J-curve – shows more than exponential growth

To calculate doubling rates, use the rule of 70… 70 / annual growth rate (2.1% in 1960’s) = number of years for the population to double Ex. 70/2.1 = 33.3 years 70/2.8=25 years

A map of population growth rates from Population is growing fastest in tropical regions and in some desert and rainforest areas that have been sparsely populated.

Is population growth a problem? Increased growth from technological innovations, improved sanitation, better medical care, increased agricultural output (less death, especially infant mortality) Birth rates have not declined, so the overall population is growing. This is a good sign for the health of our world, so long that resources can keep up and the quality of life remains the same (less space, less food, less material wealth). Increase in political, economic, and military strength

Population affects the environment by more than just the number of people… I=PxAxT (xS) Human’s total impact=population x affluence x technology (x sensitivity) Population: space, use of natural resources, waste Affluence: greater per capita resource consumption that accompanies enhanced wealth Technology: ability to exploit minerals, fossil fuels, forests, fisheries increase impact, reduction of emissions, alternative energy sources decrease impact Sensitivity: how sensitive is the environment ALL IN RELATIVE TERMS, NOT NUMBERS

Carrying capacity No organism, including humans, can grow indefinitely. Different environments have different carrying capacities.

As resources are depleted, global food production and industrial output falls, leading to a drop in population after 2030

Demography The science of human population – population size, density, distribution, age structure, sex ratio, rate of birth, death, immigration, emigration. Helps predict population dynamics and human impact

Population size Over 7 billion people Number of individuals isn’t as important as the environmental impact based on density, distribution, composition, affluence, technology, etc. China, 1.3 billion, Fiji, 1 million

Population Density and Distribution

Density is high in areas with temperate, sub-tropical and tropical climates Low in areas of extreme-climate biomes like deserts, rainforests and tundra Dense along coasts and rivers, less dense inland Dense in cities and suburbs, less dense in rural areas HUMANS ARE CLUMPED!

Age Structure Helps predict the future of a population All else being equal, where would you expect to see a larger and more rapid population increase – on a desert island populated entirely by senior citizens or one populated entirely be college freshmen?

Red = post-reproductive ageCanada-stable population Yellow=reproductive ageMadagascar-growing population Green=pre-reproductive age Canada has many more people, but a smaller annual growth rate, whereas Madagascar has a smaller population but larger annual growth rate.