Browsing by Author "Rojas, Octavio"
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- ItemA temporal analysis of the consequences of the drought regime on the water footprint of agriculture in the Guadalupe Valley, Mexico(2024) Novoa, Vanessa; Rojas Quezada, Carolina Alejandra; Rojas, Octavio; Ahumada-Rudolph, Ramón; Moreno-Santoyo, RebecaChanges in water availability have a substantial impact on the sustainability and maintenance of agriculture, with water footprint (WF) being a robust methodology to assess these transformations. The Guadalupe Valley is one of the places with the highest agricultural production in Mexico. Despite its semi-arid climatic conditions, it provides high-quality crops that are well-positioned in the world. The historical trend of rainfall and temperatures between 1987 and 2017 was analyzed to identify climatic patterns in the territory. Through the calculations of the water footprint of Grapevine and Olive crops, the sensitivity of the crops to recurrent water deficit and their adaptation in their yields to drought episodes was identified. The reduction in precipitation and occurrence of extreme temperatures have contributed significantly towards augmenting crop evapotranspiration and, consequently, intensifying crop irrigation demands. As a result, there has been an apparent increase in the consumption of WFagricultural since 2007. Thus, the period of highest WFagricultural consumption was 2014 (Extremely dry), as opposed to 2011 (Very wet). In particular, the lowest WFgreen consumptions were observed in extremely dry years, that is, > 20% of the WFagricultural intensifying drought events. Therefore, these periods were compensated with higher uses of WFblue and WFgray, which are inversely correlated with precipitation, where vine crops consume 73% more WFagricultural compared to olive plantations, showing greater interannual variability. These results contribute to analyzing the temporal evolution of water consumption for agriculture, providing a basis for rational water use strategies.
- ItemAssessment of the flood mitigation ecosystem service in a coastal wetland and potential impact of future urban development in Chile(2022) Rojas, Octavio; Soto, Evelyn; Rojas Quezada, Carolina Alejandra; López, J. Javier; CEDEUS (Chile)A worldwide increase in flooding due to climate change and population growth in exposed areas is expected, especially in coastal areas; therefore, nature-based solutions (NBS) for risk reduction are necessary to increase the resilience of cities, particularly in developing countries, which usually lack large budgets for structural measures but have natural areas such as wetlands that can be used as NBS. The flood mitigation ecosystem service of a coastal wetland in central Chile was analyzed. Using hydrological and topo-bathymetric data, two flood hazard scenarios were modeled: (i) S1 current and (ii) S2 projected, which was established based on land-use planning instruments and urban projects developed since 1954. Flood hazard maps for different return periods were obtained and indicators related to the mitigation potential of the wetland were calculated. It was proven that urban project development has intensified since 2000, mainly in the form of real estate development, with an increase in occupation of 50%, and the wetland area is projected to be further reduced by around one third, decreasing potential flood mitigation. Thus, for an extreme return period, in this case 500 years, the water volume stored by the wetland would decrease by more than 38% and the flooded area of the wetland by 30%, increasing flooding and vulnerability of the urban area, with various repercussions for surrounding neighborhoods and infrastructure. The number of people and homes affected would increase by around 6% and 8%, respectively, such that the affected land value would reach an additional US$55 million, which would be very detrimental in a city that has seen its natural spaces encroached upon by gray infrastructure. This research reaffirms the need to support the restoration and conservation of coastal wetlands under pressure from urban development in an area with a lack of green infrastructure planning.
