ENV 1050 Unit 5
Projecting global population
-Human population continues to increase -(r) has declined over last few decades _1960 (r) = 2.2% annual increase _2010 (r) = 1.2% annual increase -Global average of number of children born to each woman is 2.5 -The United Nations published low, medium, and high world population projections to 2050
What is the Earth's K and have we surpassed it
-K estimates range from 4 billion to 16 billion -Why such a range? What factors affect K? _Differences in fertility rate _Resource consumption _Technological innovations _Waste generation _Overall lifestyle
carrying capacity (K)
-K is the largest population a particular environment can support long term if there are no changes in that environment -K changes in response to environmental change -At K, (r) is near zero as population size levels off -Gause's classic experiment with Paramecium showed initial exponential growth levels out as population approaches K
Sustainable Food Production and Environmental Tradeoff
-Optimists suggest decrease in (b) will stabilize human population -Others predict widespread environmental degradation _Large areas of rainforest, such as this one in Brazil, are being cleared for cattle ranching
projecting the world's ten largest cities in 2025
8 of the 10 largest cities will be in developing countries
five recommendations for sustainable living
•Lester R. Brown, 2006. Plan B 2.0 Recusing a Planet Under Stress and a Civilization in Trouble - Eliminate poverty and stabilize human population - Protect and restore Earth's resources - Provide adequate food for all people - Mitigate climate change - Design sustainable cities
movement and fat of toxicants
•Some toxicants are particularly dangerous - Resist degradation - Travel quickly in the Movement and Fate of Toxicants environment •DDT - A pesticide banned in the US in 1972 - Causes birds to lay eggs with thin shells - Persistence, bioaccumulation
what is a "developed country" or a "developing country" based on?
-Population growth rates -Degree of industrialization -Relative prosperity _GNI PPP: gross national income in purchasing power parity _When divided by population, GNI in PPP indicates the amount of goods and services an average citizen of that particular country could buy in the US _Average GNI PPP in the US is $45,640 _Worldwide average GGNI PPP is $10,240
Global human population
-The more highly developed countries become the lower K -Note regional differences in population growth and density
India's population pressures
-World's second most populous nation (after China) - Government-sponsored family planning, economic development and adult literacy programs -Population pressure has caused environmental degradation -76% live under poverty level (less than $2 /day)
exponential population growth
-accelerated population growth occurs when optimal conditions allow a population to reproduce at a constant rate -j-shaped growth curve -the larger a population gets, the faster it grows
sustainable consumption
-affluent lifestyle leads to using more resources, which in turn leads to pollution and environmental degradation -balance between improving quality of life while reducing resource consumption -voluntary simplicity: quality of life ≠ amount of material goods
maximum population growth
-biotic potential: maximum rate of increase under ideal conditions and affected by factors Called life history characteristics -life history characteristics _age at first reproduction _reproductive fraction of life span _number of reproductive periods/events _number of offspring per reproductive event -large organisms (whales, elephants) have lesser biotic potentials -small organisms (microorganisms) have greater biotic potentials
sustainable development
-economic growth meets the needs of the present without compromising the ability of future generations to meet their needs -can only occur within the limits of the environment -cannot sustain everyone at the levels of consumption in highly developed countries such as the US, Europe, and Japan
environmental resistance: the environment controls population size
-environment resistance _limits placed on exponential growth _availability of food, water, shelter and other resources -results in increase in competition, predation and disease -eventually (b) declines and (d) increases
Advances in global health result in decrease in (d)
-greater food production -better and more accessible medical care -improved water quality -improved sanitation
Human population patterns
-how does human population growth compare to other species? -Thomas Malthus' 1798 Essay on the Principle of Population -Growth due to a decrease in (d)- why? What factors affect (d)?
