GeorgiaBeforePeople

I’ve been writing this blog for 14 years, and since its inception, the advances in the technology to extract information from minute paleo-ecological data have become amazing. Recently, scientists took 41 sediment cores from 5 sites at the Kap Kobenhavn Site in Greenland. This site has been a polar desert for almost 2 million years due to the aridity and frigid temperatures. Remains of the last forest that grew here can still be found, indicating climate change with the onset of Pleistocene Ice Ages was sudden. Sub-fossil tree stumps and limbs from trees including spruce, birch, poplar, and northern white cedar are exposed wherever erosion occurs, and they are millions of years old. The dry cold temperatures retard bacterial decay. Scientists were able to extract DNA from the sediment cores, and to date, this is the oldest DNA ever recovered. They were able to find DNA from many of the plants and animals that lived here almost 2 million years ago. This supplements the sub-fossil remains that have been found including bones from an extinct species of rabbit (which helped date the site), rabbit turds, and dung beetle parts. The site is thought to have been near an estuary 2 million years ago.

Photo of an ancient tree limb from the Kap Kobenhavn site. Today, it is a polar desert, but 2 million years ago it was a thriving ecosystem with a type of open spruce woodlands that no longer exists.

DNA degrades over time, and the scientists who studied the data from this site were able to reconstruct the past environment here from just fragments of DNA that they pieced together. It was like a gigantic jigsaw puzzle. 2 million years ago, this location was an open boreal woodland with no modern analogue. The past plant community was dominated by spruce, poplar, birch, willow, and northern white cedar with an understory of grasses, sedges, forbs, and shrubs including blueberry (now rare in Greenland). Scientists found DNA from mastodon, caribou, hare, rodent, goose, ant, and horseshoe crab. This is the northernmost known occurrence of mastodons, though mastodon fossils have been found in Alaska and the Yukon which are about the same latitude as Greenland. Mastodons lived this far north during warmer phases of climate but became extirpated at this latitude during Ice Ages. Scientists suspect the fauna here was even more diverse than what the evidence suggests, but much of the DNA is so degraded it is unrecognizable.

Chart from the below reference showing the kinds of plants that occurred in Greenland 2 million years ago.

Chart from the below reference showing the kinds of animals that lived here 2 million years ago.

The site dates to the boundary between the Pliocene and the early Pleistocene. Scientists dated the site using a combination of paleomagnetism, biostratigraphy, allostratigraphy, and the molecular clock. Here is a brief explanation of each. Dating using paleomagnetism is based on the orientation of associated magnetic pebbles which change orientation when polarity between the south and north poles shift. These shifts occurred at known pre-historic times. Scientists can determine the relative age of the associated fossils or DNA by looking at the orientation of the associated magnetic pebbles. Biostratigraphy is the use of index fossils to date the age of other fossils. Scientists have a general idea of when certain species lived, if those fossils have been found in regions where they can be dated radiometrically. Radiometric dating is not possible in all regions because it requires the presence of volcanic rock or younger biological organisms. However, the relative age dates of fossils in areas where radiometric dating is not possible can be bracketed. Allostratigraphy is the use of geological disconformities between phases of erosion and sedimentation to date fossils. And finally, the molecular clock is the use of the known rate of mutational changes in DNA to estimate the age of fossil specimens.

Reference:

Kjaer, K.; et al

“A 2 Million Year Old Ecosystem in Greenland Uncovered by Environmental DNA”

Nature 612 283-291 2022

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9729109/#:~:text=Analysis%20of%20two-million-year-old%20ancient%20environmental%20DNA%20from%20the,representing%20an%20ecosystem%20that%20has%20no%20present-day%20analogue.

Scientists recently published a study of the floral composition of the Great Dismal Swamp over the past 13,500 years. The Great Dismal Swamp is about 154 square miles in extent and is located on the border between North Carolina and Virginia. Most of it is a protected National Wildlife Refuge. The scientists took sediment cores from 7 different sites in the swamp. They analyzed the pollen composition and charcoal content (indicative of fire frequency), and they carbon dated the layers. From 13,500 years ago to 10,300 years ago the region was dominated by a cold temperate forest consisting of oak, hickory, pine, spruce, fir, alder, birch, and hemlock.

Alder became particularly abundant during the Younger Dryas cold reversal that sent average annual temperatures plummeting following the Boling-Alerod warm climate phase. The Boling-Alerod warm climate phase is considered the beginning of the end of the last Ice Age. Alder forms shrubby thickets alongside streams, and it was likely good habitat for beavers. Curiously, there was an unusual increase in the abundance of alder at a site in south Georgia near Warner Robins during the Younger Dryas. Conditions for this species must have been just right during this climate phase. Perhaps, receding wetlands caused by lower precipitation left behind moist soils that alder could quickly colonize. Hemlock increased in abundance about 12,000 years ago when northern temperate forests still prevailed here for the most part.

Map of the Great Dismal Swamp and the current distribution of vegetation types. From the below referenced study.

Pollen composition graph over the past 13,500 years from the Great Dismal Swamp. Also, from the below referenced study.

Between 10,000 years ago to 9000 years ago, sea level rose and correspondingly the water table rose. Widespread grassy marshes began to develop with peat and floating mats of aquatic vegetation. Fire frequency increased 7000 years ago, further favoring the spread of grassy marshes.

3900 years ago, fire frequency decreased and forested swamps replaced the grassy meadows. Tupelo, cypress, and Atlantic white cedar (a disjunct species) dominated the wetlands until the colonial era when Europeans attempted to drain the swamp with ditches and began to clear cut the forest. Before the arrival of Europeans Indians lived on the outskirts of the swamp, but later they moved to the interior and lived as refugees alongside escaped slaves.

The actions of man have greatly changed the character of the swamp. Following heavy logging early during the 20th century, a fire raged for 3 years from 1923-1926. Today, the Great Dismal Swamp hosts a forest dominated by red maple, sweetgum, tupelo, and pond pine. The latter species grows in pine pocosins–a type of drier wetland with sandy peat soils and shrubby thickets. White cedar requires stable water tables and frequent fires and is now less common than before European colonization.

Pine pocosin. This type of environment has become more common in the Great Dismal Swamp since man’s efforts to drain it.

Atlantic white cedar has become less common in the swamp due to man’s activities.

Note: The scientists who wrote this study assume jack pine grew in the region during the late Pleistocene based on their belief that a cold adapted species would occur here. However, as I’ve mentioned in a previous blog article, jack pine pollen can’t be distinguished from shortleaf pine pollen, and I hypothesize shortleaf pine (a species found in the region today and as far north as Ohio) is geographically more likely to be the species that occurred here then.

Reference:

Willard, D., et al.

“Roles of Climatic and Anthropogenic Factors in Shaping Holocene Vegetation and Fire Regimes in Great Dismal Swamp, USA”

Quaternary Science Reviews July 2023

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/

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