Smail gives a few reasons as to why even a fully effective populations control program wouldn’t be enough to reduce the worlds population.
Smail says that even if a program of zero population growth were implemented immediately by limiting human fertility to roughly 2.1 children per female which is called the replacement rate, global population would still continue on its path of rapid expansion. Demographers estimate that it would take two to three generations at the replacement rate to reach a point of population stability. This is because 1/3 of the population is still under the age of fifteen and have not reproduced yet.
Smail also mentions how adult longevity is contributing to the worlds population. He says the on going gains in this longevity will continue to keep the population high regardless of the fertility aspect.
Smail sees how the earths long term carrying capacity in finite. This is a problem because resources whether they are renewable or non-renewable will run out with so many people on the planet. All in all humans wouldn’t be in existence if it wasn’t for earths resources. So running out would result in the end of humanity.
What Smail means by his statement is, as of this moment in time humans view themselves in regard to the Earth as the masters of the earth. The fact that we feel entitled to destroy Eco-systems by cementing over land or polluting waters and among other things, we are acting like we own the earth. But in fact we are as important as any other living organism. We wouldn’t exist without these other ecosystems and organisms. We share this Earth and have “co evolved with literally millions of other life forms.” Smail is basically saying that we need to stop thinking in this master mentality and start thinking in a co-existing mentally with Earth and all of its life.