The issue of sustainability of guitar wood (and wood in general) is very complicated, with many different factors to consider, and I’m not going to go into any great detail about it here. This is just a (relatively) short summary of my thoughts about sustainable wood selection for guitar making.
I think that the beginning of a sustainable future for high-quality hand-made wooden guitars is to forget the idea that there are a few magical “tonewood” species which are necessary to make great guitars, and instead rationally look at the mechanical, acoustic and aesthetic properties of individual pieces of wood, and the environmental impacts of using them, then make intelligent choices based on those realities. The traditional wood choices for classical guitar making were largely dictated by what was available in 19th century Spain, which is not a particularly useful criteria for choosing wood in 21st century England: some species which were easily available then are now endangered, and some which weren’t may actually be better than the traditional choices in some ways. There is no real justification for using endangered/threatened species to build guitars when there are more sustainable and responsible alternatives which can work equally well.
Independent guitar makers often make the excuse that we aren’t the real problem, as the amount of wood we use in a lifetime isn’t enough to cause any major deforestation, but that really is just an excuse: even if you’re only a small part of the problem, you’re still part of the problem. As an analogy: saying that you only ate one panda in your whole life wouldn’t make it OK. Also, I feel that as makers of high-end expensive wooden objects, we act as some of the figureheads of the woodworking world, and what we do will be followed and copied by larger scale guitar manufacturers and other woodworkers, which then creates a much bigger part of the problem.
I have to admit that I’ve been quite lazy about actually changing my wood buying ways, because of the weight of traditional expectations about classical guitar construction, and the difficulty of finding high quality wood from sustainable sources. In the last few years, the sourcing issue has been partially solved by the increased availability of FSC certified woods, so at the beginning of 2016 I decided to put my money where my mouth is, and made up some responsible wood buying rules for myself.
Since 2016, the new wood I buy for my instruments has mostly been non-threatened (according to http://www.iucnredlist.org), non-tropical species. Any tropical species have to be from an FSC certified source (which is not a perfect system, but it’s a step or two in the right direction), or reclaimed wood. Where possible, I buy wood from sources which I personally know to be responsible/sustainable (e.g. from storm damaged trees, or small-scale timber production from sensibly managed sources).
I already have enough experience of working with a wide range of woods to be confident that I can make these changes while continuing to improve the quality of my guitars. In fact, through the process of researching and testing “new” woods, I’ve found some which I think are better options than the traditional choices.
I’ve used various soundboard woods over the last 20 years, but have mostly settled on using European spruce as my standard choice, because it gives a richness of tone colour which I don’t seem to get with other woods. European spruce is not endangered or threatened, and can be sustainably sourced, including from FSC certified sources. There is a question over the sustainable availability of trees large enough to make 2-piece tops, but a well made 4-piece top can work just as well and can be made from a much smaller/younger tree, so I have no immediate worries about the sustainability of soundboards.
Backs and sides
The standard/traditional choices for classical guitar back/sides are both on the way to becoming endangered species, due to years of unsustainable overuse:
There are many alternatives which can make equally good guitars, but the main ones that I’m using at the moment are:
sycamore maple: a very traditional choice for instrument making, including guitars (used by Stradivari, Panormo, Torres, Hauser) and easily available from sustainable sources.
You can see some photos of guitars made with these woods here: http://www.woodhouse-guitars.co.uk/back-and-sides-wood-gallery/
There is a similar story with traditional neck woods:
again, there are good alternatives:
Douglas fir: stiffer, and with a higher stiffness to density ratio (a good thing for a neck wood) than Spanish cedar, with about the same density and hardness. Available from sustainable sources.
maple, walnut and cherry can also make good necks.
katalox: harder, stiffer and more stable than ebony, and it’s available from FSC certified sources.
purpleheart: also stiffer and more stable than ebony, also available from FSC certified sources.
Rocklite Ebano: is an engineered ebony substitute material which looks and feels similar to ebony. A good choice if you want a plain black fingerboard.
plum and other fruit woods: a traditional choice for fingerboards on early string instruments (lutes, viols, etc.)
I do the majority of the work on my instruments with hand tools, but do use some power tools: I buy my workshop electricity from 100% renewable sources, from https://bulb.co.uk