Ecology and the State: a global perspective.

lecture notes for International Studies

instructor. H. D. Maher Jr.

An absolutely huge topic!

Ecology: "the study of interrelationships between organisms and their environment."

What makes us distinctly 'human', differentiates us from other organisms?

Earth system science: attempt to understand the mechanics and history of the earth as a complex system. Renewed focus on because of the question whether humanity through its collective action is changing the system.

Major components of the earth:

How can we attempt to understand complex and open systems such as these?

Population dynamics and ecologic implications:

What is the significance of the human population history and future from an ecologic and environmental perspective?

What other populations are we interested in, affected by?

Mathematical modeling of unrestrained population growth.

Malthus (1766-1834)

A specific case of doubling every generation. Take the case where every couple has 4 children which survive to parenthood and repeat their parents history, a doubling of population every generation. this would result in a sequence like: 2 -> 4 -> 8 -> 16 -> 32 -> 64 -> 128 -> 256 -> 516 -> 1032 -> 2064 -> 4128 ...... The general formula is y=2**t , where t is the number of generations (in years the= average age of parent). This produces a J shape curve, and the number 2 can be considered as a growth constant.

The general continuous case: We can describe an increment of growth with the following sentence: population growth (N) = # of reproducing units (N(i)) * growth constant (k) * time increment (t). The shorthand for this is below

N = N(i) * k * t

If you integrate then this changes into:

N(t) = N(0)* (e ** (k't )) or ln Nt = ln No + k't

where e=2.71 , where ln is the natural log (base e), N(0)=initial population at time 0, N(t) = population after time t. k' is a different growth rate. You can use this equation in plug and chug mode to predict unrestrained constant growth rate population histories (yet consider how likely is such a history to occur?).

Extrapolating present growth rate - how long before there is 1 person for every square meter of long on the the earth?

Reiterative or incremental description. For successive generations imagine a series of numbers: N(0) - N(1) - N(2) - N(3) - N(4) - N(5) - N(6) ...- N(n). If N(n) is the population at present somewhere throughout this history, then the population in the next cycle (generation), N(n+1), is given by: N(n+1)=B*N(n) , where B is the equivalent of k, a growth constant. Notice by the way that there is no reason why B can't change with time.

Growth with a restraint term and this way to chaos.

What will happen as the population begins to reach a maximum population possible (N(max)) as determined by the carrying capacity of the system? The growth constant must decline in value. Verhulst in 1845 came up with this equation for this situation:

N(n+1)=B*N(n)*(1- N(n)/N(max)) .

B is a inherent growth factor (reproduction rate when restraining factors are not significant). How does the last term behave as you approach or move away from N(max)? Simple rearrangement of the forumula may better show this behavior.

N(n+1)=B'*N(n) , where B'=B*(1- N(n)/N(max))

In this formula the growth 'constant' actually varies with time depending on how close or far away it is from some maximum carrying capacity populations.

Summary of equation behavior:

Can you think of some species whose populations show chaotic and/or large fluctations, and whether their inherent growth rate is high or low? Remember that this is a model, and if it has a sound theoretical basis it informs of possibilities, not eventualities.

Populations that show dramatic fluctuations: insects, lemmings, algal blooms, rabbits in Australia.

The lesson is simply in how such systems can behave, and that small differences can have big long term results.

What causes changes in growth 'constant', and also determines global carrying capacity?

Global scale ongoing ecologic/environmental changes:

Some examples of ongoing global scale changes.

Global climate change: We will focus on this because of the obvious importance to ecosystems and to the states.

The best predictor of future behavior is past behavior:

A model for the myriad of ways global climate can change is given below.

Some of the myriad of ways to change global climate:

Effects of present global warming?

Influence of environmental issues on matters of the state?

Rwanda - one example.

Gulf War: I will leave as self explantory.

Akkadian empire: in Tigres-Euphrates area: sudden collapse at 4170+/-150 yr B.P.Coincides with a sudden (with a sudden aridity episode 300 years long). Local climatic shift. Cullen et al., 2000, Climate change and the collapse of the Akkadian empire: Evidence from the deep sea; Geology, vol. 28, p. 379-382.

Many more examples. History courses often doesn't deal with them, but environmental issues have been a major factor in human history.

Present political framework of environmental efforts:

Changing economic perspective on environmental issues:

Closing statement: Humanity has at least two challenges ahead of us. First, to understand the complexity of systems that make up the earth, and how we affect and are affected by them. Second, to act appropriately with this knowledge. We have addressed a small bit of the first challenge. I leave the second challenge up to you. Those who argue that we are destined to survive has little appreciation for the character of history or the ways of nature, and are wearing blinders. We will ultimately have to act with collective wisdom if we are to survive as an advanced civilization.

Lecture 2

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