Tag Archives: climate change

Civilization, War and Climate Change

Over the years there has been growing debate over whether civilization and the environment are integrally linked. Many scientists believe this to be the case, as it appears that several major events in the history of civilization have had an impact on the environment, while major environmental changes have also altered the course of human history. For instance, the Mongolian conquest of the 13th and 14th centuries altered carbon emissions, whereas the Roman Empire flourished during a period of rich summers, and subsequently fell apart during a period of erratic seasons.

Illustration of a Mongol WarriorRecently, scientists have uncovered evidence that suggests the Mongolian conquest of large portions of Asia, the Middle East and Europe may have had an impact on carbon dioxide emissions. When the Mongolians invaded these areas, they often destroyed entire crops, severely affecting the regions’ agriculture. As a result, many farms were abandoned, allowing the forests to take over the land. Thus, during 13th and 14th centuries, these forests were able to grow markedly and absorb huge amounts of carbon dioxide. The study claims that the total decrease in carbon dioxide during this period would be enough to cancel out one year of modern carbon emissions from gasoline. Yet it is important to remember that the Mongolian period of conquest extended across almost two centuries, which means that the actual yearly reductions were relatively insignificant in comparison with our current level of emissions. Nonetheless, the study does show that major events in human society are capable of having an impact in on the environment.

Another study, published in the Feb. 4 issue of Science magazine, also demonstrates the relationship between civilization and the climate. According to the authors of the study, the height of the Roman Empire occurred during a period when the growing season was consistently experiencing optimal conditions. Such conditions provided great economic wealth and the means to uphold the structure of the empire. Thus, the citizens of lands conquered by the empire were much less likely to show dissent.

Conversely, the collapse of the Roman Empire occurred during a period of erratic environmental conditions (perhaps partly due to agricultural overproduction within the empire) that yielded poor or mediocre crops. Without a steady food-supply, the empire faced dissent among its citizens. As the power structure was threatened within, the empire became susceptible to invasion from without and collapsed. In this way, environmental factors defined two of the largest events in Western history: the rise and fall of the Roman Empire.

Jared Diamond expounds upon this idea in his book “Guns, Germs, and Steel.”

According to Diamond, geographical determinism has defined the prosperity of American society. For instance, the vast natural resources of the country spurred our economy tremendously in the early days of the industrial revolution and our physical isolation from the rest of Western society has allowed us to remain prosperous after two world wars. Clearly, much of what makes America dominant is the physical geography that defines it as a nation.

Although the world’s booms and busts have been influenced by environmental factors, ultimately it seems that civilization has had a much larger impact on the environment. In the last 300 years, human population has increased by a factor of 10. Two worldwide wars have been fought and industrial growth has continued to increase in developed and under-developed countries at an unprecedented level. While many of these developments have been beneficial to civilization, the impact on the environment has not been so positive.

One of the negative effects brought about by civilization is the trend of global warming. Since 1750, human beings have steadily increased their production of carbon dioxide, methane, nitrous oxide and other greenhouse gases. These gases are emitted into the atmosphere as by-products of fossil fuel burning, agriculture (in fertilizers and from increased numbers of livestock) and other industrial products, such as refrigerants and aerosols. The greater concentration of these gases in the atmosphere increases the atmosphere’s ability to retain heat radiated from the sun or earth’s surface. Thus, we are experiencing global warming: an increase in the average global temperature. This increase amounts to about 0.74 degrees Celsius. While a difference of less than one degree may seem inconsequential, the average global temperature has only shown an increase of six degrees Celsius since the ice age, which means environmentalists and scientists both have every reason to be concerned about the state of our ecosystem.

By drawing from scientific studies and historical examples, we can clearly see civilization is integrally linked to the environment. Like Genghis Khan, we haven’t undertaken our endeavors with the purpose of changing the environment. Nonetheless, the implementation of large-scale activities such as automobile use, airplane travel, and even war, have significantly impacted the environment and may have very serious consequences for civilization. However, unlike Genghis Khan, we have the scientific knowledge to evaluate and limit the negative consequences of our actions. Hopefully, we will be able to learn from history in time to make a difference.


Ashley Warner is a graduate student working toward her Masters in Conservation Biology. She currently resides in Washington state.

