Page #49
Thanksgiving Day 2010
Carson City, Nevada
MA’s Study
MA: Settling into her big chair - Thanks for stoking the fire it is getting cold outside. But it is beautiful don't you think?
Q: Oh MA it is like something out of a photograph. Have you owned this house long?
MA: Most of my life.
Q: I feel a bit like the “potted plant” in this interview, you have been so forthcoming that I seem reduced to just listening. However do please go on. Ma do we have to get into math?
MA: Well let's just see.
Would you agree that we are indeed in a human population explosion?
Q: Seems clear to me.
MA: Then there are only two outcomes available. When we speak of population explosions within a species we normally resort to a bit of “geek speak” where we describe the two outcomes as either a “r-selected” species or “k-selected” species.
What this means, in simple terms, is that an “r-selected” species is one that reproduces quickly, has a short maturation time, breeds at a young age, has a short lifespan, produces many offspring quickly, has small offspring, has a high mortality rates for their young, and give little or no parental care.
The "K-selected species" usually live near the carrying capacity of their environment. Their numbers are controlled by the availability of resources.
In other words, they are a density dependent species.
The attributes of a K-selected species include a long maturation time, breeding relatively late in life, a long lifespan, producing relatively few offspring, large newborn offspring, low mortality rates of young, and extensive parental care.
With me so far?
MA: The main point of R/K selection theory is that evolutionary pressures tend to drive animals in one of these two directions — towards quickly reproducing animals whose specialty is to adopt as many niches as possible using simple strategies
Or slowly reproducing animals who are strong competitors in crowded niches and invest substantially in their offspring.
The quick summary of R/K selection theory can be thought of as “quality vs. quantity.”
Q: Then we are obviously “K-selected” species?
MA: For the most part yes.
Page #50
Q: You said only two outcomes, what are they?
MA: Well in the “R-selected” species their populations explode, filling all the ecological niches they can endure and then they suddenly collapse with the glide ratio of a rock. The “K-selected species” also explodes while food and habitat are abundant, and then they slow down as regulatory factors such as lower birth rate and reduced food availability come into play. The rate of population growth slows down to zero, and the population reaches a fairly stable level.
Q: Are we leveling off?
MA: Yes and no. No - we are still increasing the human population on earth but yes we are now slowing that rate of increase.
Q: When did it start slowing down?
MA: Somewhere in the early 60’s we reached our peak of a 2.2% increase and then we began to moderate that rate of growth. We now have about a 1.14% rate of growth which translates to doubling in 61 years.
Q: Has it been continually slowing?
MA: Yes, for the last 40 years.
Q: So if I understand correctly, we are modulating our population as we reach the limits of the environment. That sounds like good news, is it?
MA: Well, let’s take a look at a very simple equation that will help us decide the answer to that question.
r = n - m
This simple equation means that the realized intrinsic rate of growth is measured by the difference between natality (birth rate) and mortality (death rate).
And obviously zero population growth is reached when r = 0, natality equals mortality, and the population size remains constant, even though individuals are being born and are dying.
It seems simple. To follow the perfect example of a perfect “k-selected” species - we would simply expand to the limits of our environment or as we often say –“the habitat's carrying capacity” - we would then modulate our birth rate to equal our death rate and live in the land of milk and honey.
But it is, as are many things in complicated systems, not that easy. We now understand that there are both “k-selected” and “r-selected” traits in many populations. Our species is riddled with such contradictions.
Let's start with a simple concept like rate of population growth. While it is true that the overall human rate of increase is modulating - that is not true for all components of that set. Most European countries have low growth rates. In the United Kingdom, the rate is 0.2%, in Germany it is 0.0%, and in France, 0.4%. Germany's zero rate of growth includes a natural increase of -0.2%, without immigration, Germany would be shrinking, like the Czech Republic