Re: dogmatisit on both sides
"Population rates aren't rising, they're falling."
Not sure if that's what you meant but every day, and certainly for the next few decades, assuming BAU, there will be more and more people in this world. Add in the longer life-spans where people retire later in life (or never retire) and things are not looking good. Your sentence seems to be implying otherwise.
"Land isn't becoming scarce - as we live in urban areas, we use less land."
Wherever I look the price of good land keeps rising which suggests otherwise. I know China is trying to buy land left, right and center. Why do you think that is happening?
"We have enough land to feed everyone."
And yet the price of food keeps rising. Every year it takes a larger chunk out of our income. And if you think India is not facing major problems you are ill informed http://is.gd/AkzttY
"All this is the result of prosperity - it came about by people ignoring arguments like yours about natural resource constraints - and doing inventing clever and useful ideas"
Prosperity at a price. Americans & co have all the wealth but at the price of a 'work until you die' lifestyle. Well, You might get rich but you are far more likely to die first. The Chinese are following in their footsteps and sacrificing their poor and their natural environment for a 10% rise in GDP year after year.
I agree that those that call themselves environmentalists are often full of unattainable ideals and a weird idea that a life without technology was somehow better. But I truly believe you are living in the same la-la land as them, just in a different neighborhood. But there's no need to argue, you have already won. If you look at what is happening in the world you can see that most people will never sacrifice convenience for a chance at a better future. Not until it's waay too late.