Southern Annular Mode drives multicentury wildfire activity in southern South America.

The Southern Annular Mode (SAM) is the main driver of climate variability at mid to high latitudes in the Southern Hemisphere, affecting wildfire activity, which in turn pollutes the air and contributes to human health problems and mortality, and potentially provides strong feedback to the climate system through emissions and land cover changes. Here we report the largest Southern Hemisphere network of annually resolved tree ring fire histories, consisting of 1,767 fire-scarred trees from 97 sites (from 22 °S to 54 °S) in southern South America (SAS), to quantify the coupling of SAM and regional wildfire variability using recently created multicentury proxy indices of SAM for the years 1531-2010 AD. We show that at interannual time scales, as well as at multidecadal time scales across 37-54 °S, latitudinal gradient elevated wildfire activity is synchronous with positive phases of the SAM over the years 1665-1995. Positive phases of the SAM are associated primarily with warm conditions in these biomass-rich forests, in which widespread fire activity depends on fuel desiccation. Climate modeling studies indicate that greenhouse gases will force SAM into its positive phase even if stratospheric ozone returns to normal levels, so that climate conditions conducive to widespread fire activity in SAS will continue throughout the 21st century.

Woody vegetation dynamics in the tropical and subtropical Andes from 2001 to 2014: Satellite image interpretation and expert validation.

The interactions between climate and land-use change are dictating the distribution of flora and fauna and reshuffling biotic community composition around the world. Tropical mountains are particularly sensitive because they often have a high human population density, a long history of agriculture, range-restricted species, and high-beta diversity due to a steep elevation gradient. Here we evaluated the change in distribution of woody vegetation in the tropical Andes of South America for the period 2001-2014. For the analyses we created annual land-cover/land-use maps using MODIS satellite data at 250 m pixel resolution, calculated the cover of woody vegetation (trees and shrubs) in 9,274 hexagons of 115.47 km2 , and then determined if there was a statistically significant (p < 0.05) 14 year linear trend (positive-forest gain, negative-forest loss) within each hexagon. Of the 1,308 hexagons with significant trends, 36.6% (n = 479) lost forests and 63.4% (n = 829) gained forests. We estimated an overall net gain of ~500,000 ha in woody vegetation. Forest loss dominated the 1,000-1,499 m elevation zone and forest gain dominated above 1,500 m. The most important transitions were forest loss at lower elevations for pastures and croplands, forest gain in abandoned pastures and cropland in mid-elevation areas, and shrub encroachment into highland grasslands. Expert validation confirmed the observed trends, but some areas of apparent forest gain were associated with new shade coffee, pine, or eucalypt plantations. In addition, after controlling for elevation and country, forest gain was associated with a decline in the rural population. Although we document an overall gain in forest cover, the recent reversal of forest gains in Colombia demonstrates that these coupled natural-human systems are highly dynamic and there is an urgent need of a regional real-time land-use, biodiversity, and ecosystem services monitoring network.

Amphibian malformations and body condition across an agricultural landscape of northwest Argentina.

Agricultural landscapes support large amphibian populations because they provide habitat for many species, although agriculture affects amphibians through various mechanisms. Pollution with agrochemicals is the major threat to amphibian populations after habitat loss, as chemicals alter the ecophysiology of amphibians, putting their health and survival at risk. We aimed to assess the effect of different environments, sites, width of forest buffers and sampling years on the health of amphibians, which was estimated through the prevalence of malformations and body condition. During 3 yr of pitfall trapping, we captured 4491 amphibians. The prevalence of malformations was higher in the croplands than in the forests, while the body condition was better within forests. The prevalence of malformations was higher in the narrower forest site than in the wider forest site. The prevalence of malformations and the body condition were higher in the third year. The prevalence of malformations differed by species. We found 11 types of malformation, which mainly affected limbs and were unilateral or bilaterally asymmetrical. Our results showed that the prevalence of malformations and body condition reflect different aspects of the health of amphibians and that forest individuals are healthier than those from croplands. The results also highlight the importance of spatial configuration besides the conservation of natural habitats to preserve healthy amphibians in agricultural landscapes. The types of malformation that we found suggest that agrochemicals could be an important cause of malformations.

