Linear infrastructures, especially roads, affect the integrity of natural habitats worldwide. Roads act as a barrier to animal movement, cause mortality, decrease gene flow and increase the probability of local extinctions, particularly for arboreal species. Arboreal wildlife bridges increase connectivity of fragmented forests by allowing wildlife to safely traverse roads. However, the majority of studies about such infrastructure are from Australia, while information on lowland tropical rainforest systems in Meso and South America remains sparse. To better facilitate potential movement between forest areas for the arboreal wildlife community of Costa Rica’s Osa Peninsula, we installed and monitored the early use of 12 arboreal wildlife bridges of three different designs (single rope, double rope, and ladder bridges). We show that during the first 6 months of monitoring via camera traps, 7 of the 12 bridges were used, and all bridge designs experienced wildlife activity (mammals crossing and birds perching). A total of 5 mammal species crossing and 3 bird species perching were observed. In addition to preliminary results of wildlife usage, we also provide technical information on the bridge site selection process, bridge construction steps, installation time, and overall associated costs of each design. Finally, we highlight aspects to be tested in the future, including additional bridge designs, monitoring approaches, and the use of wildlife attractants.

As biodiversity declines and climate change causes shifts in species distribution, the knowledge of species' ecological needs is vital to conserve biodiversity. On Costa Rica's Osa Peninsula and its adjacent forests, a rich mosaic of ecosystems hosting numerous threatened and endemic species, conservationists lack clarity on the basic habitat requirements of the endemic Black-cheeked Ant-Tanager (Habia atrimaxillaris). Numerous attempts have been made to understand its habitat requirements, resulting in contradictory conclusions. This study integrates new field data, thousands of community science observations, and comments in historical literature ranging over 50 years to complement the more localized studies. We explore the species' habitat requirements, diet, and distribution in protected areas and biological corridors to better understand the species' conservation needs and, in doing so, suggest a strategy to protect the Black-cheeked Ant-Tanager in a changing climate. We illustrate that Black-cheeked Ant-Tanagers occur in secondary forests, which they also use for foraging and nesting, suggesting that the conservation and restoration of secondary forests may help protect this range-restricted forest bird, especially through a targeted conservation strategy within biological corridors to build connectivity with higher elevations.RESUMEN. A medida que la biodiversidad disminuye y el cambio del clima causa cambios en las distribuciones de las especies, el conocimiento de las necesidades ecológicas de las especies es vital para la conservación de la biodiversidad. En la península de Osa en Costa Rica y sus bosques adyacentes, un mosaico diverso de ecosistemas en el cual habitan un alto número de especies amenazadas y endémicas, los conservacionistas no tienen claridad de los requerimientos básicos de hábitat de la especie endémica Estrategias de conservación resilientes al clima para un ave de bosque endémica, Habia atrimaxillaris. Ha habido muchos intentos para entender sus requerimientos de hábitat, con resultados contradictorios. Este estudio integra nueva información de campo, miles de observaciones de ciencia comunitaria y comentarios en la literatura histórica con un rango de más de 50 años para complementar los estudios más localizados. Exploramos los requerimientos de hábitat de la especie, su dieta y la distribución en áreas protegidas y corredores biológicos con el fin de comprender mejor las necesidades de conservación de la especie y sugerir una estrategia para proteger a Habia atrimaxillaris en un clima cambiante. Mostramos que Habia atrimaxillaris ocurre en bosques secundarios, los cuales también usan para forrajear y anidar, sugiriendo que la conservación y la restauración de bosques secundarios puede ayudar a proteger esta especie de ave de bosque con un rango restringido, especialmente a través de estrategias de conservación focalizadas dentro de corredores biológicos para construir conectividad con elevaciones mayores.

The carbon cycle in East Lake (Newberry Volcano, Oregon, USA) is fueled by volcanic CO2 inputs with traces of Hg and H2S. The CO2 dissolves in deep lake waters and is removed in shallow waters through largely diffusive surface degassing and photosynthesis. Escaping gas and photosynthate have low δ13C values, leading to δ13C(DIC) (DIC—dissolved inorganic carbon) as high as +5.7‰ in surface waters, well above the common global lake range. A steep δ13C depth gradient is further established by respiration and absorption of light volcanic CO2 in bottom waters. The seasonal CO2 degassing starts at >100 t CO2/day after ice melting in the spring and declines to ~40 t/day in late summer, degassing ~11,700 t CO2/yr. Thus, volcano monitoring through gas fluxes from crater lakes should consider lacustrine processes that modulate the volcanic gas output over time. The flux contribution of a bubbling CO2 “hotspot” increased from 20% to >90% of the lake-wide CO2 flux from 2015 to 2019 CE, followed by a “toxic gas alert” in July 2020. East Lake is an active volcanic lake with a “geogenic” ecosystem driven primarily by hydrothermal inputs.

East Lake and Paulina Lake are twin crater lakes in the Newberry caldera, near Bend, Oregon. Despite their proximity, the lakes are chemically different: CO 2 and H 2 S inputs in East Lake, and hot carbonate-rich fluids in Paulina Lake. Paulina Lake has four times the concentration of dissolved species as East Lake. Dissolved carbon in East Lake is isotopically much heavier (up to +5.5‰) than in Paulina Lake (0‰). Both lakes have internal P CO2 > P CO2 (atm), leading to diffusive CO 2 loss from the lake surfaces. The carbon budgets are different for the two lakes, and this study focuses on the carbon cycling in East Lake, which involves geothermal CO 2 input, diffusive CO 2 losses from the lake surface, no CO 2 uptake from the atmosphere, photosynthesis, respiration, and organic carbon burial. The isotopic composition and C:N of East Lake sediment indicates that buried organic matter is ~45% phytoplankton, 35% subaqueous vegetation, 15% cyanobacteria, and 5% pine needles. East Lake has a strong vertical δ 13 C (DIC) gradient (up to 5‰), because volcanic and biological sources and sinks of carbon in East Lake cause identical trends in DIC concentration and isotopic composition with depth. Isotopically light geothermal CO 2 enters the bottom water and evades from the surface waters (-10.5‰ δ 13 C), while isotopically light organic carbon is removed from surface waters and falls to bottom waters through the photosynthetic-respiration loop. Field flux measurements, sequential Gaussian simulations, and models indicate that both Newberry lakes evade CO 2 at comparable rates for volcanic lakes with similar surface areas and that CO 2 flux rates are highest in the early summer. East Lake evaded an average of ~71 tonnes of CO 2 per day in early June 2016, compared to ~45 tonnes of