I'm going to shortly analyse mankinds relation to the ecosystem. An ecosystem that has great diversity would also have great resiliens, but the carrying capacity for us will be less. An ecosystem that has less diversity will also have less resiliens, but in exchange it has a greater carrying capacity for us.
If the population on earth continue to grow it means that mankind will consume more of what the ecosystem produces, which means we need to get rid of other species that are consuming products from the ecosystem. Most of the time this just means we farm more efficiently (genetically engineered crops). This will get rid of a lot of species. We can of course take more active measures such as killing all whales, so that we can get more fish out of the oceans. By getting rid of the competition we can keep increasing the population of earth. Since the ecosystem will lose its resiliens mankind is going to have to develope new technology in order to keep the ecosystem in balance. So the more we are, the greater responsibility we have to take for balancing the ecosystem. This means we are going to have to build a defense system to help the ecosystem (recycle, reduced pollution). On the other hand if we try to actively control the population at some level this will give us a certain amount of diversity and resiliens that we will have to adapt to. This means that somehow mankind is going to have to set up a target population, preferably discussed and agreed upon in UN.
An argument that can be made in favour of trying to keep the population as low as possible is of course the aesthetic enjoyment that comes with biodiversity. There is a big difference between seeing a whale in the wild compared to on TV. So in addition to resiliens we also get aesthetic enjoyment.
An analogy one can do is to resemble nature to a reliable car engine. To have a large human population would be the same as putting in high performance parts in the engine. We all know what high performance parts does for reliabilty.
Humans produce offspring in order to secure their retirement. So for a society to get control over its population growth it needs to offer a secure retirement for its people.
Comment: What nature looks like one day when mankind lives in harmony with it is going to be a reflection of our soul.