Lots of small deaths and the evolution of cities.

Good cities evolve.

The Evolution of Cities

Why are things so much more expensive downtown? The truth is, valuable land is scarce there. But American cities are huge. Consider Chattanooga’s 141 square miles compared to Paris’ 41. Why then are our downtowns always such a small part of that footprint? Downtowns disproportionately fund the entire city as a whole, producing way more revenue than other parts.

Using publicly available data, this is what tax revenue is generated by properties in Chattanooga. Image courtesy of arrosmit.com. Red/yellow are properties that cannot afford or unlikely to break even with tax revenue generated, green is able to cover costs, towers are a surplus.

When you look at the economics of it, downtowns are almost exclusively the only part of a city that generate enough revenue to afford their own infrastructure, and beyond that, they subsidizes other parts of town.

Why is that? And can we take some of these attributes and spread them throughout the the city?

Evolution, if you will.

Cities develop like ecosystems with constant life and death transactions (a small business opens, grows, downsizes, shuts down) and the built environment is built to accommodate that.

What arises is sometimes called a traditional development pattern; small bets placed over time. And it’s fascinating to note that, across cultures, you usually see similar patterns. Small temporary buildings are always the first deployed in a newer place; later swapped with more permanent wooden structures that will, in many places, eventually get replaced with more-permanent stone.

Brainerd, Minnesota, 1870: wooden structures, dirt road, board sidewalk. Though many of these wooden building will die, the overall result will be life. Example from this article.

Brainerd, Minnesota, 1894: Just over two decades later. Many small businesses shuttered, and small businesses were torn down to allow for larger, more permanent businesses

Cities look similar across the world and cultures because they have to serve a similar purpose: helping humans flourish. They need an abundance of housing, businesses in close proximity, and a centralized street or public square where people meet. These naturally arise in part because they meet human needs.

Just as the many lives of your ancestors paved the way for your existence, buildings, too, owe their presence to the structures that came before them. Neighborhoods evolve and pass on ‘genes’ and have ‘mutations’ that sometimes cause premature death, or elongate life and, in that sense, exist in a sort of ‘natural selection.’

The Good Genes of Cities

So what are the good genes? Our favorite parts of cities have very similar features. Often they involved mixed uses—housing close to, or literally attached to, businesses. This creates an accumulation of lots of small businesses that help each other thrive and a public realm that fosters community interaction. Imagine then, a forest; it’s thousands of little things that act independently from each other, but help create massive amounts of life.

Now imagine that forest was taken over and a sort of modernist-order was forced on it. And we separated the different flora and fauna based on its use.

Negative Effects of Separation

1. Disruption of Pollination: Natural Ecosystem

• Many plants rely on specific creatures for pollination. For instance, orchids in rainforests depend on certain insects or birds for their reproductive processes. Separating these species could significantly disrupt their pollination and consequently their ability to reproduce.

Disruption of Community Interaction: Human Ecosystem

• Just like plants rely on specific pollinators, people in cities need diverse interactions to thrive. Think of a neighborhood café where locals mix; it’s not just about the coffee but the accidental meetings that spark ideas and foster community ties. Break these spaces up by interest or income, and you lose the magic that makes city living vibrant.

2. Loss of Habitat: Natural Ecosystem

• Many rainforest species, like certain birds and tree frogs, depend on specific plants for survival. Separating them could drastically reduce their populations.

Loss of Cultural Hubs: Human Ecosystem

• Diverse urban zones, like artistic neighborhoods or ethnic enclaves, serve as crucial habitats for cultural expression. When artists are separated from these hubs, or if ethnic communities are dispersed, the cultural richness of the city diminishes, similar to how birds lose their nesting spots when trees are cut down.

3. Interruption of Nutrient Cycles: Natural Ecosystem

• Rainforests work like they do because dead plants turn into rich soil, which supports new plant life, while animals chip in with their waste. Take ants and their plant pals as an example; the ants fend off herbivores and boost soil nutrients, which helps plants thrive. Split them up, and you shake up these vital cycles.

Interrupted Economic Cycles: Human Ecosystem

• Cities function on the principle of economic exchange and support—shops need customers, businesses need suppliers. In a mixed-use community, this cycle flows smoothly, akin to nutrient cycles in a forest. Segment cities into isolated business districts, residential zones, and shopping areas, and you disrupt these economic flows, leading to inefficiencies and lost opportunities.

4. Reduced Seed Dispersal: Natural Ecosystem

• Animals play a crucial role in seed dispersal. For example, fig wasps and fig trees have a symbiotic relationship where the wasps pollinate the figs and help distribute their seeds. Separating these partners can reduce seed dispersal, impacting plant populations and genetic diversity.

Reduced Social Mobility: Human Ecosystem

• Urban environments naturally facilitate social interactions and opportunities. When you separate high-income areas from more mixed or lower-income ones, akin to separating fig trees from their wasps, you prevent people from accessing diverse job opportunities, education, and social networks, stunting social mobility.

5. Increased Vulnerability to Pests and Diseases: Natural Ecosystem

• Diversity’s usually a good defense against pests and sickness. When ants bunk with certain plants, they help keep other pesky insects at bay. Put all one kind of plant together, and it’s like rolling out the red carpet for disease and insect invasions.

Increased Vulnerability to Social Issues:

• A mix of uses and social classes in urban areas can help mitigate problems like crime and poverty. Homogenous neighborhoods, much like monocultures in agriculture, can exacerbate vulnerabilities, concentrating problems and reducing the resilience found in diversity.

By weaving in these examples, it’s clear why not mixing things up in an ecosystem, like a rainforest, is crucial. Splitting up plants and animals not only messes with their personal survival but can also throw the whole ecosystem off balance.

The Good Bad News

The bad news is that everything within our current set up is against this. Both the political left and right think that we just need more money to pour into our system; stronger pesticides, more fertilizer. But in reality, we need less.

The good news is that, like the wild, traditional development is naturally regenerative and will in a way begin healing itself; we don’t need a $4,000,000 grant to study the effects of small business, we just need to tear down the barrier for people to get started.

In this particular cultural moment, for real progress in economic participation, focus less on adding ladders and more on lowering walls.