Tree planting skeptics really get under my skin. In general I’m in favour of skepticism, but only the well-informed, intellectually curious kind, not the knee-jerk “it doesn’t sound intuitively realistic so I’ll disbelieve it without bothering to check” kind. That’s also the key difference between skeptics of divine intervention and skeptics of climate change, but for now let’s stick to tree planting.
For the record, I have planted more than a million trees, and so has my brother and several of my close friends. My mom, Joyce Murray, who is currently running for Leader of the Liberal Party of Canada, has planted more than half a million. Don’t believe me? Read on.
Yesterday I got a cheerful email from a couple of mathematics professors at University of Massachusetts, Boston, informing me that they were using me as a case study for teaching “Quantitative Reasoning” and applied mathematics to undergraduates, and that I was even referenced in a math problem in their textbook. I felt so proud! You can view the full problem here (page 8), but I’ll just quote from the opening lines:
On May 4, 2010 Olivia Judson wrote in The New York Times that
[Baba] Brinkman, a burly Canadian from Vancouver, is a latter-day wandering minstrel, [and] according to his Web site, he has personally planted more than one million trees.
How long would it take to personally plant a million trees? Is Brinkman’s claim reasonable?
To answer that question you need two estimates – the time it takes takes to plant one tree, and the time Brinkman may have spent planting.
To plant a tree you have to dig a hole, put in a seedling and fill in around the root ball. It’s hard to imagine you can do that in less than half an hour.
At first I kept my cool and wrote back:
Here’s a video of me and my friends planting trees:
Now here’s an assignment for you: have your students watch the video and identify the flaw in your analysis… Hint: planting a tree takes ten seconds.
But upon re-reading the textbook entry I started to feel that familiar flush of agitation creeping up my neck, that feeling evolution has endowed us with to fiercely protect our precious reputations when they are publicly questioned, especially (but not exclusively) when the threatened acclaim happens to be hard fought and well deserved. The concluding sentences of the textbook read:
On balance we believe he’s planted lots of trees, but not “personally . . . more than one million.”
It’s the “personally” that makes this very unlikely. We can believe the million trees if he organized tree-planting parties, perhaps with people manning power diggers of some kind. Or if planting acorns counted as planting trees.
Acorns?! The message was emasculating enough without the added iconography, so I hastily composed a second email, the intellectual equivalent of “Are you callin’ me a liar?!?”
This is a perfect example of how applied mathematics can be rendered useless by faulty assumptions…
My question is: did you write that math problem without doing any research whatsoever into the parameters of the job you were describing, or did you do research in a way that was designed to confirm your existing (false) assumptions about the job? Either way, what lesson does your error offer to students of applied mathematics for whom relevance to reality is a high priority?
Feel free to quote any of the above in your next edition.
Even if there is no second edition, I would appreciate an amendment, as the current edition is clearly insulting not just to me but to everyone who works hard at tree planting only to be questioned by the sheltered and clueless.
In retrospect my response was probably a bit hot-headed, but this wasn’t my first encounter with the “sheltered and clueless”, and I know other tree planters often meet with the same aggravating disbelief. For instance, commenters on the original NY Times article made the same pronouncements, and now they are questioning my mom as well. At any rate, the professors were far more temperate than me. Here’s Charles Wibiralske, the adjunct professor who first initiated contact:
We are on the case. Your stern tone is appropriate. Part of my lesson with my students will be to demonstrate that if we are not careful, we can easily make errors. Our exchange will make the class better. In addition, I hope to model that when I suspected there could be a problem, I wrote to you right away. Then I hope to show that as academics we are open to making errors, questioning our assumptions, reaching out to get the best material we can, learning new things and making corrections.
His response showed that I too was open to making errors based on faulty assumptions, in this case about the social skills of math professors. The response of Ethan Bolker, the author of the textbook, was no less graceful:
I had no intention whatsoever of insulting you. I am well aware of the fact that faulty assumptions can lead to faulty conclusions – one of the things I try to teach my students is to be sure that whatever assumptions they make are explicit, so that they can be checked – or refuted by people who know better. I admit that in this case I didn’t check, for which I apologize.
With your permission, we’ll rewrite Section 1.5 and tell the whole story in the text (from wrong assumptions to correct ones, with quotes from you and links to your video), and show you the new version.
Hurray! In the end it’s a classic example of academic best practices and the drunkard’s walk towards knowledge. When our views are self-correcting and open to revision based on new evidence, they will continue to hone in on increasingly accurate representations of the real world. That’s good honest skepticism, and when it wins over bad, knee-jerk, “it’s hard to imagine” skepticism, that’s a beautiful thing.