human impacts

the environment is a phenomenon and system that is constantly interacting in terms of the biological part - living organisms - with the non biotic - non living.

biologic: soil, plants animals

non biotic: climate, geology, water

culture: belief systems, social/economic system, political organization, and personal attitudes.

human ecology: the study of the interactions among human biology, culture, and the environment

human biological ecology: adaptation through biological means - melanin production in sunlight, increased heart rate in high altitude or cold environments, immunity response to disease.

cultural ecology: adaptations through cultural means

plasticity: flexibility of an individual/grooup to adjust to changing conditions

what is culture: dynamic system of learned and shared behaviors, concepts, symbols, and beliefs that facilitates and provide meaning to a human’s interaction with their environment.

responses to environment:

technology - often first and most direct response to change, prior technology influences future choices.

Environmental Utopias:

Agrarianism:

• stewardship and sustainability practices

• ecological and socially harmonious interaction

• resistance of commercialism and industrialism

• “back to land”

Guha Critiques:

• static conception of the environment, assumes a timeless, unchanging relationship with nature, ignoring the realities of exploitation and population pressures

• idealization: romanticizes traditional agrarian societies, overlooking the fact that they were not always ecologically sustainable or free from environmental hard

Wilderness Thinking:

• american conception

• protect and expand national parks

• reduction of human population

• primitivism: hunter-gatherer

Guha Critiques:

• ignores indigenous habitation fails to recognize the longstanding human presence and management of lands by indigenous communities, treating wilderness as untouched

• execution of local communities: often leads to the forcible displacement of local populations in the name of conservation without considering their rights or needs

Scientific Industrialism:

• future oriented

• resource use

• research based state control, supported by policy and activist state

• scientific forestry

Guha Critiques:

• disregards social and ecological costs: prioritizes rapid industrialization without considering the environmental degradation and social inequalities it produces

• need based relationship with the environment: treats nature primarily as a resource to be exploited for economic gain, neglecting a sustainable, reciprocal relationship with the environment.

Modern Animals Extinction or Critical Threats to Animals

International union for conservation of nature 2024 “red list”

• 166,061 species (plants, animals, fungi) evaluated, 46,337 (28%) are threatened/endangered

• large number (2413 species (5%) of theses species are extinct or presumed extinct

Factors that endanger animals:

• habitat loss (deforestation, urban/industrial development, pollution, agricultural land)

• over hunting/harvesting (illegal trade, overfishing)

• introduction of invasive species (especially in Australia)

• anthropogenic climate change (temperature, precipitation)

Key Anthropogenic factors:

• large human populations

• overconsumption

• technology

• socioeconomic systems (capitalism)

Key Variables for Risk of Extinction:

1. body size - large-bodied animals are more at risk for extinction due to susceptibility to over hunting and fishing

2. range size - animals living in small areas are more at risk for extinction due to habitat change, species can only exist in a specific environment

Key Question about animal extinctions:

• is extinction an inevitable outcome of human interactions with animals?

• how important are these biological (body size) and human (habitat change) factors in causing earlier extinctions?

• is modern (industrialized) society unique in its threat to wildlife?

FIrst Case Studies: What Caused Major Extinctions?

• 121 genera of large Ice Age mammals in Africa, NA, SA, Asia, and Europe

• 8,000 mammal, bird, and reptile Pacific Island species

Importance of Case Studies

• Major extinction events (on scale of modern changes)

• Neither occurred with complex, large, urbanized, industrialized society.

First Case Study: The Ice Age

• By end of the Pleistocene (-13 KYA), 121 species from dozens of genera of large land mammals (>44kg, megafauna) when extinct across the globe after surviving multiple prior glacial-interglacial transitions

• Timing of extinction is generally correlated with the appearance of the first widespread appearance of fully modern humans

Global Extinctions:

• Major extinctions in other continents (Africa 160ky, Australia 72-44 ky, Europe 50-14 kya)

• Contemporary with N.A. - South America and Asia

Unusual Characteristics of North American Extinctions:

Pleistocene differs from 7 previous extinction events over last 10 my

• number of extinct species (more species than normals)

• types of animals that went extinct (only large bodied) - most living species are small, large animals went extinct at much higher rate than small, different than earlier extinctions

• speed of extinction (fast)

• appearance of new predator (humans)

How to Explain Extinctions - Key Theories (Imperfect)

1. human hunting (overkill) - human colonization of islands often followed large extinctions (people = extinction), clovis people were first wide-spread human across North America (13,300 yrs ago), clovis were very effective hunters of large herbivores late pleistocene extinct happened - 13,300 BP, the extinction occured so quickly that few kill sites would likely be preserved, “blitzkrieg” (lightning strike) extinction

2. climate change and resulting habitat collapse

Other Explanations:

3. extraterrestrial impact

4. hyperdisease

5. solar radiation

6. keystone species collapse

7. anthropogenic wildfire

Individual: impacts her own health

Microsystem: impacts surrounding community, pesticide runoff into the water, individuals who are chronically impacted may be unable to go to work or school

Local Government: EPA regulations of what pesticides can be used, one of the 2025 updates includes a recommendation that corn farmers follow a three-year extended rotation to reduce nitrate‐N concentration

Mass Media: Raising public awareness about potential health risks associated with pesticide exposure

Social Norms: Growing public knowledge about potential health risks associated with pesticide exposure, particularly for farmers and nearby residents, contributes to a social norm of minimizing pesticide use.

