About half of all seed plants are largely or completely dependent on bees, butterflies and other animal pollinators for their reproduction. The number of these animal-dependent species is estimated by an international research team in the journal “Science Advances” at around 175,000. The decline in pollinators threatens entire ecosystems and their plant diversity.
Most plants reproduce through pollination, in which pollen is carried from one flower to the next. A team of researchers from 23 institutions on five continents, led by James Rodger and Allan Ellis from the University of Stellenbosch in South Africa, has now examined the importance of animals as pollinators of wild plants.
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Effects on people too
The decisive factor for the importance of animal pollinators is their contribution to seed production – measured by comparing seed production with and without pollinators. The data required for this was available, but it was spread over hundreds of studies that focused on pollination experiments with different plants.
The team summarizes this information in a global database. This contains information from more than 1500 experiments with almost 1400 plant populations and around 1200 species from 143 plant families.
The results show that without pollinators, a third of the 350,000 species of seed plants would not produce any seeds, and half would suffer a decline in fertility of at least 80 percent. Although many plants are able to self-pollinate, this by no means compensates for the decline in pollination performance in most species.
“Studies show that many pollinator species have declined and some have even become extinct,” says lead author Rodger and warns: “Our finding that a large number of wild plant species depend on pollinators shows that their decline could cause major disturbances in natural ecosystems.”
Persistent threat to pollinators in Europe
Co-author Mark van Kleunen from the University of Konstanz adds that the consequences of such a decline do not only affect plants. Rather, animal species that are dependent on these plants and ultimately humans would also suffer.
The world’s first survey of pollinators by the World Council for Biodiversity IPBES showed how important they are for human food security as early as 2016: According to this, between five and eight percent of global agricultural production depends on this type of pollination. The resulting food is valued at between $ 235 billion and $ 577 billion.
Two years later, the European Commission decided on a package of measures to protect pollinators, but this is only slowly taking effect. According to a report from May 2021, the establishment of an EU-wide system to monitor species and their decline is proceeding successfully. However, the numbers have not changed since the start of the EU initiative: every tenth species of bees and butterflies in Europe are still threatened with extinction, and a third are shrinking populations. More needs to be done about habitat loss and the effects of pesticides.
According to the current study, such measures are important not only with regard to crop production, but also for biodiversity. “Plants that do not depend on pollinators could spread even more if the pollinators continue to decline,” notes van Kleunen.
At the same time, a vicious circle could arise if plants dependent on pollinators decline or become extinct, explains Joanne Bennet from the University of Canberra: “When self-pollinating plants dominate the landscape, even more pollinators are negatively affected because self-pollinating plants tend to produce less nectar and pollen.”
