Ecology from geology

I recently asked a geologist* to come to speak to my field biology class. The course is about the “St Lawrence Lowlands“, and throughout the term we visit farms, forests, lakes and streams, and we do natural history research.

Why then, do I have a geologist come and speak to us?

A result of glacial till: it's now supporting biodiversity.

A result of glacial till: it’s now supporting biodiversity.

Ecology is built upon geology. This may seem obvious, but requires a deeper discussion: after hearing this guest lecture year after year, I no longer see my local landscape as some farm fields, patches of forests, and some big bodies of water**. I see lands and waters shaped by a history before our time. The local landscape is a product of past geological events. We have farm fields around the Montérégie because the Champlain Sea deposited its sediments and after it departed; what remained is a flat expanse, perfect for farming. As the sea departed, it left behind remnants of beaches still visible today, as the Plateau district of Montreal, or where apple orchards grow next to Mont St Hilaire. We have some slight elevation here and there because of sandy deposits left by the departure of the last great glacier that covered our land in the very recent past. That’s where we find great white pines, stretching up above the canopies of the deciduous trees. We have Mount Rigaud because of processes hundreds of millions of years ago: an igneous intrusion that happened long, long before the age of dinosaurs. More recent igneous intrusions created the Lachine rapids, historically important as this became a key place where First Nations people, and later Europeans, set up camp along their journey up or down the big river. This was the one of the birthplaces of Montreal.

Our landscape, and the ecology of our landscape, is built upon slow but incredible processes, and I think biologists don’t consider those processes as dynamic forces that are constantly influencing our current view of the world. Ecologists often think of time in scales of decades or centuries, and we spend considerable time looking at time frames that resonate with our own life spans (in contrast, evolutionary biologists and taxonomists look much further back, and are accustomed to time frames of ‘millions of years’. I think We need to meet in the middle a little more).

As field biologists, knowing the origin of those big rocks in the forest matters a great deal: glacial till from the past creates habitats today. Moss creeps on these ancient boulders; centipedes and spiders crawl underneath. Their ephemeral life depends on much longer time frames. It’s hard to imagine how to consider discussion land management or wildlife conservation in the region without appreciating how past geological events can either help or hinder the process. There’s a geological reason why soil development is slow in some parts of our local ecosystems; why the land may be rocky, and why it’s well-drained in some areas, and wet in others. This affects long-term planning around wildlife preserves, or housing developments. There’s good reason why Mont St Hilaire is a biosphere reserve, and how it’s flora and fauna will be different that what we find elsewhere in the St Lawrence Lowlands.

Hiking at Mont St Hilaire: there are so many reasons why it's a special place, including geology.

Hiking at Mont St Hilaire: there are so many reasons why it’s a special place, including geology.

The longer I spend living here and learning about my region’s natural history, the more I recognize the value of some knowledge about geology, and this is why I have a geologist give a guest lecture. The students also tell me, year after year, that they appreciate and value this perspective, and their understanding of this part of the world is enriched by a deeper discussion about ‘why’ the St Lawrence Lowlands exists as it does.

How often do ecological classes include discussion about geology? Perhaps not often enough.
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*the geologist in question is Dr. George McCourt, who teaches often in the McGill School of Environment. I am immensely thankful for him taking time to teach us about his passion.

**when I commute to work, this is what I see: forests, field and lakes. Others in the St Lawrence Lowlands will have a different story, perhaps one that involves highrises and concrete.

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2 thoughts on “Ecology from geology

  1. Great post! I’ve been fascinated with geology since I was a child – I wanted to be a geologist for a while, but the mining boom turned me off that idea! 😉 Agree, soils & geology shape ecosystems and aboveground processes a lot more than we often give credit for. I’ve noticed a few interesting studies published recently attempting to link soils/geology with fauna/flora communities, so it will be interesting to see what other questions come along!

  2. I had one class in my environmental science masters program that included geology, and it was one of the most informative classes I’ve ever taken. Completely reshaped my thinking, as previously I was just biology-focused with the land being the backdrop for the organisms.

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