Abstract. The impact of large dams is a popular topic in environmental science, but the importance of altered water quality as a driver of ecological impacts is often missing from such discussions. This is partly because information on the relationship between dams and water quality is relatively sparse and fragmentary, especially for low-latitude developing countries where dam building is now concentrated. In this paper, we review and synthesize information on the effects of damming on water quality with a special focus on low latitudes. We find that two ultimate physical processes drive most water quality changes: the trapping of sediments and nutrients, and thermal stratification in reservoirs. Since stratification emerges as an important driver and there is ambiguity in the literature regarding the stratification behavior of water bodies in the tropics, we synthesize data and literature on the 54 largest low-latitude reservoirs to assess their mixing behavior using three classification schemes. Direct observations from literature as well as classifications based on climate and/or morphometry suggest that most, if not all, low-latitude reservoirs will stratify on at least a seasonal basis. This finding suggests that low-latitude dams have the potential to discharge cooler, anoxic deep water, which can degrade downstream ecosystems by altering thermal regimes or causing hypoxic stress. Many of these reservoirs are also capable of efficient trapping of sediments and bed load, transforming or destroying downstream ecosystems, such as floodplains and deltas. Water quality impacts imposed by stratification and sediment trapping can be mitigated through a variety of approaches, but implementation often meets physical or financial constraints. The impending construction of thousands of planned low-latitude dams will alter water quality throughout tropical and subtropical rivers. These changes and associated environmental impacts need to be better understood by better baseline data and more sophisticated predictors of reservoir stratification behavior. Improved environmental impact assessments and dam designs have the potential to mitigate both existing and future potential impacts.

Worldwide, regularly recurring wildfires shape many peatland ecosystems to the extent that fire‐adapted species often dominate plant communities, suggesting that wildfire is an integral part of peatland ecology rather than an anomaly. The most destructive blazes are smoldering fires that are usually initiated in periods of drought and can combust entire peatland carbon stores. However, peatland wildfires more typically occur as low‐severity surface burns that arise in the dormant season when vegetation is desiccated, and soil moisture is high. In such low‐severity fires, surface layers experience flash heating, but there is little loss of underlying peat to combustion. This study examines the potential importance of such processes in several peatlands that span a gradient from hemiboreal to tropical ecozones and experience a wide range of fire return intervals. We show that low‐severity fires can increase the pool of stable soil carbon by thermally altering the chemistry of soil organic matter (SOM), thereby reducing rates of microbial respiration. Using X‐ray photoelectron spectroscopy and Fourier transform infrared, we demonstrate that low‐severity fires significantly increase the degree of carbon condensation and aromatization of SOM functional groups, particularly on the surface of peat aggregates. Laboratory incubations show lower CO2 emissions from peat subjected to low‐severity fire and predict lower cumulative CO2 emissions from burned peat after 1–3 years. Also, low‐severity fires reduce the temperature sensitivity (Q10) of peat, indicating that these fires can inhibit microbial access to SOM. The increased stability of thermally altered SOM may allow a greater proportion of organic matter to survive vertical migration into saturated and anaerobic zones of peatlands where environmental conditions physiochemically protect carbon stores from decomposition for thousands of years. Thus, across latitudes, low‐severity fire is an overlooked factor influencing carbon cycling in peatlands, which is relevant to global carbon budgets as climate change alters fire regimes worldwide.