human population change and the environment
-india's population pressures -population ecology -human population patterns -demographics of countries -stabilizing world population -population and urbanization
Age structure
-number and proportion of people at each age in a population -helps predict future population growth
Population crash
-populations rarely stabilize at K but instead temporarily rise above and drop below, hovering around K -Some populations that overshoot K can crash, an abrupt decline from high to low population density as resources are exhausted -1935 reindeer population crash
population growth is a recent event- some notes
1. Until the invention of agriculture 10,000 years ago, the human population was a few million people. 2. Populations were held in check by diseases, famine and war. 3. Early societies regulated their population through cultural taboos, abstinence and infanticide. 4. Human population began to increase rapidly after 1600 due to agricultural developments, better sources of power, and better health care and hygiene
the worldwide shift from rural to urban areas
1950-2030 in 2008, a significant milestone was reached as, beginning that year over 50% of the world's population now lives in urban areas
net gain of _____ persons per second
2.3 persons
design sustainable cities
50% of world's people live in cities and 80% live in cities in US Making cities more livable -Urban transportation -Build city around people, not cars -Reduce CO2 emissions -Recycle treated waste- water -Improvement of squatter settlements
urbanization trends
51% of world's pop live in urban areas -400 cities have more than 1 million people -75% of the population in highly developed countries are urban -46% of the population in developing countries are urban megacities are cities with moe than 10 million inhabitants urban agglomerations are urbanized core regions which consist of adjacent cities or megacities and their surrounding developing suburbs (i.e. the agglomeration in Japan)
global population will double in __ years if conditions remain unchanged
62
Contraceptive use strongly linked to Lower TFR
90% of the decrease in TFR in 31 developing countries linked to information and availability of contraceptives in highly developed countries, 72% of married women of reproductive age use contraceptives
demographics of countries
Demographics is the applied branch of sociology that deals with population statistics Infant mortality rate: number of deaths under age 1 per 1,000 live births -2012 US rate was 6.1 and the world rate was 44 Replacement-level fertility: number of children a couple must produce to 'replace' themselves -Estimated at 2.1 to compensate for not reaching reproductive age Total fertility rate: average number of children born to each woman -Global TFR is 2.5, above replacement level (was 6.1 in 1970!) -TFR in Brazil in 1970 was 6.7, above global rate. Today it is 1.9! The population in many developing countries is approaching stabilization Although fertility rates in several countries have declined, many still exceed replacement-level fertility
environmental justice
Every citizen has the right to adequate protection from environmental hazards - Low-income communities/minorities are more likely to be in polluted areas, and near landfills, toxic waste facilities, etc. - Tend to have lower access to health care - Rights of the poor and disenfranchised vs. the rights of rich and powerful • The right of every citizen to protection from environmental hazards • Eco-justice - Links social and environmental ethics - Low income communities are more likely to have chemical plants and hazardous facilities • Higher exposure to environmental pollutants • Less access to health care
how do populations change in size over time?
Global scale growth rate (r) = (b) - (d) (b) = birth rate (d) = death rate Local scale growth rate (r) = (b - d) + (i - e) (i) = immigration (e) = emigration
stabilizing world population
In parts of Latin America, men do the agricultural work. This Argentinian man is harvesting grapes. In sub-Saharan Africa, women do most of the agricultural work in addition to caring for their children. Photographed in South Africa.
population growth rates
Increasing population r > 0 (d < b) Decreasing population r < 0 (d > b) Stable population r = 0 (d = b)
exponential growth
It took thousands of years to reach 1 billion people (in 1804). It took 150 years to double that to 3 billion (in 1960). The increase from 5-6 billion took only 12 years. Another way to look at it, is that the Earth's population tripled in the twentieth century.
ecosystem services
Organisms and the natural environment provide ecosystem services we need to survive - Food, medicine, energy, building, clothing materials, recreation - Protection of watersheds, agricultural lands, climate, habitats • Biological diversity and cultural diversity intertwined • Different languages, traditions and identities enrich the human experience • Indigenous cultures, such as the Yanomami, are threatened
population ecology
Population -Individuals of a particular species living in a defined area Population ecology -Branch of biology that studies individuals in a defined area -Concerned with how and why population increases or decreases over time as a result of competition, disease and predation
four steps for risk assessment
Risk assessment: quantitative and qualitative characterization of risks in order to manage - Hazard identification • Can exposure have adverse health effects? - Dose-response assessment • What is the relationship between the amount and the response? - Exposure assessment • How often are individuals exposed? - Risk characterization • Leads to risk management • How do these DDT blood levels compare? Why are Mexican American blood levels higher?
meeting challenges of a fast-growing city
Systems such as water purification, sewage treatment, education and adequate housing must keep pace with the influx of people from rural areas Although cities offer more job opportunities than rural areas, fast paced urban growth in developing nations has overwhelmed their economic growth Poverty, unemployment, violence, environmental degradation and nonexistent waste disposal are issues in fast growing developing cities
the demographic transition
There are four demographic stages that show how a population progresses as its society becomes industrialized -Stage 1: Preindustrial -Stage 2: Transitional -Stage 3: Industrial -Stage 4: Postindustrial Demographic transition is the process whereby a country moves from high (b) and (d) to low (b) and (d)
worldviews: a closer look
Western worldview - Based on human superiority over nature - Unrestricted use of natural resources - Consistent with frontier attitude Deep ecology worldview - Based on harmony with and respect for nature - All living things have equal worth - Arne Naess, Bill Devall, George Sessions
stabilizing world population: how does culture affect TFR?
