Pleistocene Hackberries (Celtis sp.)

I’ve come across anecdotal evidence, suggesting hackberry trees were locally abundant during Ice Ages. Today, hackberry is a minor component of deciduous forests. I know of 3 sites dating to the Pleistocene where the remains of hackberry have been found. Plant remains dating to the Pleistocene are relatively rare, so the occurrence of this species might be significant and not just a coincidence. Hackberry seeds were found associated with the skeletons of a flat-headed peccary herd that was buried by a sandstorm in western Kentucky thousands of years ago. (See: https://markgelbart.wordpress.com/2013/03/10/when-sand-dunes-buried-herds-of-flat-headed-peccaries/ ) Hackberry along with oak were the most abundant plant remains and DNA dating to the Pleistocene found in Hall’s Cave located on the Edward’s Plateau in Texas. (See: https://markgelbart.wordpress.com/2020/06/29/new-study-of-the-seda-dna-in-halls-cave-texas/ ) Hackberry trees are still common near the cave entrance. And hackberry leaves were found in Kingston Saltpeter Cave in North Georgia, though it’s unclear if the leaves were actually in the layer with the Pleistocene animal remains.

I hypothesize there were 3 factors why hackberry thrived when other deciduous species declined in abundance during Ice Ages. Foresters note Georgia hackberry grows well on dry rocky sites. The Ice Ages were arid because much of earth’s water became locked in glacial ice, and dry environments prevailed in many locations. Perhaps hackberry was better able than other hardwood trees to endure the lower atmospheric CO2 levels that occurred during Ice Ages. Hackberry also may not have been a preferred food of the megafauna. So, when megafauna consumed other plants, they were eliminating competition for sunlight and growing space. Though this is just speculation and probably impossible to determine because evidence has eroded away, I envision groves of widely spaced oak and hackberry trees growing with bunch grass and bare soil between the trees in dry environments across the piedmont region of southeastern North America during Ice Ages. Pollen records suggest pine was more abundant than hardwoods during Ice Ages, but pine produces much more pollen than hackberry and may be overrepresented by comparison. Hackberry pollen rarely shows up in pollen records. However, there are very few (if any) local pollen records from this region dating to the Last Glacial Maximum, and pollen records are not always all inclusive.

Hackberry trees belong to the Celtis genus and were formerly thought to be in the same family as elm, but modern botanists recently decided the Celtis genus belongs in the Cannabis family. This means they are related to hemp and marijuana. There are 66 species in the Celtis genus worldwide, and they are found in the Northern Hemisphere, South America, and central Africa. 3 species live in eastern North America–common hackberry (Celtis occidentalis), Georgia hackberry also known as dwarf hackberry (C. tenuifolia), and sugarberry (C. laevigata). Common hackberry’s continuous range is just north of Georgia, but disjunct populations do occur in the state. Georgia hackberry is found in the piedmont region of southeastern North America, plus southern Missouri and parts of Appalachia, Louisiana, and Texas. Sugarberry is found throughout the southeast.

Range map for Georgia hackberry, also known as dwarf hackberry. It prefers dry rocky piedmont soils.

Range map for sugarberry.

Georgia hackberry. It is usually a medium sized tree.

Georgia hackberry leaves.

Hackberry fruit is edible. I’ve tasted the fruit of Georgia hackberry, and it’s bittersweet and mostly skin and seed. Sugarberry looks bigger and may have more flesh. American Indians pounded the fruit, seed and all, into pemmican–a mixture of berries, jerky, and meat fat. Many species of brush-footed butterflies feed upon hackberry leaves during their caterpillar stage. The fruit stays on the tree all winter and provides food for birds.

Hackberry emperor butterfly larva like to feed upon hackberry leaves. Other caterpillars in the brush-footed butterfly family also feed upon hackberry leaves.

Sugarberry fruit. I have never eaten sugarberries, but I have tasted Georgia hackberries. They are more skin and seed than fruit, and they taste bittersweet. These look fleshier. Native Americans pounded the fruit into pemmican.

