This is a wise proverb and one that is very important. They key words here are not the difference between the words, "ancestors" and "children," but the difference between the words, "inherit" and "borrow." The point is that when it comes to the earth, no one owns it. This this sense, we do not "inherit." We are simply, "borrowing."
When we borrow something, then we need to take care of it. We cannot do anything that we want, because we do not own it. We can even say that we are entrusted with some for a time being and we need to give it back at certain point. This is a good mentality to have when it comes to the earth and something that fits into the green movement. We only have one earth and we need to take better care of it for our children and our grand children.
This advice prods us to consider the future, and not to focus on the present or on the past. Instead of living just for today and gratifying our own immediate needs, we should think about how our current actions will affect the planet and the future generations who will live on it.
Let’s use an analogy and think of the earth as a house. If we are given a house to live in, we can use it as we please. Within its walls, we can live pretty much the way we want to. We can be as neat and tidy or as messy and sloppy as we tend to be. All we have to do is to please ourselves. Now, if we know that we will have to pass this house on to someone else down the line, then we should be more careful about how we treat it. It will have to be livable for others, once we leave. The implication is that we will take better care of the place, and we will think and act more deliberately when we consider the future and the folks who will come after us. We don’t want to leave a mess with huge challenges for other people to have to deal with and clean up after we’re gone. By doing the best job possible with our home, our place, our earth, we are showing respect both to it and to its future residents. We are being altruistic: showing unselfish concern for the welfare of others. We must be mere stewards of the land and its resources, not users and consumers of everything that happens to be on it. You probably wouldn’t like it if you bought a bottled beverage and discovered that someone had already drunk more than half of its contents, would you? Leave a full bottle for the next person, too.