David Gray / Reuters

Binata Pinata stands on top of a rock holding a fish her husband Kaibakia just caught off Bikeman islet, located off South Tarawa in the central Pacific island nation of Kiribati.

David Gray / Reuters

North and South Tarawa are seen from the air. Kiribati consists of a chain of 33 atolls and islands that stand just meters above sea level, spread over a huge expanse of otherwise empty ocean.

David Gray / Reuters

A baby lies on a bed in the maternity ward of the Nawerewere Hospital on South Tarawa.

David Gray / Reuters

A pregnant woman sits inside her small hut as a boy sits on the steps below in the village of Betio on South Tarawa.

David Gray / Reuters

An abandoned house that is affected by seawater during high tides stands next to a small lagoon near the village of Tangintebu on South Tarawa, Kiribati.

Straddling the equator and spread over 2 million square miles of otherwise empty ocean, Kiribati's 32 atolls and one raised coral island have an average height above sea level of just 6 and a half feet.

Studies show surrounding sea levels rising at about 2.9 mm a year, well above the global average of 1 - 2 mm a year.

Kiribati President Anote Tong has grimly predicted his country will likely become uninhabitable in 30-60 years because of inundation and contamination of its fresh water supplies. Read the full story.

Reuters' Photographers Blog: David Gray describes 'that sinking feeling'

David Gray / Reuters

A dog sits in the shade of a mangrove tree as a woman uses a fork to dig for shellfish on the reef-mud flats of a lagoon located at South Tarawa.

David Gray / Reuters

A boy covered in reef mud reacts as he stands with other boys in the village of Ambo on South Tarawa.

David Gray / Reuters

A girl sits on a log next to the roots of a tree, which have been exposed as a result of high tides, near the village of Teaoraereke on South Tarawa.

David Gray / Reuters

Storm clouds gather above the small huts and tower on Bikeman islet, located off South Tarawa. The tower used to mark the center of the islet, but shifting sand over the years has pushed the tower further into the lagoon.

David Gray / Reuters

Newly made sandbags sit on a wall on a causeway that connects the town of Bairiki and Betio on South Tarawa.

EDITOR'S NOTE: Images taken May 23-25, 2013 and made available to NBC News today.

Related content on PhotoBlog:

Migration in the Americas: On the run from water in Panama

Edgar Su / Reuters

A 50-year-old grave digger who asked to be identified as Mr Sim exhumes a grave at Bukit Brown cemetery in Singapore on November 27, 2012.

Reuters reports — Eternal peace does not last long in Singapore.

Starting early next year, workers with heavy machinery will begin constructing an eight-lane highway across the small country's oldest surviving major cemetery, overriding the objections of nature lovers and heritage buffs.

Singapore, with its 5.3 million people crammed onto an island less than half the size of London, is already more densely populated than rival Asian business center Hong Kong, making permanent burial space unfeasible.

Edgar Su / Reuters

Mr Sim, left, breaks a tombstone with his sledgehammer as he exhumes a grave at Bukit Brown cemetery with his boss, Mr Leung.

The whole of Bukit Brown - the resting place of more than 100,000 people, including some of Singapore's pioneering business and clan leaders and their large, intricately carved tombs - will eventually be used for residential development. At least 30 people buried there have streets named after them.

Some families have begun removing the remains of their ancestors, and authorities plan to dig up the remaining graves in January. Read the full story.

Edgar Su / Reuters

Mr Sim holds two coffin nails found when exhuming a grave at Bukit Brown cemetery.

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Paula Bronstein / Getty Images

John Harris stands next to his family: wife Remedios (who holds Joshua, 3), Jamie, 11, John, 16, and Joyce, 8, at the small space where they live under a bridge in Manila, Philippines on August 21, 2012 . John is a construction worker making 250 pesos ($6) a day. The family live in a small space under a bridge alongside many other impoverished families.

Paula Bronstein / Getty Images

Irish Romes, 19, holds her 2-week-old baby Jay at the place where she lives with her family next to a highway in the slums of Binondo, Manila on August 21, 2012.