The Population of China is Projected to Dramatically Fall before the End of the Century

The population of humans on earth is over 8 billion and growing rapidly. This population explosion of a single species of large vertebrate is probably unsustainable. It is a matter of time before a threshold is reached when an increasing number of humans outstrips the ability of advanced agriculture to feed all of humanity. Most natural resources are also finite. Competition for dwindling resources could cause devastating wars, resulting in the deaths of millions. Pollution and human produced garbage from expanding populations risk turning the whole planet into a toxic waste dump. Humans can either voluntarily choose to reduce their population or the limits of the natural world will do it for them in the form of war, famine, and/or a poisoned atmosphere. China understood this over 40 years ago and instituted the 1 child per family policy. China is a totalitarian society and was able to implement this draconian policy that would be impossible to implement in a free country. From 1980-2016 the Chinese government enforced this policy using heavy fines, forced abortions, and forced sterilizations. It worked. The Chinese government ended this policy when they realized they were facing a dramatic population decline in the future that put at risk their goal of global economic dominance.

China’s 1 child policy enforced from 1980-2016 worked. China’s population is projected to fall dramatically by the end of the century. Graph from the Pew Research Center.

Sexist Chinese parents selected for woman more often than men, and today there are 30 million more men than women in China. Still, women in China are having a hard time finding suitable husbands. Graph also from the Pew Research Center.

Though the population of people on earth needs to decline because of finite resources, China’s policy was draconian. China is an inhumane totalitarian state.

China’s population is projected to begin declining by 2050, if it hasn’t already, and by 2100 they expect their population will be less than 800 million. India is projected to surpass China in number of people next year. During the time the 1 child policy was in effect sexist Chinese parents often chose to abort female fetuses because male heirs were greatly preferred. At first the birth ratio was 112 males born to 100 females born, but between 2002-2008 it was 118 males born to 100 females born. Today, there are 30 million more males in China than females. Yet, women are having a hard time finding suitable mates. The females who were born were given more family resources to put toward education, and they are more career-oriented and don’t need husbands. Women got used to having few or no children, and many like it. They don’t want to have babies. Successful career women can afford to be picky, and in China they really are. The culture has totally changed. I suppose there are many men in China who aren’t getting laid, and porn is heavily restricted there. I’m really glad I don’t live there.

Japan is a free society, but they are also facing a population decline. The Japanese are in general also a sexist people. Career women who become pregnant are expected to quit their jobs and become full-time mothers. Liberated women are choosing careers over motherhood, and the birthrate is declining. The population in Japan is expected to fall below 50 million people by 2100. By 2050 1/3rd of the population there will be over 60, and this will put a strain on the economy. It will be expensive to support that many old people. Elder care will depend heavily upon robots.

Economists hate population declines because they cause economies to shrink. However, people who care about ecology should rejoice. I don’t agree with the methods used by totalitarian China to reduce their population, nor do I condone Japanese sexism, but reducing the human population on earth should be a goal of society. Humanity should work on improving the quality of life for everybody, and that is much easier with fewer people to help. Culture and attitudes need to change. People should know it is ok to have as many kids as they want, but large families should be discouraged. People should also know it is ok, if one decides not to have children at all. There are already enough of us.

What did Entelodonts and Anthracotheres Eat?

Most species of mammals living during the Oligocene (33 million years BP-25 million years BP) left no living descendants, but some were related to ancestors of extant species. Anthracotheres and entelodonts are examples of this evolutionary tree that includes more dead ends than living branches. Anthracotheres and entelodonts were related to each other, but they were also likely related to early whales and the ancestors of hippos. Genetic studies support the vertebrate paleontologists who believe these animals were related to each other. The genetic evidence indicates hippos are the closest living relatives of whales, and the cladistic analysis by scientists is probably correct. Entelodonts and anthracotheres may have been dead ends, but they were successful for a very long time. Their known fossil record stretches from the mid-Eocene about 40 million years ago to the early Miocene about 15 million years ago. Anthracotheres were semi-aquatic and about the size of a juvenile elephant. Entelodonts were not quite as large and lived on land. Entelodonts are also known as “hell pigs,” but scientists no longer think they were closely related to pigs. Some have speculated they were highly carnivorous and rammed their prey, knocking their prey down before tearing them apart with their fearsome teeth. Entelodont teeth have been found in Eocene-aged fossil sites in Georgia. Anthracotheres and entelodonts ranged throughout Eurasia, Africa, and North America.

Anthracotheres were semi-aquatic relatives of enteledonts, hippos, and early whales. A study of tooth wear suggests they ate leaves and fruit.

Enteledonts were related to anthracotheres, hippos, and early whales. A study of tooth wear suggest they were omnivorous like wild boars.

