Ecosystems in Delicate Balance: Threatened, Endangered, and Introduced Species of the Lake Pontchartrain Basin

Objectives:

• Visualize the conceptual units which make up an ecosystem and discuss how various organisms interact in a functioning ecosystem versus a malfunctioning ecosystem.

• Develop an appreciation for the complexities of the Lake Pontchartrain Basin's varied ecosystems, as well as an understanding of how biodiversity (or a lack of) affects the health of an ecosystem.

• Understand the various relationships and roles of organisms in a food chain and how these relationships can become unbalanced.

• Realize the important role each of us plays in preserving and maintaining the health and biodiversity of the ecosystems of the Lake Pontchartrain Basin.

• List several threatened and endangered species in the Lake Pontchartrain Basin.

• Understand the status and roles of threatened, endangered and introduced species in the Lake Pontchartrain Basin.

Multiple Intelligences Learning Activities:

Verbal/Linguistic:

Develop and verbally defend a particular point of view formulated during problem-solving exercises.

Mathematical/Logical:

Reason and propose a certain course of action in a given circumstance.

Interpersonal:

Choose opposing sides to defend a current, relevant social and ecological issue.

Bodily/Kinesthetic:

Construct an "ecosystem" using building blocks to represent the various organisms involved.

Verbal/Linguistic:

Conceptualize the various organisms which comprise an ecosystem and learn their relative relationships.

Intrapersonal:

Explain personal values regarding selected environmentalissues of the Lake Pontchartrain Basin.

Ecosystems in Delicate Balance: Threatened, Endangered, and Introduced Species of the Lake Pontchartrain Basin

• An ecosystem can be thought of as a natural unit (e.g., wetlands, pine forests, or the entire Lake Pontchartrain Basin) consisting of living and non-living parts which interact to form a stable system. Examples of living and non-living parts include plants, animals, soil chemistry, temperature, nutrient supply, etc.

• Ecosystems in their natural state are finely-tuned and well-balanced.

• Ecosystems support and depend upon a tremendous diversity of plants and animals.

• Large numbers of animals and plants in the ecosystem indicate higher levels of biodiversity and greater complexity.

Biodiversity

Imagine the ecosystem as a tiny city, bustling with "people". This city has a tremendous number of important jobs which need to be carried out all day long, every day. Plants convert sunlight to energy; insects convert plant matter to energy; other animals eat insects and each other; decomposers, rippers and shredders tear everything down to make room and nutrients for new plants and animals... All of these jobs need to be taken care of by someone...BIODIVERSITY means that there are many different kinds of organisms available for employment at any given time...

• The Sun provides energy to Producers (green plants and algae, etc.).

• Producers provide energy to Primary Consumers (herbivores, or organisms that eat only plants).

• Primary Consumers provide energy to Secondary Consumers (carnivores, animals that eat herbivores, or omnivores, that eat both plants and animals).

• Secondary Consumers provide energy to Tertiary Consumers (carnivores and scavengers who occupy the tops of their respective food chains, like eagles or humans).

• Decomposers are microorganisms like bacteria and fungi which cause a breakdown of dead organic tissues (plants and animals), releasing their stored nutrients for re-use.

• Nutrients released by decomposers are re-used by producers, starting the cycle over.

• A certain amount of energy is lost in each stage of the food chain. This effectively limits the overall length of any given food chain. In other words, at some point, the energy spent getting food is greater than the energy gained from the food source, so an animal becomes weaker and weaker as time goes on until death finally occurs.

• When humans interfere with delicate ecosystems, the most common result is severe disruption of natural balances which, in turn, results in greatly reduced ecosystem function.

• When agricultural runoff and sewer discharges (unnaturally high levels of fertilizer) are emptied into Lake Pontchartrain, a dramatic increase in algal growth can be the result. This, in turn, results in turbid or cloudy water; aquatic plants die because they can't get the same levels of sunlight, and algae blooms deplete aquatic systems of necessary oxygen.

