Reported declines in native bees have led to concerns that these vital pollinators may be threatened. However, few multi-year monitoring studies employing consistent sampling techniques are available to define the current rate of decline, if any, of native bee communities. Furthermore, even less is known regarding the long-term stability of the native bee community as it exists in an urban/suburban ecosystem. The present study provides an initial assessment of year-to-year changes in native bee abundance over a four-year span. Bi-weekly sampling of bees was conducted from 2016 to 2019 using pan traps and sweep netting at six urban-to-suburban sites in Plymouth County, Massachusetts. Bees were collected, pinned and identified to genus prior to inclusion in the data set.
Results/Conclusions
Yearly bee abundance results are suggestive of a general decline in the local native bee community, but this trend failed to reach statistical significance (F3,23 = 2.90, p > 0.05). This observation is likely due to significant year-to-year fluctuations, with bee abundance declining 9.41% and 25.87% for the first two years of the study but rebounding 33.53% from 2018 to 2019. Similarly, no significant trend was detected for richness over the four years (F3,23 = 3.04, p > 0.05). From 2016 to 2017 bee richness declined by 9.09% and from 2017 to 2018 by 13.33% followed by an increase of 3.89% from 2018 to 2019. The seasonal variations in abundance and richness preclude solid conclusions at this time. Further study will be required to ascertain if the variation observed in this study is normal season-to-season fluctuation or indicative a long term decline.