Manila's population of 20 million people is rising by approximately a quarter of a million every year. Due to overcrowding a third of the Filipino capital's residents are forced to live on any bit of spare land they can manage, often in makeshift settlements under bridges, beside railway lines and even in cemeteries.

Large families are common in a conservative Catholic county that is pushing the government's already weak social care system to its limit.

See more of Getty Images photographer Paula Bronstein's work on population issues in the Philippines in Tuesday's post: Mothers give birth in an already overpopulated Manila.

Look back at PhotoBlog posts on Filipino housing issues and on the world's seven billion population milestone, reached in 2011.

Paula Bronstein / Getty Images

A boy looks out from his home in a congested slum area of Manila on August 21, 2012.

Paula Bronstein / Getty Images

A man stands next to the door of his room under a bridge in Manila on August 21, 2012. Families cram into small rooms under a bridge so they can live for free.

Paula Bronstein / Getty Images

A man washes clothes as children look out from the small room under a bridge within which they live on August 22, 2012 in Manila.

Paula Bronstein / Getty Images

A woman holds her daughter in their makeshift shack in the Binondo slums of Manila, which they rent for 1,000 pesos ($24) a month.

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Paula Bronstein / Getty Images

Mothers and their newborns share space on a bed after giving birth in the maternity ward at the government-run Jose Fabella maternity hospital in Manila, Philippines.

Paula Bronstein / Getty Images

A woman holds a cross while dealing with labor pains at the government-run Jose Fabella maternity hospital.

More than 65 babies are born at the government operated Dr. Jose Fabella Memorial Hospital in Manila, Philippines every day.

Manila is one of the most densely populated cities in the world and many of the city dwellers are forced to live on every bit of spare land they can find. Poverty causes people to live under bridges, railway lines and even cemeteries.

Getty Images photographer Paula Bronstein created these images on Aug. 18-20 and made them available to NBCNews.com today.

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Paula Bronstein / Getty Images

A mother is in pain while her newborn baby rests on her chest as she gets surgically sutured after giving birth in a delivery room at the Jose Fabella Hospital.

Paula Bronstein / Getty Images

A mother is seen on the operation table next to her new baby moments after a Caesarean operation.

Paula Bronstein / Getty Images

Mothers breast feed their babies in a special room at the Dr. Jose Fabella Memorial Hospital.

Tsering Topgyal / AP

A homeless family sleeps under an overpass in New Delhi, India, on April 25, 2012. Already the second most populous country on the planet with 1.2 billion people, India is expected to overtake China around 2030 when its population soars to an estimated 1.6 billion even as hundreds of millions of people remain trapped in abject poverty.

See more PhotoBlog posts relating to population issues and watch a video about the challenges India faces:

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Mohammed Zaatari / AP

Nurses hold newborn babies in Sidon, Lebanon, Monday, Oct. 31, 2011. As of Oct. 31, according to the U.N. Population Fund, there will be 7 billion people sharing Earth's land and resources.

Pawan Kumar / Reuters

Vinita Yadav, a 23-year-old Indian, holds her newborn baby girl Nargis, who was born at 7:20am, inside a community health center in Mall, India on Oct. 31, 2011. The world's population will reach seven billion on 31 October 2011, according to projections by the United Nations, which says this global milestone presents both an opportunity and a challenge for the planet. While more people are living longer and healthier lives, says the U.N., gaps between rich and poor are widening and more people than ever are vulnerable to food insecurity and water shortages.

What I love about these images is that while the locations, cultures, traditions and environments vary tremendously from country to country, there is the common thread of birth and motherhood at the heart of them.

Babies born today were welcomed into the world under the camera lens of photographers, all ready to capture the symbolic seven billionth baby. While experts are unable to precisely say that the population has officially hit 7 billion people, the United Nations designated the date according to estimates and projections done by the the U.N. Population Fund.

For more information: A child is born and world population hits 7 billion.