An image of the teeth used in the study. This image is from the below referenced study.

Studies of anthracothere and entelodont diet are contradictory. The latest study of their diet looked at anthracothere and entelodont teeth under a microscope. They compared the microwear on their teeth with the microwear on the teeth of 29 extant species of mammals whose diets are known. Scientists couldn’t determine which species of anthracothere the teeth used in the study came from, but they did identify the entelodont teeth to be from Entelodont magnus. The entelodont and anthracothere teeth came from a fossil site in southwest France. The results of this study suggest anthracotheres were herbivores and ate leaves, grass, and fruit. Probably, much of their forage was aquatic plants. Microwear on entelodont teeth resembled that from extant wild boar, suggesting they ate roots, tubers, plants, and meat. They may have actively hunted or scavenged meat.

Reference:

Rivals, F. ; R. Balyaev, V. Basova, N. Prilepskaya

“Hogs, Hipps, or Bears? Paleodiet of European Oligocene Anthracotheres, and Entelodonts”

Paleogeography, Paleoclimatalogy, Paleoecology 611 Feb 2023

https://www.sciencedirect.com/science/article/pii/S003101822200534X

A Camera Trap Study in the Chernobyl Exclusion Zone

I’ve stated it before and I’ll state it again: the presence of humans is worse for wildlife than radiation contamination. Ever since the Chernobyl nuclear plant suffered a meltdown in 1986, forcing the evacuation of humans from the area, wildlife populations have exploded there. Species of mammals and birds, rare or extirpated elsewhere in Europe, thrive in the Chernobyl Exclusion Zone where people are almost completely absent. Studies show wildlife populations in the Chernobyl Exclusion Zone are even higher than those in protected national parks in the region, and the diversity and abundance of wildlife here exceeds that of most American national parks.

During the 1986 meltdown a dense cloud of radiation struck a 2-3 square mile area, turning the green coniferous trees red, and today it is known as the red forest. 80% of it burned in a wildfire during 2015, and a year later scientists set up 21 camera traps here to study wildlife populations. Over a year the cameras took 45,859 images, and the scientists were able to identify animals in 19,391 of them including 14 species of mammals, 23 species of birds, and even some large insects. The height of the cameras selected for large species, but they did get images of smaller species too.

A 2-3 square mile area of forest near the Chernobyl nuclear plant turned red from radiation contamination. Scientists set up 21 camera traps to record the species of mammals that live here.

This chart is the result of the camera trap study conducted in the Chernobyl red forest. They also recorded some large insects, but that part of the chart wouldn’t fit on this image. From the below referenced study.

Endangered Przewalski’s horses live in the Chernobyl Exclusion Zone. They were recorded from 6 of the 21 camera traps.

Moose were 1 of the more common large mammals found in the camera traps. The red forest is converting to a young deciduous successional forest with the types of plants moose like to eat.

Moose, red deer, roe deer, brown hare, and wolf were photographed by most of the traps. A deciduous undergrowth is replacing the burned and dead coniferous trees. Moose and roe deer prefer to eat this type of plant growth, and this may explain why they are common here. Brown bear, bison, and beaver were not photographed in the study, but this is not surprising because they are uncommon is this part of the Chernobyl Exclusion Zone. For me the most surprising discovery were feral dogs photographed by 6 of the cameras. I thought wolves would have wiped out feral dogs, but apparently, they have found a niche.

A previous study of the red forest area in 2009 found low mammal abundance. This new study contradicts the earlier study. Perhaps animals are finally returning to one of the more contaminated areas. Possibly, the fire improved habitat for them.

Reference:

Beresford, N.; S. Gashek, M. Wood, and C. Barnett

“Mammals in the Chernobyl Exclusion Zone’s Red Forest: A Motion-activated Camera Study”

