Chapter 12 – Biodiversity, Global Climate Change, and the Future

Biodiversity, Global Climate Change, and the Future

Learning Objectives

Welcome to Chapter 12.  At the end of this chapter you will be able to:

  • Explain how the Sun is the ultimate energy source used to produce fossil fules
  • Identify the environmental, political, and societal problems that result from our dependence on and exploration and production of fossils fuels.
  • Compare and contrast the benefits and dangers of the natural Greenhouse Effect to a human-caused or enhanced Greenhouse Effect.
  • Describe how positive and negative feedbacks change a system.
  • Define the barriers and benefits to switching from fossil fuels to green energy sources.
  • Explain how Island biogeography affects biodiversity.

Energy vs. Environment? – Arctic National Wildlife Refuge

A picture of a female moose in the woods
A Female Moose Credit: R.B. Alley
Map of the U.S. with Arctic National Wildlife Refuge highlighted in the northeast corner of Alaska.
Arctic National Wildlife Refuge Location Credit: R.B. Alley

The Arctic National Wildlife Refuge (ANWR) sprawls across the North Slope of Alaska, from the Brooks Range to the coast of the Arctic Ocean, and is nearly as large as the state of Maine. ANWR is home to grizzly and polar bears, wolves loping across the tundra, moose and caribou, uncounted waterfowl, and snowy owls ghosting on white wings.

And beneath it, there probably is oil. The nearby Alaska Pipeline has pumped billions and billions of dollars worth of petroleum south from regions near the North Slope. But as that Prudhoe Bay oil runs out, the pipeline may soon be left empty–a very expensive conduit with nothing to carry. Similarity of geology suggests that ANWR also has oil to fill the pipeline, and to fuel automobiles in the U.S., or China, or somewhere. Not a lot of oil—maybe 10 billion barrels, according to the USGS. That is just over two years of U.S. oil imports at recent rates, not much more than one year of total U.S. oil use, and not exactly “energy independence,” but at $100 per barrel, it represents something like $1 trillion. The argument between wilderness and development has been going on for years, and is not ending soon; the recent emphasis on “fracking” for oil and gas in the lower-48 has temporarily shifted press attention away from the Arctic, industry interest in the north remains strong.

Fossil Fuels

Plants have an amazing ability. They take carbon dioxide (CO2) and water (H2O) and use energy from the sun to turn them into more plant material (which has an average chemical composition fairly similar to CH2O), releasing oxygen (O2) in the process. An approximate formula for photosynthesis is:


Most of the rest of us—animals, fungi, many bacteria, as well as forest fires—run this reaction backwards, combining plant material with oxygen to release energy, carbon dioxide, and water. Done rapidly, this is “burning” in a fire; done slowly, it is still burning of a sort, which you might call “respiration.” Plants usually include a bit of nitrogen that we didn’t write in the simplified formula above, and animals often use the plant material with its nitrogen to make proteins that make animals, but after the animals die, they are almost always “burned” by bacteria or fungi or other animals that eat them to release the energy.

But, what happens if dead materials end up in a place without oxygen? It turns out that a lot of burning can be done by replacing oxygen with other things such as sulfate, but if these run out too, burning is no longer possible. Then, fossil fuels—coal, oil, and natural gas—become possible.

Coal is formed when bacteria break down dead plants. When there is no free oxygen in the air or water, bacteria remove the oxygen and hydrogen that are included in the plant material, leaving mostly carbon and forming a brown material called peat. When peat is buried by more sediment, heating and pressing drive off more and more of the little remaining oxygen and hydrogen, thus forming coal. Brown coal (lignite) has not been cooked much; it is common in the western United States. “Normal” or bituminous coal, formed from lignite by heat and pressure, is common in many places including western Pennsylvania. In a few places including eastern Pennsylvania, closer to the center of the old Appalachian Mountains, the bituminous coal was cooked to metamorphic anthracite coal. Peat is found with loose sediment, lignite with not-too-hard sedimentary rock, bituminous with harder sedimentary rock, and anthracite with metamorphic rock.

Oil is something like coal, but it is formed from dead algae buried in mud, usually from marine settings but sometimes from lakes. Algae start with more hydrogen and less oxygen than wood, so they produce a different fossil fuel. Heat breaks down the algae to release liquid oil. More heat breaks down the oil and makes natural gas, which is primarily methane (CH4). Some natural gas also is made at low temperatures by bacteria. While the heat is making oil and gas, the mud is being squeezed to make shale. Pennsylvania contains some oil and natural gas, and the first oil well in the world was drilled in western Pennsylvania. Humans had used petroleum before, but from natural seeps rather than wells. The push for petroleum that led to the first oil well was fueled by a looming shortage of whale oil, as the demand for that product far exceeded the ability of the oceans to grow the whales that produced the whale oil that was used to light homes on dark nights.

Gas and oil trapped between folded shale and sandstone, explained in text
Diagram showing how gas and oil can become trapped in the spaces in a sandstone layer if an impermeable shale layer lies above the sandstone along the “top” of a fold in the rocks. Credit: R.B. Alley

Oil and gas are low in density, float on water, and so tend to rise through water-filled pores in rocks and escape at natural seeps on land or beneath the sea. In some places such as off the U.S. Gulf of Mexico coast, biological communities have been found living on oil seeps on the sea floor. (Oil is natural, and nature uses oil in small quantities. But if a supertanker wrecks or an oil well blows out, nature cannot use all that oil at once, and problems result.) Because of the tendency for oil to escape, a large accumulation of oil can form only if there is a trap of some sort. Many different types of traps exist. For example, fluids do not pass through shale easily because it has only tiny spaces; if shale lying above sandstone is folded a little, oil and gas may be trapped in the sandstone layer, as shown in the figure.

At present rates of use, and at costs vaguely similar to what we see today, the oil and gas will last for most of a century, and the coal for a few centuries. If we were willing to pay more for gasoline, say $50 per gallon, more fossil fuels would be available. Although the store of fossil fuels is certainly limited, there is a rather large quantity. Until very recently, U.S. production had been dropping, causing us to import most of our oil from other countries, although as noted in the next section, “fracking” is affecting this. World production will probably peak in the next few decades (and some experts have suggested a peak within a few years). Demand for fossil fuels is rising rapidly, particularly in China and India as they industrialize. Shortages of fossil fuels, and worries about such shortages, already cause political problems; some observers believe that such worries are one reason the U.S. government spends so much on military preparedness.

Marcellus: Millions or Mayhem?

