From Person to Planet in Ten Easy Steps

here are ten orders of magnitude between the total number of people on the planet — close to 10 billion — and the single individual. Here, we apply the “powers of 10” to the number of people on the planet….starting with you, dear reader!

ormally we use powers of ten to measure the size of things like time and space. Or in scientific language: temporal and spatial scales. Here, we apply the “powers of 10” to numbers of people.


oday you are one of 7.5 individual human beings on the planet. And while we are all more similar than different, each one of us is unique.

Each of us is embedded in the wider society, usually first through a small group of family and friends.

Close Family and Friends

nthropologist Margaret Mead suggested: “Never doubt that a small group of thoughtful, committed citizens can change the world; indeed, it’s the only thing that ever has.” Family and close friends are the first level of small groups who can change the world, starting in their everyday lives and behaviors.

Personal Network: Extended Family

nthropologist, Robin Dunbar, has suggested that most people have between one hundred and two hundred casual friends, with the average — 150 — being known as “Dunbar’s Number”, which also about the number of active friends of average Facebook users.

Obviously, whether virtually or physically, this will vary for individuals, but Dunbar proposes for most of us 150 is the limit to the number of people that a single individual can maintain in meaningful, stable social relationships.

It’s also worth considering that 99% of businesses around the world are micro (less than ten), small (less than 50), or medium (fewer than 250 people).

While we are often encouraged to “think big”, there’s a counter philosophy that says “Small is Beautiful,” especially in our everyday life.

Local Neighborhood and School

a school, organization, neighborhood or faith community, 1000 people or more is large number of people, and we may know know everyone personally, but we will likely recognize many of them and perhaps know their names. One thousand is something of a dividing line between ultra-local and local neighborhood scale. For instance, rooftop solar can work well on houses with one or more people and apartment complexes of a thousand people or so, but above that scale solar farms — ranging from small neighborhood-scale arrays of solar panels to massive solar farms serving hundreds of thousands of homes — are much more appropriate and economical.

Community: Village

any people around the world live in villages, but like neighborhoods, cities and countries, villages come in many different sizes. The city in the photo above is called Pásztó, located in northern Hungary. It has about 10,000 people and has a hospital, a factory, two high schools and two grocery stores that serve the wider community, plus many small shops.

Some people, particularly older folks, may not feel the need (or can’t afford) to travel beyond their village. But for some people, especially young adults looking for jobs and opportunities to meet other young people, Pásztó and other smaller villages are just too small to pursue their dreams.


The optimal size of government has been long debated. In The Law, Plato calculated the ideal size to be exactly 5,040 heads of families, adding “the number of citizens should be sufficient to defend themselves against
the injustice of their neighbors,” not an easy task in the era of climate change, globalization and nuclear proliferation!

Today, the magic number — at least when it comes to engaging the public and maximizing efforts to forge resilient communities — may prove to be around 100,000 people, which is around the size of Las Cruces, New Mexico, below.

Many cities of course are larger than 100,000, but even in large cities such as New York, Paris, Budapest, or Copenhagen, it is common for them to be organized in smaller clusters, respectively “community boards”, “arrondissements,” or “districts”. The size of these units that make up the greater whole is often around 100,000 people. This may prove to be the “Goldilocks” size: “not too big, not too small but just right.”


arger metropolitan regions or groups of people can have advantages if they are well designed and supported. For example, mass transportation and the efficiencies of scale can work well in concentrated populations, which may also be magnets for jobs and culture.

Utility-scale solar and wind farms, mass transit and high speed rail, all require a critical mass of people — from the hundreds of thousands to the millions — to be economically viable.

When it comes to even larger scales there are naturally pluses and minuses.


hile the average size of a country in the world (based on 194 sovereign countries divided by 7.5 billion) is 39 million people — the size of Iraq or Poland — the median size, the middle of the pack, is roughly 8 million — the size of Switzerland or Honduras.

There are around forty cities of over 10 million people, and their combined population is more than double the total number of people in nations of 10 million or less!

Organizations like, a network of the world’s megacities, has developed a “City Solution Platform” in order to “accelerate the deployment of climate solutions.” And ICLEI, now known as “Local Governments for Sustainability,” continues the work they began in 1990 as the International Council for Local Environmental Initiatives.


here are currently 13 nations over 100 million people, but the number is growing. Now, there are nearly 100 million people living along or near the Nile River. To state the obvious, that’s a very concentrated number of people in a relatively small amount of land.

In other parts of the world 100 million people may be spread out in large rural regions and/or concentrated in a few huge urban areas. In either case, efforts to transform society at this scale is possible but challenging since it will rely more on top down than bottom up or inside out transformation.


wo nations, India and China, have over a billion people, as does the African continent.

North and South America combined are about a billion, and Europe, if Russia, Turkey and the Mediterranean basin are included, has a total of around a billion people as well .


10 billion stars

the year 2050 there are projected to be 10 billion people on the planet, give or take a billion.

Whether we end up above or below this figure will depend in large measure on family planning and girls education, although war, disease or environmental collapse may also alter the final total.

Which leads us to the question, between the global and individual scale is there a “sweet spot” in the middle where ability to act and impact, where local and global converge?

Using the powers of ten exponential or logarithmic scale, we find the midpoint between the individual and global scale of 10 billion to be 10 to the fifth power, or 100,000 (although now, with 7.5 people, it is 75,000). It is a nice round number (as all powers of ten numbers are!) to demark the point where local and global converge.

We are all in the same boat — Spaceship Earth as it has been called — but we need to start thinking about lifeboats, “new arks”, or what we’ve called Climate Action Hives, to serve people at a scale of ±100,000, informing, inspiring and providing practical support for individuals and the communities they are embedded in.

If we think in terms of positive interventions to help support climate action and sustainable development goals, the scale of 100,000 is interesting since, because of the powers of ten, we would currently need 75,000 such interventions.

One thing is clear. We are in an “All hands on deck!” situation. Everyone (including you dear reader!) must think about and take action on the scales that you are able to influence. For most of us that is at the individual, household, and neighborhood scale, but some can help inform and inspire sustainable practices at much larger scales.




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Mark McCaffrey

Hydro Logic, BASIN, CLEAN, Climate Smart & Energy Wise, ECOS, Powers of 10, Fractal Superpowers, The Long Game and other assorted fun and games