Constructed wetlands do a good job in their early years of capturing carbon in the environment that contributes to climate change – but that ability does diminish with time as the wetlands mature, a new study suggests.

Polar bears in Western Hudson Bay have seen their population nearly halved over the last several decades, largely due to dwindling sea ice and limited hunting opportunities, according to the findings of a novel bioenergetic model using data spanning more than 40 years. The findings reveal the relationship between bears’ individual energy needs and environmental limitations in driving population trends, highlighting energy as the central limiting factor behind the decline of a key Arctic apex predator. The Arctic is warming faster than any other region on Earth, leading to significant sea ice loss, ecosystem transformations, and heightened threats to ice-dependent species like polar bears (Ursus maritimus). These animals rely on sea ice to hunt seals, their primary food source, but as ice melts during warmer months, they are forced onto land or into less productive waters, relying on stored energy reserves due to the lack of adequate food sources. Food deprivation caused by changes in seasonal sea ice has been linked to declines in polar bear populations. However, conservation efforts are limited by a lack of data for most polar bear subpopulations and a framework to understand how sea ice loss affects the animals throughout their lives. To investigate the relationship between declining sea ice and polar bear populations, Louise Archer and colleagues compiled population monitoring and capture data collected from polar bears in Western Hudson Bay, Canada, over the last 42 years and developed an individual-based bioenergetic model. The model, grounded in physiological principles, integrates energy acquisition and expenditure – such as feeding, body maintenance, movement, growth, and reproduction – into a unified energy budget spanning an individual bear’s life cycle. The findings show that sea ice loss and resultant feeding limitations were the primary drivers of a ~50% population decline since the mid-1990s, demonstrating how individual energetic constraints shape population-level outcomes. What’s more, Archer et al. note that this framework, although developed for polar bears, is adaptable to other species facing constraints on foraging or energy use due to environmental or human-driven changes, offering broad utility in addressing global change impacts and informing conservation and policy decisions.

In a comprehensive analysis, researchers present the divers, causes, and impacts of the catastrophic 2023 Sikkim glacial lake outburst flood (GLOF). The findings stress the urgent need to enhance GLOF hazard assessments and improve prediction and early warning systems as melting glaciers steadily raise the risk of GLOFs in the Himalayan region. South Lhonak Lake – perched at 5200 meters above sea level in the Upper Teesta basin of Sikkim, India – is among the region's largest and most rapidly expanding glacial lakes, posing severe hazards due to its potential for GLOFs. These hazards were realized on October 3, 2023, when the glacial lake experienced a catastrophic outburst, unleashing a flood cascade that claimed 55 lives, left 74 missing, and caused widespread downstream devastation, including the destruction of the Teesta-III hydropower dam. Combining high-resolution satellite imagery, seismic and meteorological data, field observations, and numerical modeling, Ashim Sattar and colleagues present a comprehensive and multidisciplinary analysis of the event. According to the findings, the outburst was triggered when a landslide containing 14.7 million cubic meters (m³) of frozen sediment collapsed into the lake, generating a ~20-meter tsunami-like wave that breached and eroded the frontal moraine containing the waterbody, releasing roughly half of the lake’s volume (~50 million m³ of water) and ~270 million m3 of sediment into the Teesta River valley. Moreover, Sikkim et al. show that climate warming intensified the event, as heavy rainfall primed the landscape for landslides that compounded sediment transport and downstream destruction in the Teesta Valley, which impacted Sikkim, West Bengal, and Bangladesh and damaged infrastructure as far as 385 kilometers away from the flood’s origin. According to the authors, the findings underscore the inadequacy of current GLOF models, which often fail to account for erosion, sediment transport, and cascading processes, and highlight the need for enhanced early warning systems, policy reforms, and adaptive risk management strategies, particularly in remote, high-altitude, vulnerable glacial regions like the Himalayas.