Showing posts with label history. Show all posts
Showing posts with label history. Show all posts

Friday, September 9, 2022

Thinking about cities: Were ancient cities greener than modern ones?

  

*This is part of a series called ‘Thinking About Cities’ which are parts of a book I am working on about urban green space that I’ve decided to cut out of the book manuscript.

 

Picture a large modern city. Undoubtedly, your mental image includes a lot of grey. Grey buildings. Grey roads. Maybe grey skies saturated with ozone and particulate matter. Yet we don’t see green as a dominant feature of a city despite the undeniable importance of vegetation and green space to the well-being of a city. 

 

Now picture an ancient city. This image probably has a lot less grey and more browns and greens. We likely see dirt (unpaved) roads, wooden structures, trees here and there, a river with a natural bank, and chickens and other livestock intermingled with human activity. 

 

Were ancient cities inherently greener than modern cities? If so, was this done by design, or by accident, or because humans lacked the technology to completely transform the landscape? Before we delve into this question, we need to think about what a city is and where it comes from.

 

History of the city

Cities have evolved from small permanent settlements to massive human-created landscapes that house large and densely packed populations. As Gordon Childe argued (Childe 1950), the city is a revolution. They represent revolutions of technology, governance, economics, and our relationship with nature and place. Nothing like cities existed in all of human history until about 9-10 thousand years ago when the first known large settlements appeared near the shores of the Mediterranean Sea ( These were Jericho in what is today the West Bank and Catal Huyuk in Turkey. These cities housed somewhere between 2 and 6 thousand people).  To understand the origins of the city, we need to look to the birth of the major civilizations, and to find these, we need to go to the banks of the major rivers of the Middle East and Asia. The Nile, Ganges, Tigris, Euphrates, Indus, Yangtze, and Yellow rivers were the cradles fostering the birth of cities. Just like a germinating seed, cities required water to grow. The rivers were the lifeblood of these new forms of civilization and was essential for the irrigated agriculture that fed populations, a supply of drinking water and for construction, a means for moving waste away from human populations, and were the express highways of the day –moving people and goods.

 

These first major cities were home to several thousand people (certainly less than ten thousand) living in loosely organized communal areas, and though these do not seem like cities by today’s criteria, they were massive by the standards of the day. Pre-agrarian societies supported population densities of about 0.04 people per square kilometre and early agrarian societies, which gave rise to the first permanent settlements, had between 1 and 5 people per square kilometre. Cities today have densities of hundreds or thousands of people per square kilometre.

 

The shift from nomadic cultures to agricultural ones was the necessary development for cities to emerge. Having a permanent source of food drastically changed how people spend their time and allowed them to produce more food than they could personally eat. Sounds trivial, but this new reality allowed for specialized occupations that were not focused on finding and gathering food. The farmer produces the food, while others pursue their own vocational callings like carpenter, artisan, priest, and so on. With new occupations involving training and expertise, innovation and technological development ensued. Metal workers tested new methods and alloys, farmers found ways to increase yield, and the priests and elites organized people and resources.

 

By this point, cities were all but inevitable. As different cultures shared information and technology, small cities began to emerge along the great rivers of the world. These rivers all supported the eventual growth of large cities of ten thousand or more people by about 5 thousand years ago. But the rivers also needed to be controlled. While they were an invaluable resource, they could also be unpredictable and devastating. The ancient city of Petra in modern Jordan, was a thriving capital city between 300 BC and 300 AD, but it was subject to floods after heavy storms and the Petroneans built damns and culverts to reduce flooding. This was not unique to Petra. Many ancient city archaeological sites include evidence of engineered structures designed to control flooding.

 

Cities also required governance. Ten thousand people living together would be chaotic if there wasn’t some sort of government in place to create and enforce rules. For these early cities, this governance was intertwined with religion. Temples were the centre of these early cities and provided guidance, worship, laws, education and were the focal points for political power. People no longer relied solely on family or clan allegiance but were increasingly tied to loyalties to king, high priest, and nation-state. These power structures were important for organizing people and pooling efforts and creativity into larger and larger projects, while promising protection from other nation-states, which were also increasing in power.

 

The emergence of cities was a slow evolution from small permanent settlements to large centrally governed and densely populated ones. It is hard for scholars to say with certainty when the first city appeared because both the evidence has been washed away by time and it is not entirely clear what a city is.