In Pennsylvania and some nearby states, there is much interest now in the natural gas being produced by “fracking” the Marcellus Shale, while Texas is fracking the Barnett Shale, North Dakota is fracking the Bakken Shale, and others are coming into play or being considered, in the U.S. and overseas. When a deep ocean ran out of oxygen back in the geologic past, mud and organic material accumulated on the sea floor, and these became black shales over time. Burial and heating broke down some of the organic material to make oil and gas, and some of that escaped from the shale, either leaking out at the sea floor or being trapped in special places that we have drilled into to get the fossil fuels.

But, a lot of organic material remains in the black shales, stuck between the very tiny clay particles that make up the shale, and not able to get out. People have learned how to drill into such layers, and then turn the drill to go along the layer. After a long hole is made, water and sand and various chemicals are pumped into the hole at very high pressure, breaking the rocks and then squirting into the new fractures to hold them open, in a process called “fracking.” Gas then leaks out along the fractures and up the hole, where it is collected and used by people.

In the big picture, this doesn’t make a lot of difference—the estimates of the total amount of fossil fuel that might be available have included the Marcellus gas since before the technology for recovering the gas became commercial, under the assumption that eventually we would figure out how to recover that gas. But, right now, there is much more gas on the market than there was a few years ago, and some oil is coming this way, some people are getting jobs or checks from gas companies for access to the land, other people are worried about the effects of the gas on the environment, and there is a lot of heated discussion going on. If you want to learn more about this particular issue, see the Enrichment.

Cost-Benefit Analysis

Let’s be honest. We use fossil fuels for good reasons. Most of our energy is obtained from fossil fuels. We run washing machines, rather than hand-scrubbing our clothes, primarily with fossil-fuel energy. Most of us are freed from the manual labor of hoeing and shoveling to grow our food because fossil-fueled tractors plow and plant and cultivate and harvest. Many of us have been freed from freezing to death in the winter, or perishing of heat stroke in the summer, or dying because we can’t get to the hospital in an emergency, because of fossil fuels. Humans have so far largely avoided the Malthusian trap of having lots of kids who have lots of kids until we exceed our food supply and then starve, primarily through being clever and through using cheap energy. Our energy use in the U.S. is equivalent to each of us having more than 100 people working to take care of us.

For humans, and for the few types of domesticated animals that have benefited from our use of fossil fuels (pigs, rice, chickens and soybeans, for example), there is little question that fossil fuels have been good. For other species on Earth, our use of fossil fuels to tame much of the planet has been less beneficial. How much easier did trains make it for humans to travel west to shoot bison? How much easier is it to cut a tree with a chain saw than with a stone hatchet? However, this is complicated by the fact that we have let some trees grow back, and we quit burning whales (or whale oil) to light evenings because we switched to burning the long-dead algae and trees that are fossil fuel.

There clearly are other costs of fossil-fuel use. Marks of oil exploration on the tundra may last for decades or longer. Acid rain from coal-fired power plants has killed the trout in headwaters streams on the Laurel Ridge of central Pennsylvania, and in some other places. Smog is not good for us, and shortens our lives. However, our lifespan continues to lengthen, so the dangers of smog and other “modern” hazards, such as industrial chemicals and radiation, are less than the advantages of the technologies that gave us all of these things. In fact, our biggest dangers are probably infectious diseases (evolution of new nasties), each other (automobile accidents, murders, and wars) and ourselves (smoking and drinking and eating too much, while exercising too little) rather than the technological things or natural disasters so many people worry about.

The Greenhouse Effect

If not for the greenhouse effect, we humans probably would not be here. The Earth’s atmosphere allows the shortwave radiation (what we usually call “sunlight”) coming from the sun to pass through to the Earth’s surface, without much interference. (There is a little interference. Among other things, blue light is scattered off air molecules a bit more than red light is, so the blue light bounces around in the atmosphere and reaches our eyes from all directions in the sky, whereas the red comes more directly from the sun, which is why the sky is blue.) The windows in a greenhouse similarly allow sunlight to enter easily.

But, the sunlight heats the Earth or the inside of a greenhouse, which then radiate longwave radiation back upwards. As we saw way back at the Redwoods, the total energy reaching the planet on average exactly equals the total energy leaving, but the arriving energy is mostly shortwave electromagnetic radiation (light that we can see) while the leaving energy is mostly longwave electromagnetic radiation (infrared radiation that we cannot see without special sensors). The windows of a greenhouse do not allow longwave radiation to pass through easily; some gets through, but some is trapped.

When the sun rises after a cold night, energy enters a greenhouse but has trouble leaving, and the extra energy warms the greenhouse. Warming makes the floor of the greenhouse emit more longwave radiation, forcing some through the glass until a new balance is reached between incoming and outgoing radiation, but with the greenhouse at a higher temperature than would occur without the windows of the greenhouse. Some gases in the atmosphere act in the same way as windows on the greenhouse, intercepting some of the outgoing longwave radiation and keeping that energy in the Earth system. Water vapor contributes the most to the greenhouse effect, but carbon dioxide, methane, and others also matter. Without these greenhouse gases in the atmosphere, the Earth would be mostly frozen. (For a brief meteorological perspective on greenhouses, see the Enrichment, which also explains why water vapor is a “slave” to the other greenhouse gases, so that carbon dioxide is more important for changing the climate.)

Human-Caused Greenhouse Warming

Human activities are increasing the concentrations of several greenhouse gases in the atmosphere. Carbon dioxide, from burning of fossil fuels, burning of forests, and a few other sources, is the greenhouse gas we hear the most about. Refrigerants (chlorofluorocarbons and related compounds) also are potent greenhouse gases, and are increasing in the atmosphere. Those refrigerants that are especially damaging to the ozone layer that protects us from harmful very-shortwave (ultraviolet) radiation are being phased out, but the less-ozone-damaging replacements are still greenhouse gases. Methane, produced in cow guts, landfills, rice paddies, and other places where carbon breaks down in the absence of abundant oxygen, also has been increasing. Eventually, the huge carbon-dioxide source and the long time that carbon dioxide survives in the atmosphere mean that carbon dioxide will dominate global warming.

The world is warming. Of this there is almost no question—thermometers, including thermometers far from cities and in weather balloons and on satellites, in the ground and in the ocean, analyzed by government and university scientists in many different countries, including with industrial funding, show that warming is occurring. So do the temperature-sensitive types of snow and ice (NOT the top of Antarctica at -40, which won’t melt even with a fairly large warming, but we see reductions in the seasonal river and lake ice, seasonally and “permanently” frozen ground, springtime snow, mountain glaciers and more). The great majority of significant changes in where plants and animals live, and when during the year they do things, are in the direction expected from warming.

