Population: Carrying Capacity and Limiting Factors in Natural systems

transcript

What Every Citizen Should Know About Our Planet

This presentation is a courtesy of

The Wecskaop Project

It is entirely free for use by scientists, students, and

educators anywhere in the world.

Part One

Carrying Capacity

How many individuals can a particular ecosystem [or

planet] indefinitely support over a long period of time

while continuing to function and without suffering severe

or irreparable damage?

For scientists, the answer to such a question constitutes the system's carrying capacity

How many individuals can a particular ecosystem [or

planet] indefinitely support over a long period of time

while continuing to function and without suffering severe

or irreparable damage?

Since ecosystems are finite in their size and resources, each

has an upper limit to the population that it can support

while continuing to

and also provide the assorted ecological services

that allow a given population to exist

provide food resources withstand impacts and damage tolerate or withstand wastes maintain, perpetuate, and repair itself

Phytoplankton in the oceans, such as these

diatoms, producemore than half ofthe oxygen that

we breathe

Since ecosystems are finite in their size and resources, each has an upper limit to the population

that it can support while continuing to

and also provide the assorted ecological services

that allow a given population to exist

provide food resources withstand impacts and damage tolerate or withstand wastes maintain, perpetuate, and repair itself

Examples of crucial ecological services include each day’s production and replacement of most of the molecular O2 that we and most other animals con-sume every few seconds

The fifty species of diatoms in the image above, forinstance, are examples of phytoplankton in the earth’s oceans

that produce more than half of the oxygen that we breathe

Pollination of vast percentages of flowering

plants everywhere,

and dramatic contributions to the

production of rainfall by the process of

transpiration.

Other ecological services include, for instance,

Environmental carrying capacities need not necessarily involve foodand water, but can also reflect critical limits to the damages, wastes,

eradications, and impacts that they can safely withstand – and totheir capabilities for self-perpetuation, maintenance, and self-repair

Imagine an elevator, for example, thatcan safely accommodate 18 passengers and yet

83 or 247 or 1058 passengers begin to squeeze aboard

It is easy to understand that thestresses of excessive loading

virtually ensure failures in oneor more components, triggering thecollapse of the entire system and the

destruction of both the vehicleand its passengers

us’s

A similar unsettling scenario can beenvisioned if one imagines

an aircraft of finite size,

only to notice that a line of more and more and more persons

continue to endlesslyboard the aircraft

It is thus important to appreciate that

carrying capacity inbiological and biospheric systems

is commonly far MORE than

simply a matter offood, or water, or “resources”

Overshoot

Thus, more and more persons endlessly boarding anelevator or aircraft or vehicle or planet

of finite capacity constitutesan egregiously-unwise behavior

Thresholds

A behavior that invites transgressions of at least one or more

Limits

Tipping Pointsand/or

Thousands of examples of thresholds, limits, and tipping points (both known and unknown) exist in

real-world natural and biospheric systems

As two quick examples of thresholds in real-world systems:

One instance in a biological system can be seen in human blood which has buffers that maintain its pH at a mildly alkaline 7.4 level. Seemingly small transgressions, how-

ever, beyond pH 7.3 (lower limit) or 7.5 (upper limit) result in acidosis or alkalosis, both of which are potentially fatal.

Real-world thresholds

All three classical examples experienced 99%-plus die-offs and collapse at a time when the combined bodies or cells of each of the populations physically-occupied roughly 2/1000ths of 1% of their surrounding environment that appeared to remain theoretically-available to them

All three classical examples experienced 99%-plus die-offs and collapse at a time when the combined bodies or cells of each of the populations

physically-occupied roughly 2/1000ths of 1% of their surrounding environment that appeared to remain theoretically-available to them

Not a very wisepolicy, was it?

Part Two

Limiting Factors

Examples of Limits, J-curves,Thresholds, and Limiting Factors

Also notice that this graph of human population growth over the past 10,000 years

is an extremeJ-curve

How worrying shouldJ-curves be?

Unfortunately, humankind first learned with horror what J-curves can do from unspeakably

deadly events at the close of World War II

Physicists know that exponential progressions and their resulting graphs

which are known as

J-curves

exhibit a decided tendency to obliterate everything

around themselves in every direction

A graph of this shape on the display monitorsof a nuclear power plant would send theplant’s engineers scrambling for the exits

Key Ideas

Appendix One

How Large is a Billion?

Appendix Two

What is Earth’s carrying capacityfor a modern, industrializedhumanity with a prosperous

standard of living for all?

Appendix Three

Links and Other Resources

Population: Carrying Capacity and Limiting Factors in Natural systems

Education