• As aquatic plants die, small fish which depend upon these plants also begin to die. In turn, larger fish which depend upon the smaller fish also die or leave. This represents the beginning of ecosystem collapse.

All is not lost, however!!

Much of the damage we inflict upon the world around us can be lessened or even reversed if we pay attention to the little changes in our ecosystems. Each of us can contribute by reducing the amount of runoff which enters the Lake Pontchartrain Basin and educating others about the importance of maintaining balanced ecosystems.

"Think Globally, Act Locally."

This often-quoted expression reminds us that, although our problems are global in nature, we need look only as far as our front door to find an ecosystem like Lake Pontchartrain that needs our help. It also serves to reinforce the idea that by working for better and more balanced ecosystems right here, we can ultimately affect the health of more distant ecosystems.

Click the illusration for a larger view.

Healthy vs. Unhealthy Ecosystems

Each step in the FOOD CHAIN contains appropriate numbers of organisms For example, there is normally a correct proportion of nutrients & sunlight to support the PROPER BALANCE of algae plants When the proportions are CONSTANT, each group efficiently feeds from the next lower group and the chain RECYCLES itself continuously The cycle is maintained in a BALANCED SITUATION and is unlikely to change without some form of outside intervention such as geological, meteorological, human induced, etc.

If one group becomes too numerous, the chain becomes UNBALANCED For example, agricultural runoff creates a SURPLUS of nutrients which can cause sudden INCREASES in algae growth Too much algae blocks sunlight from reaching vascular plants Too few plants means LESS FOOD for herbivores Less herbivores means LESS FOOD for primary consumers, etc. As the chain becomes more & more UNBALANCED, the likelihood of ECOSYSTEM COLLAPSE is increased

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.

Global

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 by the year 2000.

Local

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 rshlands. 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. (See side story by Cliff Glockner, "The Marsh's Friend, the Muskrat" Pages 136-137).

Fewer plant species results 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.

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

Where are Our Animals Going?

The Lake Pontchartrain Basin contains many diverse habitat types. Before humans interfered with the basin's ecosystems, these habitats supported an abundance of plant and animal life and were intricately woven together into a vast web of life which supported and complemented each other.

Since humans have developed much of the land surrounding Lake Pontchartrain, these once-connected ecosystems have become isolated, and their delicate balances have become disrupted. As this isolation and disturbance continues, ecosystems become unable to support certain animals, and the animals become threatened, endangered, or extinct.

Threatened Species are those species likely, in the near future, to become endangered species throughout all or much of their range. The range of an animal is that geographic region in which all of the conditions necessary for its survival are met, e.g., temperature requirements, food supply, habitat availability, clean water, adequate space, etc.

Endangered Species are those species of animals and plants identified by governmental or international organizations as being at risk of extinction because of human activity, changes in climate, changes in predator-prey relationships, etc.

Click the illustration for a larger view.

Introduced Species are species native to some other part of the world which have been brought to an area for a particular reason, e.g., ornamental plants or fur-bearing animals. These introduced species usually have some other species which keep them under control in their native lands, but lack these checks and balances when they are introduced into a different place. Without competition or predators to restrict them, introduced species reproduce extremely fast and can ultimately cause an ecosystem to become unstable. Some examples of introduced species in the Lake Pontchartrain Basin are water hyacinths and nutria. These organisms have already damaged the ecosystems into which they were introduced and are costing taxpayers a lot of money in an attempt to keep them under control. (Refer to Cliff Glockner's personal observations entitled "The Marsh's Friend, the Muskrat," culled from a life of hunting and trapping in the marsh. These observations provide one man's perspective of the traditional role of muskrat in the marshlands surrounding Lake Pontchartrain.)

Click the illustration for a larger view.

Activities: Decision Making and Issue Analysis Ecosystem Tumble

©1998 Lake Pontchartrain Basin Foundation

Lessons on the Lake is published by the
Lake Pontchartrain Basin Foundation
Metairie, LA