Wednesday, January 16, 2013

Eric and the traveling plants

A little over 1000 years ago Eric the Red sailed around the southern tip of Greenland to set up the first successful European settlement in Greenland.  But it wasn’t just people and farm animals that joined Eric in his exile- seeds of several weedy plants likely stowed away on sheep fur and hay to become their species’ first representatives on the western coast of Greenland.  For decades botanists have suspected that a suite of “Old Norse” plants first rounded the Cape by way of Viking ships. A forthcoming study in the Journal of Biogeography confirms that at least three of these species were indeed introductions, rather than simply pre-existing residents whose life-style was favored by human activities.

Researchers in the U.K. and Iceland looked for pollen from three “Old Norse” plants (Sheep’s Sorrel, Common Knotgrass, and Common Yarrow) in layers of lake sediments near farm sites in the historical Eastern Settlement of Norse Greenland. When viewed under a microscope, plant pollen takes the form of small granules whose shape depends on which species the pollen comes from. When pollen lands on the surface of small lakes, it sinks to the bottom along with other leaves and detritus, which eventually builds up a layered mud pie recording which plants lived near the lake at different points in time.

According to historical texts, the settlement was active from 985-1400 CE so the scientists looked for whether pollen was present in mud deposited before, during and after this time period to determine how the plants arrived. This record showed that the three species first appeared around the time that the settlement began, increased in abundance throughout the settlement period, and declined during the century after the settlers abandoned their farms. What’s more- the first records of each species show up close to Qassiarsuk, believed to be the location of Erik’s original farm.

It’s not that surprising that the Vikings unintentionally transported foreign plants- the introduction of exotic species is an ancient tradition among humans that continues to this day. To me, the interesting part of the story was that once the Little Ice Age kicked the settlers out of Greenland, the introduced plants also began to disappear. There is sometimes a misconception that all introduced species become invasive, causing harm to the native ecosystem. In this case that didn’t happen, likely because these plants are ruderals (i.e. weeds) that prefer to live in disturbed areas like the trampled ground around homes and farms. Once their favorite habitat was gone, the introduced plants just didn’t do as well when they had to live like the natives. At least until the Return of the Europeans.

You can find this article at:

ResearchBlogging.orgJ. Edward Schofield, Kevin J. Edwards, Egill Erlendsson, & Paul M. Ledger (2012). Palynology supports 'Old Norse' introductions to the flora of Greenland Journal of Biogeography : 10.1111/jbi.12067

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