Global Environmental & Human Health Issues Molly Kile, ScD ENVRE-115 Fall 2009
Announcements • More featuresadded to the course website http://isites.harvard.edu/icb/icb.do?keyword=k64179&pageid=icb.page286023 • Assessment of class participation will depend on in-class participation, live chat sessions, blog entries, and personal communications with teaching staff • For book report can select texts from “Additional Books To Consider” in syllabus or one of your own choosing if given instructor approval. • Pedagogical goal of assignmentsis to foster critical thinking which involves comparing, contrasting and synthesizing what one has learned which requires being open to new knowledge and actively reflecting on its meaning. • Homework #2 is due September 22 • Use the drop box to submit your assignments. If you emailed in your assignment you should go back and put it in the drop box.
Logistics of Distance Education • Lecture is available as a live streaming feed during class period and are also archived after processing (< 48 hrs) • Chat room is monitored during class • If you live outside of the New England areayou must arrange for proctored midterm and final exam a minimum of two weeks prior to scheduled exam dates • http://www.extension.harvard.edu/2009-10/DistanceEd/how-it-works/policy.jsp
Economic Literacy • There is no formal (only suggested) economics prerequisite for this course • Check your economic literacy and review concepts by taking the “Economic Literacy Self Assessment” on the course website. You should be familiar with these terms and concepts before the lecture on October 13. • If you need or want to review economic terminology you can use any undergraduate economics textbook or the “Guidelines for Preparing Economic Analyses” by the US EPA. • http://yosemite.epa.gov/ee/epa/eed.nsf/webpages/Guidelines.html
Agenda For Today • Drivers of environmental issues • Underlying Ecological Principles • Demographic and Epidemiological Transition • Linkage between human health and development • Demographic dividend
Ecological Footprint Results Question 5If everyone lived like you, how many planets would we need? • 1 • 2 • 3 • 4 • 5 • 6 • more than 6 This means it takes 36 more months for the Earth’s ecosystems to regenerate what we are using in a single year.
Global Human FootprintAs of 2003, exceeded the Earth’s biocapacity by ~25% (WWF) For how long can this go on? • Humanity’s demand will be twice the biosphere’s productive capacity in 2050 • A moderate business-as-usual scenario, based on United Nations projections of slow, steady growth of economies and populations
POPULATION DRIVER In the past 200 years, the global population has increased exponentially
Math Behind Exponential Growth Consider a country with 100 people, growing at 7% per year. In 10 years, the population will double to 200 people, in another 10 years it will double again to 400 people, etc (see graph) How long will it take this country to reach 1 million? t = ln [N(t)/N(0)] / r t = ln (1,000,000/100)/0.07 t = ln (10,000)/0.07 t = 9.2103/0.07 t = 131.5 years
Doubling Time (The Rule of 70) • The basic differential equation for exponential growth: dN/dt = rN, over the period from t=0 to t = the time period in question, where N is the quantity growing and r is the growth rate • The integral of this equation is Nt = N0 x ert where N(t) is the size of a quantity after t intervals have elapsed, N(0) is the initial value of the quantity, e is the base of the natural logarithm, r is the average growth rate over the interval in question, and t is the number of intervals • If one knows the final and initial values of N and the average growth rate, one can find the time it takes at that average growth rate for the quantity to grow from its initial value to the final value t = ln [ N(t)/N(0) ] / r • A special case is the doubling time, which is the time when N(t)/N(0) = 2. At that point rt = ln 2 = 0.69. If one knows the growth rate as a decimal fraction, then the Doubling Time = 0.69 / r. • This can be further simplified…the Rule of 70 If the growth rate is given in percent, then 0.69 must be multiplied by 100, and the doubling time = 69/r. This can then be rounded up to 70. This simplifies to: Amount of time for population to double = 70/rate expressed as a percentage
Doubling Time Examples 1. How long would it take for a population to double if the growth rate is 3.5%? Time = 70/3.5 = 20 years