See more PhotoBlog posts related to the seven billion population milestone:

• Introducing Danica May Camacho, the world's first 7-billionth baby
• World's largest family: 1 husband, 39 wives, 94 children
• Managing a growing world population with a shrinking water supply
• China's middle class booms, but aging population threatens prosperity
• Nations' birth rates rise and fall: Philippines welcomes 200 babies an hour
• 7 billion people tax the world's environment
• What do 7 billion people look like?
• Room for more? Squeeze in, the world population is about to hit 7 billion

Edgard Garrido / Reuters

A pediatrician measures the head of Linda Abigail, the third child of Lourdes Suyapa Rodriguez, 35, after she was born in the childbirth unit of the Escuela hospital in Tegucigalpa, Honduras on Oct. 31, 2011.

Albert Gonzalez Farran / AFP - Getty Images

Buthaina, a young Sudanese mother lies in bed with her newborn baby at El-Fasher Women's Hospital in Sudan's northern Darfur region on Oct. 31, 2011. As Sudan's population reaches 33 million persons, with approximately six million living in Darfur's three states.

Denis Sinyakov / Reuters

Medics hold an infant boy shortly after Alla Baturina gave birth to him, at a perinatal center of Moscow City Hospital Number 8 in Moscow on Oct. 31, 2011.

M.A.Pushpa Kumara / EPA

The symbolic seven billionth member of the world population from Sri Lanka, Muthumali receives a cuddle from her 23-year-old mother W.G. Dhanushika Dilani at the Castle Street Maternity Hospital in Colombo on Oct. 31, 2011. A special event was organized at the Castle Street Maternity Hospital to receive what is believed to be the seven billionth member of the world population.

Nathalie Bardou / AP

Newborn Pakistani babies, receive phototherapy treatment against neonatal jaundice, at the nursery room of a hospital in Rawalpindi, Pakistan, Monday, Oct. 31, 2011. Countries around the world marked the world's population reaching 7 billion Monday with lavish ceremonies for newborn infants symbolizing the milestone and warnings that there may be too many humans for the planet's resources.

Erik De Castro / AFP - Getty Images

A newly born baby girl named Danica May Camacho, the Philippines' symbolic seven billionth baby, is weighed in the Fabella Maternity hospital in Manila on October 31. The world's population will reach seven billion on October 31, according to projections by the United Nations, which says this global milestone presents both an opportunity and a challenge for the planet.

After all of the build-up, it seems the U.N. has decided that there should be more than one 7-billionth baby. Let the circus begin...

msnbc.com staff and news services report:

A string of festivities are being held worldwide, with a series of symbolic 7-billionth babies being born.

The celebrations began in the Philippines, where baby Danica May Camacho was greeted with cheers and an explosion of photographers' flashbulbs at Manila's Jose Fabella Memorial Hospital.

The Guardian newspaper reported that Danica, whose name means morning star, had been chosen by the U.N. to be one of a number of symbolic 7 billionth babies. It is not known who the actual baby is.

Erik De Castro / Reuters

Midwives hold Danica May Camacho up for the cameras.

Danica arrived two minutes before midnight Sunday, but doctors decided that was close enough to count for a Monday birthday. 

The baby received a shower of gifts, from a chocolate cake marked "7B Philippines" to a gift certificate for shoes.

"She looks so lovely," the mother, Camille Galura, whispered as she cradled the 5.5-pound baby, who was born about a month premature. Read the full story.

Ted Aljibe / AFP - Getty Images

Danica May Camacho is coddled by her mother Camille as United Nations resident coordinator Jacqui Badcock, left, hands over a gift and Philippine Health Secretary Enrique Ona, right, looks on, during a welcoming ceremony after she was born at a government-run maternity hospital in Manila. Weighing 2.5 kilos, the baby was delivered shortly before midnight October 30 amid an explosion of flash bulbs from a media contingent that had waited for hours at the delivery room.

See more PhotoBlog posts related to the seven billion population milestone:

• World's largest family: 1 husband, 39 wives, 94 children
• Managing a growing world population with a shrinking water supply
• China's middle class booms, but aging population threatens prosperity
• Nations' birth rates rise and fall: Philippines welcomes 200 babies an hour
• 7 billion people tax the world's environment
• What do 7 billion people look like?
• Room for more? Squeeze in, the world population is about to hit 7 billion

Adnan Abidi / Reuters

Family members of Ziona Chana pose for a group photograph in Baktawng village, India, on Oct. 7, 2011. Ziona is the head of a religious sect called "Chana," which allows polygamy and was founded by his father, Chana, in 1942. Ziona has 39 wives, 94 children and 33 grandchildren.

