Increased wildfire risk driven by climate and development interactions in the Bolivian Chiquitania, Southern Amazonia.

This is the final version of the article. Available from the publisher via the DOI in this record.Wildfires are becoming increasingly dominant in tropical landscapes due to reinforcing feedbacks between land cover change and more severe dry conditions. This study focused on the Bolivian Chiquitania, a region located at the southern edge of Amazonia. The extensive, unique and well-conserved tropical dry forest in this region is susceptible to wildfires due to a marked seasonality. We used a novel approach to assess fire risk at the regional level driven by different development trajectories interacting with changing climatic conditions. Possible future risk scenarios were simulated using maximum entropy modelling with presence-only data, combining land cover, anthropogenic and climatic variables. We found that important determinants of fire risk in the region are distance to roads, recent deforestation and density of human settlements. Severely dry conditions alone increased the area of high fire risk by 69%, affecting all categories of land use and land cover. Interactions between extreme dry conditions and rapid frontier expansion further increased fire risk, resulting in potential biomass loss of 2.44±0.8 Tg in high risk area, about 1.8 times higher than the estimates for the 2010 drought. These interactions showed particularly high fire risk in land used for 'extensive cattle ranching', 'agro-silvopastoral use' and 'intensive cattle ranching and agriculture'. These findings have serious implications for subsistence activities and the economy in the Chiquitania, which greatly depend on the forestry, agriculture and livestock sectors. Results are particularly concerning if considering the current development policies promoting frontier expansion. Departmental protected areas inhibited wildfires when strategically established in areas of high risk, even under drought conditions. However, further research is needed to assess their effectiveness accounting for more specific contextual factors. This novel and simple modelling approach can inform fire and land management decisions in the Chiquitania and other tropical forest landscapes to better anticipate and manage large wildfires in the future.The author(s) received no specific funding for this research. The study was mostly self-funded by the corresponding author TD as part of her PhD thesis. TD was supported by the Santander Academic Travel Award to visit INPE as part of this study

Pluto's lower atmosphere and pressure evolution from ground-based stellar occultations, 1988-2016

Context. The tenuous nitrogen (N2) atmosphere on Pluto undergoes strong seasonal effects due to high obliquity and orbital eccentricity, and has recently (July 2015) been observed by the New Horizons spacecraft. Aims. The main goals of this study are (i) to construct a well calibrated record of the seasonal evolution of surface pressure on Pluto and (ii) to constrain the structure of the lower atmosphere using a central flash observed in 2015. Methods. Eleven stellar occultations by Pluto observed between 2002 and 2016 are used to retrieve atmospheric profiles (density, pressure, temperature) between altitude levels of ~5 and ~380 km (i.e. pressures from ~ 10 μbar to 10 nbar). Results. (i) Pressure has suffered a monotonic increase from 1988 to 2016, that is compared to a seasonal volatile transport model, from which tight constraints on a combination of albedo and emissivity of N2 ice are derived. (ii) A central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that (a) large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or (b) hazes with tangential optical depth of ~0.3 are present at 4–7 km altitude levels; and/or (c) the nominal REX density values are overestimated by an implausibly large factor of ~20%; and/or (d) higher terrains block part of the flash in the Charon facing hemisphere

Diseño y caracterización de un corredor biológico entre los bosques nublados de Uyuca y El Volcán

89 p.Devisscher, Tahia. 2004. Diseño y caracterización de un corredor biológico entre los bosques nublados de Uyuca y El Volcán. Proyecto de Graduación del Programa de Ingeniería en Desarrollo Socioeconómico y Ambiente, Zamorano, Honduras. 89 p. Los esfuerzos de conservación de la diversidad biológica en Honduras se han concentrado en las áreas protegidas y particularmente en sus zonas núcleo, generándose una degradación gradual de las zonas de amortiguamiento y la cobertura boscosa entre estas áreas. Es aceptado como regla generalizada que el mayor y más serio riesgo para la conservación de la biodiversidad es la fragmentación de los hábitats. Los bosques de galería en el Valle del Yeguare, que unen los bosques nublados de los cerros de Uyuca y El Volcán, presentan esta fragmentación, pues se han visto afectados a lo largo del tiempo por diferentes factores, tanto naturales como antrópicos. Como iniciativa para proteger la biodiversidad de estos bosques y la de los bosques nublados se ha diseñado un corredor biológico que une las zonas núcleo de los cerros Uyuca y El Volcán. Esto permitirá mantener la conectividad natural del paisaje y el movimiento entre parches de hábitats. Con ayuda de fotografías aéreas, reconocimiento de campo y mapas cartográficos de la zona se diseñó un corredor de 23.5 km que cubre un área total de 1,494.7 ha. Está construido a lo largo de un sistema hidrológico conformado por dos microcuencas. Un 72% del área del corredor se encuentra en territorio de Zamorano, lo cual significa que la institución tiene gran influencia sobre las políticas de uso de suelo en el corredor. Son cuatro los ecosistemas que lo conforman y existe una clara relación entre éstos, la cobertura vegetal y los suelos que en éstos se encuentran. Un 91% del área del corredor está cubierta por masa boscosa. Sólo el ecosistema bosque muy húmedo montano bajo subtropical cuenta con bosque en estado maduro, los demás ecosistemas presentan bosques en estados sucesionales menos avanzados. De estos últimos el bosque de galería a lo largo del valle es el que se encuentra más perturbado por las actividades agrícolas. Por esta razón, es también la sección más angosta del corredor. Tomando en cuenta todos estos aspectos, el corredor biológico cumple con los criterios biológicos para su viabilidad y diseño. Se recomienda un estudio socioeconómico para poder evaluar y desarrollar los criterios socioeconómicos necesarios para hacer posible su factibilidad y establecimiento

Understanding ecological transitions under recurrent wildfire: a case study in the seasonally dry tropical forests of the Chiquitania, Bolivia

Wildfires in tropical forests are likely to become a more dominant disturbance due to future increasing feedbacks between rapid frontier expansion and more frequent droughts. This study evaluates the effects of fire recurrence on seasonally dry tropical forests of the Chiquitania region, located in the southern rim of Amazonia, eastern lowlands of Bolivia. Effects were assessed in terms of changes in biomass, forest structure, species diversity and composition. Forest plots were established in well-conserved study sites to compare unburnt forests with forests burned once, twice and three times in the period 2000-2012. Inventories were collected for trees, palms and lianas, including identification of species and measurement of morphological traits related to fire tolerance. Biomass was estimated using different allometric equations, and species composition, richness, abundance and dominance were compared. We found a significant loss in biomass, and putative effects on small and large trees after recurrent burns. The observed patterns in this study suggest that Chiquitano forests respond to recurrent fires through a shift in tree species composition with already-present fire-tolerant species becoming more dominant. This transition presented losses in biomass but increases in species richness. Insights into a possible transition to a more fire-adapted state is of great relevance for forest and fire management strategies in the region, as this transition may become irreversible in a future regime of more frequent wildfires, expected due to drier climatic conditions with increasing patterns of forest fragmentation and spreading use of fire into new forest frontiers