 

For ancient settlements, we can say that the designation as a ‘city’ corresponds to certain features that are necessary to successfully house thousands of people in a small area. These would include: sturdy streets capable of sustaining constant use, dense and organized housing, central governance and control of law enforcement, taxation to pay for services and common good building projects (e.g., aqueducts, city walls, etc.), specialized occupations and trades that provide expertise in various elements of culture, governance and construction of cities (e.g., engineers, teachers, etc.), markets allowing specialized occupations to trade goods and services, because blacksmiths do not grow much food and farmers make few metal objects, and finally cities have large and permanent impacts on local environments.

 

Let us paint a picture of an early city by looking at the largest city in the world during the 11th century –Kaifeng, China (historically called Daliang or Bianjing). Kaifeng was the capital of the Song dynasty (960 - 1279) and at the height of its glory, it was home to somewhere between six hundred thousand and one million people. We actually know a lot about Kaifeng. China is the oldest continuous civilization on Earth and has tremendous collections of historical documents. Further, Kaifeng is still a major city today with a population of about five million people –a medium-sized city by Chinese standards, but a very large one by standards elsewhere. Most importantly, one of China’s most cherished historical artifacts is a giant scroll measuring 5.25 meters (or over 17 feet) long called “Alongthe River During the Qingming Festival”, and it beautifully depicts Kaifeng life during a national holiday. 

 

A small segment of the painting “Along the River During the Qingming Festival, painted by Zhang Zeduan (1085-1145). It depicts city life in Kaifeng, China at the height of its prestige when it was the capital city and the largest city in the world.


From this beautiful illustration, you can see the elements of what it means to be a city. First, there are lots of people milling around and participating in different activities. There is trade, we see people moving goods in carts and on camels. There are specialized occupations, notice the tea houses and restaurants. There is organised building construction lining a major road. We see the overwhelming evidence of codified economics as people are buying goods and exchanging money (and gambling!). And with economics we see class inequalities as the lady pulls aside the silk curtains and looks out of the litter, or shoulder carriage, being carried by porters. There is a city gate protecting the population and regulating and taxing the flow of goods. If we move along the scroll, we would see the Yellow River and the docks and ships necessary to move people and goods over great distances. Looking at the amazingly detailed depictions in the scroll, we can almost smell the odours and aromas and hear the sounds that permeate through a dense city. Horses neighing, dogs barking, people shouting, and dishes clanging. This was a city by any definition.

 

So was Kaifeng greener than modern Beijing?

Obviously, Kaifeng, if it existed today, would be a greener city than Beijing. Modern Beijing, or any other megalopolis, is defined by a massive concentration of material and energy that results in a concrete landscape capable of housing millions of people. Keifeng simply had less impervious surface and more space for nature. So, the short answer is yes, ancient cities were physically greener.

 

But if we think of ‘green’ as being a philosophy or approach that directs how we interact with nature, then I don’t think we can say that ancient cities were greener. Humans have created cities precisely to alter local environments to better suit our needs. A city is the embodiment of our innate desire to increase our own fitness by removing threats (from predators and other people), creating security through strength in numbers, and reducing environment unpredictability. We might want to romanticize early human relationships with nature, but the reality is that once technologies were created that advance urbanization, they were implemented and spread rapidly. Being susceptible to flooding, early cities channelized rivers once they were able to. In response to threats from other groups of people, cities around the world accepted being encased in walls as the technologies emerged.

 

The history of cities can be seen as a continuum from small and low-impact settlements to large, urbanized landscapes like Tokyo. What drives a smaller and greener city towards being a megalopolis? So long as the population demand is there and the technologies to build a city exist, the megalopolis is all but inevitable.

 

Unlike previous generations, we are in a unique position to ask the question, what do we want a city to look like? Most of the technological hurdles that would limit urbanization have been overcome. We now have the conceivable ability to create a completely urbanized planet, like Coruscant from Star Wars. But most people would think that this is a bad idea. But is barely constrained sprawl around urban centres like Los Angeles, Mexico City, Delhi, and Toronto not a microcosm for these urbanizing forces that we think are ultimately undesirable?

 

The point is that neither in ancient times nor now do people have an agreed upon vision of urbanization’s endpoint. Urbanization has been and is driven by the mix of demand and technology, but we now need, more than ever, an agreed upon vision and set of principles directing urbanization. We need cities that minimize environmental impact, reduce the effects of inequality, and ensure people realize the potential benefits of green space.

 

So, were ancient cities greener than cites today. Yes and no. While they had less impact on their local environments, the megalopolises of today were written into their DNA. The devaluation of nature has always been a defining feature of cities. Now, more than ever, we need to rethink the relationship between the city and nature, and rewrite what is coded in a city’s DNA.