Earth Syst. Sci. Data 15 911-920 November 2022

https://essd.copernicus.org/articles/15/911/2023/

Some Surprising Hybrids

“Nature is a mad scientist,” said the Kramer character from an old episode of Seinfeld when he discovered his average-sized girlfriend’s parents were little people or midgets as we used to know them. (Midget is too honest a word for modern sensibilities.) The many hybrids that have occurred in captivity is an example of how crazy nature can be. Most of the big cats in the Panthera genus (lions, leopards, tigers, snow leopards, and jaguars) have crossbred in captivity, though most of these hybrids are infertile. A recent genetic study suggests some of these species interbred in the wild during the last 2 million years, and it aided their evolutionary survival. (See: https://markgelbart.wordpress.com/2020/08/13/post-speciation-admixture-in-big-cats/) But surprisingly, there are a few cases on record of cougars mating with leopards and producing viable hybrids. Cougars and leopards are not in the same genus, and they are not closely related, but in a German zoo around 1900 these species did breed. Cougars and leopards are separated by at least 7 million years of evolution, and these cases are hard to believe. In 1 case a male leopard crossed with a female cougar, and in another case a male cougar crossed with a female leopard. A cross between a leopard and a cougar is known as a pumapard. The cubs survived though they were bad-tempered and poorly behaved. They stayed small. There is also a case of a much smaller male ocelot breeding with a female cougar. 4 litters were produced, but all the cubs died due to maternal neglect. The mother even ate 1 of the litters. Some cat breeders don’t want this known, but there is no evidence domestic cats have ever successfully bred with another species other than the European wild cat which is basically the same species.

A cougar and a leopard living in a zoo together produced viable offspring. This is astonishing considering they’ve been separated by at least 7 million years of evolution.

Cubs from a cross between an ocelot and cougar. A female cougar and a male ocelot made at least 4 litters in a zoo. None of the cubs survived because the mother would not take care of them, and on 1 occasion ate them.

Other surprising hybrids have occurred in zoos. A black bear successfully produced offspring with a brown bear. These 2 species are in the same genus, and genetic studies suggest there was some interbreeding between the 2 species during the early Pleistocene. Recently, a black rhino interbred with a white rhino in a South African zoo, and in 1968 a Baird’s tapir interbred with a lowland tapir. An Asian elephant once bred with an African elephant. These 2 species are not in the same genus, and Asian elephants are more closely related to extinct mammoths, than African elephants. Many species of primates will interbreed in captivity. Lemurs will breed with other species of lemurs, macaques with other species of macaques, and baboons with other species of baboons. Male chimpanzees will mate with their more docile relatives–the bonobos. During the early 20th century a Russian scientist experimented with creating a cross between a chimpanzee and a human. Perhaps fortunately, he was killed in a political purge in 1920. The evolutionary ancestors of humans frequently interbred with the evolutionary ancestors of chimpanzees, but this was over 6 million years ago. It would be difficult to cross a human with a chimpanzee today because the human chromosome number 2 is structured like 2 ape chromosomes put together. However, horses and zebras have similar differences, and they have been bred in captivity. It seems like something from the H.G Wells novel The Island of Dr. Moreau, but it is likely a human x chimpanzee hybrid could theoretically be produced.

An Asian elephant mated with an African elephant in a zoo. The hybrid lived for 10 days. Nobody knows why it died.

A few years ago, Hungarian scientists were experimenting with ways to increase egg production for endangered Russian sturgeon. They used American paddlefish (also endangered) eggs as a control in their study. They were shocked when the paddlefish eggs were fertilized with Russian sturgeon sperm. The 2 species diverged 164 million years ago, long before dinosaurs became extinct. They called the hybrid a sturddlefish. They have no plans to sustain the hybrid.

A sturddlefish resulted from the accidental crossing of an American paddlefish and a Russian sturgeon during a scientific experiment in Hungary. This is the most astonishing hybrid of all. These 2 species last shared a common ancestor 164 million years ago.

Reference:

http://messybeast.com/genetics/hybrid-cats.htm

Pleistocene Gray Foxes (Urocyon cinereoargenteus)

Almost every major Pleistocene-aged fossil site in southeastern North America yields specimens of the gray fox. Bones of this species have been found at 58 sites across North America and 22 sites in Florida alone. The gray fox is an extremely successful species and has existed for at least 10 million years, though paleontologists assign the scientific name Urocyon cinereoargenteus just to those individuals that have lived over the past 300,000 years. Its evolutionary ancestors are barely distinguishable from modern day gray foxes. (Scientists are quick to make up new scientific names, so they can claim they discovered a new species.) The Miocene gray fox (U. webbi) grew a little larger than modern day gray foxes. The Pliocene gray fox (U. progressus and U. galushia) are known from just a few specimens and were apparently also slightly larger. The early Pleistocene gray fox (U. citrinus) in Florida anatomically resembled modern western subspecies of gray foxes, while the mid Pleistocene gray fox (U. minicephalus) in Florida resembled modern eastern gray foxes. This is consistent with a genetic study that determined eastern and western gray foxes became isolated from each other for a while 800,000 years ago. Gray foxes prefer wooded habitat, and the eastern and western halves of North America must have been separated by unsuitable arid habitat then. Eastern gray foxes evolved some minor differences during this separation that occurred during the mid-Pleistocene. This same study found northern populations of gray foxes are less diverse, reflecting their recolonization of the region following the retreat of Ice Age ice sheets. Gray foxes are considered the most primitive canid species, and they are not closely related to any other living canids.

