Dr. Feldman: So, our guest today
is Christa Brelsford.
She is a post-doc at the
Santa Fe Institute.
She has a B.S. in Civil Engineering from
Columbia University and also
a master's in Climate and Society.
She recently completed her Ph.D. in
the School of Sustainability at
Arizona State, and then came to
join us at Santa Fe. So, welcome.
Dr. Brelsford: Thank you.
It's fun to be here.
Dr. Feldman: Great. Thanks for taking
the time. So, I was wondering if
maybe you could start by telling us
a little bit about what you're working
on now at Santa Fe.
Dr. Brelsford: Yeah, the big project that
I've been working on is thinking
about the topology of cities.
Rather than the scaling ideas
of cities, what I think about is
that the problem that cities
exist to solve is the circulation of
people, goods, and ideas.
This is a connectivity problem, then,
not a geometry problem.
If you're connected, it doesn't
exactly matter how far away you are.
And the mathematical language of
topology is exactly what we
use to talk about connectivity.
So, because cities are about
a connectivity problem, we think
the mathematical language of
topology is a natural way to describe
cities.
Dr. Feldman: Nice. And what drew you
to this work? What interests
you about the sorts of questions
you're working on?
Dr. Brelsford: So, I'm lucky enough
to get to have access to some of
the best education in the world.
And I've always thought that
the purpose of this is to do
good in the world.
So, as an undergraduate civil engineer,
I thought I was going to build
bridges and
build roads
in the developing world
and that would solve problems.
Dr. Feldman: Yep.
Dr. Brelsford: It didn't take very long
of engineering school to
realize that just
better engineering
skills isn't how we solve problems
for people in cities.
In my Ph.D., when I was studying
sustainability, again, I was looking
at drivers of decision making around
urban infrastructure systems.
This was specifically applied to water
systems. But again, what I was trying
to do is figure out, okay, just
knowing how to build the infrastructure
isn't enough. Maybe if we know how
people make decisions about how
infrastructure is built
that will give us a better
understanding of how to build
better cities in the future.
As a Ph.D., again, I felt like that
wasn't enough. We need a broader
theory of the local scale processes
within cities in order to figure
out how to build better cities.
I mean, the urban
population in going
to double over
the next--
pick your number, but 40 to 50 years.
And that means we need
almost as much infrastructure
as we built in the entire history
of our species to house
and feed all of those people.
[That's the] problem, and so
we should get it right.
Dr. Feldman: Yep, so, to what extent
has some of the theory of scaling
around cities, some of the work that
Luís Bettencourt, Geoffrey West
and that group has done.
How has that informed or
motivated your work? In what ways?
Dr. Brelsford: Yeah, so I think that's
some of the best empirical theory
we have about cities right now.
And these are all aggregate answers,
right. They're looking at the average
relationships between population
and area, or population and
whichever variable you're talking
about at the city-wide level.
And that's important, and it's a really
good step in figuring out how to
understand cities from a
broader perspective. But we also
need to think about the local
and heterogeneous processes
within cities, which is what
I'm really interested in.
Dr. Feldman: So I guess maybe
this is a very coarse paraphrase
of what you just
said, and this
is a little bit how
I tend to think
of the scaling work.
As you said, it's
very empirical
so it's describing a
certain pattern
or regularity
and there's
some ideas about
where those patterns might
come from, but to a large part
it sort of begs the question of
how local processes and different
processes give rise to these sorts of
things. I think of it as intriguing
empirical work that then requires
some more mechanistic detailed work.
Is that a fair assessment, you think?
Dr. Brelsford: The mechanistic and
detailed part of it is the part
that I'm interested in.
Yeah, that the empirical relationships
are robust given the literature so far.
And there's some theories for why those
empirical relationships exist that
are based on local processes
which are the things that I'm
really interested in investigating.
Dr. Feldman: Do you think
there are any, maybe, limitations
to the urban scaling approach
or--danger is too strong a word, but--
anything to be cautious about
when thinking about that work?
Dr. Brelsford: I mean, sure, if you're
being critical, it's just bean counting.
It's a robustly observed empirical
relationship. That is absolutely
true. And that's--that could be the
end of it. It could be that
all the theories about why
this empirical relationship exists
are wrong.
