Browsing by Author "Carvajal, Mario A."

Now showing 1 - 14 of 14
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    Analyzing the Spatiotemporal Patterns of Forests Carbon Sink and Sources Between 2000 and 2019
    (2022) Alaniz, Alberto J.; Carvajal, Mario A.; Marquet, Pablo A.; Vergara, Pablo M.; Meneses, Luis; Moreira-Arce, Dario
    Here we present a global time-series of global forest above ground biomass from 2000 to 2019, analyzing spatiotemporal patterns of carbon balance, accounting for losses and gains. We generated a global Above-Ground Biomass (AGB) map for the year 2000 and assessed its correlation with different satellite products. We generated a multi-year analysis of AGB changes at the pixel level was generated, estimating carbon (C) loss and gain. Finally, we estimated the C losses due to forest clearing and wildfires analyzing their trends across biomes and countries. Our results show that the global mean annual loss was 2.88 +/- 0.33 PgC yr(-1), while global mean C gain was 2.95 +/- 0.43 PgC yr(-1), resulting in a neutral to sink behavior of -0.06 +/- 0.58 PgC yr(-1). The mean annual C loss by forest clearing was 1.04 +/- 0.03 PgC yr(-1), with an increasing trend of +0.03 +/- 0.01 PgC yr(-1). Eight biomes and 54 countries showed a significant increasing trend of C loss by forest clearing. Wildfires C losses reached 0.351 +/- 0.02 Pg C yr(-1), representing the 33.71% of forest clearing C losses. Boreal forest presented the highest C losses from wildfires, while significant increasing trends were evidenced in five biomes. We also find increasing trends of wildfire C loss in 20 countries while decreasing trends were identified in 10 countries. Our findings highlight the importance of designing strong policies to halt deforestation as agreed in the recent COP26 and provide information to identify priority areas to start implementing these policies in the short term.
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    Climate-induced tree senescence leads to a transient increase in reproductive success of a large woodpecker species
    (2022) Carvajal, Mario A.; Alaniz, Alberto J.; Vergara, Pablo M.; Hernandez-Valderrama, Carlos; Fierro, Andres; Toledo, Gisela; Gamin, Juan
    Climate change-induced mortality of trees is a concerning phenomenon for global forest ecosystems. The rapid decay and death of long-lived trees can significantly impact forest dynamics, with effects that transmit through ecological networks, becoming more evident in organisms occupying high trophic levels, such as large and spe-cialized woodpecker species. However, understanding how populations of high trophic level species respond to climate change is still a challenge. In this study it was analyzed 32-year data of social groups of the Magellanic Woodpecker (Campephilus magellanicus) in North Patagonia, a region facing increasingly frequent droughts and increased temperatures. A positive trend in the size of woodpecker social groups as a response to climate-induced tree senescence was tested. A causal structural equation model examining climate-tree senescence-woodpecker relationships was used. Increasing nonlinear trends and positive interannual growth rates (>10%) for tree senescence and group size were found. Lowland forest sites had higher levels of tree senescence and more numerous social groups. The causal model supported the positive effect of mean temperature on tree senes-cence and the positive association of woodpeckers with tree senescence. These results provide evidence of a climate-induced increase in tree senescence that causes an increase in the size of woodpecker social groups. It is suggested that accelerated decay and mortality of trees in the northern Patagonian forests will decrease the stocks of deadwood in the long term, threatening the persistence of this large woodpecker species. (c) 2021 Elsevier B.V. All rights reserved.
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    Effects of air pollution and weather on the initial COVID-19 outbreaks in United States, Italy, Spain, and China: A comparative study
    (2023) Alaniz, Alberto J.; Carvajal, Mario A.; Carvajal, Jorge G.; Vergara, Pablo M.
    Contrasting effects have been identified in association of weather (temperature and humidity) and pollutant gases with COVID-19 infection, which could be derived from the influence of lockdowns and season change. The influence of pollutant gases and climate during the initial phases of the pandemic, before the closures and the change of season in the northern hemisphere, is unknown. Here, we used a spatial-temporal Bayesian zero-inflated-Poisson model to test for short-term associations of weather and pollutant gases with the relative risk of COVID-19 disease in China (first outbreak) and the countries with more cases during the initial pandemic (the United States, Spain and Italy), considering also the effects of season and lockdown. We found contrasting association between pollutant gases and COVID-19 risk in the United States, Italy, and Spain, while in China it was negatively associated (except for SO2). COVID-19 risk was positively associated with specific humidity in all countries, while temperature presented a negative effect. Our findings showed that short-term associations of air pollutants with COVID-19 infection vary strongly between countries, while generalized effects of temperature (negative) and humidity (positive) with COVID-19 was found. Our results show novel information about the influence of pollution and weather on the initial outbreaks, which contribute to unravel the mechanisms during the beginning of the pandemic.
