He should have started with chapter 2. In chapter 1, Pearson invokes the IPCC model scenarios and the contention that human carbon dioxide emissions will produce a temperature rise of somewhere between 2-to 11 degrees F, and that will “likely” cause extinction of 20% to 70% of species. There is, however, no physical evidence which shows that human carbon dioxide emissions have a significant effect on global temperatures. That being said, let’s imagine that the world will continue to warm, regardless of cause, and examine what the consequences might be.

In chapters 2 through 5, Pearson takes the reader on expeditions to Madagascar, Costa Rica, the British Isles, North America, and South Africa where he examines how specific species are reacting to global warming. This is mainly a study of range changes pole-ward and to higher elevations for plants and animals. Some species expand their ranges, some ranges contract, while others are not affected. There are winners and losers. Pearson notes that some amphibians are more susceptible to disease as temperatures “converge on a range that is just right to promote disease outbreaks.” He also examines how plants and animals may react to changes in the onset of the seasons (phenology). Pearson notes that there may be some observation bias in these studies and does point out potential problems.

I did detect one error in this section. On page 88, Pearson says “the world’s oceans are gradually turning acidic.” Not true, the oceans are alkaline, and there is a natural cycle of pH variation within the alkaline range (see my rebuttal here).

Chapters 6 through 8 discuss extinction risk modeling and experiments. Pearson fairly points out areas of uncertainty. He also discusses the ability of plants and animals to adapt to changing conditions. Here, too, there are winners and losers. He discusses complicating factors such as habitat loss due to human encroachment. Pearson says, “we cannot really expect to accurately predict how an ecological community will respond to climate change.” And, “climate change has the potential to rearrange species, assembling new communities as plants and animals shift their ranges and adjust their phenology. The consequences of this reshuffling will be alterations to existing interactions between species as well as the creation of novel sets of interactions.”

Chapter 9, entitled, “Cry Wolf?” discusses exaggeration of scientific studies by the press, and whether scientists should or should not be political advocates. Pearson does not mention possible scientific bias in the competition for research grants.

In the final chapter, Pearson, himself, becomes an advocate for more conservation parks, connectivity between reserves, and for reducing our use of fossil fuels.

Pearson’s thesis is that the current warm period is unprecedented due to human emissions of carbon dioxide, and this may cause many adverse effects on plants and animals. He seems unaware that during the last 10,000 years the world  experienced several warm-cold cycles. At least three of the warm cycles were warmer than now and warmer than the high range of IPCC predictions. How did species cope with these changes? Except for extinction of megafauna near the end of the last glacial epoch, an extinction that was abetted by an abrupt cooling period (the Younger Dryas), where are the bodies of victims of global warming from these previous cycles?  Many studies of the fossil record during times when the temperature quickly rose at least 4 degrees C, found changes as Pearson describes in chapters 6 through 8. But those same studies found very little evidence of broad scale extinctions.

 In spite of my criticisms of this book, I found it well-written and a very interesting read.

About the author: Richard Pearson is Director of Biodiversity Informatics Research at the American Museum of Natural History. He has a PhD. (2004) from Oxford University in biogeography, and is a research scientist in the museum’s department of herpetology.

The book was published by the Sterling Publishing Co. Inc.

The Cretaceous Period (145- to 65 million years ago) was hot and steamy. There was no ice at the poles. Global temperature is estimated to have been about 18 F warmer than today. Atmospheric carbon dioxide began a 145-million-year decline from about 2,000 ppm to the 380 ppm of today, in part, due to carbon sequestration by formation of coal deposits. Flowering plants appeared.

The North American continent was split by a sea connecting the Gulf of Mexico with the Arctic Ocean. Transgressions and regressions of this sea formed conditions ripe for coal formation similar to those in the Paleozoic Era. In Southern Arizona, the lower Cretaceous Bisbee Group, consisting of the basal Glance conglomerate, the Morita formation sandstones and mudstones, the distinctive Mural Limestone (which forms the cliffs just east of Bisbee), and the sandstones and mudstones of the Cintura Formation record the changes in sea level. Upper Cretaceous rocks, the Fort Crittenden Formation lie unconformably (representing erosion or structural change) upon the Bisbee Group. The lower Fort Crittenden is dominated by marginal wetland to deep-water lake deposits, whereas the upper Fort Crittenden is characterized by wetland to deltaic deposits. These rocks contain organic geochemical evidence of wildfires which suggest that seasonal aridity and wildfires were common occurrences.