a couple is expected to have the number of children traditional in their society High TFR are traditional in many cultures to offset infant mortality rates High TFR are traditional in some developing countries as children work, contributing to the family's livelihood -in 2008, 176 million children between the ages of 5 and 14 worked full time, usually in hazardous jobs and at the expense of an education -they also tend to provide support for aging parents
urban planning in curitiba
a. Curitiba's bus network, arranged like the spokes of a wheel, has concentrated development along the bus lines, saving much of the surrounding countryside from development. b. The downtown area of Curitiba has open terraces lined with shops and restaurants.
Environmental Problems of Urban Areas
brownfields - areas of abandoned, vacant factories or residential sites that are contaminated from past uses -contaminants must be cleaned before redevelopment urban sprawl -subrubs expand around to a city, encroaching onto natural areas and farmland because development is spread out in the suburbs, having an automobile is a necessity to accomplish chores high density of commercial enterprises in urban areas causes buildup of airborne emissions cities affect water low because rainfall-absorbing soil is paved and built in urban runoff sometimes remains untreated -contributes to air pollution, water pollution, environmental and health problems -urban areas in developing nations have the worst air pollution in the world
TFR in highly developed countries
children have less value as a source of labor so children are able to attend school highly developed countries provide social services for the elderly, decreasing the reliance on offspring to carry for aging parents as seen in figure 7.16, the carpet industry in Pakistan commonly utilizes child labor
cities are urban ecosystems
city populations have far greater heterogeneity than rural ares younger age structure than rural areas resources flow into and out of the city
culture and fertility
culture -the values and norms of a society -what is considered right from wrong -what is expected of a person -language, beliefs and spirituality Gender roles -varying roles men and women are expected to fill -different societies have different gender expectations some cultures place higher value on male children and women with many sons achieve a higher status, leading to a higher TFR women who don't follow any religion have the lowest TFRs as compared to those who do follow a religion
economists often disagree with ecologists, arguing that
economic and technological growth will enable us to solve these problems
4 or 5 children are born while only 2 people die.
every second
case study: urban planning in curitiba, Brazil
example of compact development home to 3.1 million efficient mass transit system and traffic management -two million people use curitiba's mass transportation system daily instead of vehicular traffic, the center is a big sidewalk that consists of 49 blocks of pedestrian walkway connected to bus stations, parks, and bike paths first city to use low-polluting fuel that burns cleanly -fuel contains soybeans and grains that are purchase from rural areas providing economic benefits labor intensive garbage purchase program -poor people exchange garbage for bus tokens, food and school notebooks
population growth momentum
explains how a population's present age distribution affects future growth
current world population
greater than 7 billion and growing at 1.4% per year
moderately developed countries
have higher (b) and higher infant mortality rates than developed countries
less developed countries
have shortest life expectancies, highest (b) and highest infant mortality rates
highly developed countries
have the lowest (b), lowest infant mortality rates
family planning services
health and family planning services have lowered TFRs in developing countries increased availability of prenatal care have lowered TFR information on contraceptive use and access to contraceptives have lowered TFR
age structure diagrams
illustrate the number of males and females at each age, from birth to death -left side of an age structure diagram represents males in the population and the right side, the females -the bottom third represents pre-reproductive humans, middle third are the reproductive humans ad the top third are post-reproductive humans -width proportional to population sizes *Shown are countries with rapid growth, slow growth and a declining population
stabilizing world population
in the U.S., it is not uncommon for a woman to give birth to her first child In her 30's or 40's, after establishing a career smaller family size is associated with increased family income
social justice advocates argue that the root cause of he problem is...
inequitable distribution of the earth's resources
Social and Economic Status of Women
most societies have gender inequality -women have fewer rights, opportunities and privileges -women have lower political, social and economical status -more women than men live in poverty
microcredit programs
programs that extend loans of $50-500 establish businesses targets women as 70% of the world's poorest are women -providing mothers with means of self-employment is believed to alleviate effect of poverty and hunger on children
ecologists are concerned that overpopulation will cause environmental degradation that will threaten...