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    Environmental and biotic filters interact to shape the coexistence of native and introduced bees in northern Patagonian forests
    (2023) Vergara, Pablo M.; Fierro, Andres; Carvajal, Mario A.; Alaniz, Alberto J.; Zorondo-Rodriguez, Francisco; Cifuentes, Maria C.; Castro, Sergio A.
    Native and introduced species can coexist in rich ecosystems where competition for resources is less intense; however, native species can be excluded from suitable habitats hosting a high abundance of introduced species. To test these hypotheses, we estimated the probability of introduced bees (buff-tailed bumblebees and honeybees) to co-occur and dominate giant bumblebees in forested landscapes of northern Patagonia. We evaluated the effects of 29 remote-sensing variables of forest ecosystems on bee abundance using data from 56 landscapes. Then, we used a probabilistic Bayesian model to estimate the effects of the most important predictors of bee abundance on their co-occurrence and dominance probabilities. Introduced and native bees exhibited heterogeneous and scale-dependent responses to environmental conditions, with only six variables affecting their cooccurrence and dominance probabilities. A high maximum temperature was associated with both a decreased co-occurrence and an increased dominance of introduced bumblebees, and the opposed pattern was found for vegetation continuous fields, an index of canopy continuity. Similar responses were found for the co-occurrence probability of honeybees and giant bumblebees. Thus, species dominance and co-occurrence changed differently along environmental gradients, with co-occurrence increasing as native and introduced species become more abundant. A high dominance of introduced bees in unsuitable habitats suggests interspecific competition is strengthened as resources become scarcer, thus reinforcing the idea that abiotic and biotic filters interact with each other.
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    Increasing importance of heat stress for cattle farming under future global climate scenarios
    (2021) Carvajal, Mario A.; Alaniz, Alberto J.; Gutierrez-Gomez, Constanza; Vergara, Pablo M.; Sejian, Veerasamy; Bozinovic, Francisco
    In the last decades, livestock species have been severely affected by heat stress because of increasing temperatures, which has threatened animal welfare and decreased production. Based on thermal comfort indices and ensemble climate projections, we analyzed the current and future global spatiotemporal patterns of the heat exposure of cattle in 10 agroclimatic zones. The results show that similar to 7% of the global cattle population is currently exposed to dangerous heat conditions. This percentage is projected to increase to similar to 48% before 2100 under a scenario of growing emissions. Tropical agroclimatic zones are expected to face an early increase in the exposure to intense heat before 2050. Heat exposure was negatively correlated with the socioeconomic variables, showing that poor and livestock-dependent tropical countries are the most affected. Our results demonstrate the near future consequences of heat stress on livestock, emphasizing the limited time available to implement effective abatement strategies. (C) 2021 Elsevier B.V. All rights reserved.