Gray fox range map. Western and eastern populations of gray foxes diverged 800,000 years ago, but they are still the same species. The Urocyon genus is at least 10 million years old.

This gray fox entered my yard in October of 2019. They are relatively common in my neighborhood.

Gray foxes are 1 of only 2 species of Canids that can climb trees. This helps them escape larger predators.

Part of the reason for the success of the gray fox is their ability to climb trees, making them capable of escaping larger predators. Of the 35 species of canids, they are 1 of 2 species that can climb trees. (Raccoon dogs, native to east Asia, are the other species that can climb trees.) They are omnivorous–another reason for their success. They can eat a wide variety of foods, including rabbits, rodents, birds, lizards, carrion, fruit, and acorns. At the present time their main predators and competitors are bobcats and coyotes. Studies show gray foxes will live and roam closer to suburban and urban habitats than bobcats or coyotes often will. This also helps them avoid predators. Bobcats and coyotes that kill gray foxes usually will not eat them, showing they are viewed more as competition than food. Gray foxes live in my neighborhood, and I see them on occasion. Once, my wife and I saw a gray fox carrying a squirrel in its mouth in front of our house. Red foxes (Vulpes vulpes) are less common near my vicinity, but I have seen them as well. They prefer more open country in contrast to the gray fox’s favored wooded habitat. Unlike gray foxes, red foxes are a recent immigrant to North America, having crossed the Bering land bridge about 15,000 years ago.

References:

Geffen, E.; A. Mercure, P. Gorman, D. Macdonald, A. Wayne

“Phylogenetic Relationship of the Fox-like Canids: Mitochondrial DNA Restructure Fragment, Site, and Cytochrome B Sequence Analysis”

Journal of Zoology September 1992

Reding, D. et. al.

“Mitochondrial Genomes of the U.S. Distribution of Gray Fox (Urocyon cinereoargenteus) Reveal a Major Phylogeographic Break at the Great Plains Suture Zone”

Frontiers of Ecological Evolution and Population Genetics June 2020

Tedford, R.; X. Wang, and B. Taylor

“Phylogenetic Systematics of the North American Fossil Caninae (Carnivora: Canidae)”

Bulletin of the American Museum of Natural History 325 2009

Some Ecologists Think an Overpopulation of Deer could be Considered a Natural Disturbance

In 1943 Aldo Leopold conceived the notion an overpopulation of deer degraded the natural environment. He was an early expert on wildlife management science, but he was also a biased hunter perhaps seeking an excuse to kill deer. He proposed the extirpations of wolves and cougars meant human hunting was necessary to control deer populations, or they would exceed the carrying capacity of the land. Most modern ecologists still accept his doctrine and assume deer populations are above historical averages, and they believe natural environments should consist of high tree density. A new paper takes an alternative view and proposes an overpopulation of deer or high densities of deer could be considered a natural disturbance that benefits the ecology of the landscape. The authors of this study (referenced below) also take issue with the assumption modern deer populations exceed historical averages. The modern deer population in eastern North America is estimated to be about 21 million, but the authors of this study estimate the historical average was 24 million, although both estimates are guesses. Nobody was surveying deer populations from the time Columbus discovered America through the 19th century. Moreover, colonization of eastern North America by coyotes resulted in an effective replacement for wolves and cougars. Coyotes are more omnivorous and exist in higher numbers than larger predators ever did. And humans can not eliminate them. Megaherbivores were even more abundant during the Pleistocene than they are now or during written history. In addition to deer mammoths, mastodons, ground sloths, horses, bison, llamas, tapirs, and peccaries roamed the land. This suggests that what humans consider environmental degradation by large populations of herbivores should actually be considered a normal natural disturbance.