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Effects of climate change on polar bears

Polar bears (Ursus maritimus) are in the news again because of dire predictions for the coming decades on their population numbers. The effects of climate change have been predicted to impact the polar regions first and most dramatically according to most models, and indeed, it is at the poles where we are recording some of the most dramatic examples of climate change. Polar bears, being the largest of the living bear species, are charismatic and popular, and because of the likely impact that climate change will have on them they have become a poster species for the climate issue.

polar bear

Polar bear, Ursus maritimus.

In a recent interview bear expert Andrew Derocher predicted that one population of polar bears (western Hudson Bay) could see its numbers drop too low to be viable within three decades (Yale Environment 360 2010). We have explored polar bears and their populations in other posts. Here I want to examine why changes in sea ice and warmer periods are such a concern for polar bears.

Polar bears evolved relatively recently, diverging from an ancestral brown bear population about 150,000 years ago (Lindqvist et al. 2010). There is a unique population of brown bears that live on Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska’s Alexander Archipelago. This population, called the ABC bears, is the closest brown bear relatives of the polar bears—early members of this population split off to live full time on the sea ice, evolving into the modern polar bear species. Thus, polar bears are an example of rapid mammalian evolution, undergoing morphologic changes such as elongated snouts, overall size changes, furry padded feet, and color changes, as well as social and metabolic changes to adapt to the rhythms of the arctic seasons.

It is their complex adaptations to living on the rugged ice that makes them most susceptible to changes in that habitat. They use the ice as a platform for hunting seals, as a habitat for finding mates and mating, and for traveling long distances. As the ice breaks up earlier in the spring, and re-freezes later in the winter, several weeks of prime hunting time are taken away from the polar bears. Today, they are able to spend almost three weeks less on the ice hunting than they were able to several decades ago. This is critical because after the ice breaks up for the year, the bears must fast until the next season, and longer times of open water means long fasting periods.

This can be critical for a female bear that must gestate her young, birth them, and begin to nurse them to a size large enough that they can accompany her onto the ice for hunting the next season. So, she is expending a great deal of energy in contributing to the growth of her young while fasting. If she did not build enough fat reserves the year before to withstand this metabolic marathon, she and her offspring will not survive into the following year. A few additional weeks of having to fast can be the difference between life and death.

The intimate connection that polar bears have evolved with their arctic habitat means that they are finely tuned to changes in that world. And with the effects of climate change appearing in the arctic regions first, they are in fact akin to the “canary in the coal mine,” a harbinger of things to come.


Lindqvist, C., S. C. Schuster, Y. Sun, S. L. Talbot, J. Qi, A. Ratan, L. P. Tomsho, L. Kasson, E. Zeyl, J. Aars, W. Miller, Ó. Ingólfsson, L. Bachmann, and Ø. Wiig. 2010. Complete mitochondrial genome of a Pleistocene jawbone unveils the origin of polar bear. Proceeding of the National Academy of Sciences.

Yale Environment 360. 2010. For Hudson Bay polar bears, the end is already in sight. http://e360.yale.edu/content/feature.msp?id=2293.

Additional related posts:
Polar Bear Populations
Public Opinion and a Geologic Perspective on the Effects of Global Warming

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Public opinion and a geologic perspective on the effects of global warming

The topic of climate change is complex and politically charged—two characteristics that guarantee confusion in the general public. Increasingly, the subject of climate change is emerging as a partisan issue, once again dividing Republican and Democrat.

A recent Gallup poll shows that Americans are becoming increasingly less concerned about the threat. Forty eight percent of Americans believe that the seriousness of climate change is exaggerated, up from 41% in 2009 and 31% in 1997.

The doubt in public opinion is not reflected in the scientific community, however. The national science academies of all the major industrial countries have issued statements about the reality of climate change and the role of human activity in creating the change (Wikipedia).

Even if we want to assume that all public doubt over climate change is honestly acquired, a position that I do not hold, perhaps the general public can be forgiven in some measure because the issue is complex, and like every other issue in science contains degrees of uncertainty. One of my favorite quips is making predictions is tough, especially about the future. I would like to borrow that and say that making predictions is tough, especially about the past—the geologic past that is.

Huge advances have been made in recent decades in understanding past climate systems of the Earth. The picture that is emerging with increasing clarity is that the Earth and all the systems that affect climate are dynamic and complexly interrelated. A good summary of what is known about climates of the past can be found in the latest IPCC report (Jansen et al. 2007).

