Recent research has revealed a troubling decline in pollination activity among orchid species in Australia, raising concerns about the future of these vital plants and the ecosystems they support. Approximately 90 percent of all flowering plants depend on pollination to reproduce. This decline has a significant effect on both biodiversity and agricultural productivity.
Under the direction of study lead Dr. Joanne Bennett, the research observed pollination activity in 25 orchid species from the Australian National Herbarium. The research required the examination of over 10,000 specimens, establishing the greatest baseline of any study to date of pollinator change over the decades. The research has documented a dramatic decline in pollination frequency across multiple species of orchids. That’s a 61 percent drop between 1925 and 2020, with the greatest drops occurring since the 1970s.
Methodology of the Study
The study measured pollination activity by four important processes. For starters, researchers quantified pollinia removal, the small packets of pollen that the male reproductive structures of the orchids release. Second, they measured pollen deposition on the stigma, the female part of the flower. Third, researchers recorded whether flowers were fertilized.
According to Dr. Bennett, it was obvious when an orchid was “in gestation. Researchers were able to determine this by noticing the increase in mass and formation of a darkened area on the flower. Of the 25 species observed, 15 used food deception to lure in their misled pollinators, while nine used sexual deception. Of the 15 species that could be tested, only one was an unequivocal self-pollinator.
“If the pollinia is broken, that meant the insect has visited here and the pollination service was happening.” – Joanne Bennett
Impact of Climate Change and Land Use
As Dr. Bennett explained, these shifts in land use laid the groundwork for subsequent declines in orchid pollination. She said the most alarming trend that has developed is the undeniable role of climate change as the number one cause behind recent declines. Because climate change has made our summers warmer and hotter, pollination rates are dropping. This is an especially dangerous double-edged sword for orchids and their pollinators.
“Historical land-use change caused orchid pollination to decline, but now the main driver is climate, and that’s what’s changed.” – Joanne Bennett
Additionally, Graham Pyke, an expert in the field, highlighted a broader pattern of insect decline that coincides with these findings. He emphasized that the late decades of the last century represented an especially catastrophic period for insect life.
“The research fits with a much broader pattern that insects have been decreasing, and that probably the late part of last century was a pretty bad time.” – Graham Pyke
The Role of Native Bees
Australia is home to more than 2,000 native bee species. One of the groups of greatest interest are the stingless bees, which live in large colonies and produce honey. At the same time, a third of U.S. crops can’t depend entirely on native bee populations to pollinate them because these seasonal species are very limited. Professor James Cook, from the University of Sydney, said because stingless bees like it warmer they aren’t as active in cooler temperatures.
“Stingless bees don’t get out of bed at less than 18C.” – James Cook
The arrival of the parasitic Varroa mite in 2022 adds another stressor to Australia’s pollination services. Wild honey bee populations are expected to take an especially hard hit as Varroa rapidly spreads throughout the country, according to Professor Cook.
“As Varroa spreads … I expect that [wild honey bee population] to get hammered.” – James Cook
Future Research and Considerations
Because orchids are so vulnerable to specific pollen limitations, Dr. Bennett considers them a key indicator for watching a shift in pollination services. Knowing why they are in decline could help us understand what to expect in terms of future pollination shortfalls on other plants. Pyke said he was very concerned about the retrospective nature of this study.
“Unfortunately, the study … is entirely retrospective and provides no good suggestion as to how orchids might provide early warning about pollination services or anything else.” – Graham Pyke
Along with this achievement he underscored the possibilities of doing such studies on other plants. Milkweeds, for instance, have similar pollen packaging that would be worth investigating.
“Other plants, such as milkweeds have similarly packaged pollen, so similar studies with such plants may also be possible.” – Graham Pyke
