4. How Climate Change Affects Ecoystems


The Leaf Eater Worm's Food Web

To understand how climate change affects ecosystems, imagine LEW, the Leaf-litter Eating Worm.  LEW feeds on leaf litter and is food for many animals in its food web (See Food Web M1). The worm behaves in the following ways:
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  • Burrows only through soil that earthworms soften and aerate.
  • Surfaces only to hide in and eat the leaf litter.  LEW hides from birds, perched in the trees above, and spiders that hunt across the leaf litter.
  • Wriggles across the leaf litter's surface to find rotting tree stumps into which to lay its eggs. Ants and a single species of bird feed on the eggs. LEW larvae (circled) feeds on wet, rotting wood.
  • Excretes mucus as it travels, which glues the leaves, stopping them blowing away. Various species of beetle lay their eggs in the mucus, which feeds their larvae. The glued leaves protect the larvae from the birds.​

  1. ​If owls were suddenly removed from the forest ecosystem, what might happen to the population of LEW? Think in terms of birds, ants and spiders. 
  2. Is it easy to predict what happens to an ecosystem when one element is removed?

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M1: LEW's Forest Food Web


What is Climate Space

Climate Space is the area of land or water which is climatically suitable for a particular species or habitat. LEW's Climate Space partly defined by the Temperature Range in Graph M2.

1. Does LEW survive and reproduce best at cool or warm temperatures?

2. Sunlight reaching the carpet of leaves on which LEW eats, is either:

• shaded by dense canopy
• dappled if the canopy is less dense
• bright, because fallen trees allow all the sunlight in
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Microclimates, small areas with different climates, are created because of the different amounts of sunlight reaching the forest floor. When wriggling across the leaf litter in search of a tree stump suitable for its eggs, which microclimate does LEW prefer? 

3. Temperature is one dimension of climate space. Can you name another?

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M2: LEW's Climate Space - Temperature


Ecological Variables

Temperature and precipitation define Climate Space.  But there are other ecological variables that help defines a species' liveable environment.

Slide Show M3 illustrates what precipitation, soil salinity and temperature ranges LEW function best in.
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  1. Can LEW tolerate saline soils?
  2. How much rainfall does LEW need?  
  3. Saltmine Forest has cool temperatures, high rainfall and soil that is moderately saline. Is it likely for LEW to be found there?
  4. If you answered no to Question 3, which environmental variable limits LEW's abundance in Saltmine Forest?​​

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M3: Precipitation, Soil Salinity and Temperature Range for LEW


Ecological Niche

  • What other abiotic (non-living things) variables limits LEW's environment?
  • What other biotic (living organisms) variables  limits LEW's environment?
  • How does LEW affect its own environment, and the environment of other species? 

In answering the above, we define the ecological niche of LEW. An ecological niche defines:
  • The environmental space (temperature, salinity and the range of other variables) that an organism can exist in
  • The roles (functions) it plays in its ecosystem. For example LEW acts as a food resource for birds, and its mucus excretions act as a food for beetle larvae.

​Therefore, non-living (abiotic)  and living (biotic) factors define a species' ecological niche.


M4: What IS An Ecological Niche?
​You can also view an ecological niche in terms of:
  • Resources which an organism consumes, or uses to survive
  • Relationships with other organisms, which either limits or increases survivability and fertility. For example, competion, 
  • Roles an organism plays in its ecosystem. These roles help maintain other species' ecological niches, and the functioning of an ecosystem as a whole.

List the following elements of LEW's ecosystem under Resources, Relationships and Roles
  1. ​Leaf Litter as a food
  2. Earthworms that soften and aerate soil
  3. LEW's excreting mucus that glues leaves and feeds beetle larvae
  4. Soft soil
  5. LEW, being potential prey for perching birds and other animals
  6. ​Raptors that feed on perching birds
  7. Fungi, bacteria, beetles and other animals that feed on fallen trees
  8. The process of LEW's eating of leaf litter,  and excreting nutrients back into the soil

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M5: Resources, Relationships and Roles


LEW in the 22nd Century

Imagine that from 2015 to 2100, the  Global Mean Surface Temperature (GMST) increases by  3 °C.  In the region where LEW lives, the following occurs:
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  • Hotter summers, with an increase in the number of heatwaves.
  • Warmer, wetter winters, with an increase in the number of high-precipitation days (heavy rainfall). The water table rises, bringing with it salts from the bedrock below.
  • An increase in the number of severe storms throughout the year.
  • With changes in climate space, a tree-burrowing beetle migrates northward, into LEWs forest. The beetles larvae weakens trees that owls nest in, making them more susceptible to wind.

Use Slide Show M6 to help you answer:
  1. How will these changes effect LEW's climate space?
  2. How will these changes effects LEW's ecological niche?
  3. How will LEW's population be affected? Will these effects happen all at once, or in stages?
  4. What will be the effect on other species?

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M6: Clues?

Think About . . .
This is currently the end of the Climate Change short course.

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