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    Multiple environmental drivers for the Patagonian forest-dwelling beetles: Contrasting functional and taxonomic responses across strata and trophic guilds
    (2022) Vergara, Pablo M.; Fierro, Andres; Carvajal, Mario A.; Alaniz, Alberto J.; Quiroz, Madelaine
    changes in forest-dwelling beetle communities. However, the effects of multiple environmental factors can be complex to detect in ecosystems that offer a broad variety of microhabitats for a great variety of beetle species. This is the case in Patagonian temperate forests, where the use of remote sensing provides an opportunity to evaluate the sensitivity of beetle species to environmental changes. Here, we identified the environmental drivers of forest-dwelling beetle communities in the ground and canopy of 34 north Patagonian-forest landscapes. We analyzed the associations of the taxonomic and functional diversity of five trophic guilds with 30 remote-sensing variables of landscape structure, composition, and disturbances; vegetation and soil properties; and climate and physical variables. Hierarchical clustering analysis was used to identify trophic guilds responding similarly to predictors. Segmented regression analysis was used to evaluate functional redundancy from taxonomic-functional richness relationships. A total of 583 species (23,848 individuals) of beetles were recorded for both strata. The effects of environmental variables were heterogeneous across strata and guilds. Canopy beetles were especially sensitive to early successional conditions, and canopy attributes, but also benefited from the canopy openness. Forest specialists of the ground and canopy responded differently to environmental variables. Ground-dwelling beetles were mostly affected by fires, human modifications, edge closeness, high temperatures, and soil properties, responding weakly to canopy properties. Functional redundancy
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    Multiscale spatial analysis of headwater vulnerability in South-Central Chile reveals a high threat due to deforestation and climate change
    (2022) Alaniz, Alberto J.; Smith-Ramirez, Cecilia; Rendon-Funes, Adriana; Hidalgo-Corrotea, Claudia; Carvajal, Mario A.; Vergara, Pablo M.; Fuentes, Norka
    Headwaters represent an essential component of hydrological, ecological, and socioeconomical systems, by providing constant water streams to the complete basin. However, despite the high importance of headwaters, there is a lack of vulnerability assessments worldwide. Identifying headwaters and their vulnerability in a spatially explicit manner can enable restauration and conservation programs. In this study, we assess the vulnerability of headwaters in South -Central Chile (38.4 to 43.2 degrees S) considering multiple degradation factors related to climate change and land cover change. We analyzed 2292 headwaters, characterizing multiple factors at five spatial scales by using remote sensing data related to Land Use and Cover Change (LUCC), human disturbances, vegetation cover, climate change, potential water demand, and physiography. We then generated an index of vulnerability by integrating all the analyzed vari-ables, which allowed us to map the spatial distribution of headwater vulnerability. Finally, to estimate the main drivers of degradation, we performed a Principal Components Analysis with an Agglomerative Hierarchical Clustering, that allowed us to group headwaters according to the analyzed factors. The largest proportion of most vulnerable headwa-ters are located in the north of our study area with 48.1 %, 62.1 %, and 28.1 % of headwaters classified as highly vul-nerable at 0, 10, and 30 m scale, respectively. The largest proportion of headwaters are affected by Climate Change (63.66 %) and LUCC (23.02 %) on average across all scales. However, we identified three clusters, in which the north-ern cluster is mainly affected by LUCC, while the Andean and Coastal clusters are mainly affected by climate change. Our results and methods present an informative picture of the current state of headwater vulnerability, identifying spa-tial patterns and drivers at multiple scales. We believe that the approach developed in this study could be useful for new studies in other zones of the world and can also promote Chilean headwater conservation.
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    Native bees in Mediterranean semi-arid agroecosystems: Unravelling the effects of biophysical habitat, floral resource, and honeybees
    (2021) Rodriguez, Sharon S.; Perez-Giraldo, Laura C.; Vergara, Pablo M.; Carvajal, Mario A.; Alaniz, Alberto J.
    The sustainable provision of pollination services in large regions of the Nearctic and Neotropics usually involves the coexistence of a rich assemblage of native bees and introduced bees in the same agroecosystem. This requires identifying biotic and abiotic conditions that improve the quality of semi-natural habitats surrounding agricultural crops aiming to enhance native bee survival. Here we unravel the contribution of habitat conditions, diversity of flowering plants, and honeybee abundance to the taxonomic diversity, flower visitation rates and functional trait distribution of native bees. We have selected three 1.2 km diameter experimental landscapes in a Mediterranean semi-arid agroecosystem of Central Chile, where wild bees, honeybees, and flowering plants were sampled in 83 10 x 10 m plots. The effects of eleven remote-sensing indices characterizing the habitat conditions, and their interactions with honeybee abundance have been analysed. Native bees were taxonomically richer in semi-natural habitats, with higher surface temperatures and near citrus crops. The flower visitation rates of native bees were positively affected by canopy closure and decreased in sites with a higher terrain slope. Highlands had lower honeybee abundance and native bees were more specialized. We found higher flower visitation rates of native bees on large patches with low abundance of honeybees and small patches with high abundance of honeybees. Visitation rate was also higher in sites with high flowering plant richness and with high abundance of honeybees. These findings suggest that native bees and honeybees differ in their habitat use and flowering resources. This partitioning may enhance, coexistence between these pollinator groups. We suggest that management of Mediterranean agroecosystems be focused on increasing forest canopy closure on the remnants of semi-natural habitats, while maintaining the flower diversity near crops and highlands.
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    Perspectives on the timing of ecosystem collapse in a changing climate
    (2024) Alaniz, Alberto J.; Marquet, Pablo A.; Carvajal, Mario A.; Vergara, Pablo M.; Moreira-Arce, Dario; Muzzio, Miguel A.; Keith, David A.
