The biggest problem

The biggest (scientific) problem currently for survival on earth?

The are many more interactive maps at the United Nations website.  And there is a new document out

Ten Key Findings
Citation: United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019: Ten Key Findings.

Nine countries will make up more than half the projected population growth between now and 2050: The largest increases in population between 2019 and 2050 will take place in: India, Nigeria, Pakistan, Democratic Republic of the Congo, Ethiopia, the United Republic of Tanzania, Indonesia, Egypt and the United States of America (in descending order of the expected increase).