Recent ecological change in ancient lakes

Ancient lakes are among the best archivists of past environmental change, having experienced more than one full glacial cycle, a wide range of climatic conditions, tectonic events, and long association with human settlements. These lakes not only record long histories of environmental variation and human activity in their sediments, but also harbor very high levels of biodiversity and endemism. Yet, ancient lakes are faced with a familiar suite of anthropogenic threats, which may degrade the unusual properties that make them especially valuable to science and society. In all ancient lakes for which data exist, significant warming of surface waters has occurred, with a broad range of consequences. Eutrophication threatens both native species assemblages and regional economies reliant on clean surface water, fisheries, and tourism. Where sewage contributes nutrients and heavy metals, one can anticipate the occurrence of less understood emerging contaminants, such as pharmaceuticals, personal care products, and microplastics that negatively affect lake biota and water quality. Human populations continue to increase in most of the ancient lakes' watersheds, which will exacerbate these concerns. Further, human alterations of hydrology, including those produced through climate change, have altered lake levels. Co-occurring with these impacts have been intentional and unintentional species introductions, altering biodiversity. Given that the distinctive character of each ancient lake is strongly linked to age, there may be few options to remediate losses of species or other ecosystem damage associated with modern ecological change, heightening the imperative for understanding these systems

Projected changes in the near‐future mean climate and extreme climate events in Northeast Thailand

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordThis study provides an assessment of changes in mean and extreme climate in northeast Thailand, focusing on the near-future period (2021–2050). Spatiotemporal changes in climate extremes and return values are investigated compared to 1981–2010. Climate model-related uncertainties are quantified using 14 models from the Coupled Model Intercomparison Project phase 5 (CMIP5) and 8 models from phase 6 (CMIP6). CMIP6 models have a higher sensitivity to external forcings as the CMIP6 ensemble suggests an increase in maximum and minimum temperatures by 1.45°C (0.8–1.9°C) and 1.54°C (1.1–1.9°C) under the high emission scenario, which is greater than by CMIP5 ensemble: 1.10°C (0.5–1.7°C) and 1.13°C (0.7–1.6°C), respectively. No significant changes in annual rainfall are projected, although it will be temporally more uneven with decreases (6–11%) during the pre-rainy season (March–May) and increases (2–8%) during the rainy season (June–October). The bootstrap analysis technique shows the inter-model uncertainties for rainfall projections in CMIP6 have reduced by 40% compared to CMIP5. The annual number of hot days will increase more than twofold and warm nights, more than threefold. Near-future will experience an increase in the rainfall intensity, a decrease in the number of rainy days, and an increase in the 20-year return values of annual maximum 1-day rainfall and consecutive 5-days rainfall (>30%). In addition, the rainy season will be shortened in the future as onset and retreat are delayed, which may have implications in agricultural activities in the basin since cultivation is primarily rainfed. These findings suggest that anthropogenic activities will significantly amplify the climate extremes. The study results will be useful for managing climate-related risks and developing adaptation measures to improve resilience towards potential climate hazards.Natural Environment Research Council (NERC)National Research Council of ThailandThailand Science Research and Innovatio