S and J Curves for Growth Rate

S-curves and J-curves

• S-curves
• Start with exponential growth
• Above a certain population size, the growth rate slows down until population stabilizes
• Consistent with density dependent limiting factors
• Population size stabilizes at the carrying capacity (K) of the environment
• The area between the exponential growth curve and the S.curve is called environmental resistance

• J-curve
• Shows a boom and bust pattern
• Population grows exponentially then crashes
• These collapses/crashes are called diebacks
• Population often exceeds K before the collapse occurs which is referred to as overshoot

Growth Rates

• S and J curves are idealized
• In nature both types of limiting factors act on the same population and the result is an S/J combo curve
• The growth rate of the human population is slowing as we reach the K of our environment
• Peaked at 2.1% per year in 1965-1970
• Now: 1.3% and falling
• Back in the day world population was increasing slowly due to environmental resistance, diseases, epidemics, famine, and natural catastrophes
• MEDCs and LEDCs
• Countries are also economically classified based in the industrial development or GDP
• MEDCs
• are industrialized nations with high GDPs
• Relatively rich population and starvation is unlikely
• High Level of resource use per capita
• Relatively low population growth rate
• LEDCs
• are less industrialized or have none at all
• May have plenty of natural capital but usually this is exported and processed in MEDCs
• Lower GDP and high poverty rates
• Large population sector with low standard of living
• High population growth rates