Hydroclimate and vegetation variability of high Andean ecosystems.

Mountain ecosystems are sensitive to climate fluctuations; however, the scarcity of instrumental data makes necessary the use of complementary information to study the effect of climate change on these systems. Remote sensing permits studying the dynamics of vegetation productivity and wetlands in response to climate variability at different scales. In this study we identified the main climate variables that control vegetation dynamics and water balance in Cumbres Calchaquíes, NW Argentina. For this, we built annual time series from 1986 to 2019 of Soil Adjusted Vegetation Index (SAVI, to quantify spare vegetation productivity), lake area, and snow-ice cover of peatlands, as indicators of mountain productivity and hydrology. We used a decompose function to explore trend, seasonality and random signal of the three-time series, and explored for significant changes in the mean value of consecutive periods. We used correlational analysis to explore their associations with climate records at local, regional, and global scales. The results showed that, SAVI and hydrological indicators presented different fluctuation patterns more pronounced since 2012, when they showed divergent trends with increasing SAVI and decreasing lake area and snow-ice cover. The three indicators responded differently to climate; SAVI increased in warmer years and lake area reflected the water balance of previous years. Snow-ice cover of peatlands was highly correlated with lake area. La Niña had a positive effect on lake area and snow-ice cover and a negative on SAVI, while El Niño had a negative effect on SAVI. Fluctuations of lake areas were synchronized with lake area in the nearby Argentinian puna, suggesting that climate signals have regional extent. The information provided by the three hydroclimate indicators is complementary and reflects different climate components and processes; biological processes (SAVI), physical processes (snow ice cover) and their combination (lake area). This study provides a systematic accessible replicable tool for mountain eco-hydrology long-term monitoring.

Counterurbanization: A neglected pathway of forest transition.

Human settlement into rural areas (counterurbanization) is generating new patterns of reforestation, with distinctive features compared to the previously considered pathways of forest transition through "economic development" and "forest scarcity". Here, we discuss the specific features of this neglected pathway of forest recovery and describe the process with the support of study cases around the world. This pathway includes specific motivations (e.g., natural amenities, outdoor recreation), particular socio-economic processes, conflicts between newcomers and locals, and specific ecological outcomes (e.g., a larger proportion of non-native species in the new forests). Although this pathway locally affects small areas, as a widespread and expanding process around the world, counterurbanization could have a growing global effect, with the potential to modify biodiversity, ecosystem services, and cultural values. These novel characteristics should be further explored to better understand the patterns and processes of forest transitions in a context of a globally connected world.

Movement and joints: effects of overuse on anuran knee tissues.

Movement plays a main role in the correct development of joint tissues. In tetrapods, changes in normal movements produce alterations of such tissues during the ontogeny and in adult stages. The knee-joint is ideal for observing the influence of movement disorders, due to biomechanical properties of its components, which are involved in load transmission. We analyze the reaction of knee tissues under extreme exercise in juveniles and adults of five species of anurans with different locomotor modes. We use anurans as the case study because they undergo great mechanical stress during locomotion. We predicted that (a) knee tissues subjected to overuse will suffer a structural disorganization process; (b) adults will experience deeper morphological changes than juveniles; and (c) morphological changes will be higher in jumpers compared to walkers. To address these questions, we stimulated specimens on a treadmill belt during 2 months. We performed histological analyses of the knee of both treated and control specimens. As we expected, overuse caused structural changes in knee tissues. These alterations were gradual and higher in adults, and similar between jumpers and walkers species. This study represents a first approach to the understanding of the dynamics of anuran knee tissues during the ontogeny, and in relation to locomotion. Interestingly, the alterations found were similar to those observed in anurans subjected to reduced mobility and also to those described in joint diseases (i.e., osteoarthritis and tendinosis) in mammals, suggesting that among tetrapods, changes in movement generate similar responses in the tissues involved.

