Modeling

Back of the Envelope

I started this semester with what I would consider to be a very interesting class, but I couldn’t seem to make the connection between the goals of the course and the theme of this class.  It was three agonizing hours of “back of the envelope calculations”, which are rough calculations using common knowledge that can be done on the back of an envelope. I mean, sure, it’s interesting, but I don’t see how the rough calculation of how many dentists are in the Greater Montreal Area is relevant to Earth system modelling. 

There were some questions in our assignment that were quite striking. They addressed real-life environmental topics. The first was “how many pairs of shoes can be made with one cow?” My first instinct was to write “None. Make your shoes with something else” because I’m a strong believer in animal rights and veganism. But my classmates and I went ahead and somehow came up with answers ranging from 6 to 40 pairs. Regardless of what the real number is, just think about this: picture a cow and a class of 40 people. If they all had one pair of leather shoes, that’s (potentially more than) one cow. This means that to give everyone in Canada one pair of leather shoes, we would need at least 900 000 cows. I’m not trying to push my views on anyone, but just keep that image in your mind, and take into consideration that these shoes don’t last very long. 

The next question would have been incredibly interesting if I was allowed to do some research first, but we were only allowed to use our brains. It asked what area of watershed is required to meet the water needs of Montrealers. From what I know, the area of the island seems to be large enough. This assumes a yearly consumption of 300L of water and 40 cm of runoff, which in my opinion is on the low-end of consumption and the high-end of precipitation. Don’t be fooled by these numbers, because most of this water is not even usable because a lot of it is snow, or doesn’t fall in useful places. We are fortunate enough in Montreal that we have other water sources, but this does not mean that we should be careless with our water consumption. Here is a link to a list of over 100 ways that you can reduce your household’s water consumption. I cannot stress enough the extreme importance of depleting freshwater sources on Earth today. We should almost treat water as if it were gold or platinum; not expensive, but very precious.

This last question left me in a state of panic for a moment. It asked how long it would take for the livable surface of Earth to be covered in two metres thick of garbage. Just the thought of that actually happening was terrifying enough, but then I had to go ahead and attempt to estimate it. I started by looking at my own garbage production, imagining my daily waste sprawled out on the floor, and worked from there. I used a vague estimate of how many Canadas could fit into all the land on Earth since that’s the only country I roughly knew the area of. It came out to be 56 000 years. Although that may sound like a lot of time, that’s also an insane amount of garbage, meaning that that’s actually a very short amount of time. The rate at which we, in the developed world, produce waste is incredibly quick, hence why the term “overconsumption” is often used to describe our way of life.

I’m just about ready to go on a full-blown rant about overconsumption and deprivation on Earth, but I think I’ll save that for another post.

These back of the envelope calculations are simply fascinating, but after doing them, I really wish I could know the real answer! They really got me thinking about my own water consumption and waste production. Although I might think that it’s really not all that much, I now know that I should really consider the population as a whole having the same or similar impact. Just a small reduction from each person can have exponential results. I don’t live alone here on Earth, and neither do any of you. I’ll leave you with that, and all the above striking numbers up there in hopes that it will also get you thinking and consider your own consumption.

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