Furthermore, there is high confidence that the warming is from the carbon dioxide. The physics of warming from rising carbon dioxide is unavoidable. Must of this was actually worked out by the Air Force after World War II. They were not doing global warming, but instead were worrying about such things as the appropriate sensors on heat-seeking missiles to shoot down enemy bombers. Use the wrong sensor, and you can’t “see” the target because carbon dioxide is in the way. And carbon dioxide interacts with infrared radiation going from Earth to space in the same way. Satellites confirm this every day. Scientists have worked very hard to find some other explanation of the warming, but if anything, the sun has dimmed a little over the last 30 years, while volcanic eruptions have thrown up particles that blocked the sun a bit, we have put up particles from smokestacks that help the volcanoes in blocking the sun and causing cooling, we have replaced dark forest with more-reflective crops to cause a little cooling, and nature has not done anything with cosmic rays or space dust or anything else that would explain what is happening. Indeed, we see the warming from rising greenhouse gases despite the other influences primarily pushing towards cooling; really, the best answer to “How much of the warming did human-released greenhouse-gases cause?” is “More than all of it, because other things have reduced the warming.” Finally, the “fingerprint” of the warming (for example, warming down here but cooling high in the stratosphere) is just what is expected from the effects of greenhouse gases, and completely unlike the pattern expected from changes in the sun, volcanoes, El Niño, or other natural fluctuations. Computer models of the climate system, when forced with the known natural causes of climate change such as changes in the sun and volcanoes, do a pretty good job of simulating the climate changes that happened before greenhouse gases had risen much but do a lousy job of simulating recent changes; adding greenhouse-gas effects causes the models to simulate what happened quite accurately.

Even prominent “skeptics” have now publicly admitted the high probability that humans are warming the world. (One of the well-known, often-seen-on-Fox-News skeptics directly stated this during a public debate with Dr. Alley a few years ago.) If you follow the news, you know that there is a lot of argument about how large the warming will be and whether it will be good or bad, although scientific consensus is very strong that the warming will be large compared to recent natural changes, and will be more bad than good for humans and other living things.

Some of the argument involves feedbacks. Feedbacks are “extra” processes in a “system” such as the Earth’s climate. If you force a system to change by doing something to it, many other things may then change. Some of these will amplify what you just did, making the changes bigger than you could have accomplished by yourself; these are positive feedbacks. Others will oppose what you just did, making the changes smaller than what you initially forced; these are negative feedbacks.

You, for example, have all sorts of negative feedbacks built in. If you are placed in a warmer room (the forcing), your body will begin to warm up. But then a negative feedback kicks in—you start to sweat, and that cools you off. Your body temperature doesn’t change nearly as much as the temperature outside of you changed. But, if you have certain diseases, they may fool your body so that its negative feedbacks are reduced and may even become positive feedbacks. Fever is usually a good thing, helping the body fight invading germs more effectively, but people die of fever when the feedbacks become positive and the body “burns itself up.” If you’re in a canoe with a really enthusiastic golden retriever, you may try to lean as the dog leaps about in such a way as to stabilize the canoe—you are providing a negative feedback on the tipping. But if the dog tips the canoe, and the ice chest falls to the low side, the ice chest is acting as a positive feedback to amplify the dog’s motion and tip the canoe further. If you lose your balance when the dog lunges to the side, you may suddenly fall toward the dog, providing another positive feedback and perhaps flipping the canoe.

The Earth certainly has positive and negative feedbacks. The easiest stabilizing one is the very fast change in radiation—a warmer place glows more brightly and sends more heat toward space, tending to cool the hotter places faster. Other than this almost-instantaneous change, most of the feedbacks over times that matter to us (years through millennia) are positive, amplifying changes; over still-longer times (say, millions of years), the feedbacks tend to be negative, stabilizing the climate. Climate changes over years or centuries thus can be almost as large as climate changes over millions or billions of years.

Put some extra carbon dioxide in the air and the climate will become warmer, speeding the rock-weathering chemical reactions that remove the carbon dioxide to produce dissolved ions that are used to make shells, removing the extra carbon dioxide. This negative feedback, which was explained by Penn State’s famous professor Jim Kasting and coworkers, stabilizes the Earth’s climate. Given too much atmospheric carbon dioxide, the excess is removed through warming-enhanced weathering; if too little, low temperatures slow weathering and allow carbon dioxide released by volcanoes from subducted shells to build up in the atmosphere. However, this takes hundreds of thousands of years or longer to act; over mere centuries, increased weathering will have little effect on the carbon dioxide we release, much of which will stay up for centuries, millennia or longer.

If we put carbon dioxide into the air and warm the Earth a little, several positive feedbacks begin to function. Warmer air can “hold” more water vapor (the saturation vapor pressure roughly doubles for a 10oC or 18oF warming), and water vapor is an important greenhouse gas, so warming causes more warming. Some of the shortwave radiation from the sun that hits the Earth bounces right back to space without first warming the Earth. This occurs especially over snow and ice, which have very high albedo or reflectivity. But, warming the Earth removes some snow and ice, which then allows more of the shortwave radiation to be absorbed, which warms the Earth more—a positive feedback.

Clouds reflect some sunlight (so cloudy days are cool), but clouds also interfere with outgoing longwave radiation (so cloudy nights are warm). The largest uncertainties in predicting how much warming will result from a given amount of fossil-fuel burning are probably related to how clouds will change, and whether these changes will produce positive or negative feedbacks. However, these uncertainties are not nearly large enough to affect the conclusion that future warming from fossil-fuel burning is highly likely.

We clearly wish to predict the future. If burning of fossil fuels, combined with bovine belches and leaky refrigerators, are going to cause too many problems, we might want to change our ways now. To predict the future, we need to do experiments. But, we have only one world. We cannot look at many different futures of one world, nor do we wish to wait many decades for the experiments to end. The solution we use is to build little worlds in computers, and run the experiments on those.

Geologists are important in this effort in two ways: we help find out how the world works, so that the right things can be put in the computers. The computer models always will be simpler than the real world, so careful choices must be made about what to put in. And, we provide data against which the models can be tested. You wouldn’t trust a model that had never been tested, but you wouldn’t want to wait a whole lifetime for a test. If the models can successfully simulate very different, warmer and colder climates of the past, then the models are probably pretty good. So we need to know about climates of the past.

The computer models of today actually are doing very well at “retrodicting” climate, predicting things that already happened. Modelers set up the configuration of ice sheets and ocean and continental positions and orbits and solar brightness, then model the climate and see if the computer results can match the climate that is recorded by the fossils and other climatic indicators in the rock record without “cheating” (so you can’t go in and tweak a lot of things to make the model match the data and then claim that the model is great—the models actually do work on past climates without such cheating). The models are also doing quite well at predicting the patterns of change we have observed with instruments over the last decades. Predictions made by modelers over the last decades are really occurring now. (For a little more on this, see the Enrichment, which also gives a bit more on why each doubling of CO2 has about the same effect on temperature, as covered next.)

