Many practising Buddhists that I know also have strong ecological concerns. Is this concern for 'green' issues part of Buddhism or do the two things just attract the same kind of people i.e. people that like Buddhism also like green issues. Specifically does concern for the environment have any basis in canonical texts or commentaries or is it a modern development?
AFAIK there aren't any explicit references in the scriptures to ecological concerns and sustainability. I guess that in the days of the Buddha, there weren't many problems in that area. The ideas behind sustainability aren't new, but it wasn't until the second half of the 20th century (the energy crises in the 70s) that they became more prominent and that the growth of the entire human population and increased resource consumption were seen as a potential major problem for mankind.
I think what makes environmentalism and sustainability so interesting for Buddhists (or the other way around?) is that several main ideas are rather similar, or at least in line with each other. For example, the Buddha taught that everything, all life, is connected (dependent origination). Also there is no self, the self only exists in dependence upon causes and conditions (anatman). This means that if you damage the Earth then you indirectly are also damaging a part of yourself.
Buddhism also teaches us that we should take the middle way, lead a simple life, don't engage in addictive behavior or excessive consumption, be kind to others. These ideas are also prominent in sustainability. We shouldn't waste resources and should try to improve the living conditions for everyone, not just the rich people living in the Western world.
So to answer your question; I think Buddhism and environmentalism/sustainability just attract the same kind of people. People that really care for the well-being of others.
BTW, being a protem moderator of the Sustainable Living SE site, I can't resist making at least one reference to that site here. ;-)
One of the basic and profound teachings in Buddhism is about the 'precious human body'. Practitioners contemplate on how rare it is to be reborn as a human and how easy it is to lose life. Some may also know 18 qualities of human life (8 freedoms and 10 endowments). A well-functioning body is a great tool that will help us to reach progressive stages of realisation and once we deeply realise that, we will naturally be taking care of our body. Nowadays going 'green' is one of the ways to lead a healthier lifestyle and I suppose that is why many Buddhists choose to do so.
The difference is that some of the ecology-loving people treat the green issues as a goal rather than a tool. Buddhists should strive to have clean environment not because it is nice to have it but because such conditions are beneficial on their way to enlightenment. The teachings on emptiness tell us that on the absolute level everything is pure and beyond 'good' or 'bad' so even during the nuclear winter we can still reach enlightenment.
Notice that back then, humans were yet to possess the kind of technologies capable of screwing up the environment at such stupendous pace and scale as in the 21st century. Everything was bio-degradable. There was no plastic, nuclear wastes, fracking, oil drilling, massive fossil fuel burning, etc. So the problem didn't exist to require a specific teaching about it. Obviously if the Buddha was around today, He would've given teaching about the importance of keeping a safe and clean environment.
The Buddha made remarks (for lay people) about conserving wealth; for example, the Sigalovada Sutta warns against squandering wealth.
That sutta doesn't mention the environment, but modern environmentalists or economists say that degrading the environment (and other activities including the exploitation of fossil fuels, deforestation, mining, any "unsustainable" levels of fishing, etc.) is equivalent to spending capital rather than spending income ... and that we ought to be living sustainably, consuming renewable income rather than unrenewable capital.
The Buddha also made remarks about being harmless, not killing, allowing other being to live free from fear.
Again I'm not aware of his saying that in an "environmental" context, but according to environmentalists, there is such a thing as being "harmful to the environment" which isn't the same as being "harmless" or "saving the environment"; and that destruction of natural habitat and indigenous wildlife is "killing".
Lastly, there are many comments from monks (not, as far as I know, from the Buddha himself, but from monks) about some environment or other being pleasant: of enjoying the smell of a forest at night, and so on.
I've found some quotes from the Pali Canon that do seem to address ecological concerns directly.
There is a story from a Dhammapada commentary about Ananda receiving 500 robes and his recycling plans - to quote a part of it
What will you do with the old garments
We will make bed covers out of them
What will you do with the old bed covers
We will make pillow cases with them
What will you do with the old pillow cases
We will make floor covers out of them
[and so on]
Source for the quote is Puja Readings and Other Texts as used in the Triratna Buddhist Community pp 121. Unfortunately the quote doesn't appear to be on Access to Insight (well I can't find it) however this link gives details of the Dhamapada commentorial account as well as related stories in the Jataka and Vinaya.
There is also a reference in the vinaya in the Living Plant chapter which may speak to environmental concerns
Should any bhikkhunī knowingly pour water containing living beings — or have it poured — on grass or on clay, it is to be confessed.
According to the same Triratna book (pp 117) the commentary says that because of the Pali syntax the rule can be read both ways - so that pouring grass or clay into water is also to be confessed - i.e. water should not be polluted.
The path of all Buddhas is summarised as: (1) do not do evil; (2) do good; & (3) purify the mind. Purifying the mind means giving up attachment to the world. But this does not stop one from doing good. When the mind is free from attachment, it has few needs & even less wants. Therefore, the Buddhist path by nature looks after the environment & the planet as best as possible.
The Buddha taught it is right view to regard everything received as a 'gift' or 'benefaction' (MN 117), which gives rise to a reciprocal obligation in return. This includes the natural environment as a benefactor. In Pali, the word for gratitude means: "what is received; what must be done in return".
In the Vinaya (page 446) of the monks, there are rules about not polluting crops, water & other natural things that are required to support life.
Based in the Puttamansa Sutta, each day monks & some lay people reflect they use food, clothing, shelter & medicine merely to support the spiritual path & not for play, not for intoxication & not for beautification.
Buddhism attracts those that are keenly aware and concerned for the welfare of all sentient beings. With half the species extinct and more to follow, how can a Buddhist ignore environmental issues. By all the environmental affects including climate change, the suffering of billions of people will increase. Avoiding harm is a major precept of Buddhism.