The world's population may have shot up beyond eight billion for the first time recently, but some countries including the most populous, China, are seeing their populations shrink.
And the decline is set to continue as factors including rising living costs, more women entering the workforce and having children later mean people in some countries are having fewer babies.
China's population shrank last year for the first time in more than six decades, official data showed Tuesday, and it is expected to be overtaken by India this year as the most populous nation.
Other countries, mostly in Europe and Asia, can expect a demographic slump over the coming decades, according to UN figures published last July which forecast how the world's population will develop between now and 2100.
A different picture is emerging in Africa, where the population is expected to rise from 1.4 to 3.9 billion inhabitants by 2100, with some 38 percent of Earth dwellers living there, against around 18 percent today.
Europe leads decline
Eight nations of more than 10 million inhabitants, most of them in Europe, saw their populations shrink over the past decade.
Among them is war-battered Ukraine, but also Greece, Italy, Poland, Portugal, and Romania whose birth rates are particularly low -- between 1.2 and 1.6 children per woman -- according to the World Bank.
Of note is that Greece, Poland and Romania also have fewer immigrants arriving than people leaving for the rest of the European continent.
Outside Europe, Japan is also seeing a decline due to its ageing population, with women there having on average 1.3 children, along with a low level of immigration.
Japan thus lost more than three million inhabitants between 2011 and 2021.
Finally, in Syria, the population has been hard-hit by the war which has been raging since 2011.
Worse to come
These eight countries, with the exception of Syria, are expected to continue to see their population drop, according to the UN.
In particular China is expected to lose nearly half of its population by 2100, falling from more than 1.4 billion to 771 million inhabitants.
The population of Russia will start to shrink by 2030, along with Germany, South Korea, and Spain.
Thailand, France, North Korea, and Sri Lanka are forecast to follow suit by 2050.
Africa bucks the trend
For many other countries, including India, Indonesia, Turkey and the United Kingdom, the fall is forecast to come in the second half of this century.
The population of the entire planet, meanwhile, is only expected to decline in the 2090s, after peaking at 10.4 billion, according to the UN.
By 2100, European, American and Asian populations will be on their way to decline, but Africa's population is expected to continue to increase.