Herbarium Specimens Reveal Long-Term Decline in Pollination Services Since the 1970s.

Anthropogenic change has resulted in pollinator declines and altered plant-pollinator interactions. This may alter pollination services, reducing the reproductive success of plants. Yet few datasets allow us to track changes in pollination services over time. Herbaria provide a unique opportunity to assess pollination services across broad spatial and temporal scales enabling the examination of associated spatiotemporal anthropogenic drivers of change. We quantified changes in pollination services to the orchid genus Caladenia over the past century, a period of rapid land-use intensification and climate change in Australia. Examining 10,494 Caladenia flowers preserved at the Australian National Herbarium showed a reduction in pollination services totaling > 60% over the whole study period, with rapid declines occurring post 1970. Declines in pollination services occurred across species pollinated by different taxa and with varying threat status. Sexually deceptive species showed more pronounced declines in pollination services than food-deceptive species, whereas no decline was detected in the self-compatible species. Land-use intensity and rising temperatures were significant predictors of changes in pollination service. Our findings provide rare evidence of declines in pollination services and demonstrate the value of herbarium collections in understanding global change.