Monitoring and Maintaining the Environment

The third strand of "Global challenges" is the environment. Human activity is changing ecosystems and reducing biodiversity — the variety of living things — and biologists need ways to measure those changes and strategies to maintain healthy ecosystems for the future. This lesson explains why biodiversity matters and how humans affect it, the two main ways of measuring environmental change (indicator species and direct methods using sensors), and the practical steps taken to conserve ecosystems. It cross-references the sampling techniques you met in B4.

By the end of this lesson you should be able to explain what biodiversity is and why it matters, describe human impacts on the environment, explain how indicator species and direct sensors are used to monitor change, and describe ways of maintaining biodiversity and ecosystems.

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Why Biodiversity Matters

Biodiversity is the variety of different species of organisms in an ecosystem (or on Earth as a whole). High biodiversity matters because:

• ecosystems with more species tend to be more stable — they are better able to recover from change, because the loss of one species is less likely to cause the whole system to collapse;
• different species depend on one another (for food, pollination, recycling nutrients), so a rich web of life keeps an ecosystem functioning;
• humans rely on healthy ecosystems for food, clean water, materials, medicines and many other resources.

Reducing biodiversity therefore makes ecosystems more fragile and can harm the services people depend on.

These "services" that healthy, biodiverse ecosystems provide are easy to overlook but enormous. Plants and algae produce the oxygen we breathe and remove carbon dioxide; insects and other animals pollinate the crops that feed us; decomposers recycle nutrients so that soils stay fertile; wetlands and forests help to purify water and reduce flooding; and a great many medicines were first found in wild organisms. When biodiversity falls, these services weaken — which is why protecting biodiversity is not only about saving individual species but about keeping the systems that support human life working.

Human impacts on the environment

Human activity reduces biodiversity and damages ecosystems in several ways:

Human activity	Effect on the environment
Deforestation	Destroys habitats, reduces biodiversity, and releases stored carbon dioxide
Pollution of air, water and land	Harms or kills organisms; pollutes habitats
Building, farming and quarrying	Destroy or fragment habitats by using up land
Producing more waste	Pollutes habitats; uses up resources
Greenhouse gas emissions	Contribute to climate change, altering habitats

A growing population and rising use of resources mean these pressures are increasing, which is why monitoring and conservation matter.

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Measuring Environmental Change

To manage the environment we must first measure how it is changing. There are two complementary approaches: using living indicators, and using direct measurement with sensors.

Indicator species

An indicator species is an organism whose presence, absence or abundance tells us something about the conditions in an ecosystem — particularly the level of pollution. Some species are very sensitive to pollution and disappear when conditions worsen; others are tolerant and thrive in polluted conditions. By recording which species are present, we can judge the state of the environment.

Environment	Indicator	What it shows
Air quality	Lichens	Many lichens are very sensitive to air pollution (such as sulfur dioxide); lots of lichens indicate clean air, while their absence indicates polluted air
Water quality	Certain invertebrates, e.g. mayfly larvae (and stonefly larvae)	These need well-oxygenated, clean water; their presence indicates clean water
Water quality	Sludgeworms (and bloodworms)	These tolerate low-oxygen, polluted water; their presence (and few clean-water species) indicates polluted water

So a clean stream tends to contain mayfly and stonefly larvae, whereas a polluted stream tends to be dominated by sludgeworms — the change in which species are present is itself the measurement.

Exam Tip: Learn at least one air indicator (lichens — present means clean air) and one water indicator pair (mayfly larvae = clean water; sludgeworms = polluted water). State clearly whether the species' presence indicates clean or polluted conditions.

Direct methods: sensors and data loggers

Indicator species tell us about conditions indirectly. We can also measure environmental factors directly using instruments:

• pH sensors measure the acidity of soil or water.
• Temperature sensors (thermometers or probes) measure how warm an environment is.
• Oxygen sensors measure the dissolved oxygen in water — important for aquatic life.
• Pollution and other sensors can measure levels of specific pollutants, light, or moisture.

These sensors are often connected to data loggers, which record readings automatically and continuously over time. The advantages of data loggers are that they give precise, frequent readings, can run day and night in places too remote or hazardous for a person, and remove human error in reading instruments — making it easier to spot trends.

Exam Tip: If asked for an advantage of using sensors / data loggers over indicator species, good answers say they give precise, continuous readings automatically, can record in remote or hazardous places, and reduce human error.

Interpreting a monitoring survey

A common exam task gives you survey data and asks you to draw a conclusion. Suppose two sites on a river are surveyed and the invertebrates found are recorded:

Invertebrate found	Site A	Site B
Mayfly larvae	Many	None
Stonefly larvae	Some	None
Sludgeworms	None	Many
Bloodworms	Few	Many