Map of deer population by state. I wrongly thought the deer population was higher in Pennsylvania than Georgia. This info is 20 years old, and it might not be the same today.

An overpopulation of deer contributes to the development of open woodlands with abundant herbaceous growth. Deer eat saplings thus thinning a forest, but they don’t repress grass and fern growth.

Conventional ecologists believe an overpopulation of deer is detrimental to the environment, but some ecologists now believe it mimics Pleistocene environments, and they think it should be considered a natural disturbance like lightning-ignited fires and windstorms.

The benefits of a higher population of deer include a reduction of the fuel loads thus reducing wildfire intensity, and the maintenance of an open woodland environment. Many species of birds, reptiles, and insects thrive in more open environments. Open woodlands also allow the growth of herbaceous plants. Grass, flowers, and ferns require areas with more sunlight. Reduced competition from other saplings lets surviving trees grow into magnificent specimens with wide spreading limbs that foster higher mast production. Deer help spread seeds in their dung and on their fur. Many species of plants are adapted to having their seeds cling to deer hides (known as endozoochoric).

The authors of the paper acknowledge a high population of deer can have some negative results. Although deer suppress populations of palatable non-native plants such as multiflora rose and bittersweet, unpalatable non-native plants increase with less competition from palatable native plants. Rabbits prefer brushy habitats and may decline when deer suppress dense vegetation. Deer do consume some rare and endangered plants. However, most negative results are economic rather than ecological. High deer populations can destroy farmer’s crops, and they can cause frequent car accidents. I’ve lived in my house for 30 years, and there have been 3 deer-car collisions in front of it, since I moved in. It is in a quiet suburban neighborhood–not even on a busy highway.

Whether or not deer populations degrade the environment is a human conceived construct. Throughout earth’s history, wildlife populations have always fluctuated, sometimes wildly. Large herds of megaherbivores grazing and browsing their way through a landscape should probably be viewed as a natural disturbance like a lightning-ignited fire, a hurricane, a flood, or an ice storm.

Reference:

Hanberry, B; and E. Faison

“Re-framing Deer Herbivory as a Natural Disturbance Regime with Ecological and Socioeconomic Outcomes in the Eastern U.S.

Science of the Total Environment 868 (1) 2023

https://www.fs.usda.gov/rm/pubs_journals/2022/rmrs_2022_hanberry_b009.pdf

The Megafauna Release Hypothesis

The Megafauna Release Hypothesis postulates the extinction of the megafauna at the end of the Pleistocene caused an increase in the populations of species of plants that were preferred food for the megaherbivores, an increase in fire frequency due to the greater fuel load of uneaten vegetation, and the spread of non-analogue forests with no modern floral composition equivalent. Oak trees and maples did increase in abundance after megafauna extinctions because herds of animals were no longer eating acorns and saplings. And the hardwood trees were growing next to spruce trees in strange kinds of forests that no longer exist. A new study (Perotti 2022) attempted to test this hypothesis with new data from 5 sediment cores taken from lake bottoms at 5 sites, and they compared this with existing data from 14 other sites. Scientists took samples of mud from lake bottoms and carbon dated the layers. They analyzed the pollen composition to determine the abundance of various genera of plants, and they looked at the abundance of dung fungus spores used as a proxy for megafauna populations. They also looked at the amount of charcoal to determine fire frequency. With all this data they can get a general idea of the environment during past time periods. The authors of this study found the Megafauna Release Hypothesis held up well in Northeastern and Midwestern North America but did not for Southeastern North America.

Megafauna declined in abundance in the Northeast and Midwest about 14,600 years ago, and by 14,400 years ago there was a marked increase in hardwood tree abundance. However, fire frequency increased slightly before this–a clue humans were on the scene setting fires and overhunting the megafauna. In Southeastern North America the timeline doesn’t support the Megafauna Release Hypothesis. Hardwood trees began increasing about 16,300 years ago, preceding megafauna population decline by 2000 years. I have no doubt the extinction of megafauna had a major impact on floral composition, but I believe climate was a much bigger factor. I think the non-analogue forests in all regions can be explained by rapid climate fluctuations that led to temperate species growing with boreal species.

Graph showing pollen and foraminifera abundance from a core of sediment located off the coast of Georgia. The layers of sediment date from ~130,000 years ago-50,000 years ago. Oak increased during wet warm climate stages. Spruce increased during cold dry climate stages. Pine stayed relatively constant. Graph from the below reference by Huesser and Oppo.