the ecological life-support systems on which we depend
gender discrimination
the percentage of women in developing countries is higher than men 90 million girls worldwide aren't given the opportunity to receive an elementary school education -as a result, women occupy unskilled, low-paying jobs a woman's age at marriage and education affect TFR
population and urbanization
urbanization -movement of people from rural areas to densely populated cities -approximately 79% of people in U.S. lives in cities -rural occupations include fishing, logging and farming -urban occupations are not connected directly with natural resources
environmental benefits of urbanization
well planned cities reduce pollution and preserve rural areas compact development: cities in which tall, multiple-unit residential buildings are close to shopping, jobs, and public transportation (i.e. Portland, Oregon) -efficient land use -motor vehicle pollution reduced -more people walk, cycle or take public transportation -requires fewer parking lots and highways- more open spaces
education and fertility
women who marry are more likely to bear children the earlier a woman marries, the more children she is likely to have correlation with higher education and lower TFR -women with more education marry later and have fewer children
Environmental changes and emerging disease
• 25% of injury and disease is related to human-caused environmental changes • Climate change gives disease- causing agents the opportunity to thrive • Cutting forests, building dams and agriculture may bring us into contact with disease- causing agents and increasing populations of disease-carrying organisms such as mosquitoes
embracing deep ecology worldview
• All forms of life are equal • Humanshavean obligation to all other organisms • We are connected with nature • Need to curb human population growth • Requiresrethinkingofour current technologies
risk assessment of chemical mixtures
• Although humans are exposed to combinations of chemical compounds in air, food and water, most studies are done on single chemicals - Mixtures of chemicals increase level of complexity in risk assessment - Too many chemical mixtures to evaluate - Chemical mixtures interact by one of three ways: additivity, synergy, or antagonism • Additivity: the additive effect of each component of the mixture - Additivity is generally used in order to asses the risk for chemical mixtures • Synergy: the mixture has a greater combined effect than the chemicals individually • Antagonistic: mixture has a smaller combined effect than the chemicals individually
people and livestock in close proximity
• Avian influenza difficult to transfer from human to human, more common bird to human • Swine flu transferred from pigs, 2009 Mexico outbreak • Children in rural China live and play near livestock - Pigs and chickens share enough genetic similarities to facilitate disease transfer
cancer-causing substances
• Carcinogens are any substance that causes cancer • Most common method of determining cancer-causing agent is to expose groups of laboratory animals to various doses and count how many animals develop cancer - Indirect and uncertain - Humans and laboratory animals may respond differently to chemical exposure - Laboratory animals generally exposed to massive doses relative to their body size - Risk assessment assumes we can extrapolate from these experiments, determining expected cancer rates in humans and the safety of some chemicals—assumptions that may over or underestimate a toxicant's danger • EPA working with toxicologists to develop direct evidence of risk involved with exposure to low doses of cancer-causing chemicals
children and chemical exposure
• Children are more susceptible than adults - Weigh less than adults - Interact more with their environment - Undergoing growth and development - Higher metabolic rate, requires more oxygen (increased susceptibility to air pollution)
an example of high risk: Lung Cancer
• Data suggests that smoking is on the decline among younger people, although the poor and some minority groups have disproportionally high smoking rates • The graph in figure 4.3b shows the percentage of US students (grades 9-12) who smoked cigarettes on at least 1 or 2 of the past 30 days • In what year did smoking peak among males? Females?
intrinsic and instrumental values
• Deep ecology worldview - Organisms have intrinsic value - Value not based on goods and services they provide - Biocentric • Westernworldview - Organisms are valued for their utility, how useful they are to people - Anthropocentric
determining health effects of pollutants
• Different doses of chemical administered to populations of laboratory animals • Data findings used to predict effects on humans • The dose that is lethal to 50% of a population of test animals is called the LD50 • The smaller the LD50 , the more toxic the chemical • The dose at which 50% of a population will exhibit the response under study (ED50) • Threshold level - The maximum dose at which the toxicant has no measurable effect - Doses lower than threshold level are considered safe • This scientist is measuring a toxicant in human blood serum
dose-response curve
• Dose-response curve - A graph that shows the effects of different doses on a population of test organisms - Evidence suggests that there is not a safe dose for certain toxicants
social factors contribute to disease epidemics
• Drainage ditches on each side of this road clearing in the Amazon rain forest are a breeding ground for mosquito larvae • Global travel has contributed to the rapid spread of disease over great distances • Highly concentrated urban populations promote rapid spread of disease among large numbers of people • Diseases carried by animals - Malaria and West Nile Virus spread by mosquitoes - Lyme disease spread by deer ticks - Bubonic plague spread by rats and fleas • Pandemic - Disease reaches nearly every part of the world and can infect almost everyone
mitigate climate change
• Enhanced green house effect - Additional warming produced by increased levels of gases that absorb infrared radiation - Human-induced - Majority of warming is since 1975 - Shifted precipitation patterns • Needcomprehensiveenergy plan to stabilize the climate - Cut carbon emissions - Phase out fossil fuels - Improving energy efficiency
worldview: personal perspective based on values
• Environmental worldview - Help us make sense of the world and determine right from wrong behaviors - Not necessarily compatible with environmental sustainability - Based on how the environment works and our place in it - Western and deep ecology worldviews are two opposite and extreme environmental worldviews
human values and environmental problems
• Ethics is the branch of philosophy that deals with human values and morality • Environmental ethics considers the moral basis of environmental responsibility - Considers the rights of people living today AND of future generations - Critical because our actions today affect the environment in the future - What is our role in determining the fate of our resources?
