Importance of biodiversity: stability and why we conserve it
Species-rich communities are more stable and productive. We conserve biodiversity for narrowly utilitarian, broadly utilitarian and ethical reasons.
Does the number of species matter?
Ecologists believe that communities with more species tend to be more stable. A stable community should not vary much in productivity from year to year. It should be resistant or resilient to occasional disturbances, natural or man-made, and it should resist invasion by alien species. David Tilman's long-term experiments with outdoor plots gave some answers. Plots with more species showed less year-to-year variation in total biomass, and greater diversity also gave higher productivity. Rich biodiversity is not only vital for healthy ecosystems but essential for human survival.
The rivet popper hypothesis
The Stanford ecologist Paul Ehrlich compared an ecosystem to an aeroplane held together by thousands of rivets (species). If each passenger pops out a rivet to take home (a species going extinct), flight safety (proper functioning of the ecosystem) may not suffer at first. But as more rivets go, the plane becomes dangerously weak. Which rivet goes also matters. Losing rivets on the wings (key species that drive major ecosystem functions) is far more serious than losing a few on the seats or windows.
Why should we conserve biodiversity?
| Reason | What it means | Examples |
|---|---|---|
| Narrowly utilitarian | Humans get direct economic benefits from nature | Food (cereals, pulses, fruits), firewood, fibre and construction material; industrial products such as tannins, lubricants, dyes, resins and perfumes; medicines: more than 25% of drugs sold worldwide come from plants, and 25,000 plant species are used in traditional medicine |
| Broadly utilitarian | Biodiversity gives ecosystem services we cannot easily replace | The Amazon forest is said to produce about 20% of the oxygen in Earth's atmosphere (textbook figure); pollination by bees, bumblebees, birds and bats; the aesthetic pleasure of forests, birds and flowers |
| Ethical | Every species has intrinsic value, even if it is of no use to us | We have a moral duty to care for all species and to pass on our biological legacy in good order to future generations |
Bioprospecting
Bioprospecting is the exploration of molecular, genetic and species-level diversity for products of economic importance. Nations rich in biodiversity, such as India, can expect large benefits from it. Many plants not yet studied, especially in tropical rain forests, may hold new medicines. (Extra reading, not in your textbook: quinine against malaria comes from the cinchona tree, and vinblastine against cancer from the periwinkle (Catharanthus).)
Ayurveda and Siddha use thousands of plants such as neem, tulsi and ashwagandha. Bees that pollinate crops like mustard and sunflower give Indian farmers a free service from biodiversity.
2 marks: “Explain the rivet popper hypothesis.” Paul Ehrlich compared an ecosystem to an aeroplane and species to its rivets. Losing a few may not matter at first, but losing many, or key species (wing rivets), makes the ecosystem fail.
2 marks: “What did David Tilman's experiments show about species diversity?” Plots with more species showed less year-to-year variation in total biomass, and higher diversity gave higher productivity.
5 marks: “Why should we conserve biodiversity? Explain the narrowly utilitarian, broadly utilitarian and ethical arguments.” Narrowly: direct products like food, fibre, timber, industrial products and medicines (over 25% of drugs from plants); bioprospecting. Broadly: ecosystem services such as oxygen (Amazon about 20%), pollination and aesthetic value. Ethical: every species has intrinsic value; a moral duty to future generations.
Conserve for Profit, Planet and Principle: narrowly utilitarian, broadly utilitarian and ethical.