COVID-19 Y su relación con factores sociodemográficos en la etapa pre-vacunatoria, provincia de Tucumán, Argentina, 2020-2021 / COVID-19 and its relationship with sociodemographic factors in the pre-vaccination period in Tucumán Province, Argentina, 2020-2021

RESUMEN INTRODUCCIÓN El impacto de COVID-19 en una población puede explicarse a través de los factores sociodemográficos y las respuestas de intervención. El objetivo fue evaluarlo en la provincia de Tucumán en la etapa previa a la vacunación. Se analizó la incidencia, letalidad y mortalidad de COVID-19 a nivel provincial y departamental, y se identificaron los factores sociodemográficos asociados. MÉTODOS Se realizó un estudio observacional de tipo ecológico con fuentes de datos secundarias en Tucumán. El período fue de marzo de 2020 a marzo de 2021. RESULTADOS Se registró una tasa de incidencia de COVID-19 de 4941 por 100 000 habitantes y una tasa de mortalidad de 93,29 por 100 000 habitantes. La incidencia de casos fue similar en varones y mujeres, y el grupo de 30 a 49 años presentó las tasas más altas. La tasa de mortalidad y letalidad en varones fue mayor que en mujeres, y en ambos sexos el grupo de 80 años o más presentó las mayores tasas. A nivel departamental, Capital, Tafí Viejo, Cruz Alta y Yerba Buena tuvieron las tasas de incidencia más altas. Burruyacú, Monteros y Trancas registraron las mayores tasas de mortalidad y letalidad. La incidencia de casos se vio afectada por la densidad poblacional y por el porcentaje de personas en hogares con alguna necesidad básica insatisfecha. DISCUSIÓN Se resalta la importancia de conocer la estructura, funcionalidad e identidad de las ciudades para comprender mejor su capacidad de resiliencia y adaptación frente a eventos como COVID-19.

ABSTRACT INTRODUCTION The population impact of COVID-19 can be explained by socio-demographic factors and the intervention responses. The objective was to evaluate it in the province of Tucumán in the pre-vaccination stage. Incidence, lethality and mortality of COVID-19 at province and department level were analyzed, identifying associated socio-demographic factors. METHODS An observational ecological study was conducted in Tucumán using secondary data sources. The period of study was from March 2020 to March 2021. RESULTS There was an incidence rate of COVID-19 of 4941 per 100000 inhabitants and a mortality rate of 93.29 per 100000 inhabitants. The incidence of cases was similar among males and females, and the age group between 30 and 49 years showed the highest rates. Mortality and lethality were higher in men than in women, and in both sexes the age group of 80 years and over presented the highest rates. At department level, Capital, Tafí Viejo, Cruz Alta and Yerba Buena had the highest incidence rates. Burruyacú, Monteros and Trancas had the highest mortality and lethality rates. The incidence of cases was affected by population density and by the percentage of people living in households with an unsatisfied basic need. DISCUSSION This work highlights the importance of knowing the structure, functionality and identity of cities to better understand their resilience and adaptation capacity in the face of events such as COVID-19.

Environmental, land cover and land use constraints on the distributional patterns of anurans: Leptodacylus species (Anura, Leptodactylidae) from Dry Chaco.

Subtropical dry forests are among the most vulnerable biomes to land transformation at a global scale. Among them, the Dry Chaco suffers an accelerated change due to agriculture expansion and intensification. The Dry Chaco ecoregion is characterized by high levels of endemisms and species diversity, which are the result of a variety of climates and reliefs, allowing a wide variety of environments. The amphibian group exhibits a high richness in the Dry Chaco, which has been barely studied in relation to land cover changes. We used ecological niche models (ENMs) to assess the potential geographic distribution of 10 Leptodactylus species (Anura, Leptodactylidae), which are mainly distributed within the Dry Chaco. We characterized these distributions environmentally, analyzed their overlap with land cover classes, and assessed their diversity of ecoregions. Also, we evaluated how these species potential distribution is affected by the transformation of land, and quantified the proportional area of the potential distribution in protected areas. We found that temperature seasonality is the main constraint to the occurrence of the species studied, whose main habitats are savannas, grasslands and croplands. The main threats to these species are the effects of climate change over spatial patterns of seasonality, which could affect their breeding and reproduction mode; the loss of their natural habitat; the exposure to contaminants used by intensive agriculture and their underrepresentation in protected areas.