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ABSTRACT. Studies on bird-window collisions have generally drawn inferences about species' differential vulnerability from collision tallies. However, this common methodology is potentially biased because the number of collisions may simply reflect prevalence of species at the study site rather than species-specific vulnerability. Building on recent studies of abundance and collision rates, we offered a complementary methodology based on point count data that could be widely applied alongside carcass surveys. Additionally, we broadened our analysis beyond previously applied taxonomic and migratory classifications to include functional classifications of feeding guild, breeding status, and synanthropy. Our null hypothesis was that collision frequencies reflect a species' or classification group's prevalence at study sites. To test this possibility, we used collision data collected at three sites in the Research Triangle Area of North Carolina, United States. At one of these sites, Duke University's Main Campus, we also gathered relative abundances from the local bird community to develop a case study assessment of how background prevalence compared to number of collisions. Using the larger, three-site dataset, we developed an initial picture of collision susceptibility based solely on frequency, the standard practice. Then, by bootstrapping our Duke abundance data, we generated confidence intervals that simulated collision based on chance versus prevalence. We identified several instances where collision tallies produced misleading perception of species-specific vulnerability. In the most extreme case, frequencies from our Triangle Area dataset indicated locally breeding species were highly vulnerable to collisions while our abundance-based case study suggested this same group was actually adept at avoiding collisions. Through our case study, we also found that foliage gleaning was linked to increased risk, and omnivory and ground foraging were associated with decreased risk. Although our results are based on a limited sample, we argue that abundance needs to be incorporated into future studies and recommend point counts as a noninvasive and adaptable alternative to area-searches and mist netting.Traits spécifiques à l'espèce et abondance affectent la fréquence des collisions d'oiseaux aux fenêtres RÉSUMÉ. Les études sur les collisions d'oiseaux aux fenêtres infèrent généralement la vulnérabilité d'une espèce à partir des décomptes de collisions. Toutefois, cette méthodologie fréquemment utilisée est potentiellement biaisée parce que le nombre de collision reflète simplement la prévalence de certaines espèces au site d'étude plutôt que la vulnérabilité réelle de l'espèce. À partir des récentes études d'abondance et de taux de collision, nous offrons une méthodologie complémentaire basée sur des recensements ponctuels qui pourrait être appliquée à large échelle en parallèle avec les décomptes de carcasses. De plus, nous avons élargit nos analyses au-delà des classifications taxonomiques et migratoires utilisées au...

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Invasions of water bodies by floating vegetation, including water hyacinth (Eichhornia crassipes), are a huge global problem for fisheries, hydropower generation, and transportation. We analyzed floating plant coverage on 20 reservoirs across the world's tropics and subtropics, using [ 30 year time-series of LANDSAT remote-sensing imagery. Despite decades of costly weed control, floating invasion severity is increasing. Floating plant coverage correlates with expanding urban land cover in catchments, implicating urban nutrient sources as plausible drivers. Floating vegetation invasions have undeniable societal costs, but also provide benefits. Water hyacinths efficiently absorb nutrients from eutrophic waters, mitigating nutrient pollution problems. When washed up on shores, plants may become compost, increasing soil fertility. The biomass is increasingly used as a renewable biofuel. We propose a more nuanced perspective on these invasions moving away from futile eradication attempts towards an ecosystem management strategy that minimizes negative impacts while integrating potential social and environmental benefits. Keywords Biological invasions Á Dams Á Google earth engine Á Land cover change Á Urbanization Á Water-energy-food nexus Electronic supplementary material The online version of this article (

Tropical wetlands are thought to be the most important source of interannual variability in atmospheric methane (CH4) concentrations, yet sparse data prevents them from being incorporated into Earth system models. This problem is particularly pronounced in the neotropics where bottom-up models based on water table depth are incongruent with top-down inversion models suggesting unaccounted sinks or sources of CH4. The newly documented vast areas of peatlands in the Amazon basin may account for an important unrecognized CH4 source, but the hydrologic and biogeochemical controls of CH4 dynamics from these systems remain poorly understood. We studied three zones of a peatland in Madre de Dios, Peru, to test whether CH4 emissions and pore water concentrations varied with vegetation community, soil chemistry and proximity to groundwater sources. We found that the open-canopy herbaceous zone emitted roughly one-third as much CH4 as the Mauritia flexuosa palm-dominated areas (4.7 ± 0.9 and 14.0 ± 2.4 mg CH4 m-2 h-1, respectively). Emissions decreased with distance from groundwater discharge across the three sampling sites, and tracked changes in soil carbon chemistry, especially increased soil phenolics. Based on all available data, we calculate that neotropical peatlands contribute emissions of 43 ± 11.9 Tg CH4 y-1, however this estimate is subject to geographic bias and will need revision once additional studies are published.

Ongoing conflict resolution in Colombia brings an opportunity for economic development of impoverished communities and a conservation threat of deforestation in newly accessible rural areas. Ecotourism is often proposed as a ''win-win'' solution for developing countries to meet both economic and conservation needs. With the highest number of bird species of any country, including 443 rare species highly valued by bird-watchers, Colombia has a unique opportunity to develop a lucrative and conservation-friendly bird-watching tourism industry in postconflict areas. Through geospatial analysis of conflict zones, bird distributions, protected areas, forest cover, and bird-watching activity, we identify areas of Colombia with unrealized bird-watching potential that are ripe for the development of synergistic conservation-ecotourism projects. An investment in ecotourism infrastructure and training by the Colombian government may be a conservation-friendly alternative to natural resource extraction that could alleviate poverty without degrading natural capital in postconflict Colombia.