    Climate change is one of the most important drivers of ecosystem change, the global-scale impacts of which will intensify over the next 2 decades. Estimating the timing of unprecedented changes is not only challenging but is of great importance for the development of ecosystem conservation guidelines. Time of emergence (ToE) (point at which climate change can be differentiated from a previous climate), a widely applied concept in climatology studies, provides a robust but unexplored approach for assessing the risk of ecosystem collapse, as described by the C criterion of the International Union for Conservation of Nature's Red List of Ecosystems (RLE). We identified 3 main theoretical considerations of ToE for RLE assessment (degree of stability, multifactorial instead of one-dimensional analyses, and hallmarks of ecosystem collapse) and 4 sources of uncertainty when applying ToE methodology (intermodel spread, historical reference period, consensus among variables, and consideration of different scenarios), which aims to avoid misuse and errors while promoting a proper application of the framework by scientists and practitioners. The incorporation of ToE for the RLE assessments adds important information for conservation priority setting that allows prediction of changes within and beyond the time frames proposed by the RLE.
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    Rapid behavioral recovery based on environmental enrichment of a white-throated toucan (Ramphastos tucanus: Ramphastidae) affected by collision trauma
    (2022) Alaniz, Alberto J.; Astudillo-Hinojosa, Karina; Soto, Ana Francisca; Vergara, Pablo M.; Carvajal, Mario A.; Moreira-Arce, Dario
    Captive animals that have experienced traumatic events require a high range of care prior to reintro-ducing them into their natural habitat; and this care should ensure their welfare in captivity. This re-port shows the ethological evolution of beneficial effects attributed to environmental enrichment. Specif-ically, the report focuses on the recovery of a white-throated toucan (Ramphastos tucanus: Ramphastidae) affected by a collision trauma resulting in a skull fracture, which received treatment and care in the Taricaya wildlife rescue center (Madre Selva, Peru). An environmental enrichment protocol was imple-mented for 30 days, recording all activities during this period. We performed generalized linear models to identify significant trends in the observed activities. We showed that inactive time and self-mutilation significantly decreased, while walking, eating, and washing activities increased during the study period. Temporal improvement in toucan welfare may be associated with higher energy (walking), better nutri-tion (eating), and decreased stress, as shown by reduced self-mutilation. Our report provides evidence on the favorable outcome of environmental enrichment in a toucan, raising its importance as a management tool for veterinary practitioners in wildlife rescue centers. (c) 2022 Elsevier Inc. All rights reserved.
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    Remote-sensing estimates of forest structure and dynamics as indicators of habitat quality for Magellanic woodpeckers
    (2021) Alaniz, Alberto J.; Carvajal, Mario A.; Fierro, Andres; Vergara-Rodriguez, Valentina; Toledo, Gisela; Ansaldo, Diego; Moreira-Arce, Dario; Rojas-Osorio, Alejandro; Vergara, Pablo M.
    Bridging remote-sensing ecosystem indices with biodiversity conservation implies converting these indices into habitat quality indicators for species playing an important role in communities and ecosystems, such as woodpeckers. However, an ecologically reliable estimation of habitat quality necessarily involves an assessment of fitness components ultimately responsible for population persistence. Here, we assessed the relationship between remote-sensing indices of forest structure, dynamics and composition with the breeding performance of Magellanic woodpeckers in conservation areas of southern Chile. We used a Bayesian-spatial model based on age and sex information from woodpecker?s social group data collected seasonally in seven years. The probability of a young remaining in the group decreased with the mean group size during the previous year, with group size fluctuating temporally in all conservation areas. Tree senescence had a positive effect on the pairing probability of woodpeckers, but this effect became more marked in sites of higher altitude. Paired woodpeckers were more likely to be observed in sites supporting more than 69% of forest cover. The probability of the young remaining in the territory was positively affected by the interaction between forest canopy continuity and altitude, with retention of the young being more likely in sites located higher than 1000 masl. Social groups were larger in sites where the continuity of canopy increased over time. Those findings suggest that remote sensing indices representing the structure and dynamics of forest ecosystems are important indicators of the habitat quality for woodpeckers. Thus, forest biodiversity that depends on the woodpecker?s engineering function may be conserved through the retention of senescent trees and the maintaining of critical levels of forest cover ensuring high habitat-quality for breeding woodpeckers.
