My own view is that we do not have an obligation to do anything about this issue. My main reason for saying this is that I do not believe that overpopulation is really an issue in our world today.
We do not have a problem with overpopulation. We do have a problem with using too many resources. People who can afford to do so tend to use a lot of resources. We use a lot of fossil fuels in particular. This leads to problems like global warming. We also have problems because our resources are not well-distributed around the world. We have too many people who live in places where there are few resources. These people tend to have problems because they lack food and other important things. These factors, more than overpopulation, cause the problems that we have. We should attack these problems, not something like overpopulation, which is not the true problem.
That said, we should make it easier for people to only have the number of children that they want. We should try to make sure that people, particularly in developing countries, have access to contraception. We should try to improve education in those countries because that can lead to lower birth rates. But these are things that we should be trying to do for the sake of giving people a better quality of life, not because overpopulation is a serious problem in the world today.