Some are based on biological records requiring corrections for sampling effort ( 1, 4, 6, 7), while others only provide a comparison of discrete points in time ( 4, 10). However, each assessment of a decline has its various strengths and weaknesses. Long-term monitoring data indicate that abundances of many arthropod species are declining, as shown in a meta-analysis study that documented declines in abundances of >450 invertebrate species globally ( 9). The abundance and diversity of terrestrial arthropods are under threat from several anthropogenic pressures (e.g. Our results reiterate the need for more basic research into the life-history, ecology, and adaptation of arthropod species to better understand their sensitivity to global changes. Finally, we found clear differences among species within single families of arthropods, indicating that an apparent lack of change in abundance at broader taxonomic or functional levels could mask substantial species-specific trends.
Although the abundances of many taxa were correlated, we detected both positive and negative correlations, suggesting that multiple processes are affecting arthropod populations even in this relatively simple Arctic food web. These trends are more pronounced in the most recent decade, with change point analyses suggesting distinct non-linear dynamics within some functional groups such as predators and detritivores. Despite a strong warming signal in air temperature, we only find evidence of weak temporal trends in arthropod abundances across most taxa. Here, we utilise 24 years of abundance data from Zackenberg in High-Arctic Greenland, which is the longest running Arctic arthropod monitoring program, to study temporal trends in abundance. Monitoring data from the Arctic are particularly underrepresented, yet important to assessments of species abundance changes because many anthropogenic drivers of change that are present in other regions are absent in polar regions. Consequently, variation in population dynamics among taxa and habitats remains poorly understood. However, most arthropod monitoring programs are short-lived and limited in taxonomic resolution and spatial extent. Time-series data on arthropod populations are critical for understanding the magnitude, direction, and drivers of abundance changes.
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