How do plants get to the islands? It seems like a silly question, but think about it: plants don’t move, they have to use other strategies to expand their range. Furthermore, it is not easy to cross an arm of the sea and travel hundreds or thousands of kilometers without legs or wings.
Until now, the most popular hypothesis on this topic was linked to the adaptations of the plants themselves: it was thought that those that colonized the islands were those that had developed characteristics that facilitated their dispersal. In fact, a study published on Ecology Letters now explain that… it’s not true: plants don’t need to be adapted to long journeys, the birds take care of that.
The Settlement of Surtsey. It’s not often that you have an entire piece of “virgin” land in your hands and can directly study its colonization by plants and animals. a golden opportunity presented itself in 1963, in the middle of the North Atlantic, when following volcanic activity the island of Surtsey emerged from the depths. Studying its vegetation today therefore means understanding which plants arrived first, and trying to identify the characteristics that allowed this long journey from the mainland (32 km from the coast of Iceland).
Long range dispersion. According to the prevailing theory so far, one would expect to find plants with specific adaptations for long journeys: for example, plants that produce particularly succulent fruits that attract birds, which in turn help to disperse the seeds. In fact, Surtsey’s 78 plant species have none of the traits typically associated with wide-ranging dispersal.
All thanks to the birds. The real responsible for the arrival of vegetation on the island of Surtsey, says the study, are the birds, in particular those known for their long flights: seagulls, geese, terns… It was they who ate fruits and seeds of all types of plants and transported them to the island, then depositing them on the ground in the form of faeces. All of these seeds belong to plants that would have had no other way of reaching Surtsey, the study says, at least according to classical theories.
The discovery of the role of birds in the colonization of islands is not only a theoretical revolution, but also has practical implications: bird migration routes become even more important because they also serve plants to migrate and potentially colonize new environments – something essential in a world where the climate changes so quickly.
