A third of flowering plants would produce no seeds without pollinators

(CN) — If pollinators were to disappear, half of all flowering plants around the world would suffer a drastic reduction in fertility, according to a new study — the first to provide global estimates for the importance of pollinators in ecosystems.

The study, published Wednesday in the journal Science Advances, notes that 175,000 plant species, or half of all flowering plants, mostly or completely rely on animal and insect pollinators in order to make seeds and reproduce. 

“Recent studies show that many pollinator species have gone down in numbers, with some even having gone extinct,” James Rodger, postdoctoral fellow of mathematical sciences at Stellenbosch University in South Africa​ and the study’s lead author, said in a statement.

 “Our finding that large numbers of wild plant species rely on pollinators shows that declines in pollinators could cause major disruptions in natural ecosystems,” he warned.

As Rodger noted, pollinator species populations have been declining. In a separate study published in August, researchers found that pollinator species — such as bees, hummingbirds and butterflies — have rapidly declined in six regions around the world due to habitat destruction, land management techniques and pesticides.

Another study found that agricultural chemicals, such as pesticides and herbicides, are having a greater impact on bee mortality than previously believed. And a third study found that, since the 1990s, up to 25% of reported bee species have disappeared or become too rare to be routinely observed in their natural habitats.

While most plants depend on pollinators, many have a bit of auto-fertility, meaning they can make at least some seeds without pollinators. But until Wednesday’s study, it wasn’t clear how important pollinators are for wild plants at the global level. Smaller studies existed, but those findings were spread out in hundreds of papers each focusing on pollination experiments on different plant species. 

So a team of 21 scientists from 23 institutions across five continents set out to consolidate the data from 1,528 separate experiments representing 1,392 plant populations across all continents except Antarctica.

The team — led by Rodger and professor Allan Ellis from Stellenbosch University in South Africa​ — found that, without pollinators, a third of the globe’s flowering plant species would produce no seeds at all and half would suffer an 80% or more reduction in fertility.

The findings indicate that, while auto-fertility is common in some plants, it does not fully compensate for reductions in pollination.

If pollinator-dependent plants decline or go extinct, “It also means that plants that do not rely on pollinators, like many problematic weeds, might spread even more when pollinators continue to decline,” study co-author Mark van Kleunen of the University of Konstanz in Germany said in a statement. 

And “if auto-fertile plants come to dominate the landscape, then even more pollinators will be negatively affected, because auto-fertile plants tend to produce less nectar and pollen,” added Joanne Bennet, another co-author from the University of Canberra in Australia.

The scientists warn that with fewer pollinators or even just a change in which ones are most prevalent, there will be ripple effects on plants. Affected plant species will potentially decline, which will further harm animal species and human populations that depend on those plants.

“Pollinators aren’t only important for crop production, but also for biodiversity,” Kleunen said.

But the good news is that, because plants are long-lived, pollinator populations could be restored before affected plants become extinct.

“We hope that our findings will stimulate more of this kind of research, so that we can detect pollinator declines and mitigate their impacts on biodiversity,” Rodger said.

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