How 300 Years of Urbanization and Farming Transformed the Planet

Three centuries ago, humans were intensely using just around 5 percent of the Earth’s land. Now, it’s almost half.

Humans are transforming the Earth through our carbon emissions. Arctic sea ice is shrinking, seas are rising, and the past four years have been the hottest since record-keeping began. But long before the first cars or coal plants, we were reshaping the planet’s ecosystems through humbler but no less dramatic means: pastures and plows.

Environmental scientist Erle Ellis has studied the impact of humanity on the Earth for decades, with a recent focus on categorizing and mapping how humans use the land—not just now, but in the past. And his team’s results show some startling changes. Three centuries ago, humans were intensely using just around 5 percent of the planet, with nearly half the world’s land effectively wild. Today, more than half of Earth’s land is occupied by agriculture or human settlements.

“Climate change is only recently becoming relevant,” said Ellis, a professor at the University of Maryland, Baltimore County. “If it keeps going how it is, it will become the dominant shaper of ecology in the terrestrial realm, but right now the dominant shaper of ecology is land use.”

 

In contrast to the typical division of the world into ecological “biomes,” Ellis and his team at the Laboratory for Anthropogenic Landscape Ecology map what they call “anthromes,” or “anthropogenic biomes.” These show the intersection of ecology and human land use.

Using a range of sources, Ellis’s team mapped out that land use, dividing the planet into grids and categorizing each cell based on how many people lived there and how they impacted the land. The densest areas were cities and towns, followed by close-packed farming villages. Less populated areas were categorized by their dominant land use—crops, livestock pasture, or inhabited woodlands—while other areas were marked as largely uninhabited.

Below is an animation using a simplified version of Ellis’s data:

 


Human land use 1700 to 2000

Even with only one snapshot per century, the animation makes some of the trends obvious. Large swaths of Russia and the United States become cropland over the 19th century, while livestock occupies increasing amounts of previously semi-wild land in Africa and Asia.

“Asia is pretty much the dominant transformed area, and transformed the earliest,” Ellis said. “Europe is also pretty dense ... The rest of the world has a different trajectory. Much slower, less dense.”

All of this is a mixture of estimates and approximations. One reason Ellis and his team only looked every hundred years and divided the world into cells that stretch for miles was to avoid giving a false impression of precision.

 

People ask Ellis, “‘What was my backyard like?’” he said. “Well, we don’t have any solid evidence … The further back in time you go, the more you have to consider [this], in a sense, educated guesswork.”

Even more recent data can have issues, based on political decisions that countries make about how to self-classify their land. Saudi Arabia, for example, reports “almost every part of their country as being rangeland” even though much of that arid land is seldom if ever grazed.

Humans shape even “seminatural” biomes

Significant portions of the world, both now and in the past, have been what Ellis’s team terms “seminatural.” These are areas—frequently forests—with low but real human habitation. This could reflect a large cell of the grid that has a farming village or two but mostly natural forests. But frequently, Ellis says, humans have taken a much bigger role in shaping seemingly natural wilderness than people think.

Take the “pristine myth”—the idea that the Americas before European colonization were dominated by pristine wilderness untouched by human hands. In fact, modern researchers believe that indigenous tribes had actively shaped their landscapes through agriculture and regular burning of American forests.

Because of this, the devastating spread of epidemics among indigenous populations after 1492 also had a huge impact on climate—and not just locally. Some scholars believe disease-ravaged peoples significantly cut back on their management of American forests, which meant far less carbon dioxide put into the atmosphere from fires and far more absorbed into newly grown forests. The combination could have played a significant role in the “Little Ice Age” that lowered global temperatures for several centuries between around 1500 and 1850 C.E.

This kind of active land management was done not just by sedentary populations, but by hunter-gatherers, too. This, Ellis says, is a shortcoming in the data.

“There’s no direct mapping of hunter-gatherers’ land use in these datasets. That’s something we’re trying to rectify now,” he said, noting that evidence suggests even non-agricultural people have major effects on the environment.

The data also shows the massive impact made by cities, the most dramatic way humans transform their environment. In 1700, a negligible portion of the Earth’s surface was covered by cities. Over the three centuries that followed, this boomed by around 40 times. Cities are still just half a percent of the planet’s land area, but they have had the most dramatic increase in impact of any of Ellis’s “anthromes.”

