Ongoing decline in insect-pollinated plants across Danish grasslands

Area of Science:

• Ecology
• Botany
• Conservation Biology

Background:

• Habitat loss, eutrophication, and reduced grazing intensity are known drivers of plant species changes.
• The impact of declining insect abundance on plant communities remains poorly understood.
• Pollinator decline can reduce plant reproduction, potentially altering species composition.

Purpose of the Study:

• To investigate the ongoing consequences of insect decline on plant species richness in Danish grasslands.
• To assess whether insect-pollinated plant species are declining and if this trend differs from wind-pollinated species.
• To examine the influence of grazing intensity on the loss of insect-pollinated plants.

Main Methods:

• Utilized nationwide monitoring data of plant species richness from 244 Danish grassland sites (2004-2014).
• Analyzed data encompassing over 790 flowering plant species.
• Compared trends in insect-pollinated versus wind-pollinated plant species richness across different grassland types and grazing intensities.

Main Results:

• An ongoing decrease in insect-pollinated plant species was observed across various grassland types, while wind-pollinated species showed no significant decline.
• The loss of insect-pollinated plants was most pronounced in grasslands with low grazing intensity, but also occurred at sites with higher grazing.
• Plant species with specialized pollination requirements exhibited the greatest decline.

Conclusions:

• Pollinator loss is a significant factor contributing to the reduction of insect-pollinated plant richness, alongside land-use changes.
• The ongoing decline in floral resources may exacerbate threats to insect populations.
• Findings highlight the interconnectedness of insect and plant communities and the need for conservation strategies addressing pollinator health.