Models predict that the world will warm about 3oC or just over 5oF for a doubling of CO2. The full warming will be delayed a few decades behind the rise in CO2, because the air can’t warm all the way until the ocean and ground have warmed and some ice has melted, which takes a while. The global warming to date, somewhere between 1oF and 1oC, is similar to the typical temperature variability at most places, so you really have to be paying attention to know that anything is changing. If we proceed to burn all the fossil fuels, something like an 8-fold increase above “natural” levels is possible over the next few centuries, or a warming of about 9oC or over 16oF, large enough that no one would have any doubt about the change. As noted in the Enrichment, uncertainty in the models is about 50%—the models project that the warming may be only about half this much, or more than one-and-a-half times this much, if we continue with business as usual and octuple CO2. However, because data on past climates are very difficult to explain if the models showing smaller changes are correct but are easy to explain if the models showing mid-range or large changes are correct, the low-end changes are less likely than the high-end changes.

So What?

Few people care about the temperature, and many care about what the temperature means for humans and other living things. Impacts are harder to estimate, both because of the additional uncertainties involved in turning temperature change into economic change, and because of the involvement of human values. For example, if warming causes species to become extinct, but those species were not economically important, how bad is that? You will find really strong differences of opinion across the political spectrum in the U.S. and the world.

Some disagreement is expected. Many places are already too hot for comfortable human habitation; making them hotter will not be good. Other places are too cold for comfortable human habitation today, so warming them might be good for humans there, unless you melt their ice and flood the coasts. Warming may remove one of the barriers that help keep malaria and other tropical diseases from spreading into today’s temperate zones, which is not good. Sea-level rise from warming is almost inevitable, as glaciers melt and the warming causes the ocean water to expand. Drying of the great grain-growing regions of the world during summers is likely. As a crude summary, most models indicate that human-induced warming will make our lives harder. People in the developed world are likely to cope; some in the developing world will cope, and others may fail (and die). A little warming is likely to hurt most of the world’s people (who live in too-warm places) but help most of the world’s economy (which is concentrated in fewer people in colder climates); too much warming then hurts everyone. A lot of loud radio commentators focus on the slight possibility of good outcomes, but ignore the possibility of disaster. (For a bit more on this, see the Enrichment.) Many professionals in the field note the benefits of caution—slow the ship in the fog until you have time to see how many icebergs are ahead, while starting to turn now to avoid the icebergs we already see.

Much of the argument focuses on economic concepts such as discount rates. Economically, something in the future is worth less than something today because of uncertainty (an apple in 30 years may do me little good, because I may be dead). If one uses this sort of reasoning, then any environmental change that takes more than a few decades to occur is of little concern—we humans will just deal with it when the time comes, using the great economic engine we’ve built.

But some people argue that intergenerational transfers should be treated differently—“we” humans who will “deal with” the changes will be our grandchildren, not us. Do we have the right to give them a greatly altered (probably degraded) Earth? Thus far, classical economic reasoning is “winning” in the real world, but the best science says that humanity will be better off if the reality of climate change is included in the decision-making.

Serious scholarship shows that, with a few decades of real investment in science and engineering, abundant energy can be provided while controlling greenhouse gases for a cost of roughly 1% of the world economy. That is in line with the costs of other clean-ups—sewers and garbage and catalytic converters and others. That is much smaller than most recent estimates of the coming damages from global warming if we do nothing. That also is a whole lot of money—roughly $400 billion per year now. Depending on one’s politics, the clean-up of greenhouse gases can be presented as a money-making prospect, as a low-cost obligation to the future, or as frighteningly expensive. Eventually, the switch away from fossil fuels must be made, because the fossil fuels are finite. And one can argue that $400 billion per year is a potential future industry that merits a real investment in research now. If we move away from fossil fuels, good jobs will be lost in fossil-fuel industries, but most studies point to a gain of more jobs in other fields. Note the problem, though—people in the industry who are worried about losing their jobs know who they are, and vote. People who will get the new jobs are students now, and don’t know about the new jobs. So, there is some learning to be done.

Island Biogeography, Yellowstone and the Next Mass Extinction?

See caption.
A mother grizzly bear and two cubs crossing the highway near Glacier National Park, Montana. Credit: R.B. Alley

Most of the national parks were established to preserve geological features. A few parks, such as Sequoia and Redwood, were established for biological reasons. Increasingly, however, the national parks are visited, used, preserved, and managed for biodiversity. We humans continue to spread. More and more land is brought under cultivation. More of the produce of the sea is netted and served to humans. Some estimates are that we and our immediate friends—cats and corn and cows—now use about half of everything that the world makes available for us and everything else. And, with about 7 billion of us here now, heading for 9 or 10 billion, and with a couple of billion of us not using much but hoping to use more, all humans taken together may double what we’re using. Ultimately, this leads to extinctions and loss of biodiversity.

Map of the U.S. with Yellowstone National Park highlighted, primarily in Wyoming but extending slightly into Montana, and Idaho.
Yellowstone National Park Location Credit: R.B. Alley

This is a geology class, and biodiversity is a bit far-afield, but we have time for a quick detour. We saw that there have been mass extinctions in the past—times when many living types became extinct in a short interval. There is a real chance that a geologist far in the future would place our current time as the latest mass extinction, the end of the Cenozoic, and the start of the Anthropocene.

Early humans were surprisingly hard on biodiversity. Wherever humans arrived with their efficient tool kits—in Australia, New Zealand, other islands, the Americas—extinctions of large animals followed. Direct human hunting, or competition from the rats, pigs, dogs, and others that arrived with the humans, likely contributed.

Some people don’t like the idea that early humans were hard on biodiversity. Many people, including good scientists, have argued that the extinctions of large animals in the Americas were caused by climate change, which happened to occur at about the same time as human arrivals in some places. Dr. Alley has listened to talks in which data he helped produce were used to argue that the climate changes were so large and rapid that they must have been responsible. But, the work by Dr. Alley and others showed that dozens of such abrupt climate changes occurred, and the extinctions did not occur until the humans arrived. It is hard to imagine that a couple of dozen abrupt climate changes happened without killing off many species, and that just when fluted-point spears showed up in the rib-cages of mammoths, the next abrupt climate change was solely responsible for killing the mammoths, and humans did not play a role.

But, the earlier extinctions were mostly of large creatures. Since the industrial revolution, “modern” humans have contributed to extinctions of various creatures. And, the rate of extinction may pick up soon as we increasingly occupy the planet. To see why, let’s take a little detour into island biogeography.

