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

Trends in Urban Forestry Research in Latin America & The Caribbean: A Systematic Literature Review and Synthesis

Research on urban forests has expanded in the last 30 years in the US, Canada, Europe, and Australia. Nonetheless, urban forestry has been explored to much less extent in the Latin America and the Caribbean region, despite being one of the most urbanized and biodiverse regions in the world. We address this gap by providing a baseline understanding of urban forest research in the region based on a systematic review of the academic literature. Of the 55,000 studies found, 195 were selected for review, and 182 were analysed and synthesized. These studies came from 13 countries and were published from 1970 to mid-2018 (inclusive) in English, Spanish, and Portuguese. Almost half of the studies were based in Brazil, followed by Mexico and Chile. To comparatively assess article output by country, we accounted for country population and Brazil, Chile, Nicaragua, and Puerto Rico had higher than average per capita article output. Most articles were ecological studies (64%) that used field surveys (58%) to research urban vegetation diversity. Most ecological studies did not include any social or management considerations. Only a few studies focused on spatiotemporal dynamics (12%) or the direct opinions of stakeholders (9%). We observed a notable increase in article output from the region during the last decade. The units of analysis targeted by these studies mostly focused on single trees in public areas (streets and parks). Understanding urban forests regionally could be strengthened by scaling up research across multiple units of analysis and across regional cities, which could provide a better understanding of regional spatiotemporal dynamics. To respond to current global trends and nurture regional strengths, research could also focus on a wider range of ecosystem services provided by urban forests, and the relationship of urban forests with poverty, crime, climate vulnerability, biodiversity loss, and social equity. These findings can inform key stakeholders in the regi

The impact of land titling on agricultural production and agricultural investments in Tanzania: a theory-based approach

This paper uses cross-sectional agricultural and household surveys conducted in 2008 and 2009 to examine the impact of land titles on agricultural outcomes combining the use of a theory-based approach and a propensity score matching. The results of the analysis reveal no significant impact of land titles on agricultural production, agricultural investments and long-term maximisation agricultural behaviour once differences in covariates between households and plots with and without land titles are taken into account. In fact, there is no indication of relevant impacts of land titles on access to credit and on perceived tenure security either, pointing to a break at an early stage in the causal chain of impact. The results are overall robust to the selection of the matching method and to different specifications of the matching equation. Finally, the study discusses some aspects of the institutional context that could help to explain why land titling in Tanzania has failed to bring about the expected changes in agricultural outcomes