GINAMO

Genetic diversity in nature is declining, likely due to human impact – this is what this paper demonstrates, using a massive dataset across numerous species and ecosystems. The authors collected all available studies analysing changes in genetic diversity, i.e. those where data were available for more than one time point. They then combined all these individual studies in an overarching statistical analysis (meta-analysis). Across species, geographical regions, and Red List categories, they found a clear pattern of genetic diversity loss over time. Some species groups are hit especially hard, for example birds.

Can conservation action slow this loss of diversity? Yes! For example, the authors found that supplementation (the addition of individuals from other populations to increase genetic diversity) has a positive effect. Habitat restoration, while not increasing genetic diversity, at least halted the decline. This study provides very strong evidence for the hidden biodiversity losses driven by human impact and supports the need for genetic monitoring and management of populations.

This review showcases the role of evolutionary and conservation genetics in an interdisciplinary context. Modern river management often takes biology into account – for example, fish passes ensure connectivity between river sections separated by dams or weirs – and the effects of human-made structures on river habitats are increasingly well-understood. However, this paper argues that river system management should specifically integrate the role of evolution and genetics: Human interventions like dams and flow regulation can create strong selective pressures on fish and other river organisms. Sometimes, this can lead to evolutionary changes within just decades, affecting traits such as body size, behaviour, and life-history strategies.

In turn, these biological shifts can feed back into river processes: For example, because many fish species move around sediments when building nests, changes in fish size and spawning behaviour can influence channel structure and habitat availability. In this sense, rivers might not only shape life in them – life and its evolution might also reshape rivers.

The paper frames these interactions as “hydro-evolutionary feedbacks”. Further studies of these feedbacks are needed, and analysis and monitoring of both neutral and adaptive genetic variation is required to fully understand the effects of river management on stream organisms. This becomes ever more important under climate change, increasing numbers of invasive species, and growing human pressure.

Pesticides are often blamed for biodiversity declines, but demonstrating their effects at large scales is difficult: Agricultural intensification involves many overlapping changes that can be hard to disentangle under real-world conditions.

This study addresses that problem by combining nationwide pesticide purchase records from France with long-term bird monitoring data collected through citizen science. Examining 64 common bird species, the authors find that most species were less abundant in areas with higher pesticide use. This pattern remained after accounting for other aspects of intensive farming, such as land use and farming practices, and climate. Notably, the relationship was not restricted to specialist farmland birds but was also evident in widespread species that regularly use cropland habitats. While the study cannot identify the exact pathways involved, its results suggest that pesticide use is associated with broad changes in farmland bird communities and may contribute to declines across a much wider range of species than previously appreciated.

Conservation measures are of course applied to benefit biodiversity – but how often do they actually work? This large meta-analysis tackles that question by bringing together evidence from 186 studies across a wide range of species and ecosystems. The conservation measures included cover a range of approaches – for example, the implementation of protected areas, measures against invasive species, and the restoration of natural ecosystems. Rather than simply tracking whether biodiversity increased or decreased, for each species, the authors compared the scenario with a conservation intervention to the scenario without.

The overall picture is encouraging. In roughly two-thirds of cases, conservation measures either improved biodiversity or reduced the rate of decline compared with doing nothing. Positive effects were observed across multiple levels of biodiversity, from genetic diversity to species and entire ecosystems. Not every intervention was successful, though. Some projects performed worse than the no-action scenario, often reflecting the complexity of ecological systems, unintended side effects, or shortcomings in implementation. Even so, the results suggest that conservation is generally effective. The key challenge is therefore to ensure that conservation measures are prioritised and actually implemented at large scale.

In this paper, we see a clear example of how management action positively affects connectivity and genetic population health. The arctic fox suffered dramatic declines due to hunting for fur in the 19th century, compounded by competition with the non-native red fox. In Scandinavia, conservation measures such as red fox culling, feeding, and supplementation of populations with individuals bred in captivity have increased census population sizes – but the genetic effects of these measures have so far been unknown.

Using analyses with microsatellite markers on samples collected over eight years, the study shows that within-population genetic diversity has increased over time. Differences between populations have decreased, reflecting improved exchange between populations – partly because of the re-establishment of previously extinct “stepping stone” populations between core populations. Like the paper recommended by Sean, this study demonstrates that conservation action works – this time with a focus on the genetic diversity in a single species that previously suffered dramatic declines.