Island Biogeography

If you were to visit a lot of islands that are more-or-less the same distance from the mainland, and count the number of species on each island and measure its area, you would find that the bigger islands have more species. Roughly, an island with ten times the area as another will have twice as many species. If you visited islands of about the same size at different distances from the mainland, you would find that those closer to the mainland have more species.

At least some of what controls these observations is not too difficult to understand. If you have a small island, it can hold only a few individuals of a species. From year to year, populations go up and down depending on food supply, predators, and other things. With a small population, a small drop can hit the absorbing boundary of zero individuals and cause extinction, but a large population can survive a small drop. So, extinction is more likely on a smaller island, and smaller islands have fewer species. The mainland is there to supply new individuals to islands to replace those that die, and repopulation is easier for islands closer to the mainland, so those islands closer to the mainland have more species.

These patterns of island biogeography are well-established. Studies of repopulation of islands sterilized by volcanic explosions, and even of very tiny islands that were deliberately depopulated and then allowed to come “back to life,” have shown that this is the way the world works naturally.

Now, think about Yellowstone. Originally, the boundaries drawn for the park separated wilderness inside from wilderness outside. Today, as shown in the satellite photo, some of the park boundaries are easy to see from space because loggers outside the park work right up to the boundaries. Yellowstone remains connected to other wilderness regions in other directions; it is not an island (yet).

See caption.
Landsat-7 image of mature forest in Yellowstone (right) beside logged forest (clearcuts in pink; two are indicated by pink arrows) in Targhee National Forest (left), Montana. North is toward the top. The blue arrow at the top points along the park boundary. It is easy to see many national-park boundaries on satellite images such as this one, because the extensive human modification of the land surface outside the park is evident next to the unmodified conditions in the park. Credit: Earth Observatory, NASA

But what if Yellowstone were an “island,” as some other parks are or soon will be? Suppose a park becomes surrounded by farmland, which is used to feed humans and keep us alive. Farmland does not support a lot of wild orchids or wolves. Farmland is impoverished in biodiversity, with just a few species, carefully selected to feed us. A park surrounded by farmland is an island, because many species have great difficulty crossing the farmland just as many species have difficulty crossing the ocean. And, from the well-established principles of island biogeography, isolation of a parkland from other wilderness will cause extinctions in the park. Perhaps more worrisome, if the only remaining wilderness is in parks, there is no longer a “mainland” to replace species lost to local extinction on the island—extinction in the park is then extinction from the world.

We know that as climate changed in the past, plants and animals migrated long distances to stay with their preferred climate. As the climate changes in the future, migration will be required, but may be impossible if the parks become isolated.

So, Who Cares?

Photo of a white Mountain Goat
Mountain goat, Glacier National Park, Montana. Credit: R.B. Alley

One can ask whether biodiversity is worth preserving. This is proving to be a difficult topic, and one that will be discussed much in the future. Certainly, many of our medicines have come from plants, and if many plants become extinct before we can study them carefully, we are likely to lose many possible medicines. Engineers and designers are increasingly using “biomimetic” techniques—mimicking nature. Evolution has worked over vast times to select the most successful biological patterns, and we can learn from them, if they are here to be learned from.

More-diverse ecosystems seem to be more productive (if you have hot-loving and cold-loving and wet-loving and dry-loving types in a region, then something will grow well no matter what weather arrives; if you have only one type, and the weather is bad, so is the crop), so if producing more is good, biodiversity seems good. But, the difference is not huge.

Living things have frequently served as “canaries in coal mines”. Miners would take a canary along in the mine, not only for companionship, but because the birds were more sensitive to bad air than were people, and a sick or dead bird would warn miners to get out before the miners became sick or dead. Birds of prey served that function for us with DDT. This chemical was going to free us of pests, increase crops, wipe out diseases—until the falcons, hawks, eagles and other predatory birds started disappearing. A little DDT on a plant led to more DDT in an insect that ate lots of plants, and still more DDT in a bird that ate a lot of those insects, and became so concentrated in a falcon that ate the birds that the falcon’s eggs broke and young ones couldn’t be raised. It became clear that such “bioconcentration” threatened us with problems as well—the other living things gave us a warning. Loss of biodiversity means loss of warning sensors.

And, many people like diversity (look at the money spent on zoos, and the interest in charismatic macrofauna in parks). Further, some people see a moral issue—do we really have the right to terminate the existence of other living things?

Some planners today are trying to establish corridors connecting wilderness areas, so that the parks do not become islands and lose species. How successful this plan will be remains to be seen. The “simple” answer is that, to maintain many species on Earth, we have to maintain much wilderness. And that in turn has implications for how we humans choose to behave.




Credit: Dr. Richard Alley

Two identical terrariums, and in each of these terrariums, you have the rare and beautiful geosite daisy that is so endangered, and it’s such a great thing to have. And all the people come from around to look at them. The difference is in the upper terrarium, it is divided into two by an unbreachable purple glass wall. Now, what’s going to happen?

Well, as you might imagine, things are not perfect in terrarium land, and the blight comes. And the blight kills off one of your geosite daisies in each of the terrariums. But if you’re down here, you’re not worried, because you can grow this beautiful daisy, and it will grow back.

And it has its poesy, and it just gets grown back when, oh my goodness, the rust comes, and it wipes out one of the daisies in each of the terrariums. And if you’re down below, you’re still not worried, because it can grow back. And pretty soon, you have a beautiful display. But if you’re up above, you’re really worried, because now you’re extinct.

Now, suppose that instead of this being worried geosite daisies in our terrariums that we were worried about Glacier National Park seen in a map and Yellowstone National Park seen in a map down here. And at the present time, Glacier and Yellowstone are connected by corridors that are essentially wilderness running down the Rocky Mountains.

What is going to happen if we lose those corridors of wilderness that connect the two and turn them into islands? And the simple answer is you don’t lose everything, but you probably do lose some of the things that live in both of the parks, just as for the terrariums you get extinction.



Optional Enrichment Articles (2)

The So-Called Greenhouse Effect

As an aside, some of our friends over in meteorology are not happy that the effect of CO2 on climate is called the “greenhouse effect.” They fully understand that CO2 does warm the planet, and they know that the glass of a greenhouse affects radiation in much the same way that CO2 in the atmosphere does—the shortwave radiation from the sun comes through glass or CO2 more easily than the longwave radiation from the Earth goes out through glass or CO2. But, the meteorologists note that this effect of glass on radiation is not the only reason why a greenhouse is warm, nor is this the major reason. Greenhouses also are warmer than their surroundings because the glass blocks the convection currents that take much of the sun’s heat away from the ground outside of greenhouses. Some meteorologists have even suggested renaming the atmospheric phenomenon to avoid possible confusion. But, the “greenhouse effect” is catchier than “the effect that warms the Earth through modulation of radiation balance, akin to the radiative effect that contributes to but does not dominate daytime warming of greenhouses.” Maybe our meteorological friends would be wise to “chill out” on this one. Notice that this little discussion about terminology in no way affects the reality that more CO2 in the atmosphere warms the planet—nature works, regardless of what words we use to describe it.