- ItemCoastal Evolution in a Wetland Affected by Large Tsunamigenic Earthquakes in South-Central Chile: Criteria for Integrated Coastal Management(MDPI, 2021) Martínez Reyes, Carolina Del Pilar; Sepúlveda-Zuñiga, Einer; Villagrán, Mauricio; Rojas, Octavio; Gómez, Matias; López, Pablo; Rojas Quezada, Carolina Alejandra; CEDEUS (Chile)The coastal evolution of the microtidal Tubul-Raqui wetland in south-central Chile (36 degrees S), which historically has been affected by large earthquakes and tsunamis, particularly the 1960 (Mw = 9.5) and 2010 (Mw = 8.8) subduction earthquakes and their associated tsunamis, is analyzed. Historical aerial photographs and topographic and bathymetric surveys from the 1961-2017 period, as well as salinity, sediment, and flora data obtained following the 2010 earthquake were used for comparison with data from prior to the event. A steady state of the shoreline was established, with an average erosion rate of -0.016 m/year in the 1961-2017 period. However, erosion predominated in the period between these two large earthquakes (1961-2009), with an average rate of -0.386 m/year. The wetland dried up, partially recovered saline intrusion a year later, and recovered the salinity conditions it had before the earthquake two years later. The postearthquake effects on the floristic composition were not significant, with the species Spartina densiflora, which presented a high tolerance to these types of changes, predominating. Moreover, 75 percent of the taxa in pre- and postearthquake conditions coincided, with the halophyte species Spartina densiflora, Sarcocornia fructicosa, and Cotula coronopifolia predominating, while the best-conserved community was Spartina-Sarcocornia association located in the saltmarsh. Seven years after the earthquake, the shoreline presented an accretion rate of 2.935 m/year; if the current tectonic conditions prevail, an erosive trend can be expected in the coming decades. The morphological variability and the changes associated with the shoreline in this wetland are strongly controlled by tectonic factors. Criteria aimed at integrated coastal management to promote its occupancy and use in accordance with its evolutionary dynamics are proposed.
- ItemCoastal Wetlands: Ecosystems Affected by Urbanization?(2020) Rojas Quezada, Carolina Alejandra; Novoa, Vanessa; Rojas, Octavio; Ahumada-Rudolph, Ramón; Sáez, Katia; Fierro, Pablo; CEDEUS (Chile)Coastal wetlands are ecosystems that provide multiple benefits to human settlements; nonetheless, they are seriously threatened due to both a lack of planning instruments and human activities associated mainly with urban growth. An understanding of their functioning and status is crucial for their protection and conservation. Two wetlands with different degrees of urbanization, Rocuant-Andalién (highly urbanized) and Tubul-Raqui (with little urbanization), were analyzed using temperature, salinity, dissolved oxygen, pH, turbidity, granulometry, fecal coliform, and macroinvertebrate assemblage variables in summer and winter. In both wetlands marked seasonality in salinity, temperature and sediment texture classification, regulated by oceanic influence and changes in the freshwater budget, was observed. In the Rocuant-Andalién wetland, the increases in pH, dissolved oxygen, gravel percentage, and coliform concentration were statistically significant. Urbanization generated negative impacts on macroinvertebrate assemblage structure that inhabit the wetlands; greater richness and abundance (8.5 times greater) were recorded in the Tubul-Raqui wetland than in the more urbanized wetland. The multivariate statistical analysis reflects the alteration of these complex systems.
- ItemFlooding in Central Chile : Implications of Tides and Sea Level Increase in the 21st Century(2018) Rojas, Octavio; Mardones, María; Martínez Reyes, Carolina del Pilar; Flores, Luis; Sáez, Katia
- ItemMapping coastal wetlands using satellite imagery and machine learning in a highly urbanized landscape(2022) Munizaga, Juan; García, Mariano; Ureta, Fernando; Novoa, Vanessa; Rojas, Octavio; Rojas Quezada, Carolina Alejandra; CEDEUS (Chile)Coastal wetlands areas are heterogeneous, highly dynamic areas with complex interactions between terrestrial and marine ecosystems, making them essential for the biosphere and the development of human activities. Remote sensing offers a robust and cost-efficient mean to monitor coastal landscapes. In this paper, we evaluate the potential of using high resolution satellite imagery to classify land cover in a coastal area in Concepción, Chile, using a machine learning (ML) approach. Two machine learning algorithms, Support Vector Machine (SVM) and Random Forest (RF), were evaluated using four different scenarios: (I) using original spectral bands; (II) incorporating spectral indices; (III) adding texture metrics derived from the grey-level covariance co-occurrence matrix (GLCM); and (IV) including topographic variables derived from a digital terrain model. Both methods stand out for their excellent results, reaching an average overall accuracy of 88% for support vector machine and 90% for random forest. However, it is statistically shown that random forest performs better on this type of landscape. Furthermore, incorporating Digital Terrain Model (DTM)-derived metrics and texture measures was critical for the substantial improvement of SVM and RF. Although DTM did not increase the accuracy in SVM, this study makes a methodological contribution to the monitoring and mapping of water bodies’ landscapes in coastal cities with weak governance and data scarcity in coastal management.
