Those are very current problems.

As said, birth rates are already below replacement rates in developed countries and decreasing everywhere else. Projections are that the global population may stop growing by the end of the century.

The seemingly "easy" option of immigration is causing big societal issues in Europe with a growing backlash against it.

The global environmental crisis is caused by the booming population of the last century or so combined with economic growth.

So this is very much a "now" issue.