protect and restore earth's resources
• Forests - Unsustainable logging making them a non- renewable resource • Biodiversity is the number and variety of organisms - 5/6 of all species have yet to be described - 80% species we depend on are found in developing countries
food volatility since 2002
• From 1975 until the end of the last century, global food prices were mostly in decline • Beginning in 2002, food prices have been increasing and less predictable - Food price index adjusted for inflation • What sort of relationship does this graph suggest between prices of food and energy at that time?
eliminate poverty and stabilize human population
• Global distribution of resources is uneven - US 5% of world's pop controls 25% of resources - 24,000 infants and children die each day - Raising the standard of living of the world's poor • Universal education of children • Eliminate illiteracy • Improving the status of women • Stay within the Earth's carrying capacity
case study: endocrine disrupters
• Many industrial and agricultural chemicals are endocrine disrupters • Some disrupters mimic hormones • Can cause reproductive disorders, infertility, and hormonally-related cancers • Congress amended Food Quality Protection Act and Safe Drinking Water Act of 1996 - EPA to develop plan to establish testing for potential endocrine disruptors • Lake Apopka, Florida, alligators have abnormalities in their reproductive systems
pesticides and children
• More harmful to children than adults - Greater exposure • Playing in contaminated fields • Putting hands/objects in mouth - Greater response • Developing bodies more sensitive • Range of effects - Cancer, mental and/or physical disabilities • Intelligence • Motor skills
Disease-causing agents in the environment
• Pathogen:disease-causinginfectiousorganism - Viruses, bacteria, protozoa, parasitic worms - Typhoid, cholera, bacterial dysentery, polio • Transmissible through contaminated food and water, and considered environmental health hazards • Sewage-contaminatedwater - Environmental threat to public health - Periodic testing of drinking water supplies - Fecal coliform test • Tests water for coliform bacteria such as E.coli - 1993 U.S. outbreak of Cryptosporidium - 2000 waterborne E. coli outbreak in Canada - 2009 cholera outbreak in Zimbabwe and 2010 in Haiti
a curious dilemma
• People are more concerned about small risks than large risks - Large risk: complications associated with obesity and smoking - Small risk: EPA permitted amounts of chemicals in water - Average life expectancy is reduced by 8 years for smokers and 1/3 of smokers die from related-illness - The red area of the right lung in figure 4.3a indicates cancer • Why the difference in concern? - Habit and culture (vs. analysis) - Perceptionofrisks - Trust in institutions - Feeling that some risks cannot be controlled
environmental insight
• Persistence - Stable and takes years to break down • Bioaccumulation - Chemical stored in organisms with higher concentrations found at the top of the food chain • Biological magnification - Increased concentration as toxicant passes through levels of the food chain - Note how the level of DDT increased in the tissues of various organisms as DDT moved through the food chain
voluntary simplicity
• Requires behavioral change • Commitment at the individual level • Values and character define a person, not what they own • Includes car-sharing and using public transportation • Technological advances can help promote the acceptance of voluntary simplicity, such as compact florescent light bulbs and LEDs
perspective on risks
• Risk - The probability of harm (human or environmental) occurring under certain circumstances - Inherent in our actions and our environment - Risk management is the process of identifying, assessing, and reducing risks - Note the 2011 data for lifetime probability of death by selected causes in the U.S.
