Here’s my two cents on this issue, so I suppose you can take it for what it’s worth if you like.
I think population size is a matter that should be given careful consideration by everyone, and shouldn’t simply be blithely ignored. I neither believe that we’re at a point of rapid population growth that will tend toward our own destruction through overpopulation, nor do I believe that we’re at a point of rapid population decline that will tend toward our own destruction.
That said, neither rapid growth, nor rapid decline are desirable ends, and I don’t think we as a specie have carefully considered this issue such that we’ve taken proper measures to manage ourselves in this regard.
On the one hand, it is irresponsible to reproduce without due consideration of resource constraints. Responsible family planning is not about not trusting in God’s providence. Suggesting as much is like suggesting that we shouldn’t bother with medicine because God will provide. That is simply not the Catholic approach.
On the other hand, it is also irresponsible to curtail reproduction artificially. This doesn’t lend the proper respect to our reproductive power that it deserves.
Irresponsible reproduction damages our environment, while artificial birth control damages ourselves.
A great range of issues here have been considered, but rather than working toward a common understanding that might lead to a unified vision of how to proceed, entrenched argumentation has taken place.
Both overpopulation and underpopulation should be concerns for good Catholics. God did command humanity to increase and multiply, and we have done so. Does this mean infinite expansion? Christ tells us that in the end, there will be no marriage. If this is the case, does this mean that in Heaven we will no longer continue to reproduce? If this is so, then might we also consider that infinite reproduction was not what was intended by God’s command to be fruitful and multiply? Priests do not procreate, nor do celibate brothers and sisters, and this is good.
God also gave us dominion over the earth. What does that mean? What does that look like? It means that the earth is our domain, it is our house, and we must rule it. The earth does not only consist of humans. We are the heads of this household, earth. As the head of the Church, Christ gave Himself up for us, sacrificed Himself for us. He loved us. Likewise are husbands commanded to love their wives. Masters, leaders, rulers are called to be the servants of those they rule.
I am not placing plants and animals above humans, nor even on equal standing with humans. Our value is beyond theirs. Nevertheless, it is our obligation, our OBLIGATION, not only to care for one another, but also to care for those creatures that have been put in our charge. As a specie, we have failed, and are failing, on both fronts.
The Catholic approach is “both/and.” We cannot separate this issue into “humans or animals/environment”. We must consider both, and care for both. Therefore, we must consider what effects our population growth is having and will continue to have on those creatures whom God commanded us to have dominion over. Likewise, we must also be obedient to God’s command to be fruitful.
We must carefully consider what extension of our lifespans through improved medicine will have on our population size, both in relation to how that will affect peoples’ economic situations and standards of living, as well as how it will affect the other species on our planet.
We must consider better methods of resource management, and population localization. For example, is it better to build horizontally (ie, the "urban sprawl’) or to build vertically (both upward and downward)? How will each of these methods affect our economic situations, and the other species on our planet?
We must consider our consumption practices. Do we live sustainably, both individually and as a society? How do our consumption practices affect each other, and the other species on our planet? Should we consume less? Redistribute resources for more equal consumption? Find alternative sources of energy?
Even if we changed all of our practices so as to maximize personal economy, and environmental protection, should we consider ourselves free to multiply indefinitely? What impact would that have not only on our consumable resources, but also our material resources for construction?
I think it behooves us to ask the question, “what is a responsible population size?” This shouldn’t be asked selfishly, so as to maximize one’s own personal comforts. Rather it should be asked selflessly, so as to understand what size is too great for the earth to hormoniously sustain, as well as to understand what size is too small for us to properly care for each other and for the earth.
Ignoring this question is not responsible. I will reiterate that I am not someone who thinks overpopulation is a problem, nor do I think underpopulation is a problem right now either. I am not a person who holds animals in an inordinate esteem relative to humanity. I simply recognize that higher species that ourselves serve us (angels), as well as the ultimate being Himself, and therefore we also should care for those beings who are lesser than ourselves, except where that care represents a neglect of care for our fellow man. I am also against forced population control, in case you were wondering. And ABC is also out of the question, as I am a faithful adherant to the Magesterium.