The alpine and tundra wildflower Dryas octopetala has the honour of lending its name to a period of climate change called the Younger Dryas, around 10,000 years ago, when glacial conditions rapidly set in across the higher Northern Hemisphere. Pollen from the Dryas flower suddenly began to appear in ice cores. The abrupt arrival of the alpine flower in the record signalled a dramatic change in climate.
The idea that climate could change abruptly challenged the gradualistic world view of the time. Now, the prevailing theory for the cause of the Younger Dryas is that a sudden influx of water from North America shut down the thermohaline circulation.
How will our present epoch be defined? The world is currently entering a period where human influences on our environment will leave clear and discernible fingerprints in the geological record. The pollen record will tell of cultivated plants, wheat and cereal crops, all the tell-tale spore of humanity, of agriculture replacing native plants.
What about uncultivated plant species? In the pollen record, imported plants, exotics and escapees would appear as sudden spikes in sites all over the world. Pollen dispersal, previously restricted by geography, that has been facilitated by human activity.
The world still has its uninhabitable regions, where the vegetation has not been directly altered by human influence. Nonetheless it too will show the signature of the Anthropocene.
The climate is changing once again, but this time Dryas octopetala is not moving South, leafing down from its northern latitudes. However, the taiga is moving north. As the treeline migrates into the tundra, as the tundra retreats and the permafrost melts, our epoch may come to be defined not by the abundance of Dryas, but by its absence.