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The United Nations forecast Thursday that the world's population will increase from 7.2 billion today to 8.1 billion in 2025, with most growth in developing countries and more than half in Africa. By 2050, it will reach 9.6 billion.

India's population is expected to surpass China's around 2028 when both countries will have populations of around 1.45 billion, according to the report on "World Population Prospects." While India's population is forecast to grow to around 1.6 billion and then slowly decline to 1.5 billion in 2100, China's is expected to start decreasing after 2030, possibly falling to 1.1 billion in 2100, it said.

The report found global fertility rates are falling rapidly, though not nearly fast enough to avoid a significant population jump over the next decades. In fact, the U.N. revised its population projection upward since its last report two years ago, mostly due to higher fertility projections in the countries with the most children per women. The previous projection had the global population reaching 9.3 billion people in 2050.

John Wilmoth, director of the Population Division in the U.N.'s Department of Economic and Social Affairs, said the projected population increase will pose challenges but is not necessarily cause for alarm. Rather, he said, the worry is for countries on opposite sides of two extremes: Countries, mostly poor ones, whose populations are growing too quickly, and wealthier ones where the populations is aging and decreasing.

"The world has had a great experience of dealing with rapid population growth," Wilmoth said at a news conference. "World population doubled between 1960 and 2000, roughly. World food supply more than doubled over that time period."

"The problem is more one of extremes," he added. "The main story is to avoid the extreme of either rapid growth due to high fertility or rapid population aging and potential decline due to very low fertility."

Among the fastest-growing countries is Nigeria, whose population is expected to surpass the U.S. population before the middle of the century and could start to rival China as the second-most populous country in the world by the end of the century, according to the report. By 2050, Nigeria's population is expected to reach more than 440 million people, compared to about 400 million for the U.S. The oil-rich African country's population is forecast to be nearly 914 million by 2100.

The report found that most countries with very high levels of fertility — more than 5 children per women — are on the U.N. list of least-developed countries. Most are in Africa, but they also include Afghanistan and East Timor.

But the average number of children per woman has swiftly declined in several large countries, including China, India, Indonesia, Iran, Brazil and South Africa, leading to a reduction in population growth rates in much of the developing world.

In contrast, many European and eastern Asia countries have very low fertility levels.

"As a result, these populations are aging rapidly and face challenges in providing care and support to their growing ranks of older persons," Wilmoth said.

Wilmoth cautioned that "there is a great deal of uncertainty about population trends." He said projections could change based on the trajectories of three major components — fertility, mortality and migration.

Still, population growth until 2050 is all but inevitable.

The U.N. uses the "medium-variant" projection, which assumes a substantial reduction in the fertility levels of intermediate- and high-fertility countries in the coming years. In the "high-variant" — if women on average had an extra half of a child — the world population would reach 10.9 billion in 2050. In the "low-variant" — if women on average had half a child fewer — the population would be 8.3 billion in 2050.

Among the notable findings in the report:

• The population in developing regions is projected to increase from 5.9 billion in 2013 to 8.2 billion in 2050. In contrast, the population of developed countries is expected to remain largely unchanged during that period, at around 1.3 billion people.

• Africa's population could increase from 1.1 billion today to 2.4 billion in 2050, and potentially to 4.2 billion by 2100.

• The number of children in less-developed regions is at all time high at 1.7 billion. In those regions, children under age 15 account for 26% of the population. In the poorest countries, children constitute 40% of their populations, posing huge challenges for providing education and employment.

• In wealthier regions, by contrast, children account for 16% of the population. In developed countries as a whole, the number of older people has already surpassed the number of children, and by 2050 the number of older people will be nearly twice the number of children.

• Low-fertility countries now include all of Europe except Iceland plus 19 countries in Asia, 17 in the Americas, two in Africa and one in Oceania.

據(jù)美聯(lián)社報道，聯(lián)合國6月13日最新報告預(yù)計，世界人口到2025年將從72億增長至81億，到2050年世界人口將達(dá)96億。

印度將為第一人口大國

聯(lián)合國《世界人口展望》報告稱，印度人口有望在2028年左右趕超中國，屆時兩國人口均在14.5億左右。報告還預(yù)測，印度人口增長到16億后開始逐漸減少，2100年降至15億；中國在2030年后人口開始減少，2100年可能降至11億。

報告發(fā)現(xiàn)，雖然全球生育率下降迅速，但依然無法阻止今后十年人口的大幅增加。事實上，聯(lián)合國已經(jīng)修訂了兩年前的人口預(yù)測報告。此前，聯(lián)合國預(yù)計的2050年世界人口是93億。

