The Ebola epidemic. The Syrian crisis. The murderous Islamic State campaign.
These might sound like serious worries at the moment, but by the end of this century they'll seem about as frightening as a cricket match.
Why? Because the Earth will have up to 13 billion people then, according to the latest demographic projections. And the population won't even have stabilized yet.
These are astounding conclusions, and they result from the most robust population projections yet conducted, by a team of leading demographers using the latest United Nations data. The results appeared recently in the world-leading journal Science.
Why does our population continue to skyrocket? A key explanation: Africa. Unlike much of the rest of the world, fertility rates (the average number of children borne per woman) haven't fallen in Africa.
Fertility rates have also remained stubbornly high in the predominantly Muslim nations of the Middle East -- and these are growing rapidly as well.
Conclusions like this should scare us all, but Europeans should be petrified. Legal and illegal immigrants are already streaming into Europe from Africa and the Middle East, in some cases causing serious social and economic conflicts.
Concern over this has led to a resurgence of anti-immigration political parties across Europe.
But imagine the situation in the year 2100, when Africa's population has quadrupled. When the population of Nigeria -- already teetering on the edge of political and economic chaos -- has increased by 500%.
Today's steady stream of desperate immigrants will become a tsunami.
There's one vitally important lesson here: It doesn't have to be this way. Populations in Africa and the Middle East are exploding because women there don't have access to adequate family-planning information and contraception.
It's also happening because educational and economic opportunities for young women are inadequate.
She has fewer children. Those children are better-off economically. As a result, they have better educational opportunities, and are healthier. And rates of divorce and domestic strife are, on average, much lower.
As they grow up, children from such families are far less likely to become involved in crime, or to be unemployed and socially disenfranchized -- a key correlate of violence and radicalization of young people by extremist groups.
It all comes down to delaying the age of reproduction -- everything else follows from this one simple change.
If we want to avoid a truly calamitous future, we have to tell our politicians -- loudly and emphatically and often -- that they must invest in family planning and educational opportunities for young women.
It has to happen now -- today. And our biggest focus should be Africa and the Middle East, as well as other rapidly growing regions of the developing world.
Forget about the latest screaming headlines -- the crises of the moment. This is our biggest crisis -- the one that, most of all, will determine the ultimate fate and health of our planet.