A4.2 Conservation of biodiversityIB Biology SL: Revision notes

Biodiversity is the variety of life in all its forms, levels and combinations. Three levels:

• Ecosystem diversity: the variety of habitats and ecosystems in an area.
• Species diversity: the number of species (richness) and how evenly individuals are spread among them (evenness).
• Genetic diversity: the variety of alleles within a species or population.

Millions of species have been discovered, named and described, but many more remain undiscovered. Fossil evidence suggests that there are more species alive today than at any time in the past.

NOS: classification is pattern recognition, and the same observations can be classified in different ways. Splitters recognise more species in a group; lumpers recognise fewer. For example, giraffes have been treated both as one species and as four.

The current sixth mass extinction is caused by humans (anthropogenic). Case studies:

• North Island giant moa (Dinornis novaezealandiae): large flightless bird, hunted to extinction within about 150–200 years of human arrival in New Zealand; loss of terrestrial megafauna.
• Caribbean monk seal (Neomonachus tropicalis): hunted for blubber oil; last seen 1952; loss of a marine species.
• Add one local example of your own.

Ecosystem loss: e.g. mixed dipterocarp forest in Southeast Asia, lost to logging and clearance for oil palm plantations.

Evidence comes from IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) reports and other surveys across a wide range of habitats. Surveys must be repeated to show change in richness and evenness.

Citizen scientists add huge amounts of data but raise concerns: variable identification skill, unequal recording effort, unstandardised methods.

NOS: to be verifiable, evidence usually comes from a published, peer-reviewed source whose methodology can be checked.

The overarching cause is human population growth. Specific causes:

• Hunting and other over-exploitation
• Urbanization
• Deforestation and land clearance for agriculture, with loss of natural habitat
• Pollution
• Spread of pests, diseases and invasive alien species through global transport

No single approach is enough, and different species need different measures:

• In situ conservation: protecting species in their natural habitats; management of nature reserves.
• Rewilding and reclamation of degraded ecosystems.
• Ex situ conservation: zoos and botanic gardens.
• Storage of germ plasm in seed banks or tissue banks.

The EDGE of Existence programme prioritises species that are Evolutionarily Distinct and Globally Endangered: they have few close relatives, so losing them loses a large amount of unique evolutionary history.

NOS: deciding which species to prioritise has ethical, environmental, political, social, cultural and economic implications and must be debated.