North American bird populations are shrinking most rapidly in the very areas where they are still most abundant, according to a new study leveraging citizen science data for nearly 500 bird species. The findings reveal both urgent threats and potential opportunities for targeted conservation and recovery. Bird populations are experiencing steep declines globally, with North America losing more than 25% of all breeding birds since 1970. While long-term monitoring has revealed these troubling trends, effective conservation requires knowing where populations are declining most. However, this goal has been limited by the lack of fine-scale, spatially comprehensive data on bird population trends, making it difficult to prioritize efforts or detect localized patterns of decline and recovery. To address this need, Alison Johnston and colleagues compiled citizen science data from over 36 million eBird checklists, spanning 2007 to 2021, to generate fine-scale population trends for 495 bird species across North America, Central America, and the Caribbean. By analyzing changes in bird sightings at a high spatial resolution, the authors were able to separate actual shifts in bird populations from differences in observer behavior. Their approach involved using a specialized machine learning model, which enabled the detection of nuanced population changes with high statistical reliability.

The analysis revealed a complex patchwork of local population dynamics; although overall trends show that 75% of bird species are declining across their ranges – and 65% significantly so – nearly every species (97%) is experiencing both gains and losses depending on location within their ranges. Notably, Johnston et al. found that bird populations are declining fastest in the very places where they remain most abundant. This pattern – observed in 83% of species – suggests that even the strongholds of bird populations are no longer safe. The declines are especially severe in birds that breed in grasslands and drylands, and declines are more closely tied to local abundance than geographic position within a species’ range, the findings suggest; this points to ecological stress – climate change and habitat loss – as the primary driver of decline. Habitats that support abundant populations may be more vulnerable to these pressures, while species in marginal habitats may have greater resilience. Yet, despite widespread declines, the study revealed pockets of stability, such as in the Appalachians and western mountains, which may offer refuge or point to conditions that could facilitate recovery.

For reporters interested in trends, a 2019 Research Article in Science (science.sciencemag.org/lookup/doi/10.1126/science.aaw1313) reported that North America had lost nearly three billion birds since 1970.

New findings challenge assumptions about species’ ability to persist under climate change. Following a nine-year study of over 100,000 individual Drummond's rockcress plants – a common plant found in mountains across North America – researchers reveal that climate change is outpacing natural gene flow, threatening population survival even within a broadly distributed plant species’ native range. The findings highlight the potential role of assisted gene flow in plant conservation. Climate change is rapidly altering where species can survive and thrive. While many plant and animal species span broad geographic areas, their populations are often finely tuned to the specific climate of their local environments. This local adaptation means each population may tolerate only a narrow slice of the climate conditions the full species can endure. Evolutionary processes, including genetic variation, rapid adaptation, and gene flow, have the potential to dramatically alter population persistence under climate change – a process known as evolutionary rescue. However, these factors are rarely integrated into ecological models that predict how species will respond to climate change.

Using Drummond's rockcress (Boechera stricta), a widely-distributed, short-lived mountain plant in the mustard family, Jill Anderson and colleagues investigated how plants may adapt – or not – to a rapidly changing climate. In a nine-year-long field experiment in Colorado, Anderson et al. planted more than 102,000 individual plants across a range of elevations and manipulated snowpack to mimic climate variation. By integrating the genomic and fitness data into evolutionary demographic models under preindustrial, current, and projected climates, the authors found that climate change increases extinction risk for locally adapted populations by eroding their genetic advantages and outpacing natural gene flow. This was true across all elevations and not just at the warmest range edges. According to the findings, the direction of gene flow in adapting species is crucial. For example, in some mountain species, gene flow predominantly moves downhill, which may hinder the ability of populations to adapt to warming conditions at higher elevations. Compounding this challenge, the pace of climate change is outstripping the capacity of many species to shift their ranges upslope. Anderson et al. note that assisted gene flow – deliberately moving pre-adapted individuals to new locations – could help maintain genetic diversity and species persistence but must be carefully managed. “The lessons from Anderson et al. are sobering with respect to the ability of natural populations to adapt to, and persist under, rapid global warming,” writes Sally Aitkin in a related Perspective. “Although the capacity for persistence will vary among species and with life history traits, populations cannot persist simply because their locations remain within the overall range of climatic tolerances for that species as a whole.”

The global climate is in an imbalance. Potential "tipping elements " include the Greenland ice sheet, coral reefs, and the Amazon rainforest. Together they form a network that can collapse if just one individual component tips. Researchers from Bonn University Hospital (UKB) and the University of Bonn have now shed light on seemingly sudden and rare, often irreversible changes within a system, such as those that can be observed in the climate, the economy, social networks or even the human brain. They took a closer look at extreme events such as epileptic seizures. Their aim was to better understand the mechanisms underlying such changes in order to ultimately make predictions. The results of their work have now been published in the journal "Physical Review Research".

The Wilkes Center for Climate Science & Policy at the University of Utah has announced this year’s finalists for the $250,000 Wilkes Climate Launch Prize, one of the largest university-affiliate climate awards in the world. The prize is specifically calibrated to support unconventional or first-of-a-kind projects that often have difficulty getting funding.