Reuters reports:

The more, the merrier is certainly true for Ziona Chana, a 66-year-old man in India's remote northeast with 39 wives, 94 children and 33 grandchildren -- and he wouldn't mind having more.

They all live in a four story building with 100 rooms in a mountainous village in Mizoram state, sharing borders with Myanmar and Bangladesh, media reports said.

"I once married 10 women in one year," he was quoted as saying.

Adnan Abidi / Reuters

Zuali, 37, twentieth wife of Ziona Chana, adjusts his shirt as his sons and driver watch before heading toward the construction site of a church in Baktawng, India, on Oct. 5, 2011.

Adnan Abidi / Reuters

Ziona Chana's family members wave from a vehicle on their way to a church construction site in Baktawng, India, on Oct. 5, 2011.

His wives share a dormitory near Ziona's private bedroom and locals said he likes to have seven or eight of them by his side at all times.

The sons and their wives, and all their children, live in different rooms in the same building, but share a common kitchen.

The wives take turns cooking, while his daughters clean the house and do washing. The men do outdoor jobs like farming and taking care of livestock.

EPA

Children of 67-year-old Ziona Chana have lunch at their home on Oct. 28, 2011.

The family, all 167 of them, consumes around 200 pounds of rice and more than 130 pounds of potatoes a day. They are supported by their own resources and occasional donations from followers.

"Even today, I am ready to expand my family and willing to go to any extent to marry," Ziona said.

"I have so many people to care (for) and look after, and I consider myself a lucky man."

Ziona met his oldest wife, who is three years older than he is, when he was 17.

Adnan Abidi / Reuters

A view of Ziona Chana's house in Baktawng, India, on Oct. 6, 2011. He lives in this 4-story, 100-room house with 181 members of his family.

He heads a local Christian religious sect, called the "Chana," which allows polygamy. Formed in June 1942, the sect believes it will soon be ruling the world with Christ and has a membership of around 400 families.

Hindu, India's dominant religion, does not allow polygamy, but the nation's laws allow Muslim men to have more than one wife.

India, the world’s second-most populous country behind China, has a birth rate of 2.6 babies for each woman. That pace is expected to keep India's population rising. Analysts say India will reach 1.53 billion population by 2030, when it will surpass China as No. 1 in population.

The United Nations Population Fund, which predicts the world population will reach 7 billion by Oct. 31, says that the world will be on its way to 9 billion 20 years later.

- msnbc.com editors Natalia Jimenez and Jim Gold, with wire service reports.

See more posts and images related to the seven billion population milestone

Reuters

A farmer takes water from a mostly dried-up pond to soak his vegetable field on the outskirts of Yingtan, China, on Dec. 10, 2007.

Akhtar Soomro / Reuters

Two-year-old Saghar, a flood victim, takes a bath in a relief camp in Sukkur, Pakistan, on Sept. 7, 2010.

No resource is more precious and vital than water.

As the world population grows to 7 billion on Oct. 31, as projected by the United Nations Population Fund, the amount of water available per person shrinks.

Yet the per-person consumption of resources — especially in industrialized nations — grows exponentially, analysts warn. Shifting rainfall patterns exacerbate the problem.

Marcio Silva / Amazona Spress via Reuters

A woman carries water she drew from a pool of a drying tributary of the Amazon River as the season drought worsens to one of the worst in recent years, in Parana do Paraua, Brazil, on Nov. 24, 2009. After a rainy season that caused some of the worst flooding in recent history, the seasonal drought that followed proved to be especially bad as well.

The International Water Management Institute (IMWI) predicts that by 2025 about 1.8 billion people will live in places suffering from severe water scarcity. Many already do.

"Take the Horn of Africa for example: Somalia's population has risen roughly fivefold since the middle of the 20th century," Jeffrey Sachs, director of the Earth Institute at Columbia University, said at an Oct. 17 meeting of academics. "Precipitation is down roughly 25 percent over the last quarter century. There's a devastating famine under way right now after two years of complete failure of rains, and [there is] the potential that this is entering a period of long-term climate change."

