CLASS ONE - human impact on the enviroment

Holocene Epoch

The current geological time period that began after the last major ice age, approximately 11,700 years ago

Early Holocene

Had relatively low human population size and density; people lived in small, often nomadic communities

Early Holocene Animal Extinctions

The early stages of extinction of megafauna such as woolly mammoths, potentially caused by hunting and/or climate change

Early Agriculture

The beginning of humans intentionally changing and selecting plant genes to produce plants that grew more abundantly or tasted better

Geological Time Period

A chapter in Earth’s history marked by major changes in Earth’s rocks and fossils

Anthropocene

A proposed geological epoch defined by significant human dominance and impact on Earth’s environment and geology

Paul Crutzen

A Nobel Laureate who made the Anthropocene concept famous in the early 2000s by arguing that human environmental impacts were significant enough to justify a new geological epoch

Anthropocene Working Group

A group of geologists, paleontologists, and other scientists created in 2009 to investigate whether the Anthropocene should be recognized

Crawford Lake

A lake near Milton, Ontario, that became important evidence in the study of the Anthropocene because its sediments contain markers of significant human activity

Crawford Lake Geological Markers

Markers such as microplastics, radioactive materials, metals, and industrial pollutants found in lake sediments

Crawford Lake Sediments

Because the upper and lower layers of Crawford Lake do not regularly mix, materials that fall into the lake can become preserved in layers of sediment

Meromictic Lake

A lake whose upper and lower water layers do not regularly mix

Crawford Lake as a Time Capsule

The lake’s sediment preserves evidence of human environmental impacts over time

Agricultural Revolution

An approximately 12,000–15,000-year-old transition toward agriculture that allowed human populations to grow beyond what the environment could naturally support

Carrying Capacity

The maximum population size that an environment can naturally support with its available resources

Human Impact on Carrying Capacity

Humans became the first animal species to significantly change the carrying capacity of their environment

Industrial Revolution

A period of major technological and industrial change that introduced machines, automation, and major changes to living conditions

Industrial Revolution and Population Growth

Improved sanitation and medical care, including vaccines and antibiotics, reduced death rates and contributed to population growth

Industrial Revolution and Carrying Capacity

Human technology and improved living conditions increased the carrying capacity of the planet

Anthropocene Rejection

The International Union of Geological Sciences did not formally recognize the Anthropocene as a new geological epoch

Reasons Against the Anthropocene

Arguments included insufficient time having passed, a lack of clearly noticeable extinctions or geological changes, and evidence that some proposed markers began earlier than the proposed Anthropocene boundary

Anthropocene Takeaway

Humans have made a very significant impact on Earth’s environment even though the Anthropocene was not formally established as a new geological epoch

Rachel Carson (1907–1964)

Environmental and science writer credited with helping launch the modern environmental movement

Rachel Carson in the 1950s

She wrote about science and the environment and was skilled at translating complex scientific information into accessible writing

The Sea Around Us

A book by Rachel Carson about the oceans

Silent Spring

A groundbreaking Rachel Carson book that examined the environmental and human impacts of DDT and other pesticides

DDT

A synthetic pesticide widely used during and after World War II to control insects and disease-carrying mosquitoes

DDT Wartime Use

DDT was scaled up during wartime for disease control, particularly to protect soldiers from diseases such as malaria

Postwar DDT Use

After World War II, DDT production increased and it was widely used for residential pest control, mosquitoes, tent caterpillars, and spongy moths

Spongy Moths

Invasive insects that consume large amounts of foliage and can severely damage or kill trees

Tent Caterpillars

Native North American insects that consume vegetation and were considered a nuisance, although generally less destructive than spongy moths

DDT Environmental Concerns

DDT could affect non-target organisms and could enter water systems and soil, potentially affecting ecosystems, crops, wildlife, and humans

DDT and Dead Birds

An increase in dead birds raised concerns about DDT and helped bring environmental issues to Rachel Carson’s attention

Silent Spring Research

Rachel Carson conducted approximately four years of research, gathering scientific papers and data about the effects of DDT

Silent Spring’s Importance

Carson brought scientific concerns about DDT to public attention and helped expose major human and environmental effects

Problems with DDT

Persistence, toxicity, transport, resistance, bioaccumulation, and biomagnification

Persistence

The ability of a chemical such as DDT to remain in the environment for a long period of time

Toxicity

The ability of a substance to cause harm to living organisms

Transport

The ability of pollutants to move through air or water to areas where they were not originally intended to go

Resistance

The ability of organisms to survive exposure to a chemical; similar to antibiotic resistance

Bioaccumulation

The gradual buildup of a substance such as DDT inside a single organism over time

Bioaccumulation Example

An organism living in a contaminated environment can accumulate increasing amounts of a toxin throughout its lifetime

Biomagnification

The increasing concentration of toxic substances as they move up through the food chain

Bioaccumulation vs. Biomagnification

Bioaccumulation occurs within one organism over time, while biomagnification refers to increasing concentrations across higher levels of the food chain

Biomagnification and Apex Predators

Top predators can accumulate high concentrations of pollutants because they consume many contaminated prey

DDT and Bald Eagles

DDT exposure contributed to reproductive problems in bald eagles, including eggshell thinning

DDT and Peregrine Falcons

DDT exposure contributed to reproductive problems and population declines in peregrine falcons

DDT and Bird Eggs

Scientists found that DDT exposure caused eggshells to become abnormally thin and fragile, reducing successful reproduction

Non-Target Species

The organisms unintentionally affected by pesticides, such as birds affected by DDT

DDT Ban in the United States

DDT was banned in the United States in 1972

Bald Eagle Recovery

Recovery efforts included banning DDT, protecting habitats, conservation programs, captive breeding, and reintroduction

Bald and Golden Eagle Protection Act

A law protecting bald and golden eagles

Endangered Species Act (1973)

A law that provides protection for endangered and threatened species and their habitats

Eagle Conservation

Conservationists restored and protected bald eagle nesting and feeding habitats and used captive breeding and reintroduction programs

Industry Response to Rachel Carson

Some industries used aggressive public relations campaigns to discredit Carson and question her scientific credibility

Sexism and Rachel Carson

Carson faced criticism and attacks on her scientific credibility that were influenced in part by the sexism of the 1950s

Scientists and Policymakers

There was debate over the role of environmentalists and scientists in influencing public policy

Rachel Carson’s Contributions

She increased public awareness, helped form the modern environmental movement, contributed to pesticide regulation and bans, and helped create momentum for the EPA

EPA

The Environmental Protection Agency, established in the United States in 1970 to protect human health and the environment

Environmental Movement

The organized effort to increase awareness and take action to protect the natural environment

Rachel Carson Quote

“In nature nothing exists alone.”

DDT Legacy

The DDT controversy demonstrated how human actions can affect ecosystems and non-target species and helped inspire stronger environmental protections