Of significance is the evidence that global climate trends track closely with the levels of atmospheric carbon dioxide—a pattern that is 400 million years old. The prehistoric levels of CO2 can be directly measured from ice cores for almost the last 1 million years. Before that, we obtain estimates of CO2 levels by examining proxies, things that we can measure directly within fossils or the geologic system that reflect CO2 levels indirectly.

It is like estimating a family’s income by looking at the house they live in—certainly not a perfect system, but a proxy that in general will work as we do tend to display income prosperity through home selection.

The proxy data of CO2 levels through geologic time show those periods of low concentrations correspond with periods of increased glaciation, with peaks in glacial activity around 300 million years and again in more recent times with the last Ice Age. Both those periods had lower CO2 levels. Between those periods, CO2 was high, much higher than today, and average global temperatures were much higher as well. Areas of the Earth today that are temperate were often inhabited by plant and animal species that we only find today in more tropical environments.

Carbon and temperature over 400 million years

Shaded area and the colored lines show various proxy estimates for CO2 levels over the last 400 million years. The blue bars represent periods of glacial activity. During times of low CO2 concentration temperatures were also low with ice accumulation.

Does this mean that since CO2 levels in the past were much higher than today (and higher than even predictions for the next century or more of increased carbon emission) that we can be unconcerned? The Earth has seen much higher levels of CO2 and much higher average temperatures in the past, after all.

True, but that misses the point. The point is not that we are setting up environmental conditions that are unprecedented in geologic history. The point is that the rapidity of the change we are seeing today is without precedent and is anticipated to cause natural and social changes of significant consequence.

In the past, plants and animals could respond to fluctuation in climate because the changes occurred slowly. Organisms either changed their range to stay with favorable conditions, evolved to meet the new demands of their environments, or went extinct. But they did it on geologic time scales of hundreds of thousands, or millions, of years.

The modern changes driven by human activity are causing very rapid changes, on the order of decades to centuries, and natural systems are in a crisis of adaptation. And the bigger issue is that the ecosystems of the Earth are interrelated in complex ways, such that changes will inevitability have a ripple effect. Those are the same ecosystems that we depend upon for our food, water, and other resources, and that we have built our economies on.

There are several dimensions to the crisis of global climate change. One is a crisis of nature. Charismatic species like the polar bear are threatened, but the world will not collapse when the polar bear goes the way of the dinosaur. Although I think a strong case can be made that we have some moral obligation to not stand idly by while it happens, it may be “no skin off our teeth” to have a world without polar bears.

Consider the analogy of an airplane in flight. As we fly along we could go around the structure of the airplane and pop out the rivets that hold it together. No doubt we can take out one here, another one there, and the plane will stay aloft. But if you are in the plane, how many will you be comfortable losing? At some point, you take out enough rivets and the plane will fall apart.

The loss of the polar bear is only a single rivet. But there are hundreds, even thousands more that are likely to be lost through the effects of climate change. How long before the complex systems that we rely upon come falling out of the sky is an open question—we do not know.

However, I think the real vexing issues we face are the social and political issues, which are far thornier. What actions should we take to mitigate CO2; who should pay for it; what will the effects be on developing and low-lying countries and who should take responsibility; what are our obligations to developing economies; how aggressively should we make a transition to non-carbon-based energy systems, and who will pay, and who stands to lose; how will climate changes affect agriculture, water supplies, and the general balance of political power? Questions like these are not scientifically based—they are economic, political, or moral decisions, and are the real issues of the public climate change debate.

Those who want to confound the issue for political gain often resort to throwing mud at the scientific debate, pointing to known uncertainties of the models, or dredging up scientists who are dissenters, or other similar political “gotcha” tactics. Evidence suggests that they are succeeding—the public is less certain about the reality of climate change, and the political parties are capitalizing on their confusion. This may make good political theater, but I think that this level of discourse diminishes us all.

Perhaps it is too much to hope for that we have intellectual integrity in public debate, but I keep hoping. I think Thomas Jefferson said it best, “If we are to guard against ignorance and remain free, it is the responsibility of every American to be informed.”

Gallup Poll: Americans’ Global Warming Concerns Continue to Drop

Jansen, E., J. Overpeck, K. R. Briffa, J. C. Duplessy, F. Joos, V. Masson-Delmotte, D. Olago, B. Otto-Bliesner, W. R. Peltier, S. Rahmstorf, R. Ramesh, D. Raynaud, D. Rind, O. Solomina, R. Villalba, and D. Zhang. 2007. Palaeoclimate. Pp. 433-497. In S. Solomon, D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor, and H. L. Miller, eds. Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, New York.

