Science Current Events | Science News | Brightsurf.com
 

Agricultural methods of early civilizations may have altered global climate, study suggests

August 17, 2009
Massive burning of forests for agriculture thousands of years ago may have increased atmospheric carbon dioxide enough to alter global climate and usher in a warming trend that continues today, according to a new study that appears online Aug. 17 in the journal Quaternary Science Reviews.

Researchers at the University of Virginia and the University of Maryland-Baltimore County say that today's 6 billion people use about 90 percent less land per person for growing food than was used by far smaller populations early in the development of civilization. Those early societies likely relied on slash-and-burn techniques to clear large tracts of land for relatively small levels of food production.

"They used more land for farming because they had little incentive to maximize yield from less land, and because there was plenty of forest to burn," said William Ruddiman, the lead author and a professor emeritus of environmental sciences at the University of Virginia. "They may have inadvertently altered the climate."

Ruddiman is a climate scientist who specializes in investigating ocean-sediment and ice-core records. In recent years he has searched across scientific disciplines - anthropology, archaeology, population dynamics, climatology - to gain insight into how humans may have affected climate over the millennia.

He said that early populations likely used a land-clearing method that involved burning forests, then planting crop seed among the dead stumps in the enriched soil. They would use a large plot until the yield began to decline, and then would burn off another area of forest for planting.

They would continue this form of rotation farming, ever expanding the cleared areas as their populations grew. They possibly cleared five or more times more land than they actually farmed at any given time. It was only as populations grew much larger, and less land was available for farming or for laying fallow, that societies adopted more intensive farming techniques and slowly gained more food yield from less land.

Ruddiman notes that with the highly efficient and intensive farming of today, growing populations are using less land per capita for agriculture. Forests are returning in many parts of the world, including the northeastern United States, Europe, Canada, Russia and even parts of China.

The positive environmental effects of this reforestation, however, are being canceled out by the large-scale burning of fossil fuels since the advent of the Industrial Revolution, which began about 150 years ago. Humans continue to add excessive levels of carbon dioxide to the atmosphere, contributing to a global warming trend, Ruddiman said.

Five years ago, Ruddiman made headlines with a hypothesis that humans began altering global climate thousands of years ago, not just since the Industrial Revolution. That theory has since been criticized by some climate scientists who believe that early populations were too small to create enough carbon dioxide to alter climate.

According to projections from some models of past land use, large-scale land clearing and resulting carbon emissions have only occurred during the industrial era, as a result of huge increases in population.

But Ruddiman, and his co-author Erle Ellis, an ecologist at UMBC who specializes in land-use change, say these models are not accounting for the possibly large effects on climate likely caused by early farming methods.

"Many climate models assume that land use in the past was similar to land use today; and that the great population explosion of the past 150 years has increased land use proportionally," Ellis said. "We are proposing that much smaller earlier populations used much more land per person, and may have more greatly affected climate than current models reflect."

Ruddiman and Ellis based their finding on several studies by anthropologists, archaeologists and paleoecologists indicating that early civilizations used a great amount of land to grow relatively small amounts of food. The researchers compared what they found with the way most land-use models are designed, and found a disconnect between modeling and field-based studies.

"It was only as our populations grew larger over thousands of years, and needed more food, that we improved farming technologies enough to begin using less land for more yield," Ruddiman said. "We suggest in this paper that climate modelers might consider how land use has changed over time, and how this may have affected the climate."

University of Virginia


Related Global Climate Current Events and Global Climate News Articles


Study: Climate change and air pollution will combine to curb food supplies
Many studies have shown the potential for global climate change to cut food supplies. But these studies have, for the most part, ignored the interactions between increasing temperature and air pollution - specifically ozone pollution, which is known to damage crops.

Stanford study shows how to power California with wind, water and sun
Imagine a smog-free Los Angeles, where electric cars ply silent freeways, solar panels blanket rooftops and power plants run on heat from beneath the earth, from howling winds and from the blazing desert sun.

Stanford biologist warns of early stages of Earth's 6th mass extinction event
The planet's current biodiversity, the product of 3.5 billion years of evolutionary trial and error, is the highest in the history of life. But it may be reaching a tipping point.

Strengthening community forest rights is critical tool to fight climate change: New report
Strengthening community forest rights is an essential strategy to reduce billions of tonnes of carbon emissions, making it an effective way for governments to meet climate goals, safeguard forests and protect the livelihoods of their citizens, according to a major new report.

Urban heat boosts some pest populations 200-fold, killing red maples
New research from North Carolina State University shows that urban "heat islands" are slowly killing red maples in the southeastern United States.