Amit Dave / Reuters

People gather to get water from a well in the village of Natwarghad, India, on June 1, 2003, in the midst of a severe drought. Dams, wells and ponds went dry across the western and northern parts of Gujarat, forcing people to wait for hours around village ponds for the irregular state-run water tankers to show up as the temperature soared to over 110 degrees.

Conflicts over water shortages could play out as class warfare as the rich commandeer the water and other resources of the poor, Upmanu Lall, director of the Columbia Water Center, warned at the academics meeting.

But solutions are possible.

“Nations need to find ways to deliver food security across regions facing water scarcity and ensure that poor farmers who underpin global food production are resilient enough to cope with future challenges,” IMWI says.

Ahmad Masood / Reuters

An Afghan man pushes a hand cart with water containers near a public water pump in Kabul on Jan. 13, 2010.

Increasing agricultural productivity through effective management of water resources not only helps eliminate hunger, it also leads to long-term increases in rural wealth and lifts poor farmers beyond subsistence-level farming, IMWI says.

"There's quite a bit of land that could produce food if we had the water to go with it," said Lester Brown, an environmental analyst who heads the Earth Policy Institute in Washington. "It's water that's becoming the real constraint."

- msnbc.com editors Natalia Jimenez and Jim Gold, with wire service reports.

See more posts and images related to the seven billion population milestone

Eliana Aponte / Reuters

A resident shows the water she gets at her home in a poor neighborhood in Mexico City on Dec. 17, 2009. A lack of rainfall and the growing needs of a thirsty capital city full of leaky pipes is draining the many lakes that once covered Mexico City's vast urban plain. City residents know their water by the brownish color as it leaves the spout.

Carlos Barria / Reuters

Women walk in the financial area of Pudong in Shanghai, April 26, 2011.

China remains the world's most populous nation with 1.34 billion people and has grown to No. 2 behind the United States in economic power, but its own policies contribute to potential changes in both rankings.

When the world welcomes its 7 billionth person on Oct. 31, as the United Nations Population Fund predicts, China will still be home to more than one in every seven inhabitants of the planet.

But changing demographics brought on largely by birth-limit rules may slow China's growth, analysts say. The country allows urban women to have only a single child; rural women, two. That's fewer than the 2.1 overall necessary to keep the population count level.

India, with a higher rate of 2.6 births per woman, by 2030 may overtake China as No. 1 in population.

Carlos Barria / Reuters

Students attend their college graduation ceremony at Fudan University in Shanghai on July 2, 2011. A 2011 study by the state-run Chinese Academy of Social Sciences paints a rosy picture of graduate employment, saying only 6.7 percent of 2010 graduates with four-year or vocational degrees were still looking for work six months after leaving campus. The vast majority had found jobs or were pursuing further studies. Unemployment was down almost 3 percent from 2009.

China's birth policy also has made the nation one of the most rapidly aging countries in the world, analysts say. The demographic change may be an Achilles' heel in China's economic growth as well as its population count, CNBC reported.

China over the past 30 years became the world's major manufacturing center. Its export-dependent prosperity lifted hundreds of millions out of poverty and into the middle class.

However, a global economic downturn in 2009 reduced demand for Chinese exports. To help keep the economy rolling along, China's 12th Five-Year Plan adopted in March 201 emphasized the need to increase domestic consumption in order to make the economy less dependent on exports.

"The more Chinese population ages, that's more of a headwind against internal consumption," Michael Yoshikami, Founder & CEO of YCMNET Advisors, told CNBC. "There're studies out that suggest the Chinese aging population is going to skyrocket particularly as a result of the one child rule."

Carlos Barria / Reuters

A boy sleeps as he is pushed in a shopping cart at an IKEA store in downtown Shanghai on May 11, 2011. China's headline consumer price inflation slowed to 5.3 percent in the year to April from 5.4 percent in March, according to the National Bureau of Statistics.

China counted its people age 60 and up at 178 million, or 12.5 percent of the total population, in 2010. That figure is expected to double by 2030.

In comments published Oct. 22, Chinese Premier Wen Jibao addressed issues such as inflation, housing costs, weakened demand from rich economies, and the pressure to secure jobs for millions of university students and rural migrants. 

