The U.N.-declared landmark underscores the challenges faced by many countries in providing for the growing numbers of people on an already over stretched and crowded planet.
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With the world's population more than doubling over the last half century, basics like food and water are under more strain than ever, say experts, and providing for an additional 2-3 billion people in the next 50 years is a serious worry.

Water usage is set to increase by 50 percent between 2007 and 2025 in developing nations, while food security remains a challenge with 925 million people going hungry.

To feed the two billion more mouths predicted by 2050, food production will have to increase by 70 percent, the U.N.'s Food and Agricultural Organisation says. But climate change may be the greatest impediment to meeting this target, say experts.

Growing numbers of people on earth is also resulting in rapid urbanisation, placing serious strains on towns and cities as migrants move from poor rural areas to richer urban centres.
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The vast majority of the population growth comes from people who really shouldn't be having kids.

I agree there is something wrong there, most of the wealthy countries have 1-2 kids and then al of the poor countries are highlighted with at least 4-6 kids!!!
Random.

but if they adults in the poor countries had fewer kids their kids would have a better chance of surviving and getting a better education.

Humans interfere too much.

Let mother nature take care of things.