How Much CO2 to Warm?

Many different models have been constructed of the Earth’s climate system, ranging from attempts by large teams to include essentially all Earth-system processes into models that tax the world’s largest computers, to small-group or individual-scientist efforts to build fast and flexible models that allow exploration of uncertainties in many parameters. Across a range of models, the equilibrium warming from a doubling of CO2 is often stated to be between about 2oC (maybe as low as 1.5oC) and 4.5oC, with a central value near 3oC (and with the most recent results pointing to a bit above 3oC). Comparisons to the past, for both the last century and for much longer times, largely exclude the low end of that range—models that change global average temperature near 1.5oC for a doubling of CO2 are not able to accurately simulate the changes of the past, whereas models with larger temperature change in response to CO2 do better in simulating past changes. Based on the paleoclimatic record, warming of near 3oC or more for a doubling of CO2 seems reasonable, and values above 4.5oC cannot be totally excluded.

Why Not Water Vapor?

Water vapor is the most important greenhouse gas in terms of the warming being provided now, but we usually don’t talk about water vapor with global warming. Why not? Simply, water vapor is almost entirely a slave to other things. Put some more CO2 up in the atmosphere, and the atmospheric concentration of CO2 remains high for centuries or millennia or longer before chemical processes remove it. Put more water vapor up, and in just over a week, on average, that water has rained out. The burning of fossil fuels makes equal numbers of water-vapor and CO2 molecules, but because the water vapor stays up less than two weeks and the CO2 perhaps 2000 years, our effect on the atmospheric concentration is more than 100,000 times larger for CO2 than for water vapor. We can change CO2 fairly easily (and are doing so!), but we can’t put up water vapor fast enough to make much of a difference, nor can most other natural processes affect global water-vapor loading very much. However, changes in the atmosphere’s water-vapor content are easily caused by changes in temperature.

Remember from back at the Redwoods that cooling reduces the equilibrium water-vapor pressure or “water-holding capacity of the air” (by about 7% per degree Celsius of cooling). Remember that as full-of-water air came in from the Pacific and was forced up over Redwood National Park and then Yosemite and Sequoia National Parks, the air cooled by about 0.6oC/100 m, raining on the way. The temperature at the top of the Sierra was controlled by the height of the Sierra and the temperature of the air before the rise began, and the amount of water left in the air at the top was controlled by the temperature at the top. The air then goes down over Death Valley, and the water-vapor content of the air there depends on the temperature at the top of the Sierra.

So, if the temperature is increased over the Pacific by an increase in CO2, the water-vapor content and its greenhouse effect are increased over the Pacific, going up the Sierra, going back down over Death Valley, and on to the Atlantic or Gulf of Mexico. Water vapor acts as a positive feedback—warming increases the water-vapor content of the atmosphere, causing more warming.

You can find lots of climate-change skeptics or contrarians or denialists who love to point out that water vapor is the big greenhouse gas, CO2 less so, so the scientists must be out to lunch by focusing on the small one and not the big one. Sounds sensible, right? But, it is totally stupid or deliberately misleading, or somewhere in-between. If we pulled all the water vapor out of the air, more would evaporate in a week or so. Pull all the CO2 out of the air, and the cooling would remove a lot of water vapor, with a rather high chance that the whole Earth would freeze over into a snowball. Thus, although water vapor gives us more warming than CO2, you can argue that the CO2 is more important overall.

Why All the Noise?

Environmental problems seem to follow a fairly predictable path. First, someone has a good idea. Refrigerators and air conditioners and freezers are useful, but if you use ammonia in the pipes and you’re in the way when a pipe breaks, you might die, so chlorofluorocarbons were a great idea. Then, scientists discover an unintended consequence—the chlorofluorocarbons might break down ozone and allow harmful ultraviolet rays to give living things “super-sunburns,” causing cancer and other problems. There follows a period when the scientists work to improve their understanding.

But, there also follows a lot of yelling and not-entirely-scientific discussion. Some people fear that they are going to lose their jobs, or lose a lot of money, and these people respond to the scientists by arguing that there is no problem, that the problem that does not exist must be caused by nature rather than humans, and that this natural problem that does not exist would cost way too much to clean up. A very common approach is to attempt to convince the public, or policymakers, that scientists are still having a big debate, even if they are not. It is fairly easy to find a few skeptics, fund them and promote their statements, and to “cherry-pick” favorable results from the scientific literature and present them out of context.

Politics often feeds into this. Usually, if a problem is identified that affects a lot of people, the government ends up dealing with the problem. You are not allowed to tear out your sewer or septic system, poop in a pot, and dump it over the fence into my yard. Nor are you allowed to smoke in many public places now, or a number of other things and these are laws that are passed by and enforced by the government. So, if you don’t much like government, you may not want the government trying to clean up a problem. And, if you can keep the argument focused on whether or not the science is good, rather than on possible wise responses to the problem, there is little danger that the government will do anything—we usually don’t do much about a problem until we agree that there is a problem.

The press makes all of this worse, attempting to maintain “balance” by presenting both sides of a “scientific dispute,” even if one side is being manufactured and does not have much scientific basis of its own. Recent scholarship has demonstrated clearly that a reader of the mainstream press in the U.S. would have a very skewed view of the degree of scientific agreement over global warming, for example—many press outlets present a conflict that really doesn’t exist.

But, some forward-looking people also see the problem as a possibility—a new invention may make a lot of money. And, history indicates that problems usually are followed fairly quickly by new inventions, the cost of dealing with the problem typically is much less than previously stated (often about 10% of the previously stated cost), the cleanup becomes part of the economy, and life goes on. (Imagine life without toilets and sewers…)

The twin energy problems—finding replacements for the finite fossil fuels, and doing so before the world is changed too much in bad ways—are arguably the biggest environmental problems we have ever faced, but they can be solved. Because of the huge size, the solutions will take longer, and more inventions will be required than for the ozone hole or DDT or lead in gasoline. The scholarship is clear that the sooner we start, the better off humanity will be.

A Bit More on the Marcellus

A Caution

In Pennsylvania, as this is being rewritten (autumn of the year 2017), the Marcellus Shale is the center of a “fracking” industry to extract gas and sell it. Some jobs have been created, and some economic activity. Some people have received money because gas companies paid for the right to extract the gas. Other people who did not own the mineral rights of their land are rather unhappy that the money from the gas on their land is going to someone else.