An increase in temperature by 2050 may be advantageous to the growth of forage plants
A 2°C increase in temperature around the world by 2050, according to one of the scenarios predicted by the Intergovernmental Panel on Climate Change (IPCC), may be advantageous to the physiology and the biochemical and biophysical processes involved in the growth of forage plants such as Stylosanthes capitata Vogel, a legume utilized for livestock grazing in tropical countries such as Brazil.

Calcification in Changing Oceans Explored in Special Issue of The Biological Bulletin
What do mollusks, starfish, and corals have in common? Aside from their shared marine habitat, they are all calcifiers-organisms that use calcium from their environment to create hard carbonate skeletons and shells for stability and protection.

Global warming 'pause' reflects natural fluctuation
In a paper published this month in Geophysical Research Letters, Lovejoy concludes that a natural cooling fluctuation during this period largely masked the warming effects of a continued increase in man-made emissions of carbon dioxide and other greenhouse gases.

Mixing it up: Study provides new insight into Southern Ocean behaviour
A new study has found that turbulent mixing in the deep waters of the Southern Ocean, which has a profound effect on global ocean circulation and climate, varies with the strength of surface eddies - the ocean equivalent of storms in the atmosphere - and possibly also wind speeds.

Size and age of plants impact their productivity more than climate, study shows
The size and age of plants has more of an impact on their productivity than temperature and precipitation, according to a landmark study by University of Arizona researchers.
More Global Climate Current Events and Global Climate News Articles

Global Climate Change: A Primer

Global Climate Change: A Primer
by Orrin H. Pilkey (Author), Keith C. Pilkey (Author), Mary Edna Fraser (Author)


An internationally recognized expert on the geology of barrier islands, Orrin H. Pilkey is one of the rare academics who engages in public advocacy about science-related issues. He has written dozens of books and articles explaining coastal processes to lay readers, and he is a frequent and outspoken interviewee in the mainstream media. Here, the colorful scientist takes on climate change deniers in an outstanding and much-needed primer on the science of global change and its effects.After explaining the greenhouse effect, Pilkey, writing with son Keith, turns to the damage it is causing: sea level rise, ocean acidification, glacier and sea ice melting, changing habitats, desertification, and the threats to animals, humans, coral reefs, marshes, and mangroves. These explanations are...

The Global Warming Reader: A Century of Writing About Climate Change

The Global Warming Reader: A Century of Writing About Climate Change
by Bill McKibben (Author)


Our most widely respected environmental writer brings together the essential voices on global warming, from its 19th-century discovery to the present
With the rise of extreme weather events worldwide--witness the devastation wrought by Hurricanes Sandy, Irene, and Katrina, and the sustained drought across the American West--global warming has become increasingly difficult to deny.

What is happening to our planet? And what can we do about it? The Global Warming Reader provides more than thirty-five answers to these burning questions, from more than one hundred years of engagement with the topic. Here is Elizabeth Kolbert's groundbreaking essay "The Darkening Sea," Michael Crichton's skeptical view of climate change, George Monbiot's biting indictment of those who are...

Global Weirdness: Severe Storms, Deadly Heat Waves, Relentless Drought, Rising Seas, and the Weather of the Future (Vintage)

Global Weirdness: Severe Storms, Deadly Heat Waves, Relentless Drought, Rising Seas, and the Weather of the Future (Vintage)
by Climate Central (Author)


Global Weirdness summarizes everything we know about the science of climate change, explains what is likely to happen to the climate in the future, and lays out, in practical terms, what we can do to avoid further shifts. In fifty easy-to-read entries, Climate Central tackles basic questions such as:
-Is climate ever “normal”?
-Why and how do fossil-fuel burning and other human practices produce greenhouse gases?
-What natural forces have caused climate change in the past?
-What risks does climate change pose for human health?
-What accounts for the diminishment of mountain glaciers and small ice caps around the world since 1850?
-What are the economic costs and benefits of reducing carbon emissions?

Illustrated throughout with clarifying graphics,...

Global Climate Change: Turning Knowledge Into Action

Global Climate Change: Turning Knowledge Into Action
by David Kitchen (Author)


The science of climate change is a complex subject that balances the physical record and scientific fact with politics, policy, and ethics—and is of particular importance to the geosciences. This thoughtfully crafted new text and accompanying media encourage non-science majors to practice critical thinking, analysis, and discourse about climate change themes. Taking a cross-disciplinary approach, acclaimed educator and researcher, David Kitchen, examines not only the physical science, but the social, economic, political, energy, and environmental issues surrounding climate change. His goal: to turn knowledge into action, equipping students with the knowledge and critical skills to make informed decisions, separate facts from fiction, and participate in the public...