There are no early Cretaceous rocks recognized in northern Arizona. Thick sequences of upper Cretaceous rocks were deposited on what is now the Colorado Plateau. These represent near-shore marine, coastal, and river-deposited sands, mudstone, and coal. Coal is mined from the Dakota sandstone at Black Mesa in Navajo County, AZ. This is overlain by the Mancos Shale, and several other sedimentary formations.

The Laramide orogeny of late Cretaceous to early Tertiary time (80- to 40 million years ago) built the Rocky Mountains and closed the inland Cretaceous sea. Subduction of oceanic crust under continental rocks along the west coast caused compression and uplift of the continent.

This was the time of emplacement of most of the porphyry copper deposits in the western U.S. Volcanism was extensive, and included the volcano that produced the rocks of the Tucson Mountains. (See the Tucson Mountain story).

 Dinosaurs roamed the land, including Arizona’s Sonorasaurus thompsoni, a new species of brachiosaurid dinosaur whose remains were first discovered in the Whetstone mountains by UofA graduate geology student Richard Thompson in 1994. Sonorasaurus is estimated to have been about 50 feet long and 27 feet tall, about one third of the size of other brachiosaurus. It may have been a juvenile or just a small dinosaur species. Sonorasaurus was an herbivore. Tooth gouges on its bones suggest it was killed and eaten by a larger dinosaur. A single blade-like tooth of a huge meat eater called Acrocanthosaurus was found near the bones and suggests that this was the predator that killed Sonorasaurus. You can see an exhibit dedicated to Sonorasaurus at the Arizona-Sonora Desert Museum.

The end of the Cretaceous Period saw another major extinction of life. Dinosaurs, pterosaurs, many marine reptiles, some marine invertebrates, some groups of mammals, and a few plant groups became extinct. The reasons are still controversial. We know that an asteroid impacted near Yucatan, Mexico and formed the Chicxulub crater about 65 million years ago. The impact is said to have vaporized rock into clouds of dust, that cooled temperatures, and created clouds of sulfurous gas, which may have killed plants with acid rain. The impact is also said to have deposited a thin clay layer containing iridium and strained quartz. However, the extinction occurred during an 800,000-year eruption of basalts that form the Deccan Traps in India. Volcanic eruptions can also product dust and sulfur dioxide emissions (and layers of iridium which characterize the K/T boundary). More precise dating shows that the Chicxulub impact occurred 300,000 years before the mass extinction. Evidence suggests that the extinctions occurred over a period of several million years.

Cretaceous Trivia:

The white cliffs of Dover, England are Cretaceous age chalk deposits.

Paul Spur, a rail stop between Bisbee and Douglas exists because Mural limestone was mined for smelter flux.

Hills carved from Cretaceous beds east of Bisbee. View is northward across Mule Gulch. The prominent white band is the upper member of the Mural limestone, forming the top of Mural Hill on the left and showing the dislocation due to the Mexican Canyon fault. Cochise County, Arizona. December 1, 1902. Plate 9-B in U.S. Geological Survey. Professional paper 21. 1904, figure 7 in U.S. Geological Survey Folio 112. 1904.

See more of geologic history:

Precambrian, Early Paleozoic, Late Paleozoic, Triassic, Jurassic

Arizona Geological History 7: The Cenozoic Era

References:

Dickinson, W.R., et al., 1989, Cretaceous Strata of Southern Arizona, in Geologic Evolution of Arizona, Arizona Geological Society Digest 17.

Finkelstein, D.B, et al., 2005, Wildfires and seasonal aridity recorded in Late Cretaceous strata from south-eastern Arizona, USA, Sedimentology, Volume 52, Issue 3 , Pages587 – 599, International Association of Sedimentologists

Krantz, R.W., 1989, Laramide Structures of Arizona, in Geologic Evolution of Arizona, Arizona Geological Society Digest 17.

Nations, J.D., 1989, Cretaceous History of Northeastern and East-Central Arizona, in Geologic Evolution of Arizona, Arizona Geological Society Digest 17.

Arizona warms from ice age, becomes tropical again, gets flooded by the ocean, suffers another ice age, warms up, makes coal, and suffers a major extinction of life.

In this chapter we will complete the Paleozoic Era with four periods: Devonian (416- to 359 million years ago), Mississippian (359-318 mya), Pennsylvanian (318- 299 mya), and the Permian (299-251 mya). In the European classification, the Mississippian and Pennsylvanian are, together, called the Carboniferous period because it was during this time that most coal deposits were formed.