The issues related to the Marcellus have been contentious for a decade, and it remains virtually impossible to write anything that is not: i) quickly out of date, and ii) likely to make a lot of people mad. But, we cannot ignore the big issues, so here is a little more background.

Some History

The estimates of available fossil fuels that you see in various publications may be very different things. Textbooks often list the total amount that is considered to be available if we continue inventing new technologies and pushing the price slowly higher. This is a fuzzy number—how high can the price go before alternatives are cheaper and we quit trying for fossil fuels? But, this sort of calculation has long assumed that we would go after the gas in the Marcellus and other shales, and the oil in oil shales, and tar sands, and more.

Other numbers on fossil-fuel reserves are much smaller because they count only the nearly-ready-to-pump-out-of-the-ground fuels or some other similar definition. Over the last few years, a lot of gas in the Marcellus and other such black shales has moved from the “available in theory” to “available in practice” column, which has changed a lot of business balance sheets. You will see estimates, often communicated by industry, that the Marcellus and other such deposits contain “100 years of gas,” although other estimates (including from the government) have been lower, including 25 years of gas. But, gas is supplying a little over one-quarter of U.S. energy use, so an all-gas system might last 6 to 25 years based on those estimates. That is lots of energy, lots of money, but not even vaguely close to a long-term, sustainable energy solution.

Some Geologic History

When conditions are right, organic materials accumulate in sea-floor muds. Gases dissolve more easily in colder waters (heating a carbonated beverage drives off the fizz). So, when the climate has been hotter in geologic history, there has been a tendency to have less oxygen in the ocean and lakes. Extra fertilizer at the surface may favor the growth of so many plants that the oxygen in the deeper water is used up in “burning” the plants after they die and sink, before the dead plants are used up. Low oxygen in deep water is also favored by restricted ocean basins that prevent vigorous currents to supply newly oxygenated waters. The still conditions of a deep, restricted ocean basin mean that mud isn’t washed away, but that no big chunks such as sand or gravel are washed in. So, an organic-rich mud forms in such places, especially during hot-climate, well-fertilized times.

Eventually, this is a stabilizing feedback on Earth’s climate—when high CO2 makes the climate hot, CO2 is removed from the air by being converted to plants that are buried in these muds. In just a few hundred thousand years, this can make a big difference to how much CO2 is in the air, especially because a hot climate can also remove a good bit of atmospheric CO2 by rock weathering in a few hundred thousand years. Nature thus will remove the CO2 that we are putting up now, and if you have a few hundred thousand years to wait, our CO2 is no big deal. If you care about your great-great-great-great grandchildren, though, these natural processes just aren’t fast enough to help much.

Anyway, the muds in the low-oxygen ocean or lake basins are often black, partly from the organic material, and a lot from having iron sulfide and other black stuff that forms in low-oxygen environments (add oxygen, and the iron in iron sulfide rusts and turns red). As more mud accumulates on top, the black muds get hotter from the heat of the Earth, and the mud slowly is squeezed and recrystallized to make a rock called shale. Shale is the commonest sedimentary rock, and there is a lot of black shale on Earth.

The heating also changes the organic material, making oil and gas. Most oil, and a lot of gas are formed in this way.

However, the spaces between clay particles in the mud/shale are tiny, and even tiny gas molecules and the smallest of oil molecules have trouble moving rapidly through. As more oil and gas are produced, the pressure inside rises (splitting molecules off dead things tends to increase the total volume taken up by the organic materials). Eventually, this opens cracks and allows the oil and gas to leak out. As noted in the main text, most of the leaking oil and gas escape, slowly, to the Earth’s surface, where they are broken down by bacteria or other living things that use the stored chemical energy in the fossil fuels. A little of the leaking oil and gas are trapped in special geologic places on the way, and oil companies have gotten very good at finding those places, drilling into them, and recovering the oil and gas.

Much of the organic material remains in the black shales, though, unable to make its own fractures and escape.

Some Fracking History

Oil companies have been “fracking” for a long time. Suppose that oil and gas leaked from a black shale into one of the special reservoirs that oil companies like to drill into, arriving in just a million years. That is fast compared to many geologic processes, but if it took the oil company another million years to get the oil out of the rock, the oil company would be very unhappy. So, for rocks that allow oil and gas to move slowly, but that contain a lot of oil and gas, the oil companies learned to make fractures that let the fossil fuels move faster.

one of history’s fascinating stories, the actor John Wilkes Booth, before he shot President Lincoln, was an investor in a Pennsylvania oil well. With much of his money committed, and the well yielding slowly, Booth and his co-investors decided to “shoot” the well, exploding gunpowder to fracture the rocks and yield more oil. Instead, they destroyed the well. Now much poorer, Booth switched his focus and soon thereafter shot President Lincoln. But, a new invention, the Roberts Torpedo, from a Union soldier who saw an exploding Confederate shell fracture dirt, soon made shooting wells much safer and more widespread.

Imagine you’re working for the gas company. If you blow up a balloon too vigorously, it breaks. Pump too much air into the bicycle tire, and it may rupture. This is the basis for fracking rocks. Drill a hole to the rocks you want to break. Put in some sort of plug with a tube or pipe going through (so that when you “blow up the balloon” on the other side of the plug, the pressure is pushing against the rock down there and not squirting out of the hole up here). Then, pump water through the pipe into the space below the seal, and pump hard enough that you really raise the pressure, “break the balloon” by cracking or fracturing the rocks. Release the pressure, and oil and gas can leak out of the new cracks to your hole, and up the hole to the surface, perhaps aided by a well pump that you use. (Companies that generate geothermal power also may “frack” to make spaces for hot water to move easily.)

Notice, though, that if you pry open a crack, and then quit prying, nature may squeeze it back closed. But, if you put some sand in below the plug, when the rocks break, the sand can squirt into the cracks and keep them from closing. A crack that is twice as wide carries eight times more fluid, all else equal, so this can make a big difference.

In addition to the sand, you might add something to keep microbes from growing in your new cracks, eating your valuable methane and clogging the cracks with dead-bug “gunk.” And, you might want to add some surfactants. For example, many antacids include a chemical (simethicone) that reduces surface tension so that small bubbles in the stomach can combine into larger ones that can be moved along more easily; chemicals to do the same job may be added to fracking fluids, for the same reason. You might even think of other things to add.