"Currently, economic growth is slowing and external demand is falling, and we should make employment even more of a priority in economic and social development, doing our utmost to expand employment," Wen told officials in Guangxi, a poorer region next to export-driven Guangdong province, the official People's Daily reported.

Those efforts would include "ensuring an appropriate rate of economic growth" and supporting labor-intensive industries, small businesses and private firms, he said.

- msnbc.com editors Natalia Jimenez and Jim Gold, with wire service reports.

See our slideshow: China's booming middle class

See more posts and images related to the seven billion population milestone

Carlos Barria / Reuters

A man looks at the Huaxi village, China, on Dec. 2, 2010. In China's richest village of Huaxi, a booming market town of 36,000 in the affluent eastern province of Jiangsu, every family has at least one house, two cars and $250,000 in the bank.

Cheryl Ravelo / Reuters

Babies lie on a bed in the maternity ward of the government run Dr. Jose Fabella Memorial Hospital in Manila on June 1, 2011. The ward, the busiest in the country, sees an average of 60 births a day. The Philippines' population growth rate of around 2.0 percent is above Southeast Asia's average of around 1.7 percent, with an estimated 200 babies born every hour.

The world population is going through a growth spurt, but its pace varies widely from country to country due in large part to differences in birth rates. Some nations see declines while others see sharp increases.

The United Nations Population Fund estimates the world population will reach 7 billion on Oct. 31.

Women on average are having 2.5 babies each, according to UN data. That’s still above the population replacement level of 2.1 but just half of the five babies apiece they averaged in 1950, when the world population was 2.6 billion. It reached 6 billion in 1998.

In the Philippines, with a population of 101.8 million, the 2011 birth rate is 3.19 babies per woman, says the CIA World Fact Book. Hospitals estimate about 200 births an hour across the country.

Cheryl Ravelo / Reuters

Women await weigh-ins during prenatal checks at the Dr. Jose Fabella Memorial Hospital in Manila on June 6, 2011. The Philippines lacks a national policy on birth control and access to modern family planning methods frowned upon by the powerful Catholic Church. Those factors and others led to the country's population ballooning to more than 100 million, according to various government and private sector estimates. The Philippines is the second-most populous nation in the region after Indonesia.

Cheryl Ravelo / Reuters

A woman uses her cell phone while her baby lies on top of her inside the maternity ward of the Dr. Jose Fabella Memorial Hospital in Manila on June 1, 2011.

The world’s highest birth rate is in Niger, at 7.60 children per woman, according to the World Fact Book; the lowest is Macau, at 0.92. The United States rate is 2.06.

These rates affect a nation's population, which also changes due to longevity rates, immigration and other factors.

"Fertility begins to decline slowly in most developing countries, and then it declines fast, around three to four children, and then it slows down again," Gerhard Heilig, the UN chief of population estimates and projections, told Life's Little Mysteries.

Cheryl Ravelo / Reuters

The maternity ward of the Dr. Jose Fabella Memorial Hospital in Manila is crowded on June 1, 2011.

As the world hits a population milestone, Western Europe, Japan and Russia are experiencing low birth rates and aging populations leading to economic squeezes and population declines.

Money-tight Spain, with a 1.47 birth rate, can no longer afford $3,000-per-newborn government grants that were used to encourage families to boost the nation's birth rate.

In Japan, with a 1.21 birth rate, fewer working-age people will be around to support the elderly. Russia, at 1.42, faces a similar problem and has seen its population fall 6 percent since the mid-1990s.

Cheryl Ravelo / Reuters

A baby lies on a scale inside the maternity ward of the Dr. Jose Fabella Memorial Hospital in Manila on June 1, 2011.

China’s birth rate has fallen to 1.5 under three decades of strict family planning rules that limited urban families to one child and rural families to two.

India, the world’s second-most populous country behind China, has a 2.6 birth rate expected to keep its population rising for years to come.

- msnbc.com editors Natalia Jimenez and Jim Gold, with wire service reports.

See more posts and images related to the seven billion population milestone

David Gray / Reuters

A garbage collector walks atop a massive pile of garbage at the Bloemendhal dump in central Colombo, Sri Lanka, on April 23, 2009.

