[v-erne]

>> The world population is collapsing at a rapid pace.

Maybe the second derivative of world popultion is collapsing but not the "world" population (at least if you mean world as a whole and not "developed world" only, because population of "developed world" maybe getting there).

>> Our economic prosperity is based on a growing productive population.

If by prosperity you mean key economic indicators like GDP, then yes. But those economic models are so primitive that I question they usefulness and validity. The nature of work changed so much for last 100 years due to technology that it amazes me that we still belive that it can be summed up with few simple agregate numbers. Even the most important domains such as Agriculture, despite growing population, are needing less and less people to produce almost enough (if we include the food waste it's more than enough, but lacking fair distribution). At this moment about 800 milion people are working in or around farming - that's only 10% of overall population. In year 2000 agriculture was employeeing more than 1 billion, that is - 16 % of population.

This is the real reason of production growth - technology advancements and popularisation, not population growth.