The description of
Isengard - on a larger scale
Mordor, on a smaller scale the new mill in
the shire - centers very much on pollution, by industrial processes. There has been massive pollution in JRRT's time: Birmingham in his youth, Leeds during his fist university post. Later, in letters, he commented more on an aspect that does not appear in
Middle-earth, the pollution by what he called the
infernal combustion engine - air and noise pollution. I suppose everyone who remembers the exhaust stink in traffic jams before pollution control equipment for vehicles became ubiquitous will agree that pollution control equipment is a good thing. I don't even want to
imagine today's even more congested traffic conditions with those old stinkers - which included my first three cars between 1978 and 1987. JRRT didn't live long enough to see the spread of pollution control equipment, though I'd guess he'd still be not amused by the increase in traffic.
Cutting down
trees certainly was something he didn't approve of. But then the UK turned to coal quite early because of early massive deforestation. Not that this switch helped the air pollution problem, quite the contrary. Had to do the the UK's early industrialization, too. And I'd guess those pits in Isengard also were for another, much older pollution problem: mining. Hardly anything is as environmentally destructive as that, especially the huge open-pit variant used to go after low-yield sources.
There is one inconsistency in Middle-earth, in metal-working. Oh, where the
Orcs are, there are also huge slag heaps. Where are they around
Erebor, or
Moria? How did the
Noldor fashion their
swords, where did they get the raw
materials from? Were there slag heaps in
Valinor?