They have been expanding,

urbanization has been expanding,

at an exponential rate in the last 200 years

so that by the second part of this century,

the planet will be completely dominated

by cities.

Cities are the origins of global warming,

impact on the environment,

health, pollution, disease,

finance,

economies, energy --

they're all problems

that are confronted by having cities.

That's where all these problems come from.

And the tsunami of problems that we feel we're facing

in terms of sustainability questions

are actually a reflection

of the exponential increase

in urbanization across the planet.

Here's some numbers.

Two hundred years ago, the United States

was less than a few percent urbanized.

It's now more than 82 percent.

The planet has crossed the halfway mark a few years ago.

China's building 300 new cities

in the next 20 years.

Now listen to this:

Every week for the foreseeable future,

until 2050,

every week more than a million people

are being added to our cities.

This is going to affect everything.

Everybody in this room, if you stay alive,

is going to be affected

by what's happening in cities

in this extraordinary phenomenon.

However, cities,

despite having this negative aspect to them,

are also the solution.

Because cities are the vacuum cleaners and the magnets

that have sucked up creative people,

creating ideas, innovation,

wealth and so on.

So we have this kind of dual nature.

And so there's an urgent need

for a scientific theory of cities.

Now these are my comrades in arms.

This work has been done with an extraordinary group of people,

and they've done all the work,

and I'm the great bullshitter

that tries to bring it all together.

(Laughter)

So here's the problem: This is what we all want.

The 10 billion people on the planet in 2050

want to live in places like this,

having things like this,

doing things like this,

with economies that are growing like this,

not realizing that entropy

produces things like this,

this, this

and this.

And the question is:

Is that what Edinburgh and London and New York

are going to look like in 2050,

or is it going to be this?

That's the question.

I must say, many of the indicators

look like this is what it's going to look like,

but let's talk about it.

So my provocative statement

is that we desperately need a serious scientific theory of cities.

And scientific theory means quantifiable --

relying on underlying generic principles

that can be made into a predictive framework.

That's the quest.

Is that conceivable?

Are there universal laws?

So here's two questions

that I have in my head when I think about this problem.

The first is:

Are cities part of biology?

Is London a great big whale?

Is Edinburgh a horse?

Is Microsoft a great big anthill?

What do we learn from that?

We use them metaphorically --

the DNA of a company, the metabolism of a city, and so on --

is that just bullshit, metaphorical bullshit,

or is there serious substance to it?

And if that is the case,

how come that it's very hard to kill a city?

You could drop an atom bomb on a city,

and 30 years later it's surviving.

Very few cities fail.

All companies die, all companies.

And if you have a serious theory, you should be able to predict

when Google is going to go bust.

So is that just another version

of this?

Well we understand this very well.

That is, you ask any generic question about this --

how many trees of a given size,

how many branches of a given size does a tree have,

how many leaves,

what is the energy flowing through each branch,

what is the size of the canopy,

what is its growth, what is its mortality?

We have a mathematical framework

based on generic universal principles

that can answer those questions.

And the idea is can we do the same for this?

So the route in is recognizing

one of the most extraordinary things about life,

is that it is scalable,

it works over an extraordinary range.

This is just a tiny range actually:

It's us mammals;

we're one of these.

The same principles, the same dynamics,

the same organization is at work

in all of these, including us,

and it can scale over a range of 100 million in size.

And that is one of the main reasons

life is so resilient and robust --

scalability.

We're going to discuss that in a moment more.

But you know, at a local level,

you scale; everybody in this room is scaled.

That's called growth.

Here's how you grew.

Rat, that's a rat -- could have been you.

We're all pretty much the same.

And you see, you're very familiar with this.

You grow very quickly and then you stop.

And that line there

is a prediction from the same theory,

based on the same principles,

that describes that forest.

And here it is for the growth of a rat,

and those points on there are data points.

This is just the weight versus the age.

And you see, it stops growing.

Very, very good for biology --

also one of the reasons for its great resilience.

Very, very bad

for economies and companies and cities

in our present paradigm.

This is what we believe.

This is what our whole economy

is thrusting upon us,

particularly illustrated in that left-hand corner:

hockey sticks.

This is a bunch of software companies --

and what it is is their revenue versus their age --

all zooming away,

and everybody making millions and billions of dollars.

Okay, so how do we understand this?

So let's first talk about biology.

This is explicitly showing you

how things scale,

and this is a truly remarkable graph.

What is plotted here is metabolic rate --

how much energy you need per day to stay alive --

versus your weight, your mass,

for all of us bunch of organisms.

And it's plotted in this funny way by going up by factors of 10,

otherwise you couldn't get everything on the graph.

And what you see if you plot it

in this slightly curious way

is that everybody lies on the same line.

Despite the fact that this is the most complex and diverse system

in the universe,

there's an extraordinary simplicity

being expressed by this.

It's particularly astonishing

because each one of these organisms,

each subsystem, each cell type, each gene,

has evolved in its own unique environmental niche

with its own unique history.

And yet, despite all of that Darwinian evolution

and natural selection,

they've been constrained to lie on a line.

Something else is going on.

Before I talk about that,

I've written down at the bottom there

the slope of this curve, this straight line.

It's three-quarters, roughly,

which is less than one -- and we call that sublinear.

And here's the point of that.

It says that, if it were linear,

the steepest slope,

then doubling the size

you would require double the amount of energy.

But it's sublinear, and what that translates into

is that, if you double the size of the organism,

you actually only need 75 percent more energy.

So a wonderful thing about all of biology

is that it expresses an extraordinary economy of scale.

The bigger you are systematically,

according to very well-defined rules,

less energy per capita.

Now any physiological variable you can think of,

any life history event you can think of,

if you plot it this way, looks like this.

There is an extraordinary regularity.

So you tell me the size of a mammal,

I can tell you at the 90 percent level everything about it

in terms of its physiology, life history, etc.

And the reason for this is because of networks.

All of life is controlled by networks --

from the intracellular through the multicellular

through the ecosystem level.

And you're very familiar with these networks.

That's a little thing that lives inside an elephant.

And here's the summary of what I'm saying.

If you take those networks,

this idea of networks,

and you apply universal principles,

mathematizable, universal principles,

all of these scalings

and all of these constraints follow,

including the description of the forest,

the description of your circulatory system,

the description within cells.

One of the things I did not stress in that introduction

was that, systematically, the pace of life

decreases as you get bigger.

Heart rates are slower; you live longer;

diffusion of oxygen and resources

across membranes is slower, etc.

The question is: Is any of this true

for cities and companies?

So is London a scaled up Birmingham,

which is a scaled up Brighton, etc., etc.?

Is New York a scaled up San Francisco,

which is a scaled up Santa Fe?

Don't know. We will discuss that.

But they are networks,

and the most important network of cities

is you.

Cities are just a physical manifestation

of your interactions,

our interactions,

and the clustering and grouping of individuals.

Here's just a symbolic picture of that.

And here's scaling of cities.

This shows that in this very simple example,

which happens to be a mundane example

of number of petrol stations

as a function of size --

plotted in the same way as the biology --

you see exactly the same kind of thing.

There is a scaling.

That is that the number of petrol stations in the city

is now given to you

when you tell me its size.

The slope of that is less than linear.

There is an economy of scale.

Less petrol stations per capita the bigger you are -- not surprising.

But here's what's surprising.

It scales in the same way everywhere.

This is just European countries,

but you do it in Japan or China or Colombia,

always the same

with the same kind of economy of scale