Recommending use of a compass cactus without the caveats
From BearWiki
Claim: Bear recomments the use of a compass cactus, saying that they always point south. This is not the case.
In the "Moab Desert" episode, Bear recommends that travellers who are lost in the desert orient themselves via a "compass cactus" (barrel cactus), stating that it always points south. Like the "moss only grows on the north side of a tree"[1] and other such notions, this isn't a reliable way to get your bearing, and could send you in entirely the wrong direction.
First off, the reason why such directional biases exist is due to sunlight. A plant may try to orient itself to get more sunlight for photosynthesis, or less sunlight to reduce water loss. Right there lies a problem: other factors beside sun position, such as rocks or other plants, can bias the sunlight reaching a plant.
Secondly, different barrel cacti have different biases. Some don't point at all, so any bias may well be random. Some grow southwest[2][3]. Some, like Bear's claim, grow to the south.[4][5]. There may be other biases in a given cactus.
Put simply, plant growth directions may be biased, but they are not reliable.
[edit] Analysis
Oppose: Bear mentions it would be unwise to rely on one cactus to orient yourself and implies the unreliability of them. He advises looking to see if all or many of the plants in the area are pointed in the same direction; if so that direction is south. This may or may not have been in the revised version, but either way it didn't seem misleading to me when I watched it. The whole idea of miseducating viewers as a strike against the show is weak: if I were stuck in the Moab Desert I wouldn't try to use the cacti to guide my way, because I wouldn't know well enough what to look for. No one decides to watch Man v. Wild before deciding to get lost in the desert anyway.
- Support: So, the swimming under a debris jam in a slot canyon was a GOOD idea?!? Going deeper and deeper into a slot canyon to find civilization was a good idea?!? The Urine Hat was a good idea (as opposed to just not being out in the heat of the day)? So much bad advice in one episode.