 



Childe,V. G. (1950). The urban revolution. Town Planning Review, vol. 21, pg. 3-17.


Tuesday, August 30, 2016

#EcoSummit2016 Day 2 History and ecology go hand in hand.

The role for history in ecology can be tough to generalize. For a neo-ecologist, 5 years may be a long time scale, for a restoration ecologists, 50 years might be, for a paleoecologists, millions of years could matter. But multiple talks today argued that without considering history we are lost. Whether it is using climate history to understand how the effects of past climate change are still being felt today (from Jens Christian-Svenning), or the oft-mentioned debate about whether local biodiversity is truly in decline, the past is necessary to understand our changing planet. [The various papers on this debate came up in at least 3 of talks I saw]. Regardless of which way the diversity relationship goes, Frederic De Laender pointed out that loss of functioning due to increased environmental stress meant that local communities were changing anyways.

Related to this is the question of how ecologists should incorporate and understand the role of human history in their studies. Are humans simply a disturbance? A covariate in a statistical analysis? Or an intrinsic component of ecology across the globe? What is a baseline for ‘naturalness’ in the absence of humans anyways? Further, human records can be potentially misleading as ecological research tools. For example, P. Szabo showed that the popular conception in the Czech Republic (based on archival data) is that beech forests are the true ‘natural’ forest, and coniferous forests were simply the result of forestry plantations. Policy reflects this and promotes preservation of broad leafed forests. However, analysis of paleo-pollen data showed that in fact spruce and other conifers appeared to have dominated for thousands of years in some regions. What then is the true ‘natural’ forest? From Emily Southgate’s fascinating talk showing how the development of an oil refinery in the 1800s and its impacts could be investigated using historical land surveys, to maps showing the still-unfilled ranges of European tree species, the legacy of the past is clear in present day data.

Friday, May 6, 2016

What’s so great about Spain? Assessing UNESCO World Heritage inequality.

Some places are more valuable than others. We often regard places as being of high or unique value if they possess high biological diversity, ancient cultural artefacts and structures, or outstanding geological features. These valuable places deserve special recognition and protection. The sad reality is that when we are driven by immediate needs and desires, these special places are lost.

The natural world, and the wonderful diversity of plants and animals, is on the losing end of a long and undiminished conflict with human population growth, development, and resource extraction. We don’t notice it when there is ample natural space, but as nature becomes increasingly relegated to a few remaining places, we place a high value on them.

The same can be said for places with significant cultural value. Ancient temples, villages, and human achievement are too valuable to lose and we often only have a few remnants to connect us to the past.

In either case, natural or cultural, when they’re gone, we lose a part of us. That is because these special places tell us about ourselves; where we come from, how the world shaped us, and what unites all of humanity. Why did the world cry out in a united voice when the Taliban destroyed the Buddhas of Bamiyan in 2001, even though many of those concerned people were not Buddhist? The answer is simple –the expansion of Buddhism out of India along ancient trade routes tells us why many Asian nations share a common religion. They tell us about ourselves, the differences that interest us, and the similarities that bind us. The same can be said about the global outcry over the recent destruction of the ancient city of Palmyra by ISIS.

Before and after photos of the taller of the Buddhas of Bamiyan. Image posted by Carl Montgomery CC BY-SA 3.0.

Similarly, the natural world tells us about ourselves. The natural world has constantly shaped and influenced what it means to be human. Our desires, fears, and how we interact with the natural world are products of our evolution. If I flash a picture of a car to my 500-student ecology class, very few students, if any, screech in fear. But if I flash a photo of a hissing cobra or close-up of a spider, invariably a bunch of students squirm, gasp, or scream. Rationally, this is an odd response, since cars are the leading cause of death and injury in many western countries. Snakes and spiders kill very few people in Canada.

These special places deserve recognition and protection, and that is what the UNESCO World Heritage designation is meant to achieve. To get this designation for a site requires that countries nominate ones that represent unique and globally significant contributions to world heritage, and are adequately protected to ensure the long-term existence of these sites.  World Heritage sites are amazing places. They represent the gems of our global shared heritage. They need to be protected in perpetuity and should be accessible to all people. Though some I have visited seem like they are loved too much with high visitation rates degrading some elements of Heritage sites.

Examples of UNESCO World Heritage sites. A) The Great Wall of China. B) The Gaoligong Mountains, part of the Three Parallel Rivers of Yunnan. C) Angkor Wat in Cambodia. D) An example of a site that may be too loved -Lijiang in Yunnan. All photos by Shirley Lo-Cadotte and posted on our family travel blog -All The Pretty Places.