聯(lián)合國經(jīng)濟和社會事務(wù)部人口司司長約翰•威爾莫斯說，人口增長給世界帶來了挑戰(zhàn)，但無需恐慌。但有兩個極端的情況值得擔(dān)憂：貧困國家人口增長過快，而富裕國家人口正在下降和趨于老齡化。

“關(guān)于如何應(yīng)對人口急劇增長，現(xiàn)有的世界經(jīng)驗豐富，”威爾莫斯在新聞發(fā)布會上說道?！笆澜缛丝谠?960年至2000年約翻了一番，而這期間世界食物供應(yīng)增長了兩倍以上?！?/SPAN>

“問題更多在于極端狀況”他補充道?！耙皇且蚋呱识鴮?dǎo)致人口快速增長，一是由于急劇人口老齡化和極低生育率導(dǎo)致人口潛在下降?！?/SPAN>

尼日利亞人口將超美國

報告稱，尼日利亞是全球人口增長最快的國家之一，其人口有望在本世紀(jì)中葉前超過美國，在本世紀(jì)末將與中國爭奪世界第二人口大國席位。2050年美國人口將達(dá)4億左右，與之相比尼日利亞人口將高達(dá)4.4億。據(jù)估計，2100年非洲富油國人口將接近9.14億。

報告發(fā)現(xiàn)，大部分生育率極高的國家都是聯(lián)合國所列的最不發(fā)達(dá)國家，以非洲國家為主，不過也包括阿富汗和東帝汶，平均每個婦女生育的孩子超過五個。

但是，一些大國的生育率卻下降迅速，包括中國、印度、印度尼西亞、伊朗、巴西和南非，導(dǎo)致許多發(fā)展中國家人口增長率下降。

相比之下，很多歐洲國家和東亞國家生育率極低?！耙虼?，這些國家正加速人口老齡化，面臨為越來越多的老年人提供養(yǎng)老保障的挑戰(zhàn)。”威爾莫斯說。

威爾莫斯提醒道， “人口趨勢有很大的不確定性”，可能會因影響人口的三大要素——生育、死亡和遷移——的改變而變化。不過，世界人口將在2050年之前一直保持增長幾乎不可避免。

聯(lián)合國采用了“中等水平變量（medium-variant）”預(yù)計方法，該方法假定中高生育率國家在接下來幾年里生育率將大幅下降。而用“高水平變量”法——即平均每個婦女的生育數(shù)比中等多0.5 ——2050年的世界人口將達(dá)109億。用“低水平變量”法——平均每個婦女的生育數(shù)比中等少0.5——2050年的世界人口將是83億。

報告中值得注意的數(shù)據(jù)：

•發(fā)展中地區(qū)的人口預(yù)計將從2013年的59億增加至2050年的82億。相反，發(fā)達(dá)國家的人口在這段時期基本保持在13億左右不變。

•非洲人口可能從現(xiàn)在的11億增加至2050年的24億，2100年可能達(dá)42億。

•欠發(fā)達(dá)地區(qū)的兒童數(shù)量在17億居高不下。15歲以下的孩子占這些地區(qū)總?cè)丝诘?6%。在最貧窮的國家，兒童占總?cè)丝诘?0%，為教育和就業(yè)帶來巨大的挑戰(zhàn)。

•富裕地區(qū)恰恰相反，兒童占總?cè)丝诘?6%。發(fā)達(dá)國家總的來說老年人數(shù)已經(jīng)超過兒童數(shù)，而且到2050年老年人數(shù)將接近兒童數(shù)的兩倍。

•目前，低生育率國家包括除冰島之外的所有歐洲國家，外加亞洲19國，美洲17國，非洲2國和大洋洲1國。

•一些國家的人口到2050年預(yù)期將減少15%，包括白俄羅斯、保加利亞、克羅地亞、古巴、格魯吉亞、拉脫維亞、立陶宛、摩爾多瓦、羅馬尼亞、俄羅斯、塞爾維亞和烏克蘭。

•世界預(yù)期壽命有了整體提升，從1950-55的47歲升至2005-2010的60歲，預(yù)計2045-2050年達(dá)76歲，2095-2100年達(dá)82歲。

• The populations of several countries are expected to decline by more than 15% by 2050, including Belarus, Bulgaria, Croatia, Cuba, Georgia, Latvia, Lithuania, Republic of Moldova, Romania, Russia Serbia, and Ukraine.

• Life expectancy at birth for the world as a whole rose from 47 years in 1950-55 to 69 years in 2005-2010 and is projected to reach 76 years in 2045-2050 and 82 years in 2095-2100.