One of the interesting things I learned about in the phytogeography course was that there was a glacial refugium right here in B.C., located on the Brooks Peninsula of Vancouver Island (see point A on the map).
So I wondered, how was it determined that this was a glacial refugium, and what evidence was taken into consideration to support this? One great paper on this, was written by an expedition team who went to the Brooks Peninsula to look for evidence to support this idea of a glacial refugium (Hebda, R.J., 1997).
The researchers looked at geographical evidence, as well as biological and paleoecological evidence. For example,they found a glacial “trim line” with different features above and below this line.
Evidence of glaciation below the trim line includes stoss and lee forms (whalebacks) and striations on the bedrock ridges in saddles just below the trim line as well as other formations. Above the trim line, the topography is more rugged and jagged with steep slopes indicating a non-glaciated terrain.
They also looked at the soil type, at higher elevations. This podzolic soil, contained gibbsite (which is a clay mineral, largely unkown in Canadian soils), and high levels of talc – suggesting that this soil may be older than the postglacial soils found elsewhere on Vancouver Island.
Biological evidence included the existence of fossil pollen data, such as pollen from a coastal endemic plant – Ligusticum calderi in late glacial sediments, indicating that it survived the last Fraser glaciation in this area. The possibility that the pollen was wind blown to this area after the ice melted is weakened by the fact that this plant is not well adapted for long distance dispersal.
It was also found that most insect species with disjunct distributions have their nearest neighbouring populations in northwest Washington State, which was largely beyond the glacial ice limits. And in addition to this, a high percentage of flightless ground beetles were also found, which is another indicator of a glacial refugium.
As for macro or microfossil evidence, unfortunately none was found. However, taking into consideration the above data, it appears likely that the Brooks Peninsula in BC was indeed a glacial refugium.
- Reference: Hebda, R.J, Howes, D., Maxwell B. (1997). Brooks Peninsula: An ice age refugium on Vancouver Island – Chapter 15: Brooks Peninsula as an Ice Age Refugium. Occasional Paper No. 5, Ministry of Enviornment, Land & Parks: Victoria