Densely populated farming villages—which often have similar concentrations of people per square mile as American suburbs—are also big, especially in the developing world. (Ellis’s team don’t map any urban areas in the Americas or Australia before 1900, and never apply the “villages” category to those continents, because those areas didn’t have “histories of intensive subsistence agriculture.”)

Huge portions of India and China are occupied by these kind of villages. So, too, were the hinterlands around major European cities before improvements in transportation enabled produce to be brought from farther away. Paris, for example, used to be surrounded by suburban “market gardens” which, historians André Jardin and André-Jean Tudesq note, could produce five or six harvests per year and had a “virtual monopoly of the Parisian market” for food until the second half of the 19th century.

How cities drive land-use changes

That kind of intensive agriculture to feed a demanding urban market is part of the huge impact that cities have on the use of land even well outside their boundaries. Those thousands or millions of urban dwellers aren’t producing their own food, and thus need more food produced elsewhere in order to eat.

Ellis describes two different ways that cities impact far-away anthromes through their demands for food—one of them devastating to natural ecosystems, the other surprisingly beneficial.

 

The first sees new land being put under the plow, as societies try to produce more food for a growing population. This is often low-productivity agriculture, reflecting the marginal quality of the farmland: If it was good for farming, it would have been farmed already. But later, as populations grow, comes an “intensification” process as technology increases the yields on low-productivity farmland.

Agricultural expansion has a massive impact on natural biomes, and has for millennia. But the second process, intensification, has the potential to restore some of the natural biomes that humans previously plowed under.

“Dense cities actually have the potential to help areas recover, because dense populations in cities often are basically pulling people out of the rural areas where they’re farming low-productivity land,” Ellis said. The increased production on good land means the marginal farmland is no longer needed.

Author Charles Mann described this process taking place in New York’s Hudson River Valley in his 2018 book, The Wizard and the Prophet. In the late 19th century, this region was dominated by “hardscrabble farms and pastures ringed by stone walls.” Now many of those “hardscrabble farms” are gone. Six counties in the lower Hudson Valley had around 350,000 people and 573,000 acres of timberland in 1875; today those same counties have more than 1 million people but three times as much forest.

 

“Many New England states have as many trees as they had in the days of Paul Revere,” Mann writes. “Nor was this growth restricted to North America: Europe’s forest resources increased by about 40 percent from 1970 to 2015, a time in which its population grew from 462 million to 743 million.”

But while this intensification of agriculture is allowing the return of nature in parts of developed countries, the first phase—expansion—is still playing out in the developing world. Erle’s maps show the expansion of crops and livestock into areas like Africa’s Sahel and South America’s Amazon rainforest over the past century.

“Land transformation is the big story of biosphere transformation so far,” Ellis said. “If you’re trying to understand how we produced the ecology we have now, it’s the story of land-use transformation.”

What’s next for Earth

So what will a future mapmaker show for the world’s land use in 2100? Ellis said he expects urbanization to continue, at least doubling the share of the planet’s land devoted to urban areas over the next century.

Similarly, he expects developed countries to see an intensification of agriculture that enables marginal land to be returned to the wild—a process already under way in newly developed countries like China. Poorer countries, on the other hand, may continue to convert marginal wild land into farmland.

“It’s only poor farmers without much investment that can make that work,” Ellis said. “When you’re investing large amounts of money in farm equipment and fertilizers, you don’t invest that in marginal land.”

Much depends, however, on political, economic, and technological changes that will unfold over the next 80 years. For example, Ellis said, the United States has recently seen “a huge shift from beef to chicken” in consumer demand. “That changes the kind of land that’s in demand, from grassland to production of maize and soy.”

Among the factors that could affect the future of Earth’s land use are political decisions in Brazil, where new President Jair Bolsonaro wants to open up more of the Amazon rainforest to agriculture, and technology, where a potential breakthrough in electrical generation such as fusion power could enable transformative changes such as vertical urban farming. Conservation efforts, or lack thereof, could also impact areas of intensive agriculture in developed countries.

“The future of the biosphere… depends partly on economics, partly on politics, but also partly on vision,” Ellis said. “It depends on what people’s values are.”

Image: Pixabay

Source: City Lab

This article is culled from daily press coverage from around the world. It is posted on the Urban Gateway by way of keeping all users informed about matters of interest. The opinion expressed in this article is that of the author and in no way reflects the opinion of UN-Habitat.