar los impactos de la variabilidad climática y las influencias humanas en los ecosistemas de latitudes medias del hemisferio sur (HS). Los Vientos del Oeste del Sur (SWW) constituyen el principal componente atmosférico que controla los patrones de precipitación en HS, existiendo una fuerte correlación positiva entre la intensidad del viento zonal y la precipitación local en este sector. Por esta razón, durante las últimas décadas, se han realizado diversos estudios paleoclimáticos en PNO que han inferido cambios en el equilibrio hidrológico atribuidos a variaciones de los SWW. No obstante, existen amplias discrepancias acerca de la evolución de los SWW durante el Holoceno en la vertiente pacífica de PNO. En virtud de su sensibilidad y especificidad, las diatomeas son ideales para examinar los cambios pasados en los ecosistemas acuáticos y descifrar los rangos de variabilidad bajo condiciones naturales e inducidas por el hombre. Hasta la fecha, sin embargo, muy pocos estudios basados en diatomeas han examinado en detalle la evolución ambiental durante el Holoceno en PNO. Aquí presento un nuevo registro de diatomeas de Lago Pichilaguna (41°S), un lago de cuenca cerrada y poca profundidad situado en las tierras bajas de la Región de los Lagos de Chile. Las variaciones en los ensambles de diatomeas más importantes sugieren cambios en el balance hídrico, la estratificación térmica y la mezcla de la columna de agua a escalas milenial y centenal. Entre ~12,6-11,5 ka, detecté el predominio de ensambles de diatomeas planctónicas relacionados con aguas templadas, oligotróficas y bajo nivel hídrico (e.g., Cyclotella distinguenda), lo que sugiere una influencia moderada de los SWW durante este periodo. A continuación, entre ~11,5-5,7 ka, observé un incremento en las especies planctónicas indicadoras de mayor estratificación térmica e incremento de nutrientes (e.g., Discostella stelligera). Este periodo fue interrumpido por intervalos dominados por ensambles ticoplanctónicos (grandes Aulacoseira spp.) relacionados con niveles de lago muy bajos y con una mayor mezcla en la columna de agua. Estas condiciones sugieren un mínimo en la influencia de los SWW. A partir de ~5,7 ka detecté una elevada inestabilidad climática, caracterizada por fluctuaciones de escala centenal, donde infiero periodos de mayor estratificación térmica entre ~5,1-4,2 ka; ~4-3,4 ka; ~3,2-3 ka; ~2,4-1,9 ka; ~1,6-1,1 ka; 1-0,9 ka; 0,6-0,3 ka, bajo una tendencia multimilenial frío/húmeda marcada por el predominio de ensambles perifíticos (pequeñas fragilarioides y pequeñas rafidias). Basado en lo anterior, infiero un fortalecimiento de los SWW con variaciones de escala centenal atribuibles a cambios en la intensidad y/o amplitud latitudinal de la influencia del SWW. Finalmente, a partir de los ~0,2 ka detecté los cambios más conspicuos en la composición de los ensambles de diatomeas del registro, marcados por una abrupta transición en la dominancia de las diatomeas perifíticas a las planctónicas, lo que sugiere el inicio de la fase más seca de los últimos milenios. Este periodo coincide con la quema deliberada del paisaje por parte de los colonos para la agricultura, la explotación del bosque nativo y el establecimiento de pastizales durante el siglo XIX en PNO. Mis resultados revelan que las perturbaciones humanas durante el período histórico sobrepasaron los rangos naturales de variabilidad y resiliencia de los ecosistemas acuáticos y terrestres durante el Holoceno, generando cambios abruptos en la biodiversidad, la composición de las especies y la estructura de las comunidades.
