Due to environmental changes, bee and butterfly populations in North America are decreasing. A study highlights trends in the region and calls for increased monitoring and conservation efforts to fill research gaps and protect pollinating insects. In major regions of North America, the population of bees and butterflies is decreasing due to ongoing environmental changes. Our ability to conserve these species is limited by huge gaps in pollinator research. Sarah Souther and colleagues at Northern Arizona University in the United States published a study today (May 15, 2024) in the open access journal PLOS ONE.
Recent studies have found that pollinator populations are declining, alarming scientists and policymakers who fear that this will have a negative impact on ecosystems and agriculture. These reductions are linked to a variety of factors such as climate change, habitat loss, and invasive species, but reporting is often limited to species that have been well studied in easily accessible areas.
In this study, Souther and colleagues used compiled data from the four major bee and butterfly families to construct a species distribution model, allowing them to assess changes over time and space across North America.
A flowering fishhook barrel cactus (Ferocactus wislizenii) in Arizona, USA, is being visited by native bees. The study found that the number of pollinators in the western United States has been declining over the past few decades. Image courtesy of Sara Souther CC-BY 4.0
The West Coast of North America has the highest species richness, especially in California and the Rocky Mountains. However, models show that species richness has declined in all four families in western North America over the past century. In contrast, species richness has increased disproportionately in eastern North America. The authors also conducted a similar data assessment of a wider sample of potential pollinator species, including protected invertebrate and vertebrate species, and found similar trends.
Comparisons with climate data suggest that these population changes are at least partly related to the effects of recent climate change, such as prolonged drought and habitat degradation, while areas with significant population declines are also severely affected by anthropogenic land use. The authors also note that the apparent increase in the eastern U.S. may partly reflect the increased number detected in these densely populated areas due to increased citizen science and similar data collection efforts.
Species increases and decreases of (a) Apidae, (b) Megachilidae, (c) Papilionidae and (d) Pieridae in the projected species distribution from 1980 to 2020 and 1939 to 1979. Subtracting the 1980-2020 threshold species distribution model outputs from the 1939-1979 threshold species distribution model outputs for all species yields a species distribution map with three possible values: -1 (species predicted in a particular area in 1939-1979, but not in 1980-2020), 0 (species predicted in a specific area in two time periods), and 1 (species predicted in a specific region in 1980-2020, but 1939-1979). years no). Each map is the result of the addition of these differential rasters for all species within each family. The golden area represents the location where a large number of species are expected to disappear from the first to the second time period. The dark grey areas represent locations where a large number of species increases are expected from the first to the second time period. Source: Souther et al., 2024, PLOS ONE, CC-BY 4.0
Overall, the study identified a broad trend in changes in the populations of bees and butterflies, as well as other potential pollinating insects. These results help identify areas where populations are declining and where researchers and policymakers can prioritize conservation efforts. The study also identified gaps in existing knowledge of pollinators, including areas with fewer samples and fewer studied species, limitations that may be overcome by improving surveillance methods and strengthening citizen science efforts.
"The existing North American pollinator record suggests a general decline in pollinator diversity in the western United States and southern Mexico in recent decades," the authors added. This loss is consistent with climate change and demonstrates the need for enhanced monitoring to inform conservation and mitigation actions."
编译来源：ScitechDaily