Why biodiversity matters

What is a species worth?

Suppose a stranger asks you why we should save a small frog that lives in one stream. What would you say? There are three kinds of answers.

Narrow utilitarian reasons

Utilitarian means useful. The narrow reasons are the direct uses that people get from living things.

• Food, firewood, fibre, construction material and industrial products come from living things.
• Medicines come from them too. More than 25 per cent of the drugs that are sold today come from plants. About 25,000 species of plants are used by the traditional healers and communities of the world for medicine.
• Many species may carry other useful products that we have not found yet. When a species is lost, we lose the chance to find them.

Broad utilitarian reasons

The broad reasons are about the services that ecosystems give to everyone.

• The Amazon forest is said to produce, through photosynthesis, about 20 per cent of the oxygen in the Earth's atmosphere.
• Pollination. Bees, bumblebees, birds and bats pollinate the plants that give us fruits, seeds and flowers. We could not do this work ourselves.
• Beauty. Walking in a forest, or watching birds, gives us pleasure. This is the aesthetic value of nature.

Some scientists have tried to put a price on these services. Robert Costanza and his colleagues estimated the value of nature's life support services at about 33 trillion US dollars each year. NCERT says that this is about 1.8 times the global gross national product, which was about 18 trillion US dollars each year.

You should find that the ratio is 33 divided by 18, which is 1.83. NCERT rounds it to about 1.8.

Ethical reasons

The ethical argument does not ask what a species gives us. It says that every species has an intrinsic value, even if it has no use to us. We share the Earth with them. We also have a duty to pass on the biological legacy to the next generations in good condition.

Try it in Python

The program works out the ratio of the services to the product, with the figures of NCERT.

Practise with new numbers

Common mistakes

• Putting the Amazon forest as the source of all the oxygen. NCERT says about 20 per cent.
• Calling pollination a narrow reason. It is a service that the ecosystem gives to everyone, so it is a broad reason.
• Writing 18 trillion for the services. The services are about 33 trillion US dollars, and the global product is about 18 trillion US dollars.
• Thinking that ethical reasons depend on the use of a species. They say that a species has a value of its own.

Remember these

• Narrow utilitarian: direct uses. Food, firewood, fibre, construction material, medicines (more than 25 per cent of the drugs from plants).
• Broad utilitarian: services. Amazon forest and about 20 per cent of the oxygen, pollination, beauty.
• Costanza: about 33 trillion US dollars a year for nature's services, about 1.8 times the global product of about 18 trillion US dollars.
• Ethical: every species has an intrinsic value, and we must pass on the legacy.

Check yourself

Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.

1. Name the three kinds of reasons for conserving biodiversity.

2. Is the pollination of crops by bees a narrow or a broad reason? Give the reason.

3. What share of the drugs sold today come from plants, according to NCERT?

4. What did Robert Costanza and his colleagues estimate?

5. Explain the ethical reason in one sentence.

References

• NCERT (2023). Biology, Textbook for Class XII, chapter 13, Biodiversity and Conservation, section on why we should conserve biodiversity.
• OpenStax Biology 2e (2018), chapter 47, Conservation Biology and Biodiversity, section on the importance of biodiversity.
• Campbell Biology, 12th edition (2021), Pearson, chapter 56, Conservation Biology and Restoration Ecology.