Once you have this fluid, some of it will stay in the cracks you make. And, the fracking is generally way down, so it is very unlikely that the cracks will reach all the way to the surface, or to the shallow level of water wells. But, some of the fracking fluids must come back up the hole to get out of the way so your gas can come out. You may recycle this “flowback,” or dump it in the creek or at the sewage treatment plant, or pump it into even deeper wells somewhere just to get it out of the way. Deep disposal and recycling have largely replaced earlier techniques. But, in Oklahoma and elsewhere, when some of this fluid was pumped into deep wells, it seems to have triggered earthquakes. (The quakes happened where and when the pumping was going on, not huge quakes but big enough to crack plaster and otherwise damage houses.)

A gas well used in fracking must be drilled through shallow and intermediate depths on the way to the shale to be fracked. The plan is to seal the well so that there are no leaks of gas or other fluids into those shallow and intermediate depths where people may have water wells. But, if the sealing isn’t done properly, it could leak. Leaks of that sort from gas and oil wells have been reported, but there aren’t a lot of public data on just how often, and just how large the leaks are. The mix of chemicals may be a trade secret, so people worry may not even know exactly what is there to leak.

Some Global-Warming Considerations

Regardless of what your politician or pundit may have said, the science really does give us high confidence that a long-term shift away from fossil fuels is economically beneficial to avoid the damages of changing climate. Natural gas produces more energy from the same number of carbon molecules than coal (or oil from tar sands), so if natural gas is used in place of coal, this can reduce warming. However, if natural gas is used in addition to coal, then it increases warming.

And, there is a qualification. If you let natural gas (which is almost entirely methane) leak into the air without burning it, the methane is a greenhouse gas. Per molecule at current levels, methane causes more warming than CO2, and after a decade or so the methane is oxidized to CO2 and then stays up typically for additional centuries. So, if natural-gas production is too leaky, that may be even worse than coal in terms of causing warming; leakage also wastes money for the gas companies.

A Bit on Policy

In Pennsylvania over the last few years, the public discussion included everything above, but especially focused on jobs and the economy and taxation. Every major gas-producing state in the US except Pennsylvania had taxes or fees that provided notable funds to the public coffers, with Pennsylvania having only a relatively quite small local impact fee. Those who favored the no-taxes approach in Pennsylvania typically have argued that taxes might drive away the gas companies. Supporters of taxing have often noted that no gas company would be stupid enough to come into Pennsylvania assuming the no-tax position was guaranteed for the long term. The companies can look across the nation, see that every gas-producing state except Pennsylvania had levied taxes, and that Pennsylvania had budget problems that could be eased by levying taxes, and it seems reasonable that a planner for a company would run the numbers assuming that Pennsylvania would follow all the other states.

However, once a company decided to enter the state, a good business person would note that production achieved before any taxes were levied would be more valuable. This might justify hiring more workers and otherwise working faster, which would stimulate the economy but provide less long-term stability. It also might justify cutting some corners, allowing more leakage or otherwise adopting less-efficient but faster approaches. Reliable studies balancing these issues have been lagging behind the pace of development.

A Resource Curse?

Lurking behind all of this discussion is something that economists argue about a lot, called the “Resource Curse.” With certain notable exceptions, countries that rely heavily on the extraction of concentrated valuable resources (diamonds or oil, for example) have often had less economic growth than might be expected based on the size of the economic input from the resource, and many residents of western democracies do not like the social conditions in such resource-producing states. (You can think of the leading oil exporters in recent years, including Saudi Arabia, Russia, Norway, Iran, United Arab Emirates, Venezuela, Kuwait, Nigeria, and Algeria, and decide whether this “academic” view of the resource-reliant economies seems accurate, nearly accurate with maybe a few exceptions, or really wrong.) Mere production of fossil fuel is not seen as an economically bad thing by the economists who have recognized the resource curse; the worry is attached to reliance on the money from the valuable resource (the US is a major oil producer, but oil production is not a dominant part of our economy). There are many ideas on why the resource curse exists (and a few experts who still deny that it exists); perhaps the most common idea is that if people put effort into controlling the temporary resource rather than building a sustainable society, they end up with a poorer place to live.

The observation of the author is that there has been rather little public discussion in Pennsylvania on whether reliance on a soon-to-be-depleted natural resource is the best way forward for the Commonwealth.

The author will also state that he isn’t coming out for or against Marcellus Shale gas development, that it may ultimately turn out to be more “good” than “bad,” or the other way around. Furthermore, even if the author did take a side, almost no one would care. The development has been going fast, many people love it, and many people don’t.



Key Takeaways for Biodiversity, Global Climate Change, and the Future


  • Plants turn carbon dioxide, water and sun’s energy into more plants and oxygen.
  • Other life forms “burn” plants with oxygen to get that energy.
  • If buried without oxygen, plant isn’t burned, and heating makes fossil fuel.
  • Woody plants–>peat (in sediment; Bear Meadows) –>lignite (in sedimentary rock)–>bituminous (in harder sedimentary rock, western PA) –> anthracite (in metamorphic rock, eastern PA).
  • Algae–>gas from bacteria (Bear Meadows)–>oil (with gas) (western PA)–>gas (eastern PA) (float up and escape to be burned unless trapped by geology).

Take It to the Limit

  • Fossil fuels are NOT infinite:
    • nature really is efficient at recycling;
    • oil & coal companies good, found the easy stuff;
    • not a lot set aside
  • World oil production peak likely in next decades
    • at vaguely recognizable prices and current demand, probably close to a century of oil and gas, a few centuries of coal,
    • but demand rising rapidly, so less time.

You’re in the Greenhouse Now

  • some gases let visible light through (sun) but partly block infrared (return from Earth);
  • makes planet warmer than otherwise, so we “glow” brighter to force energy past the gases;
  • we are increasing these gases (esp. carbon dioxide) a lot, and they will stay up for centuries, millennia or longer.

With High Confidence

  • Our greenhouse gases will warm world, amplified by feedbacks such as melting of reflective ice increasing warming
  • positive and negative impacts on us, but mostly negative for warming more than a few degrees:
    • sea-level rise from ice melt, expanding ocean;
    • summertime drying of grain belts;
    • not-nice tropical heat.

Making Money

  • We have to switch from fossil fuels; will we do so before or after we change the world?
  • Reasonable estimates say switch needs few decades of serious research and 1% of economy:
    • this is in line with other clean-up costs now;
    • this is something like $400 billion per year now.
  • Not a lot of scientific disagreement on these points,  but much political, social, economic disagreement

Lions and Tigers and Bears?

    • Why save biodiversity–medicines, other useful things from living types; more-diverse ecosystems produce more; living types “canaries in coal mine” to warn us of trouble; ethics
    • Early and modern humans hard on biodiversity–next mass extinction?
    • Climate change will complicate, forcing migration when there may not be migration pathways.



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The Geology of North American National Parks Copyright © 2022 by Dr. Richard Alley, Evan Pugh, and Sridhar Anandakrishnan is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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