Our global community is growing all the time. The Earth is now home to 6.7 billion people, and the question is looming: Just how many of us can the planet support? LEVANTE JANOS/ISTOCKPHOTO

In many discussions about the environment, population growth is the last thing anyone wants to talk about. For one thing, family size is a subject that quickly becomes very personal. And when you consider that one of the most important decisions that people make is whether to have children — and if so, when, how many and with whom — it’s no surprise that even theoretical discussions about population concerns and family planning can turn into awkward conversations.

Nonetheless, global population growth is an issue that begs to be discussed. After all, population size is directly tied to many other issues that affect everyone on the planet — access to clean air and water, wealth and poverty, and global supplies of food and energy.

So let’s start with a simple question. How many of us are there?

By the Numbers

As I’m writing this, the population clock on the U.S. Census Bureau Web page estimates world population as 6,724,401,912. What do you want to bet that’s off by at least one or two people? But you get the idea the clock is meant to convey: World population is growing rapidly and continuously, and 6.7 billion is a good estimate of where we are today. Another population counter on this page puts the U.S. population at about 305 million.

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Trying to predict future population growth requires a little more guesswork. For a good discussion of this issue, check out this recent article from the nonprofit Worldwatch Institute. It notes that most demographers expect that by 2050 world population will be between 8 billion and 11 billion people. However, as the author points out, these estimates assume a slowdown in birth rates that may not materialize. Here’s a graphic showing different population projections based on high and low estimates of growth. And that leads us to a more difficult question: What do these different possibilities mean for the planet? How many people is too many?

A Global Issue

There’s a lot of debate about how many people the Earth can reasonably sustain, but you don’t have to look far to find evidence that we’re already experiencing a few problems. Here are a handful of articles linking population growth to the loss of forests and biodiversity, and increases in the greenhouse gas emissions that are causing climate change. Population growth also puts a strain on water resources and food supplies.