Dr. Feldman: I wonder also...
I mean, you're interested in, I think,
not just how--to put it broadly--
how cities
are built, but how to build
them better, where better
could mean more sustainable,
fairer, more justly. And so, I sometimes
wonder if these power laws--yes, it's
a nice, robust relationship, but
maybe that's actually a sort
of bad relationship and there's
some way we could do better.
In other words, that a city is doing
it right if it's on the line
maybe isn't necessarily true.
You know what I mean?
Dr. Brelsford: Yeah. I mean,
you could talk about not whether
it's on the line or off the line,
but its distance from the line,
the residuals in these regressions.
Again, that might be
something that's interesting
to think about. Is it possible
to shift that, to change
the relationship
between crime and population?
Or, for a city that's above the line
to get closer to the line and
think about what local scale processes are
driving it to be an outlier
and have more crime per population
than our theories think it should.
Dr. Feldman: Yep. Is there a--either
in terms of your own work or some of
the more aggregate-level scaling work--
is there some recent developments or
directions that you're particularly
excited about? Things that you think
hold great promise?
Dr. Brelsford: I'm an empiricist, and the
data set that I'm currently really
excited about working with is
looking at census [track] level data
in Brazil. There's been a lot of work
on this kind of stuff, especially in
the developed world, in the U.S.
and Europe. And starting to use
the census style and real
small-scale demographic information
in the developing world,
and also in slums, which is a big
part of the work that Luís and I
have been working on for a while,
I think is really important.
Dr. Feldman: And what are you hoping
to learn or figure out from all that?
Dr. Brelsford: I think you can't
understand cities if you don't
understand slums.
Dr. Feldman: Can you say how
you're using the word
"slum" just in
case people aren't familiar with
that term?
Dr. Brelsford: Okay. When I'm being
more precise with my language
I say "informal settlement."
Dr. Feldman: Right.
Dr. Brelsford: In the way that I
look at it, a slum is any place where
lots of people don't have access
to formal urban infrastructure systems.
So, there may not be--
within a city, so there may
be running water in the city,
but people who live in this
particular neighborhood don't have
access to that. Or power systems,
or whatever.
Dr. Feldman: Yep. So, sorry, so you
were saying that this data set--
you're optimistic or excited that it's
going to shed new light
on the dynamics of slums
and informal settlements?
Dr. Brelsford: Yeah. I think
that we can use what we can learn
about slums and informal setttlements
to inform a broader understanding
of cities. Thus far, more or less all
we've measured is the formal
parts of cities, which by 2050
might be only half of the world's
urban population. So, by getting
some empirical handle on
what's going on in slums,
we'll start to know more
about how cities function.
Dr. Feldman: So, do you think
--this may be an unfair question to ask
you to predict the future, but
do you think when you look at
--if you try to look at various
aggregate or empirical statistics,
would slums look the same as cities
or would they look--
have sort of different signatures?
Dr. Brelsford: That's a
really interesting question.
From a topological perspective,
which is what
I spent a
long time
looking at.
I can tell you that
slums are
qualitatively
different,
not just
quantitatively different,
but they're
topologically qualitatively
different, which is
really interesting.
And we think
those topological
differences, which,
again, are about
connectivity,
mean that there are
likely to be very
big differences in
how people
who live in slums
interact with the
rest of the city
than people who
are able to live
in formal
neighborhoods.
Dr. Feldman: Yep, great.
Dr. Brelsford: But we haven't tested
that yet.
Dr. Feldman: Well, we look--
I look forward to hearing about that.
That definitely sounds like
exciting work.
Are there any other thoughts on
urban scaling or science of
cities that you want to leave
us with? Any bits of advice
for the students in the course?
Dr. Brelsford: I think that
understanding cities is the way
to solve problems in the world
over the next century. I think
that we can't solve the big
problems we face
without a good understanding
of cities. So that's why
I do what I do.
Dr. Feldman: Great. Sounds good.
Well, thanks so much for your time
and sharing some thoughts with us.
Dr. Brelsford: Yeah, thanks
for having me.
Dr. Feldman: Take care.