Will the sheer scale of 7 billion people living on the planet doom human existence to extinction?

Not likely, many scientists say, but they do worry about how many people a disturbed and soiled Earth will support.

The United Nations Population Fund predicts not only that the planet’s population will reach 7 billion by Oct. 31, but another billion will be here by 2025, and the total will reach 10 billion before the end of the century.

China Daily via Reuters

A worker cleans away dead fish at a lake in Wuhan, central China's Hubei province, on July 11, 2007. More than 110,000 pounds of fish died due to pollution and hot weather, local media reported.

Beawiharta Beawiharta / Reuters

Deforestation is evident on Indonesia's Sumatra island on Aug. 5, 2010. Indonesia, like Brazil, is on the front line of efforts to curb deforestation, a major contributor to mankind's greenhouse gas emissions that scientists blame for heating up the planet.

All those people will need water, food, clothing, shelter, energy – all of which take resources to create or distribute and which can foul the environment as they’re processed and used up.

In 1798, when the world’s population was close to 1 billion, British-born economist Thomas Malthus wrote, "The power of population is so superior to the power of the Earth to produce subsistence for man, that premature death must in some shape or other visit the human race."

Malthus did not take into account the then-coming industrial age and people’s inventions and ingenuity that meant more efficient use of Earth’s resources. However, population growth could be catching up to problems it creates.

Reinhard Krause / Reuters

Cars jam a Beijing road on Jan. 15, 2008. More than 400,000 new cars, or more than 1,000 a day, hit the roads in China's capital in 2006, state media said.

Asahi Shimbun / Reuters

Medical staff use a Geiger counter to screen a woman for possible radiation exposure at a public welfare center in Hitachi City, Japan, on March 16, 2011. The woman tested negative for radiation exposure after she was evacuated from an area within 12.4 miles of the Fukushima Daiichi nuclear plant, which leaked radiation when it was badly damaged by a massive earthquake and tsunami on March 11.

Modern scientists warn that the Earth’s climate is warming and access to clean water is dwindling. Oil spills contaminate beaches and oceans; poisons leach from dumped waste into soil and water; the burning of fossil fuels pumps more carbon dioxide into the atmosphere than it can absorb.

New energy sources will be needed as known sources of fossil fuels are depleted or remain locked away.

Reuters

A man works at the site of a rare earth metals mine at Nancheng county, China, on Oct. 20, 2010. China reportedly produced 118,900 metric tons of rare earth in 2010, well above the 89,200 metric ton official production quota. The production figure exceeded 96 percent of global output, The Wall Street Journal reported .

Pawel Kopczynski / Reuters

Steam emerges from the cooling towers of Vattenfall's Jaenschwalde brown coal power station near Cottbus, Germany, on Dec. 2, 2009.

"Hunger and poverty are challenges we all face together - we must act now," said Pierre Ferrari, president of Heifer International, which provides cows, goats, water buffalo and other livestock to thousands of people in more than 50 countries. The charity focuses on helping the poor become self-sufficient and urges the people it helps to go on to train others.

"Our global agricultural system can feed 7 billion people today," Ferrari said. "It is a matter of equity and distribution."

"The real issue to be faced is the next 30 years when another 2 billion people will be with us," he said. "It is forecasted that the global food supply will need to double to meet the needs of the global population.  The small holder farmer (650 million of them) produces 70 percent of the world food today."

Heifer is an example of a non-government organization that works to improve agricultural productivity.

But will such efforts be enough?

"The constraints of the biosphere are fixed," Harvard University sociobiologist Edward O. Wilson wrote in his 2002 book, "The Future of Life."

As reported by Life’s Little Mysteries, Wilson predicted the Earth’s resources could be stretched to support a population of 10 billion, just about where UN population estimators say growth will level out by the end of the century.

- msnbc.com editors Natalia Jimenez and Jim Gold, with wire service reports.

See more posts and images related to the seven billion population milestone

Michael B. Watkins/U.S. Navy via Reuters

Oil is seen on the surface of the Gulf of Mexico in an aerial view of the Deepwater Horizon oil spill off the coast of Mobile, Alabama, on May 6, 2010.