Wikipedia–Global warming controversy

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Musk ox say no to hunting

As we face the uncertain effects of climate change ourselves in the future it is instructive to look back in time to see how other species fared. (See also a geologic perspective on the effects of climate change.) Paleontology is one of the main sciences involved in this research and so proves to be very relevant to this modern issue.

A recurring mystery in paleontology is the cause of the most recent major extinction event at the end of the Pleistocene or Ice Age. Many large species of mammals, collectively referred to as megafauna, became extinct relatively recently, a mere 10,000 years ago more or less. Charismatic animals such as mammoths, mastodons, giant ground sloths, and saber toothed cats vanished from the Earth forever.

It has long been debated what the primary cause of this extinction event was. Just as with other major extinctions observed in the fossil record, there are a number of suspected causes for Ice Age extinctions: disease, climate changes, and extra-terrestrial phenomena like asteroids. But the Ice Age extinctions have another factor that previous extinction events do not have—the emergence of humans as a major player upon the landscape. Did human activities, maybe the over hunting of the megafauna, drive them to extinction?

Many studies have tried to get at this question, but it is very difficult to separate all the confounding issues from each other to focus on just one to test its potential effects. A new study however was able to do just this.

In a recent paper (Campos et al., 2010) DNA material was extracted and analyzed from one of the species that did survive the Ice Age extinctions, the musk oxen. This Ice Age relic lives today mainly in the high-latitudes of Greenland and Canada, but was once more wide-spread. Indeed, its remains have even found as far south as Nebraska, New York, and Ohio during the Pleistocene.

Musk oxen are well adapted to the extremes of arctic living with sturdy bodies and thick coats of hair.

Musk oxen are well adapted to the extremes of arctic living with sturdy bodies and thick coats of hair.

The researchers collected samples from across the musk oxen’s former range for the last 60,000 years. They examined the DNA to look for patterns of population dynamics over that period. Basically, when a population is strong and has many members the DNA samples show an increase in diversity—more genetic variation in the mix. When populations suffer and numbers decrease the results show up in the DNA as a decrease in diversity, sometimes referred to as a genetic bottleneck. So, the DNA diversity over time shows a proxy for population numbers and health.

Therefore, if humans were a prime driver of population declines for musk oxen at the end of the Ice Age we would expect to see genetic bottlenecks within the DNA corresponding to the timing of human activity within the musk oxen’s range.

The DNA results show that the geographic origin of all the musk oxen DNA is northeast Siberia with a large diverse population. However, the population in that region crashed about 45,000 years ago. After that population decline, there was a world-wide genetic diversity increase about 30,000 years, followed by another decline about 18,000 years ago, and finally a slight recovery about 5,000 years to the modern relict populations.

With these data we can directly test for the first time the correlation of population declines of the musk ox with human activity. And, in fact, they do not correlate very well, suggesting that humans played little role in the population dynamics of musk oxen.

So, if not humans, what then was driving the populations to decline?  The most likely cause was environmental changes, particularly climate changes. The Pleistocene is characterized by shifts in climate patterns with the best-known effect being glacial advance and retreat over the last 2 million years. It seems, at least in the case of musk oxen populations, that the pattern of boom and bust was driven by their ability to adapt to climatic changes in their environment. Musk oxen almost went the way of the mammoths and succumbed fully to extinction, but managed to just hold on by their horns in greatly reduced numbers until today.

Of course, whether they, or any other species that are similarly at risk, will weather the next several decades, and any modern climate changes, remains to be seen. The effects of climate change may well prove to be too much for them after all.

CAMPOS, P. F., E. WILLERSLEV, A. SHER, L. ORLANDO, E. AXELSSON, A. TIKHONOV, K. AARIS-SØRENSEN, A. D. GREENWOOD, R.-D. KAHLKE, P. KOSINTSEV, T. KRAKHMALNAYA, T. KUZNETSOVA, P. LEMEY, R. MACPHEE, C. A. NORRIS, K. SHEPHERD, M. A. SUCHARD, G. D. ZAZULA, B. SHAPIRO, AND M. T. P. GILBERT. 2010. Ancient DNA analyses exclude humans as the driving force behind late Pleistocene musk ox (Ovibos moschatus) population dynamics. Proceeding of the National Academy of Sciences.

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