The Lessons on the Lake Logo Chapter 7: Ecosystems in Delicate Balance
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Lessons on the Lake -> Chapter 7 -> Biodiversity


Just as plants and animals in the Lake Pontchartrain Basin are entirely dependent upon each other, more distant ecosystems are ultimately dependent upon the health of the Lake Pontchartrain Basin. The reasons for this can be traced to the complexities of BIODIVERSITY.


The rapidly accelerating loss of plant and animal life on our planet can be largely attributed to human population pressures and the demands of economic development.

Rainforests are cleared. Huge areas of forest are killed by pollution, and continued population growth threatens countless plants and animals.

The current extinction rates from deforestation alone are estimated to be 10,000 times greater than the naturally occurring background extinction rates that existed before the appearance of human beings.

If the current rate continues, approximately 15% to 20% of all species will become extinct within the next few years.


Loss of biodiversity in the Lake Pontchartrain Basin is somewhat less dramatic than these examples, yet no less significant.

Introduced species like nutria compete with native species like muskrat and dramatically increase herbivore damage to marshlands. Whereas muskrat eat only certain plant species and do not appear to be as widespread as nutria, nutria are ubiquitous and eat everything in vast areas of marshland, sometimes leaving only mudflats behind. These mudflat marshes are more prone to erosion than were the marshes with plants. (Refer to side story by Cliff Glockner, “The Marsh’s Friend, the Muskrat”).

Fewer plant species result in fewer animals which depend upon them for food and shelter. Increased development and damage to local wetlands put increased pressure upon the biodiversity of the region.

Already some plants and animals like the Louisiana Black Bear have almost completely disappeared from the Lake Pontchartrain Basin.

Other animals and plants like the Bald Eagle or the West Indian Manatee have become increasingly rare and are threatened or endangered.

The continued introduction of alien species threatens the health and continued existence of local animals and plants.

EXAMPLES of introduced problem plants include:

  • Water hyacinths which completely clog bayous and ponds every summer,
  • Kudzu, a tenacious vine which climbs over everything in its path and blocks sunlight from other plants, eventually killing them, and
  • Chinese tallow trees, which compete with local plants for nutrients and space.

EXAMPLES of introduced animals which are presenting problems include:

  • Nutria which eat all vegetation, and
  • Zebra mussels which are clogging water intake pipes all across the country.
“Biological diversity is the key to the maintenance of the world as we know it. Life in a local site struck down by a passing storm springs back quickly: opportunistic species rush in to fill the spaces. They entrain the succession that circles back to something resembling the original state of the environment.”

Edward O. Wilson,
The Diversity of Life

Increased BIODIVERSITY in the Lake Pontchartrain Basin increases the likelihood that our valuable ecosystems will continue to function properly…

Preserving HABITAT in the Lake Pontchartrain Basin preserves BIODIVERSITY

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Manatees are closely related to elephants.
  1. Ch. 7 Intro
  2. Essential Questions
  3. Ecosystems
  4. Energy Flow Through an Ecosystem
  5. Healthy vs. Unhealthy Ecosystems
  6. Biodiversity
  7. Threatened and Endangered Species in the Basin
  8. Decision Making and Issue Analysis
  9. Ecosystem Tumble
  10. Activity: I'm a Survivor