Screw Pines, Volcanism, and Diamonds

The association between geology and botany has always fascinated me. The closer you look, the more you can't separate the two. Rocks and minerals influence soil characteristics, which in turn influences which plant species will grow and where, which in turn influences soil properties. Take for instance the case of kimberlite.

Kimberlite is a volcanic rock whose origin is quite intense. Kimberlite is found in the form of large vertical columns, often referred to as pipes. They are the result of some seriously explosive volcanism. Intense heat and pressure builds deep within the mantle until it explodes upward, forming a column of this igneous rock. 

Over long spans of time, these pipes begin to weather and erode. This results in soil that is rich in minerals like magnesium, potassium, and phosphorous. As anyone who gardens can tell you, these are the ingredients of many fertilizers. In Africa where these sorts of pipes are well known, there is a species of plant that seems to take advantage of these conditions. 

It has been coined Pandanus candelabrum and it belongs to a group of plants called the screw pines. They aren't true pines but are instead a type of angiosperm. Now, the taxonomy of the genus Pandanus is a bit shaky. Systematics within the family as a whole has largely been based on fragmentary materials such as fruits and flowers. What's more, for much of its taxonomic history, each new collection was largely regarded as a new species. You might be asking why this is important. The answer has something to do with the kimberlite P. candelabrum grows upon. 

There is something other than explosive volcanic activity that makes kimberlite famous. It is mostly known for containing diamonds. In a 2015 paper, geologist Stephen E. Haggerty made this connection between P. candelabrum and kimberlite. As far as anyone can tell, the plant is a specialist on this soil type. As such, prospectors are now using the presence of this plant as a sort of litmus test for finding diamond deposits. This is why I think taxonomy becomes important. 

If P. candelabrum turns out not to be a unique species but rather a variation then perhaps this discovery doesn't mean much for the genus as a whole. However, if it turns out that P. candelabrum is a truly unique species then this new-found association with diamond-rich rocks may spell disaster. Mining for diamonds is a destructive process and if every population of P. candelabrum signals the potential for diamonds, then the future of this species lies in the balance of how much our species loves clear, shiny chunks of carbon. A bit unsettling if you ask me. 

Photo Credit: to.pbs.org/1NQUXqU

Further Reading:
http://econgeol.geoscienceworld.org/content/110/4/851.full