A study of sediment taken from Ocean Drilling Project 1059A covers the period from 130,000 years BP to 50,000 years ago, long before megafauna became extinct. The location of the core is the South Atlantic off the Georgia coast. The time period includes the Sangamonian Interglacial and the first half of the Wisconsinian Ice Age. I wrote about this study in a long blog article about 12 years ago. (See: https://markgelbart.wordpress.com/2011/05/09/ocean-drilling-project-1059a-found-a-treasure-for-paleoecologists/ ) During warm wet climate phases hardwood trees such as oak increased in abundance, while spruce decreased. During cold dry climate cycles spruce increased in abundance, while hardwood trees decreased. Pine abundance stayed relatively stable during all climate phases. Broadleaf trees thrive in atmospheres high in carbon dioxide concentrations with higher precipitation rates, and they outcompete spruce trees under these conditions. Spruce trees are more resistant to the windy and icy conditions that occur during Ice Ages, and they can tolerate lower carbon dioxide levels as exist during a stadial. Transitions between stadial and interstadial likely always fostered transition (non-analogue) forests.

The extinction of megafauna has a big impact on various species of plant and animal abundance. A new study posits the impact was greater in the Midwest and Northeast than in the Southeast. Illustration from the below reference by Gallett et. al.

Landscapes were much richer when megaherbivores roamed the land. Their foraging and trampling created a variety of different habitats. They fertilized the soil and spread seeds with their dung. They provided food for predators, scavengers, and parasites. Their extinction had a major impact on the environment, but it was less than the influence of climate.

References:

Gallett, M.; M. Moleon, P. Jordeno, and J. Suenim

“Ecological and Evolutionary Legacy of Megafauna Extinction”

Biological Reviews October 2007

Huesser, L. and D. Oppo

“Millennial and Orbital Scale Climatic Variability in Southeastern United States during MIS 5: Evidence from Pollen and Isotope in ODP site 1059A”

Earth and Planetary Science Letters 214 (2003)

Perrott, A. et. al.

“Diverse Response of Vegetation and Fire after Pleistocene Megaherbivore Extinction across the Eastern United States”

Quaternary Science Review 294 October 2022

Megafauna Survival in Southeast Asian Landscapes Varies

The presence of humans is detrimental to megafauna survival, and humans are responsible for the extinctions and extirpations of many species across the globe. Furthermore, in regions where megafauna still survives, humans depress their overall populations with hunting and habitat degradation. A new study of megafauna in Southeast Asia analyzes the differences in species survival rates in the presence of human impact. An impressive assemblage of megafauna still survives in the region despite a continuous and growing human presence. Humans have lived in the region for 60,000 years. The region enjoys a rich tropical climate with an abundance of food sources and variety of habitats that support megafauna populations. The authors of the study set up camera traps at many sites in Thailand, Malasia, Singapore, and parts of Indonesia. They recorded the abundance of 14 species including tiger, leopard, clouded leopard, dhole, sun bear, sambar deer, Malay tapir, Sumatran rhinoceros, Asian elephant, wild boar, bearded pig, mainland serow (a species of tropical goat), and banteng and guar–2 species of wild cattle. Wild boar was the most common species and was found at 65% of the sites. Sumatran rhinos were the least common species and were not found at all. The study considers Sumatran rhinos to be functionally extinct. Banteng and guar were among the less common species as well. People like to eat their beef. No 2 sites had identical species assemblages demonstrating the varied response of megafauna to human presence.

Megafauna populations decline or are extirpated in regions where they suffer from human hunting and habitat degradation. Some megafauna species in southeast Asia follow this trend, but others defy it. The reasons for this disparity are complex and poorly understood. Chart from the below reference.

Chart showing body size and whether a species was herbivore or carnivore didn’t matter in the frequency of extirpations at different sites in Southeast Asia. Charts also from the below study.

