The appeal to nature fallacy us to claim that something is right because it's "natural". It's not necessarily wrong to say that something can't (practically) be changed because it's natural. In this sense, natural means "an (emergent) property of nature". For example, as much as we may dislike it, people will continue to fall to their death in the near future, as gravity and its associated risks are natural.

I believe Paul means that these economic properties are to be expected because they arise naturally and it is not practical to eliminate them.