Charles Darwin carried out numerous experiments to investigate ways in which seeds might be dispersed. Ever since I first read about them, these experiments have held a particular fascination for me, not least because some of them were pretty bizarre. Darwin floated dead pigeons in water for days on end, then tried to get the seeds in their crops to germinate; he fed seeds to fish to see if they might survive passage through a heron; he examined the mud on the feet of freshly shot ducks for seeds. His experiments were, on the whole, successful, showing that there were many unusual ways in which seeds might be dispersed.
Now we have another dispersal mechanism:
New Scientist: Plant invaders enjoy life in the fast lane
Motorists are not the only ones to benefit from high-speed roads. Life in the fast lane also helps plant seeds travel far from home. So say Moritz von der Lippe and Ingo Kowarik of the Technical University of Berlin, Germany, who have shown that traffic may account for up to half of seed dispersal near motorways…
Among their samples, von der Lippe and Kowarik found seeds from 39 problematic invasive species that are damaging biodiversity in some parts of the world. "Many countries, including the US, spray roadsides with herbicides," says von der Lippe.
I'm not at all surprised by these results. I have often observed how oil seed rape plants appear for many miles on either side of oil seed rape fields on the central reservation of motorways. It seems like an obvious way in which seeds might be dispersed—but all credit to von der Lippe and Kowarik for testing the obvious: that's what good science is all about, and Darwin would have loved it.
Motorways aren't the first transport routes to help spread invasive plant species. The spread of ragwort throughout the UK in the Nineteenth Century has been attributed to the growth of railways in the 1840s. On an international scale, air- and sea-travel has wreaked havoc spreading invasive species throughout the world.
Invasive species are a serious problem, but I disagree with the idea of spraying roadsides with herbicides to combat them. The UK's rail and motorway networks provide vital corridors and green livingspaces for British wildlife. Destroying them would do untold damage to our native flora and fauna.