case study: Loess Plateau in China
• Semiarid plateau suffered centuries of deforestation and overgrazing - Turned into nonproductive desert • In the past - Fertile agricultural soil - Important resource for China • Hope for the future - Loess Plateau Watershed Rehabilitation Project was established in 1994
envirodiscovery: smoking: a significant risk
• Single largest cause of preventable death • Causes serious diseases - Lung cancer, emphysema, heart disease, premature death • Passive smoking also increases risk of cancer • Fewer in developed nations smoke and public bans working • Smoking is increasing in developing nations • 2005 international treaty to ban tobacco advertising worldwide
global ban of persistent organic pollutants
• Stockholm Convention on Persistent Organic Pollutants, 2001 - UN treaty to protect human health from the 12 most toxic persistent organic pollutants (POPs) - Requires countries to develop plans to eliminate the production and use of intentionally produced POPs • Exception: DDT still used to control malaria mosquitoes • The mosquito net in the accompanying image was treated with DDT
the precautionary principle
• The idea that we should not adopt a new technology, practice, or material until it is demonstrated that: - The risks are small - The benefits outweigh the risks • Puts the burden of proof onto the developers • "An ounce of prevention is worth a pound of cure"
the precautionary principle: common sense
• There is also controversy - Scientists feel it endorses the making of decisions without the input of science • The EU (European Union) banned beef from U.S. and Canada because of the use of hormones to make cattle grow faster • The EU uses precautionary principle with respect to GMOs (genetically modified organisms) • Precautionary principle or economic protectionism?
Cascading Responses of Increased Carbon Dioxide Through the Environment
• There is not a cause-and-effect relationship between an increase in atmospheric CO2 and climate warming - Instead it is a cascade of interactions in the environment • Increasing CO2 may cause a cascade of interaction responses throughout global systems • This example shows ocean acidity is lowered, coral bleaching increases, changes in ocean food webs and increased extinctions may occur • Terrestrial system are also affected as changes in precipitation and warming cause tundra to melt, changes in plant communities, and changes in food webs • Where do human activities fit into this diagram?
environmental working group
• Thiswatch-dog organization analyzed five common herbicides found in drinking water • 3.5 million people in the Midwest have elevated cancer risk due to exposure to herbicides • EPAhasmandateda reduction in the use of those herbicides
Environmental health hazards
• Toxicants - Chemicals with adverse effects on health - All chemicals are toxic if exposure is high enough • Toxicology - Studies the effects of toxicants on living organisms - Evaluates the mechanisms that cause toxicity - Develops ways to prevent or minimize adverse effects • Handling and exposure guidelines • Epidemiology - The study of how toxicants, biological agents (disease), and physical agents (accidents, radiation) affect the health of human populations - Studies large groups of people and investigates range of causes and types of disease and injuries - Toxicant exposure can be acute or chronic • Acute toxicity - Immediate effects after a single short period, high- level exposure - Symptoms include dizziness, nausea, death • Chronic toxicity - Prolonged effects to long-term, low-level exposure - Symptoms can mimic other chronic disease - We know much less about chronic toxicity • Pandemic - Disease reaches nearly all parts of the world • Influenza (flu) • Avian influenza affects birds and then infects humans - Hard to transmit to humans, but once infected, human mortality is high • H1N1 (Swine) Flu - Late Spring 2009, Mexico - Pandemic by early Summer - Understanding and controlling pandemics requires: • Understanding of the environment and conditions that allow the virus to survive and travel • Cooperation among many governments and individuals
mobility of pesticides in the environment
• Toxicants can move through soil, water, air •Agricultural pesticides run off into rivers and streams, harming aquatic life - Adverse effects on aquatic plants and animals • Bonedegeneration in fishes • Toxicantsidentifiedin drinking water, 1994
determining health effects of pollutants
• Toxicity determined by the dose that produced adverse effects • Dose - The amount of a toxicant that enters the body •Response - Type and amount of damage to a particular dose - Lethal dose: causes death - Sub-lethal dose: causes harm
Thomas Malthus
•(1798) An Essay on the Principle of Population showed that human populations increase exponentially. •Population growth is checked by famine, disease, and cultural factors (e.g. late marriage). •Debate about whether human population growth causes environmental degradation (Malthus) or whether human population growth results from poverty and resource depletion (Karl Marx).
provide adequate food for all people
•Food insecurity - Lack of access to food needed to live healthy, productive lives - 800 million people worldwide live in chronic hunger and malnutrition - Mostly rural areas, developing countries Improved agriculture is the highest priority for global sustainability - Multicropping - Conservation tillage - Aquaculture