After recovery from the Ordovician ice age (about 440 mya), Arizona was apparently a highland on the southwest edge of a continental mass, about 30 degrees south of the equator. I say apparently, because there is no record from the Silurian period (444- to 416 mya ), so Arizona may have been dry land that was subject to erosion.

During the last four periods of the Paleozoic, Arizona was mainly under water. The rocks deposited during this time represent deposition on a continental shelf environment. There were several episodes of transgression (encroaching) and regression of the sea from the west. Only what is now the northeastern corner of the state remained above sea level for most of the time. The rise and fall of the sea was due to both tectonic shifting of land and changes in water volume from the glacial epochs.

Limestone was the principal rock deposited during this time along with relatively minor shale and sandstones. All the formations contain fossils. These limestones currently make up most of the mountain ranges south of Tucson.

Mississippian rocks rest unconformably (not at the same angle or with evidence of erosion) on Devonian and older rocks. This means that there was some tectonic adjustment and erosion between the two Periods. (And by the way, the geologic Periods are usually defined by their distinct fossil assemblages). The principal formation of the Devonian is called the Martin Formation with type area in Bisbee. The principal Mississippian limestone is called the Redwall Limestone near the Grand Canyon and the Escabrosa Limestone in southern Arizona. Kartchner caverns are in the Escabrosa Limestone, but the caves formed recently.

Pennsylvanian and Permian rocks represent complex cycles of transgression/regression by the sea, caused by changes in water volume due to glacial epochs, and by tectonic uplift and sinking of the continent. This tectonic shifting was the result of the collision of Gondwana on the south with Pangea on the north. Carbonate rocks dominate in the northwest and southeast, while sandstones and conglomerates dominate in central and northeast Arizona.

 Most coal deposits developed during the Carboniferous period. Arizona caught some of this in the northeastern part of the state. Coal is mostly carbon accumulations from fossil plant material deposited in swamps so devoid of oxygen that bacteria and other critters couldn’t survive to feed on their remains. This implies that climate was warm and wet, and that the cyclic transgressions/regressions of the sea were relatively quick enough to bury the swamps before the luxuriant plant life could be destroyed.

Arizona coal was formed about 300 million years ago. It is mined in Navajo county, and, according to the Arizona Department of Mines and Mineral Resources, ranks second only to copper in economic importance.

Worldwide coal formation stripped the atmosphere of carbon dioxide. Beginning in mid- Devonian time, about 380 mya, through early Mississippian time, atmospheric carbon dioxide dropped from around 4,000 ppm to near current levels of 400 ppm by 340 million years ago. Temperature, however, remained high (about 68 F world average vs 57 F today). But near the Pennsylvania-Permian boundary time, about 270 million years ago, the planet was plunged into another ice age. Note the 70-million-year gap between lowered carbon dioxide and decreased temperature. By the end of the Permian, temperatures rose again to an average of about 63 F, soon followed by a rise in carbon dioxide to just under 3,000 ppm. (Rising temperature causes more carbon dioxide to be exsolved from the oceans.) Volcanism contributed to the rising carbon dioxide.

The first known land vertebrates, amphibians, appeared in late Paleozoic time. Devonian rocks contain fossils of amphibians called stegocephalians (roofed head) because of flat, broad heads. Most were one- to two inches long, but later forms became as large as a crocodile and most were probably carnivorous judging by the teeth.

Reptile fossils appear in Pennsylvanian rocks. The first were small like amphibians, but later Permian reptiles got up to eight feet long. One group, the Therapsids, had teeth differentiated into incisors, canines, and molars similar to present-day mammals.

The Permian ended with a mass extinction in which about 90% of species disappeared, including marine fauna, plants, and terrestrial animals. The reason for this extinction is unknown although there are many speculative theories. This extinction happened over a period of several million years and is coincident with the coalescing of continents and extensive volcanism.

When Pangea and Gondwana collided is reduced marine habitats and brought deep, oxygen-poor ocean water to near surface environments. Major volcanism, in what is now Siberia, lasted for about one million years and annually spewed billions of tons of sulfur dioxide and carbon dioxide into the atmosphere. These two events are probably contributory to the extinctions.

But, with the dawning of the new Mesozoic era, life rebounded and became more diverse and more robust.

PHOTO: Omphalotrochus (snail) from the Permian Colina formation, collected about 2 miles southeast of the Tombstone airport. Notice also the pits made by rain drops differentially eroding the limestone.

See Chapter 1: the Precambrian, and Chapter 2, the Cambrian and Ordovician periods.

Chapter 4: the Triassic Period