UNESCO World Heritage sites should also be representative. What I mean by this is that they should be designated regardless of national borders. Heritage sites are found on all continents across most countries –though a number of politically unstable countries (e.g., Liberia, Somalia, etc.) do not possess Heritage sites, likely because they lack the organization or resources to undertake the designation application process, and they lack the governance to ensure a site is adequately protected. But there are substantial differences in the number of World Heritage sites across nations[1]. Some countries, because of inherent priorities, national pride, resources or expertise, are better able to identify and persuade UNESCO that a particular place deserves designation.

The distribution of the number of UNESCO World Heritage sites across countries and the top ten.

Why do we see such disparity in the number of World Heritage sites -where many countries have few sites, and a few countries have many sites? This is a difficult question to answer, and to do so I took an empirical approach. I combined data on the number of sites per country with Gross Domestic Product (GDP)[2], country size[3], and country population size[4]. I then ran simple statistical analyses to figure out what predicts the number of Heritage sites, and identified those countries that are greatly over-represented by Heritage sites, and those that are very under-represented. A couple things to note, the best statistical models included variables that were all log-transformed, I excluded the World Heritage sites that spanned more than one country, and I did not include countries that did not have any Heritage sites. The data and R code have been posted to Figshare and are freely available.

All three of GDP, area, and population size predicted the number of World Heritage sites. It is important to note that these three country measures are not strongly correlated with one another (only moderately so). So, larger, richer and more populous countries had more World Heritage sites. This makes sense –big countries should contain more unique sites due to random chance and more populous countries tend to have longer historical presence of organized states, and so should possess more cultural relics (especially China). GDP is more difficult to assign a reason, but high GDP countries should have robust national parks or other bureaucratic structures that assess and protect important sites, making them easier to document and justify for UNESCO.  GDP is quite interesting, because it is the single best measure for predicting the number of Heritage sites, better than population size and area. Further, neither country density (population/area) nor productivity (GDP/population) are strong predictors of the number of Heritage sites.

The relationships between the number of World Heritage sites and GDP, area, and population. Note that the axes are all log-transformed.

While these relationships make sense, it is also clear that countries are not all close to the main regression line and some countries are well above the line –meaning they have more Heritage sites than predicted; as well as some below the line and thus having fewer sites. When I combine the different measures in different combinations and look for the best single statistical explanation for the number of World Heritage sites, I find that the combination including GDP and population size, and their interaction (meaning that population size is more important for high GDP countries) is the best. For aficionados, this model explains about 65% of the variation in the number of Heritage sites.

Now, we can identify those countries that are over or under represented by UNESCO World Heritage sites according to how far above or below countries are from the predicted line (technically, looking at statistical residuals).

The deviation of countries from the predicted relationship between the number of sites and GDP and population (and their interaction). The top 5 over-represented and under-represented countries are highlighted.


The top five over-represented countries are all European, which means that given their GDP and population size, these countries have more World Heritage sites than expected. At the other extreme, countries under-represented come from more diverse regions including Africa, the Middle East and Southeast Asia.

An interesting comparison to think about is Germany and Indonesia. Germany has more World Heritage sites than expected (residual = +0.61) and is a moderately sized, high GDP country. Let me say, I like Germany, I’ve been there a half a dozen times, and it has beautiful landscapes and great culture. However, does it deserve so much more World Heritage recognition than Indonesia, which has fewer sites than expected (residual = -0.63)? Indonesia has spectacular landscapes and immense biodiversity and great cultural diversity and history. To put it in perspective, Germany has 35 World Heritage sites and Indonesia has just 8.

To answer the question in the title of this post: what’s so great about Spain? Well, it not only has beautiful and diverse natural landscapes and cultural history, but it appears to have the infrastructure in place to identify and protect these sites. It's place at the top of UNESCOs relative (to GDP and population) ranking of the number of World Heritage sites means that Spain's natural and cultural wonders are in good hands. However, for the countries at the other end of the spectrum, having relatively few World Heritage sites probably is not a reflection of these countries being uninteresting, or that they have little to offer the world, rather it is something more alarming. These places lack the financial capacity or national will to fully recognize those places that are of value to the whole world. The problem is that the globally important heritage that does exist in these places is at risk of being lost. These under-represented countries serve as a call to the whole world to help countries not just identify and protect heritage sites but to aid these countries with infrastructure and human well-being that empowers them to prioritize their natural and cultural heritage.