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    Unraveling the socio-environmental drivers during the early COVID-19 pandemic in China
    (2023) Alaniz, Alberto J.; Vergara, Pablo M.; Carvajal, Jorge G.; Carvajal, Mario A.
    The effect of environmental and socioeconomic conditions on the global pandemic of COVID-19 had been widely studied, yet their influence during the early outbreak remains less explored. Unraveling these relationships represents a key knowledge to prevent potential outbreaks of similar pathogens in the future. This study aims to determine the influence of socioeconomic, infrastructure, air pollution, and weather variables on the relative risk of infection in the initial phase of the COVID-19 pandemic in China. A spatio-temporal Bayesian zero-inflated Poisson model is used to test for the effect of 13 socioeconomic, urban infrastructure, air pollution, and weather variables on the relative risk of COVID-19 disease in 122 cities of China. The results show that socioeconomic and urban infrastructure variables did not have a significant effect on the relative risk of COVID-19. Meanwhile, COVID-19 relative risk was negatively associated with temperature, wind speed, and carbon monoxide, while nitrous dioxide and the human modification index presented a positive effect. Pollution gases presented a marked variability during the study period, showing a decrease of CO. These findings suggest that controlling and monitoring urban emissions of pollutant gases is a key factor for the reduction of risk derived from COVID-19.
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    Unravelling the cavity-nesting network at large spatial scales: The biogeographic role of woodpeckers as ecosystem engineers
    (2024) Alaniz, Alberto J.; Carvajal, Mario A.; Quiroz, Madelaine; Vergara, Pablo M.; Marquet, Pablo A.; Fierro, Andres; Sieving, Kathryn E.; Moreira-Arce, Dario; Hidalgo-Corrotea, Claudia; Rodriguez-San Pedro, Annia; Allendes, Luis; Machuca, Katerine
    AimPrimary cavity nesters (e.g. woodpeckers) act as ecosystem engineers by providing tree cavities to several vertebrates that use them as nests or refuges. Although diverse assemblages of primary excavators are assumed to increase the number of tree cavities, environmental factors can limit populations of primary excavators, thus weakening their ecological function. We aim to test the biogeographical-scale relationships between primary excavators and cavity users by distinguishing the contribution of environmental variables.LocationSouthern South America.Materials and MethodsWe used species distribution models, which combine bioclimatic and remote sensing derived variables, to map the richness of vertebrates composing the cavity-network of temperate and Mediterranean forests of South America. Based on a resampling procedure for ensuring spatial independence, we fitted structural equation models to estimate relationships between forest characteristics and cavity user vertebrates.ResultsRichness of secondary cavity users (mammals, obligated, habitat generalists and forest specialists) were positively and strongly influenced by the richness of primary excavators. Environmental variables affected differently the richness of primary and secondary cavity users. The richness of primary cavity users responded to tree richness and height while that of habitat specialist secondary users was positively affected by primary productivity and negatively by sclerophyll forests.Main ConclusionsOur results confirm the role of primary excavators as ecosystem engineers but highlight the importance of considering large spatial scales when analysing cavity-nesting networks. Biogeographical patterns of tree diversity and forest structure can be important drivers of cavity nesting networks that remain hidden when studies are conducted over fine spatial scales.
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    Using sonic tomography to assess the relationship between internal wood decay and saproxylic beetle communities
    (2022) Vergara, Pablo M.; Fierro, Andres; Carvajal, Mario A.; Alaniz, Alberto J.
    Although wood-inhabiting beetle species are known to contribute to the progressive degradation of wood by building larval galleries and dispersing fungal propagules, the relationship between decaying wood and beetle communities is difficult to be assessed. The ecological properties of trees, such as their mortality status and species, could modify the relationships between beetle communities and decaying wood. We used recently developed techniques of sonic tomography for the first time to address how the trophic structure of beetle communities varies with the internal wood decay. We developed a paired design where sonic tomograms taken in the trunk sections of live and dead trees of the Patagonian forest were related with beetles sampled with emergence traps. Beetles captured in the trunks of live trees responded weakly to the internal wood decay. Indeed, the diversity of predators in live trees was likely influenced by bark microhabitats. Conversely, most of the guild assemblages in the trunks of dead trees were impoverished as wood decay was more advanced, possibly due to decreasing microhabitat quality. Our preliminary study suggests sonic tomography offers the opportunity to distinguish how beetles modulate decaying wood, but also provides insights about the assessment of live trees with tomograms. (C) 2022 The Author(s). Published by Elsevier B.V.