The authors of the study note 74 extirpations of megafauna that formerly ranged throughout the region. 58 extirpations occurred during the Holocene from 11,700 years ago to 1950. 16 extirpations have occurred in the region during the Anthropocene (since 1950). (Scientists don’t agree among themselves about when the Anthropocene began. The Anthropocene is regarded as the time when humans became the dominant force in earth’s environment. Some scientists think it should be considered as beginning in 1611, while others believe 1950 should be the starting date. Still others think the Anthropocene began 50,000 years ago. This study goes by the 1950 date.) They found no pattern for megafauna survival or failure to survive. Size didn’t matter nor did whether or not they were a carnivore or herbivore. Some species actually favored areas where habitat was degraded. Wild boars thrive near human habitations. They benefit from foraging on farmer’s crops, and the local Muslims won’t hunt them because they don’t eat pork. Asian elephants, tigers, and clouded leopards were also common in degraded habitats. However, the most disturbed sites had 2.5 times more extirpations than the least disturbed sites. There is some good news: as long as anti-poaching regulations are enforced, megafauna can survive near human settlements. Unfortunately, large, protected parks in remote areas are hard to patrol, and megafauna can become extirpated in areas that otherwise offer excellent habitat.

Reference:

Amir, Z.; J. Moore, P. Negret, and M. Irvin

“Megafauna Extinctions Produce Idiosyncratic Anthropocene Assemblage”

Science Advances 8 (42) Oct 2022

https://www.science.org/doi/10.1126/sciadv.abq2307

Snowy Winters and Dry Summers Prevailed in Southwestern North America during the Late Pleistocene

Ice Age climates spawned dramatically altered weather patterns compared to those of the present day. The result of those different weather patterns is evident in how changed Southwestern North America has become since then. During Ice Ages Southwestern North America was a land of vast lakes, abundant springs, and widespread wetlands. There even was a lake in Death Valley, California where it almost never rains today. There were especially large lakes in Utah, Nevada, and central Oregon–areas that today are quite arid. Scientists debate the source of the greater precipitation that occurred then. Some think the source was summer rains coming from fronts originating in the tropics, while most believe the polar jet stream carried moisture from the North Pacific that fell as heavy snows during winter. A new study of carbon and oxygen isotope ratios in tooth enamel from Pleistocene mammals supports the latter scenario.

Scientists analyzed 39 teeth from mammoth, bison, horse, and camel excavated from the Tule Spring Fossil Bed National Monument in Nevada. They can determine how precipitation was delivered based on the ratios of carbon and oxygen isotopes in the teeth because the animals ate the plants that absorbed the water, and the animals directly drank it. Most of the precipitation in the region came from heavy snows, and the lakes refilled every spring and early summer from snow melt. They believe summers were relatively dry, and lakes began to evaporate until seasonal snowfall. Mammoths, bison, and horses ate a lot of the fresh grass that grew tall on water from snowmelt. Horses may have eaten more grass here during Ice Ages than they do today. But camels browsed on saltbush (Atriplex sp.). The presence of this species indicates dry summers and arid localities within the lush landscape. Scientists think glaciers to the north of the region split the polar jet stream, and the lower stream carried moisture from the North Pacific, causing winter precipitation. Lake levels were highest during the Last Glacial Maximum following Heinrich Events that occurred when ice dams melted, and massive pulses of freshwater studded with ice bergs flooded into the oceans. Moisture in earth’s atmosphere increased following Heinrich events.

Map of Southwestern North America during the Late Pleistocene. Meltwater from much snowier winters caused the formation of giant lakes in the region then. From the below reference by Munroe and Laabs.

Beth Zaiken’s depiction of wildlife in Nevada during the last Ice Age. Vegetation was much lusher than it is today due to higher annual precipitation.

When glaciers retreated at the end of the Ice Age, the polar jet stream recombined and began to flow to the north. Winter snowfall was greatly reduced, and the lakes gradually evaporated. The Great Salt Lake of Utah is a remnant of a much larger freshwater lake that existed during Ice Ages.

The abundant wetlands and lakes of the region hosted many species of birds that today breed in the Arctic during summer. These species could not live in the Arctic during the Ice Ages because their present-day ranges were under miles of glacial ice. Their breeding ranges shifted to the Southwest. See also:

Ice Age Western Lakes and Altered Bird Migrations

References:

Kohn, M. et. al.

“Seasonality of Precipitation in the Southwestern U.S. during the Late Pleistocene Inferred from Stable Isotopes in Herbivore Tooth Enamel”

Quaternary Science Review 290 November 2022

Munroe, J.; and B. Laabs

“Temporal Correspondence Between Pluvial Lake High Stands in Southwestern U.S. and Heinrich Event 1”

Journal of Quaternary Science 28 (11) 2013