IB Biology HLProtecting BiodiversityPaper 1 & 2~9 min read
Ecosystem Loss
Hunting a species to extinction removes one branch. Destroying an ecosystem removes the tree it was growing on — every species living there, and every relationship between them, at the same time.
📚 What you need to know
An ecosystem is all the living organisms in an area, their interactions with each other, and the non-living environment.
Human activities are responsible for damaging and destroying ecosystems worldwide, for example through deforestation.
Case study: mixed dipterocarp forest in Southeast Asia. Dipterocarps are a family of tropical trees that formed a crucial part of a complex rainforest ecosystem.
Some parts of Southeast Asia have lost more than 50 % of their forests.
Forest is often lost by clear-cutting, where all the trees in an area are cut down and removed.
This provides timber and clears land for agriculture, such as palm oil plantations.
You need a second case study of your own choice, from a local or familiar region, caused by human activities.
What an ecosystem actually is
Definition
An ecosystem is all of the living organisms in an area, together with their interactions with each other and with the non-living environment
Three parts, and students usually remember only the first. The interactions are as much part of the ecosystem as the organisms themselves.
The third box is the one people forget. Clear an area and the feeding, pollinating and decaying relationships go with the organisms.
Case study: mixed dipterocarp forest in Southeast Asia
Dipterocarps are a family of trees that occur in the tropics. They once formed a crucial part of a complex rainforest ecosystem that dominated Southeast Asia.
These rainforests are being gradually lost. Some parts of Southeast Asia have lost more than 50 % of their forests.
Forest is often lost through clear-cutting: a practice where all of the trees in an area are cut down and removed.
Clear-cutting provides timber and clears land for agriculture, for example palm oil plantations.
Selective logging takes some trees and leaves an ecosystem behind. Clear-cutting takes the ecosystem as well as the timber.
A palm oil plantation is still green, still full of plants, and still photosynthesising. It is not an ecosystem in any useful sense: one species, planted in rows, with almost none of the interactions the forest had. “It looks fine from the air” is exactly the trap this case study is here to expose.
Second case study: your own choice
You need a second case study, chosen and researched by you, using the same criteria as before.
Requirement
What it means in practice
From a local or familiar region
Somewhere you can find real detail about, and remember under exam pressure
Loss due to human activities
Not a natural change such as a volcanic eruption
Same level of detail
What the ecosystem was, what has been lost, how, and why
Examples of ecosystem loss from around the world include the Great Barrier Reef in Australia, the Northern Great Plains in North America, and mangrove forests in many locations.
What the exam expects. Two case studies of anthropogenic ecosystem loss: mixed dipterocarp forest in Southeast Asia, plus one of your own choosing. For each, you should be able to discuss the causes.
Worked examples
WE 1
Explaining a named ecosystem loss
Discuss the causes of ecosystem loss in the mixed dipterocarp forests of Southeast Asia. (4 marks)
Point 1: what is being lost
Dipterocarps are tropical trees that formed a complex rainforest ecosystem dominating Southeast Asia.
Point 2: the scale
Some parts of the region have lost more than 50 % of their forest.
Point 3: the method
Much of it is lost by clear-cutting, in which every tree in an area is cut down and removed.
Point 4: the human motive
This supplies timber and clears land for agriculture such as palm oil plantations, so there is a strong economic incentive.
Named ecosystem, scale of loss, method, and human reason“discuss” wants causes and consequences, so add why people do it, not just what they do
WE 2
Ecosystem loss versus species loss
Explain why the loss of an ecosystem can reduce biodiversity more than the extinction of a single species. (3 marks)
Point 1: many species at once
An ecosystem contains all the organisms living in that area, so destroying it threatens many species simultaneously.
Point 2: the interactions go too
The interactions between organisms, such as feeding and pollination, are also lost, so surviving species may not be able to live there.
Point 3: all three levels
Habitat diversity falls, species diversity falls, and genetic diversity falls as populations shrink.
One habitat lost hits all three levels of biodiversitybringing back the three levels from the first page turns a good answer into a full-mark one
💡 Exam tips
Learn the ecosystem definition in three parts: organisms, interactions, non-living environment.
Use the number: more than 50 % of forest lost in parts of Southeast Asia.
Name the method: clear-cutting, and say all trees are removed.
Give the human motive: timber and agriculture, e.g. palm oil.
Have a second case study prepared with equivalent detail.
Link back to the three levels of biodiversity where you can.
⚠ Common mistakes
Defining an ecosystem as just the living things. The non-living environment and the interactions are part of it.
Confusing clear-cutting with selective logging. Clear-cutting removes every tree.
Treating a plantation as a restored forest. A monoculture has very low biodiversity.
Only describing the damage. A “discuss” question also wants the reasons humans do it.
Choosing a second case study with no data. You need figures and specifics.
Up next: Loss of Biodiversity — how the evidence is gathered, who gathers it, and the full list of causes behind the current crisis.
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