Doubling Time 2. In a country where the GDP is growing at 4.5% per annum and the population is growing at 1.0 % per annum, how long will it take for the per capita GDP to double? Doubling time = 70/(4.5%-1% ) = 70/3.5 = 20 years 3. In 1971, global population was 3.8 million and it is currently 6.8 million. What was the global population growth rate during this time frame? Time= 70/rate(%) 36 years = 70/rate rate = 70/36 rate= 1.9%
AFFLUENCE & TECHNOLOGY DRIVERS Global Income Distribution
Global distribution of income by economic class Source: Sutcliffe, 2005. Department of Economic and Social Affairs.WP 2. United Nations
Consumer Preferences • Increasing wealth changes pattern of demand and ability to afford reducing externalities • Kuznets curve illustrates the relationship between economic development and environmental degradation
Economics & Environmental Degradation (Kuznet’s Curve) Relationship between air pollution problems in cities and the level of development. As a city experiences development, the air pollution problems in the city increase rapidly, before stabilizing and declining as air pollution controls are implemented (Source: Based on Haq et al, 2002; Peters 2003)
Ehrlich Identity: I=PAT • Environmental Impact is a multiplicative product from small changes in Population, Affluence and Technology • Mathematically represented as: (I + ΔI) = (P + ΔP)(A + ΔA)(T + ΔT) Divide through by the identity (1 + ΔI/I) = (1 + ΔP/P)(1 + ΔA/A)(1 + ΔT/T) Where ΔI/I, ΔP/P, and ΔT/T is the percentage increase in impact, affluence and technology
Quantifying Impact • Example: Lead in gasoline from 1946 to 1968 in the US • Pop. increased 42% • Vehicle mile per capita doubled • Amount of lead per vehicle mile increased 81% (I + ΔI/I) = (P + ΔP/P)(A + ΔA/A)(T + ΔT/T) (1 + ΔI/I) = (1 + 0.42)(1 + 1.0)(1 + 0.81) (1 + ΔI/I) = 5.14 ΔI/I = 5.14 – 1 =4.14 Or 414% increase in lead
Population Impact Depends on Underlying Distribution 6.0 million Mentally Gifted 6.0 million Mentally Deficient
Population Impact of Subclinical Lead Toxicity 57% Increase in Mentally Deficient Population 2.4 million Mentally Gifted 9.4 million Mentally Deficient
Carrying Capacity Ecological definition: the number of individuals in a population that the resource of a habitat can support Other definitions: Point at which the birth rate equals the death rate The number of individuals an environment can support without significant negative impacts The population size is constrained by whatever resource is in shortest supply (Malthus)
Tragedy of the [Unregulated] CommonsGarrett Hardin “Picture a pasture open to all. It is to be expected that each herdsman will try to keep as many cattle as possible on the commons. Such an arrangement may work reasonably satisfactorily for centuries because tribal wars, poaching, and disease keep the numbers of both man and beast well below the carrying capacity of the land.” What are the consequences of adding one more animal to my herd? • “The population problem has no technical solution; it requires a fundamental extension in morality.” Science 1968
Overshoot • A rapidly growing population can exceed (overshoot) the ecological carrying capacity due to the “momentum” of its growth. • Indicators of Overshoot • Deterioration in renewable resources • Rising levels of pollution • Growing demands by military and industry to secure resources • Investment in human capital postponed to meet immediate consumption demands • Rising debt • Eroding goals for health and environment • Growing instability in natural ecosystems • Growing gap between rich and poor
Ecological Evidence In 1944, 29 reindeer were introduced to St. Matthew Island. In 1963, there were 6,000. One winter later, there were less than 50. By 1980, there were none. Klein, 1968
Human Population Growth Factors that influence human population growth: • Fertility • Age structure of population • Mortality
Fertility • Birth rate is defined as the number of live births per 1,000 women aged 15-49 in a given year • Replacement level fertility • Net reproduction rate of 1 • Every woman of childbearing age has 1 daughter • Total fertility rate of 2.1 • Every woman of childbearing age has 2.1 children
Fertility Rates Are Declining Average number of children per woman Source: United Nations, World Population Prospects: The 2004 Revision, 2005.
