Which Functional Changes Indicate Ecosystem Degradation?

• Water storage function: a block of water like a sponge
• Habitat function: a bird flying over the wetland
• Water quality function: a water drop with a tick

What you will learn

• Name the main functions of an ecosystem such as a wetland.
• Recognise what lost function looks like through sourced examples.
• Tell looking at function apart from looking only at appearance.

Before you start

You only need to know that an ecosystem is made of organisms and the environment around them. No specialist knowledge is needed.

What is a function of an ecosystem?

It is a job the ecosystem does that benefits people and species. A U.S. Environmental Protection Agency (EPA) page on wetlands lists wetland functions: protecting and improving water quality, providing fish and wildlife habitats, storing floodwaters and maintaining surface water flow during dry periods. According to the page, these functions result from the unique natural characteristics of wetlands.

More broadly, an EPA page on ecosystem services says ecosystem goods and services provide clean air and water, fertile soil, pollination and flood control.

• Reeds still in place
• A bird that has a place to live
• Bare ground: no plant cover left

What does lost function look like?

It looks like a job that used to be done and no longer is. The EPA sources give two examples.

The first is storing floodwater. Wetlands function as natural sponges that trap and slowly release water, and this combined storage lowers flood heights. The wetlands along the Mississippi River once stored at least 60 days of floodwater. In EPA's published example they store only 12 days because most have been filled or drained.

• Past flood storage: a long bar
• Present flood storage: a short bar
• The amount of shrinking

The second is habitat. Many species of birds and mammals rely on wetlands for food, water and shelter. Some migratory birds depend completely on certain wetlands and would become extinct if those wetlands were destroyed. Losing habitat means losing a function that whole species rely on.

How can degradation be spotted through function?

Compare each function with how it was before. EPA describes rehabilitation as working on a site with the goal of repairing the natural or historic functions of a degraded wetland. So degradation goes together with those functions being impaired.

The EPA page on ecosystem services adds that estimating the production of services requires the type and condition of the ecosystems, and that the degradation and loss of services may affect people. In an illustrative case, a place may still have plants while its water retention has declined. Assess water retention separately rather than judging only by green vegetation.

• Three functions when the ecosystem is intact
• Three functions when the ecosystem is degraded
• The direction from intact to degraded

Real-world example

Think of inspecting a house. You do not only look at whether the paint is pretty, you test whether the roof still keeps out rain, the drain still carries water and the door still locks. An ecosystem is the same: you ask whether it still does what it used to do.

Ask yourself: if a wetland still has many plants but no longer holds floodwater as before, would you call it healthy or degraded? The question shows that function matters more than looks.

Common misunderstandings

Green plants do not mean the ecosystem still has its full functions. Function is judged by whether it still does the job, such as storing floods or providing habitat.

Degradation is not only about losing species. Losing floodwater storage is also lost function, as in the Mississippi example.

Degradation is not always visible at once. Comparing each function with its earlier state helps examine what appearances alone cannot establish.

Frequently asked questions

What are the functions of a wetland?

According to EPA: protecting and improving water quality, providing fish and wildlife habitats, storing floodwaters and maintaining surface water flow during dry periods.

What is one example of lost function with numbers?

The wetlands along the Mississippi River once stored at least 60 days of floodwater and store only 12 days in EPA's published example because most have been filled or drained.

Does degradation affect people?

It may. EPA says the degradation and loss of ecosystem services may affect people.

Summary

• Wetland functions include water quality, habitat, flood storage and dry-season water flow.
• Lost function appears as shrinking flood storage or species losing habitat.
• The way to spot it is to compare each function with how it was before.