The causes are co-option and destruction of ecosystems, and various sorts of pollution. I do agree that it's inaccurate to focus on overpopulation. Still, some impacts, such as ecosystem co-option for agriculture, and harvesting wood for fuel, are substantial even without industrial development.
Also, expecting industrial development to moderate growth rates in rapidly growing populations is iffy. Time lags could push systems into regimes with positive feedback. Ultimately, though, human populations will crash, and stuff will head back toward equilibrium.
The only possible solution is policy changes that force a significant decrease in resource usage among a wide swath of the developed and less-developed population. That solution would be necessary regardless of the level of population increase we're going to see. The population increase is going to correct itself. The resource usage so far does not seem like it's going.
And certainly, populations in less developed areas have done and can quite a bit of damage - but that damage can only be corrected by state policies to prevent poor resource usage.
Also, expecting industrial development to moderate growth rates in rapidly growing populations is iffy.
This has occurred in a fairly predictable rate over the majority of the world's area. India, the Mid-East and Africa are basically the primary areas of growing population in the world.
Also, expecting industrial development to moderate growth rates in rapidly growing populations is iffy. Time lags could push systems into regimes with positive feedback. Ultimately, though, human populations will crash, and stuff will head back toward equilibrium.