Hardnesses of Wood

I know that there are huge areas of knowledge that I've barely or never encountered, so it's always fun to brush up against one. It happened again the other day when I saw this randomly shared on Facebook via Home Handyman:

From it I learned that:

• There's a thing called the Janka Rating.
• There are two kinds of wood I've never heard of that are harder than hickory (Ipe and Bubinga).
• Bamboo — which I thought was strong when used as an upright but not hard per se — is harder than any kind of oak.

Ipe is from South America, and it doesn't sound endangered… though who knows what that means when it comes to the rain forests. It's also called Brazilian walnut. It's so hard, that it requires carbid-tipped tools. Bubinga is an endangered African wood.

I never thought of Mesquite as a lumber, probably because I don't think of it as being long enough to make boards — and it sounds as though that is fairly true.

Rosewood covers a number of species, and it sounds like its good lumber properties and slow-growing nature have meant humans have driven it close to extinction, despite the fact that its various types grow in much of the tropical world. 

Wenge, another one I've never heard of that's harder than oak, is from Africa. It's also endangered.  

All of this, and realizing how many of these trees are endangered, makes me think of that quote I recently posted from Hope Jahren's Lab Girl:

Human civilization has reduced the plant, a four-hundred-million-year-old life form, into three things: food, medicine, and wood.