New study shows timescale is crucial for assessing extinction risk

Researchers from Wageningen University & Research, the Norwegian University of Life Sciences (NMBU) and several international partners combined camera-trap observations with fossil records and species distribution data covering the past 130,000 years. Their analysis, spanning 64 study sites across Africa, Asia and the Americas, demonstrates that the timeframe used in conservation research can strongly influence which species appear to be most vulnerable.

The researchers examined extinction patterns for 210 mammal species from the Eemian interglacial period to the present. Across this long timespan, species with large body sizes, small brains, carnivorous diets, long generation times and ground-dwelling lifestyles consistently faced higher extinction risks. These patterns were remarkably similar at global, regional and local scales.

However, when the researchers compared these long-term patterns with present-day local camera-trap data, some conclusions changed.

For example, species with smaller brains were more likely to disappear over evolutionary timescales, whereas contemporary studies sometimes identify larger-brained species as being more vulnerable. Likewise, large, slow-reproducing mammals appeared particularly susceptible over the past 130,000 years, yet often seem to fare relatively well in today's protected areas where most camera-trap studies are conducted.

The findings highlight an important consideration for conservation science. Researchers and conservation practitioners frequently use global or historical studies to identify species that require local conservation action. This study suggests that such comparisons are valuable, provided the timeframe of the evidence matches the question being asked.

Douglas Sheil of Wageningen University & Research, who contributed to the study design, analysis and interpretation, explains: "Camera traps have transformed what we can observe in nature, revealing species that would otherwise remain undetected across vast areas and in near real time. But a short local snapshot is not the same as the complete picture. Recent monitoring tells us what is happening today, while the historical record reveals what has already been lost. Understanding extinction risk requires both perspectives."

By combining ecological monitoring with palaeoecological records, the study provides a more complete picture of how extinction risk develops over time and offers guidance for interpreting modern biodiversity data in a broader evolutionary context.