According to a new UN report, there are now 8 billion people on Earth

People around the world are living longer and having fewer children. These are just some of the trends outlined in a United Nations report on the world population.

Life expectancy is expected to increase from 72.98 in 2019 to 77.2 in 2050 as global growth rates continue to slow, the report released on Tuesday said.

The world reached 7 billion people in 2011, and the United Nations predicts it won't reach 9 billion for another 15 years.

While the milestone is significant, George Mason University public policy professor Jack Goldstone says the exact size of the world's population is less important than the mobility of people living, working and moving around.

"I think what's important about the 8 billion is going to be connectivity, and so we have to get used to the idea that what happens in other places will directly affect our quality of life here," Goldstone told NPR's Morning Edition.

This slower population growth has been explained by several factors, including more accessible birth control and better education. Some countries have birth rates so low that the United Nations predicts they will not be able to sustain their population.

Life expectancy in the least developed countries is seven years behind that of most developed countries as of last year. The United Nations has warned that countries with ageing populations need to develop better systems to care for their elders, including social security and universally available health care.

Goldstone says that despite limited resources and climate change, the world can still manage with a population of 9 or even 10 billion as long as it pays attention to "what people are doing, how they're living and what specific regions or groups are growing". " "quickly"

The report predicts a reshuffle of the most populous countries. The report predicts that India will overtake China as the number one populous country in 2023 and remain so until 2050. The United States will displace Nigeria as the third most populous country in the same period.

According to the report, immigration, and international migration, in particular, is a major drivers of population change. All countries - experiencing an "inflow or outflow" of migrants - should do what they can to create order and stability in these changes, the authors say.

In an opinion piece in USA Today, UN Secretary-General Antonio Guterres warned that global population inequality threatens the overall stability and longevity of the world's population.

"Divisions are causing delays and deadlock on issues ranging from nuclear disarmament to terrorism to global health," Guterres wrote. "But I never bet against human intelligence and I have great faith in human solidarity."

Guterres praised advances in science and public health around the world but warned that the "human family" is at great risk if it continues to be further divided.

If climate change doesn't slow and more famines occur, Goldstone says, the big priority should be helping countries facing energy booms — and who are now major energy donors — move to a cleaner fuel path.

"The sooner we get to that cleaner, lower-cost future, the better for the world," he added.