Fewer bees, less plant diversity
In an unexpected twist on Darwin’s survival of the fittest, a research collaboration from Princeton University, USA, and the Swiss Federal Institute of Technology (ETH), Zürich, found that while that plants compete for a declining population of visitors pollinators (bees, butterflies and other insects), they are experiencing a decline in population and an overall decrease in species diversity.
This goes against ecological theory, which suggests that environmental pressures such as competition from pollinators would cause plants to adapt, making species more diverse, not less.
The research team planted five species of annual flowering plants (including poppies, cornflowers and wild fennel) in a meadow, gradually changing the planting density – i.e. the number of plants close to each other. Some sections were exposed to normal levels of pollination – by bees (honeybees, bumblebees, solitary bees), hoverflies and butterflies, in this case. Other sections got an extra helping hand (literally), with humans physically transferring extra pollen.
Researchers found that in situations where plants competed for the attention of bees, flies, and butterflies (without human help), population growth and diversity decreased further.
To live as a thriving population, plants develop niche differences that interact with the unique adaptations of other plants in a kind of system balance or equilibrium. When this balance is broken – when the number of pollinators decreases, for example – the imbalance tends to favor common species at the expense of rare species. The reasons for this are many and complicated, but include factors such as the ease with which pollen is picked up and dispersed by pollinators, the already inflated number of more common varieties, and the increased likelihood of receiving common pollen from a pollinator in visit.
“Climate change, habitat modification and pesticides are considered the main drivers of pollinator decline,” says Dr Christopher Johnson, a researcher and engineer at the University of Washington, USA, and the one of the authors of this study, and it could “alter the competitive playing field for plants, causing some plant species to become extinct.”
There are important implications; not only for how we understand ecological evolution in this context, but also potentially to feed a growing world population. “Food security is essential for a growing global population – which is also putting increasing pressures on plant and pollinator communities – so it is important to better understand plant pollinator communities and work towards their conservation worldwide” , says Johnson.
In the future, we may have artificial pollinators, such as “RoboBeeswhich can help plants maintain diversity and population, but for now it’s worth focusing on conserving natural pollinators. “What I can say from being in the field, painting plants by hand with a brush, is that pollinating insects are really, really good at their jobs, so there’s no substitute for healthy plant pollinator communities. and diverse,” says Johnson. .
For those lucky enough to have a vegetable or flower garden, Johnson’s message is simple: “Grow a wide range of plant species and take advantage of the diversity of pollinators that visit your garden.