I watched the video and afterwards had something of a realization. I was disagreeing with MonteQuest earlier (
here) about whether human population growth was currently exponential because of the shape of the population growth curve over the past couple of decades. Over this period, world population growth has dropped from about 87.5 million per year to about 73 million per year. In the past couple years the raw number of people added to the population has risen slightly, but only a little bit. This gives the appearance of linearity, more or less.
http://www.census.gov/ipc/www/worldpop.html
Now here's the important point and it's actually a rather sophisticated one. As long as there are more people, year after year, the human population is growing by a certain
rate. The reason for this is that every year there are more people to have more babies. Each family has a certain number of children. In aggregate this means that as long as population is growing, the number of children added to the population each year is dependent on the number of people that already exist.
We look at populations as having a birth rate and a death rate. If the birth rate is higher than the death rate, then the population is growing at a certain rate. Growth at a certain rate is by definition exponential. More people can have more babies: therefore, the same birth rate and death rate with more people means exponential growth.
I recently attended a screening of
The End of Suburbia, followed by a panel discussion with Richard Heinberg and some officials involved in San Francisco local government. It was quite obvious from the comments made by the local goverment panelists that they did not understand the implications of exponential growth. As Dr. Bartlett said, officials in government from the local to the national level fail to understand the exponential function.