Economic System: affect

Environmental Impacts of food and agriculture:

• 26% of greenhouse gas emissions come from food

• 50% of the world’s habitable land is used for agriculture

• 70% of global freshwater withdrawals are used for agriculture

• 78% of global ocean and freshwater pollution

• 96% of global mammal biomass is livestock

• 71% fo global bird biomass is poultry livestock.

Key Issues: Is modern agriculture unique? Did earlier versions of farming change people and their environment?

Major Transformative Events: Tool Use (-3 mya), Agriculture (16,000-2000 ya), Urbanization and State Formation (6,000-3,000 ya), Industrialization (350 ya)

Lifestyle Shift 99.95% of our genus (homo sp.) history occurred as hunter-gatherers, domesticates only in last - 16,000 years (domesticate: an animal or plant adapted to have an intimate association with humans)

Types of interactions with plants and animals:

• simple foraging: collecting available wild resources without modification to environment

• management: increase yield of wild resources by encouraging growth and reducing competitors (clear cutting vegetation, replanting, irrigating).

• horticulture: growing domesticated fruit, plants, and vegetables in small gardens (small-scale farming)

• agriculture: producing food, feed, fiber, fuel, and other goods by systematic raising of domesticated plants and animals (large scale farming)

Mutualism: relationship in which both species derive benefit

Intensification of production: increase in the productive output per units of. land or labor

Low Intensification of Plant Production:

• type is management of wild species, 1 to 3 years cropping duration, 20 to 25 years fallow duration, technology is simple (ex. axe, fire, sticks), labor needs are limited (land clearing, bruning, dispersal of seeds)

Medium Intensification of Plant Production:

• type is horticulture, 2 to 8 year cropping duration, 6 to 10 year fallow duration, technology is simple (ace, hire, hoe, household storage), labor needs are moderate (land clearing, application of simple additives like manure, redirect surface runoff, planting and weeding)

High Intensification of Plant Production:

• type is agriculture, continuous cropping duration, months to two year fallow duration, technology is complex (plough, animal traction, communal storage, terraces, canals), labor needs are heavy (land clearing, systematic planting and weeding, intensive additives like manure, constructing canals, terraces, storage facilities).

How does domestication happen?

• artificial selection: human intervention in animal/plant breeding creating an animals they could live with

• self selection: animals/plants develop close relationships with humans on their own

Biological and Physical Changes Resulting from Domestication

• allows species to better adapt to anthropogenic (human created) environments.

• increases separation from wild populations (both in space and genetically)

• appearance of some specific phenotypic changes (observable difference to body)

Primary (first) changes in animal domesticates:

• decreased reaction to stimuli

  • decreased brain size (10%-30%) and complexity and less developed sensory organs (ears, nose, and eyes)

• decreased activity and aggression levels

  • more serotonin, less adrenaline and corticosteroids, and less developed heart, adrenal and thyroid glands

• increased fertility

  • earlier sexual maturity, larger litters sizes, reduced seasonality of reproduction

Secondary (later) changes in animal domesticates

• coloration and physiology

  • fur coloration (multi-color coats) and texture

  • shortening of snout (overbite and underbite)

  • changing limb or extremity proportions (tails and ears) and body size

  • reduced dimorphism between sexes

  • changes in reproductive organs (milk)

Primary changes in plant domesticates:

• improved success in germination

  • higher rates of and predictability for gemiation

  • uniform timing of germination and ripening

  • change in life cycle (seed: perennial to annual; vegetables; annuals to biennial)

• changes in structure of edible reproductive parts

  • increased size of reproductive organs (seeds, fruit, roots, etc)

  • lower toxicity (less self defense)

  • greater energy allocation to edible parts (more fruits, roots, stems)

Example:

Wild Corn (Teosinte)

• small and few kernels

• seeds drop easily (shattering)

• germinate and ripen at different rates

Domesticated Corn (Maize)

• large and many kernels

• seeds do not drop

• uniform germination and ripening.

How quick can domesticates appear?

• experiments in selective breeding (selecting for tamest or specific sex ratio)

  • dmitri belyaev - soviet fox farm project (1959 to present)

Three Pathways to domestications (Melinda Zeder 2006)

1. Commensal domesticates (self-domesticated): species adapt to lives with humans,

   ex. dogs, cats, pigs, chicken, turkey

2. Prey domesticates (artificial domestications): humans manage limited food, ex. goat, sheep, cattle, llama, reindeer

3. Directed domesticates (artificial domestications): humans select species for second dary resources (food and nonfood).

Farming (potential benefits)

• increase productivity for unit of land

  • possibly create surplus

  • feed more people

• control location of important resources

• non food benefits:

  • fiber, labor, donsiments, narcotics, ornamnetations/containers

• food that is easily consumable and digestible by weaning children.