Four factors that influence fertility • The proportion of women of childbearing age who are married or in a sexual union • The percent of women using contraception and the level of abortion • The proportion of women of childbearing age who currently are unable to conceive a child (usually from postpartum infecundity from breastfeeding) • Educational attainment of girls and women
Association Between Fertility and Education of Girls Percent of Girls Enrolled in Secondary School Total Fertility Rate Source: Population Reference Bureau, Population & Economic Development Linkages 2007 Data Sheet.
Association Between Fertility and Female Labor Force Participation Female Labor Force Participation Rate 2004 Total Fertility Rate 2000-2004 Source: United Nations, World Population Prospects: The 2004 Revision, 2005; International Labor Organization, Yearbook of Labor Statistics 2006.
Association between fertility and wealth Average Number of Children Born to a Woman During Her Lifetime Source: ORC Macro, Demographic and Health Surveys.
2. Age Structure of a Population • A large proportion of young people guarantees that population will continue to grow even with declining fertility • Takes two or three generations (70-100 years) before each new birth is offset by a death • Referred to as population momentum
Population MomentumThere is a growing population of women in their childbearing years that will contribute to future world population growth even if fertility continues to decline Source: United Nations, World Population Prospects: The 2004 Revision (medium scenario), 2005.
Population growth rate Birth rate 3. Mortality • Death is the ultimate determinant of population growth • Falling mortality precedes a decline in fertility Rate Death rate Time
How To Shift Causes of Mortality • Improved sanitation and drinking water supplies • Medical advances (vaccination, antibiotics) • Social advances (improved nutrition, access to health care) • Occupational Health & Safety (injury prevention, chemical safety) • Infrastructure Improvements (roadways, housing, energy) • Consumer Safety (injury prevention, chemical safety) • Economic growth
Epidemiological Transitionthe study of factors affecting the health and illness of populations Systematic Shift in Disease Non-communicable diseases Mortality Rates Infectious diseases • Conceptually describes the interaction between causes of mortality, life expectancy and development Epidemiological Transition
Systematic Shift In Disease Mortality Rates Infectious diseases Socio-Economic Development Type 2 Diabetes CHD Cancers Trauma
Premise • Fertility has a fixed upper limit but not mortality so mortality is the fundamental factor that controls population dynamics • Diseases and injuries control mortality • Investment in public health shifts the causes of death (Epidemiological Transition) and this will influence population structure where women and children benefit the most • During the late phase of the demographic transition when fertility and dependency rates fall countries can harness the demographic dividend when output per capita rises
Stages in Epidemiological Transition • The Age of Pestilence and Famine • Mortality is high and fluctuating no sustained population growth • Life expectancy between 20-40 years • The Age of Receding Pandemics • Epidemics less frequent high population growth • Life expectancy between 30-50 years • The Age of Degenerative and Man-Made diseases • Mortality declines and stabilizes at a low level fertility rate determines population growth • Life expectancy exceeds 50 years
Influence of Municipal Water on Mortality Sewer system built & expanded Reservoir/Aqueduct expansions Protected watersheds
Public Health Benefits From Municipal Water Supply US from 1900-1940 Cholera and Typhoid Fever eliminated Total mortality 140 to 20 per 100,000 Child mortality 130 to 60 per 1,000 live births Life expectancy 16 years Cost-benefit analysis conducted by Cutler & Miller, 2005 1:23 cost-benefit ratio Every life saved cost $500* resulting in $11,500 gain * 2002 US$
Morbidity and mortality associated with level of development http://www.nytimes.com/2007/11/26/nyregion/26manhole.html