- ItemPatrones de urbanización en la biodiversidad de humedales urbanos en Concepción metropolitano(2015) Rojas Quezada, Carolina Alejandra; Sepúlveda Zúñiga, Einer; Barbosa, Olga; Rojas, Octavio; Martínez Reyes, Carolina del Pilar
- ItemRisk factors and perceived restoration in a town destroyed by the 2010 Chile tsunami(2017) Martínez Reyes, Carolina del Pilar; Rojas, Octavio; Villagra, Paula; Aránguiz, Rafael; Sáez Carrillo, Katia
- ItemSpatial interactions between perceived biophilic values and neighborhood typologies in urban wetlands(2024) Villagra, Paula; Rojas Quezada, Carolina Alejandra; Rojas, Octavio; Alves, SusanaWetlands provide a wide range of ecosystem services; however, little is known about their perception value or use for improving urban planning and wetland management. This study explores the perception values towards the Los Batros Wetland in Chile, by inhabitants from different neighborhood typologies. A sample of 457 responses evaluated the wetland by applying the Kellert framework of 9 biophilic values using a Public Participation Geographic Information Systems (PPGIS) approach. A spatial autocorrelation analysis with hotspot revealed that the spatial distribution of biophilic values varies by neighborhood typology. Subsequent ANOVA and T-test suggest that such distribution is affected by perceived accessibility and visitation purposes, and is influenced by socio-demographic aspects that vary among neighborhood typology. Inhabitants of the garden city typology located next to the wetland area, whose residents have higher education and income levels and who have easy and moderate access to the wetland, agreed with a diverse type of biophilic values. In the garden city, the ecologistic-scientific value has the higher spatial concentration. In the condominium typology, with similar education and income levels and accessibility, but situated far from the wetland, there was less agreement with biophilic values, and these were more dispersed, i.e. biophilic values are less representative. In this case, the aesthetic value prevails over others. At the north area of the neighborhood unit, where residents had lower education and income levels along with moderate to difficult physical access to the wetland, but they developed horticultural activities alongside the wetland, inhabitants agree with various biophilic values, highlighting its symbolic value. Conversely, biophilic values of people in the favela were not in agreement nor disagreement, regardless they have similar physical access and distance to the wetland as residents in the condominium typology, but have the lowest income and education level. Findings suggest that effective wetlands management requires appreciation of the clusters of values assigned to wetland environments, which in this case relate to neighborhood typologies. These clusters should be considered when planning to restore, protect, and improve urban wetlands.
- ItemUrban development versus wetland loss in a coastal Latin American city : lessons for sustainable land use planning(2019) Rojas, Carolina; Munizaga, Juan; Rojas, Octavio; Martínez; Reyes, Carolina del Pilar; Pino, Joan; CEDEUS (Chile)
- ItemUrban Growth and Flood Disasters in the Coastal River Basin of South-Central Chile (1943–2011)(2017) Rojas, Octavio; Mardones, María; Rojas, Carolina; Martínez Reyes, Carolina del Pilar; Flores, Luis
- ItemWater footprint and virtual water flows from the Global South: Foundations for sustainable agriculture in periods of drought(2023) Rojas Quezada, Carolina Alejandra; Novoa, Vanessa; Rojas, Octavio; Ahumada-Rudolph, Ramón; Arumí, José Luis; Munizaga, Juan; Cabrera-Pardo, Jaime R.; CEDEUS (Chile)Freshwater availability has decreased alarmingly worldwide, with agriculture playing a vital role in this trend. The assessment of the agricultural water footprint (WFagricultural) and virtual water flows (VWF) is fundamental not only in local water resources management and protection, but also in our understanding of the synergies between local water consumption and global markets. Thus, the WFagricultural – broken down into its components (blue, green, and gray) – of the leading 21 crops (grouped in fruit, legumes, cereals, and vegetables), grown in four basins with the most significant agricultural activity in central Chile was determined, estimated in two consecutive years 2017–2018. In addition, due to their great importance in exports, VWFs were assessed, establishing connections according to their origins and destinations. The results show that the green and gray water footprints increased significantly in the south-central basins, while blue water consumption increased in the basins of the central zone, reflecting an evident WFagricultural transition in accord with latitude and climate conditions. Furthermore, VWF showed an annual increase of 44 %, in about 116 destinations, with Asia, Europe, and North America being the preferred destinations, with annual variations of VWFblue- gray associated with increases in exports of apples, cherries, grapes, blueberries, and walnuts, market preferences and growing areas. The present study is an initial step toward sustainable agriculture in a commodity exporting country, one that is relevant in the exploitation of virtual water yet faces severe water deficit problems, distribution, and local water policies. Therefore, contributing to encouraging the efficiency and value of water in the process of a new institutional framework.