A Climate for Change: Global Warming Facts for Faith-Based Decisions

A Climate for Change: Global Warming Facts for Faith-Based Decisions
by Katharine Hayhoe (Author), Andrew Farley (Author)


Global warming: it's one of the hottest scientific and political issues of today. And yet we've all found ourselves asking . . .

- It's freezing outside--where's global warming now?
- Climate is always changing--how do we know this isn't just a cycle?
- Why should Christians care about global warming when we know the world won't end that way?

For all the talk about climate change, there's still a great deal of debate about what it all means, especially among Christians. A CLIMATE FOR CHANGE offers straightforward answers to these questions, without the spin. This book untangles the complex science and tackles many long-held misconceptions about global warming. Authored by a climate scientist and a pastor, A CLIMATE FOR CHANGE boldly explores the role our Christian...

Global Crisis: War, Climate Change and Catastrophe in the Seventeenth Century

Global Crisis: War, Climate Change and Catastrophe in the Seventeenth Century
by Geoffrey Parker (Author)


Revolutions, droughts, famines, invasions, wars, regicides – the calamities of the mid-seventeenth century were not only unprecedented, they were agonisingly widespread.  A global crisis extended from England to Japan, and from the Russian Empire to sub-Saharan Africa. North and South America, too, suffered turbulence. The distinguished historian Geoffrey Parker examines first-hand accounts of men and women throughout the world describing what they saw and suffered during a sequence of political, economic and social crises that stretched from 1618 to the 1680s. Parker also deploys scientific evidence concerning climate conditions of the period, and his use of ‘natural’ as well as ‘human’ archives transforms our understanding of the World Crisis. Changes in the prevailing...

The Global Warming / Climate Change Hoax: Fraud, Lies, Deception & Threats are the Tools of the Global Warming / Climate Change Hoax Folks

The Global Warming / Climate Change Hoax: Fraud, Lies, Deception & Threats are the Tools of the Global Warming / Climate Change Hoax Folks


Don’t you just hate it when people lie to you? I know I do. I especially dislike it when it is conspiratorial. First we were told we were facing “Global Warming.” When it began to seem that that was not the case, they changed the name to “Climate Change.” Well, they can give it any name they want because it is not proved by any reasonable science. Get the real truth and the science with this book. I promise you will be better informed. You will learn about: MATHEMATICAL MODELING, SURFACE PRESSURE, SURFACE TEMPERATURE, CARBON SEQUESTRATION, CAP-AND-TRADE, CARBON TAX and much much more. You will enjoy reading this fun book while you learn.

Global Climate Change: Turning Knowledge Into Action, Books a la Carte Edition

Global Climate Change: Turning Knowledge Into Action, Books a la Carte Edition
by David Kitchen (Author)


This edition features the exact same content as the traditional text in a convenient, three-hole-punched, loose-leaf version. Books a la Carte also offer a great value for your students–this format costs 35% less than a new textbook.   The science of climate change is a complex subject that balances the physical record and scientific fact with politics, policy, and ethics–and is of particular importance to the geosciences. This thoughtfully crafted new text and accompanying media encourage non-science majors to practice critical thinking, analysis, and discourse about climate change themes. Taking a cross-disciplinary approach, acclaimed educator and researcher, David Kitchen, examines not only the physical science, but the social, economic, political, energy, and...

Global Climate Change

Global Climate Change
by Arnold J. Bloom (Author)


Mark Twain s comment everybody talks about the weather, but nobody does anything about it no longer applies: human activities have altered the global climate, and governments are implementing policies to avoid more extreme perturbations. Global Climate Change examines the factors responsible for global climate change and the geophysical, biological, economic, legal, and cultural consequences of such changes. The book highlights the complexity of decision-making under uncertainty, contrasting the methods that various disciplines employ to evaluate past and future conditions.

Climate Change: The Science of Global Warming and Our Energy Future

Climate Change: The Science of Global Warming and Our Energy Future
by Edmond A. Mathez (Author)


Climate Change is geared toward a variety of students and general readers who seek the real science behind global warming. Exquisitely illustrated, the text introduces the basic science underlying both the natural progress of climate change and the effect of human activity on the deteriorating health of our planet. Noted expert and author Edmond A. Mathez synthesizes the work of leading scholars in climatology and related fields, and he concludes with an extensive chapter on energy production, anchoring this volume in economic and technological realities and suggesting ways to reduce greenhouse-gas emissions. Climate Change opens with the climate system fundamentals: the workings of the atmosphere and ocean, their chemical interactions via the carbon cycle, and the scientific framework...

© 2014 BrightSurf.com