- ItemTendencia evolutiva decadal e inundación por estresores naturales en el estuario del Maipo, Región de Valparaíso: incorporación del conocimiento (técnico/científico) en la gestión local del riesgo(2023) Peña Nocetti, Paola; Martínez Reyes, Carolina del Pilar; Handke, Michael; Pontificia Universidad Católica de Chile. Instituto de GeografíaThe estuary of the Maipo River corresponds to the river mouth of an Andean basin located in central Chile, which is permanently connected to the sea by river discharge. Its main characteristic is a coastal bar, parallel to the coast, located at the distal part of the estuary that serves as a natural protection of the system against wave action. In recent years, the frequency of extreme events such as river floods and extreme waves has increased. During the period from 2021 to 2023, the Maipo River estuary was affected by different extreme events. In January 2023, an episode of bar closure occurred that caused two mechanical openings, while in July 2023, a large part of it was destroyed due to the increase in the channel caused by intense mountain rains, attributed to El Niño effects. These episodes have caused flooding risk, overflows, and other conflicts, which have required the eneration of methodologies applicable to scientific monitoring, to guide decision-making on a scientific basis. To analyze the short- and medium-term spatiotemporal changes of the coastal bar system, a methodology based on the use of satellite images and aerial photographs was implemented. Five geomorphological maps were made for 1945, 1967, 1976, 2011, and 2023 to establish the evolutionary trend of the estuary. Likewise, a multitemporal analysis of the estuary bar under low tide conditions was carried out, based on PlanetScope satellite images. The supervised classification provided a zoning of dry sand surface, wet sand, dune vegetation, and water, between June 2021 and June 2023. In addition, morphometric parameters of the bar (surface, length, and width) were obtained. On the other hand, through semi-structured interviews, it was determined how the variations of the bar affect the population and how scientific knowledge is incorporated into the local management of the estuary’s flood risk. The geomorphological maps generated in this work, together with the interviews carried out with different local actors, allow to reconstruct the geomorphological history of the estuary over the last 70 years, through different milestones and timeframes. The evolutionary trend of the estuary shows that the bar presents episodes of breakage and destruction associated with river overflow and tsunami events, while the closure of the bar is linked to a significant decrease in river discharge, which is consistent with barrier-type estuaries, which have an intermittent bar at their distal part, influenced mainly by the action of the river and wave action. In the period studied, the average bar parameters are 860 m. long, 254 m. wide and 160,000 m² of surface area. Since October 2022, a considerable increase in the periodic measurements of the surface, length and width of the bar has been observed before its closure in January 2023. After the mechanical opening, the values tend to return to the initial ones, so the bar would be in a "recovery phase". The extreme event of the river flood in June 2023 destroyed the bar, which is evidenced by a significant decrease in its surface area (remaining in a third of the size it had before the flood) and length (from 870 m. to 330 m.), while its width does not show great variations (253 m. to 232 m.). On the other hand, minor variations associated with storms and the subsequent recovery of the bar were observed during the studied period. This information was contrasted with the time series of wave, tide, and flow parameters to complement the behaviour of the bar under natural stressors. The resulting evolutionary model establishes that variations in flow river affect its morphometric parameters, while extreme wave events generate forms of erosion and/or deposition on the bar, which is consistent with classical models of generation and destruction of spits. The flooding of the estuary caused by the increase in the river channel mainly affects the inhabitants of Llolleo, in the sector of the fishermen’s homes, and the informal homes located on the edge of the El Sauce stream, as well as the farmers who grow vegetables on the estuarine banks. Additionally, a lot of anthropogenic waste arrives from the river basin. On the other hand, the closure of the bar produces stagnation and an increase in the level of the estuarine lagoon affecting the inhabitants of Llolleo. The change in water salinity affects the fishermen as it harms fishing and agriculture upstream. On the other hand, although storms are extreme wave events, they are not considered a flood threat by the risk managers of the Maipo estuary, since they only affect the bar, and these events have not had direct interference with the population. Finally, the tsunami flooding affected the inhabitants of Llolleo, and in the 2010 event, the waves reached the Lo Gallardo sector. Therefore, a containment barrier was built on the beach and riverbank as a mitigation measure after the tsunami. Currently, there is a local flood risk management in the estuary, which operates from the municipality of San Antonio, in line with the provincial delegation, when the emergency escapes the scope of the commune. The municipality authorities are clear about what to do during an emergency caused by a tsunami, and by a river flood. In addition, they have the support of SENAPRED, which leads the aid and provides instructions for proper management. Additionally, there are efforts to create a technical coordination committee for the management of the Maipo estuary, which is composed of intersectoral organizations, and is led by the provincial delegation, and its technical counterparts are the Coastal Observatory and the Millennium Institute in Coastal Socioecology, SECOS. This committee has been convened at least twice this year, whose main objective is to develop an opening protocol to future bar closure and to continue integrally managing the estuary. However, it is important to note that this management is top-down, based on relevant institutional and technical actors, and now it does not involve the rest of civil society, so we cannot yet speak of a governance system. Knowledge is a key component in governance systems and risk management, as it is incorporated into decision-making. This is why the choice of scientific knowledge to be produced must meet the needs and concerns of all actors involved, which is why a coproduction approach to knowledge is recommended. The exchange of scientific knowledge reduces disputes among actors and increases transparency, so it is essential to generate instances that promote access to science for the community. These can be generated by formal knowledge-generating institutions, such as government organizations, through seminars, talks, and workshops. The information provided must be relevant, clear, and accurate. The incorporation of scientific knowledge is key to enhance disaster risk management. In the case of the Maipo estuary, the coordination committee is a good opportunity to design and promote guidelines for the generation of new scientific knowledge and its subsequent implementation in estuary management. However, it must establish mechanisms to include the demands of the rest of the community. future scientific research should include the effect of longshore drift on bar recovery and adjust the effect of wave erosion, including bathymetry.