📖 In-Depth Theory
What is Biodiversity?
BIODIVERSITY is the variety of life on Earth.
It has two components:
SPECIES DIVERSITY — the number of DIFFERENT SPECIES in an area AND the relative abundance of each species.
GENETIC DIVERSITY — the variety of ALLELES (different versions of genes) within a species.
High species diversity means many different species, each present in reasonable numbers.
High genetic diversity within a species means the population has a wide range of alleles — making it adaptable.
Why genetic diversity matters:
A genetically diverse population can cope with new diseases, climate shifts or environmental changes — some individuals will have alleles giving resistance or tolerance.
A genetically uniform population (like a monoculture crop) is vulnerable — one disease can devastate the whole population.
Why Biodiversity Matters
High biodiversity provides essential ECOSYSTEM SERVICES that humans depend on:
Food PRODUCTION — diverse ecosystems provide diverse foods. Wild relatives of crop plants are a genetic reservoir for future crop improvement.
POLLINATION — approximately 75% of the world's food crops depend on animal pollinators (bees, butterflies, hoverflies). Loss of pollinator diversity threatens food security.
Clean WATER — wetland plants and soil organisms filter pollutants from water naturally.
Clean AIR — forests and vegetation absorb CO₂ and other pollutants.
MEDICINES — many drugs come from wild species: aspirin from willow, penicillin from a mould, cancer drugs from the Pacific yew tree. Undiscovered species may hold future cures.
ECOSYSTEM STABILITY — more species = more connections = more resilience. If one species declines, others can take over its role.
CLIMATE REGULATION — forests absorb CO₂ and influence rainfall patterns.
ETHICAL RESPONSIBILITY — many argue that all species have a right to exist, regardless of utility to humans.
Threats to Biodiversity and Conservation
THREATS:
HABITAT DESTRUCTION — deforestation, draining of wetlands, urbanisation, agricultural expansion → loss of living space for species.
POLLUTION — pesticides, plastic, oil spills, acid rain damage habitats and directly kill organisms.
INVASIVE SPECIES — introduced species outcompete or prey on native species (e.g. grey squirrels, American mink, Japanese knotweed).
OVEREXPLOITATION — overfishing, overhunting, illegal wildlife trade reducing populations below viable levels.
CLIMATE CHANGE — shifting temperature ranges, sea level rise, altered rainfall patterns displace or eliminate species.
CONSERVATION MEASURES:
PROTECTED AREAS — national parks, nature reserves, marine protected areas prevent habitat destruction.
CAPTIVE BREEDING PROGRAMMES — zoos and wildlife centres breed endangered species to prevent extinction.
SEED BANKS — e.g. Svalbard Global Seed Vault stores seeds of thousands of plant varieties as insurance against loss.
REINTRODUCTION PROGRAMMES — reintroducing species to habitats where they once lived (e.g. beavers in Scotland, white-tailed eagles in England).
LEGISLATION — laws protecting endangered species and their habitats (e.g. CITES, Wildlife and Countryside Act).
HABITAT RESTORATION — rewilding projects restore degraded habitats.
SUSTAINABLE FISHING — quotas, minimum catch sizes, protected areas to allow fish stocks to recover.
⚠️ Common Mistake
Biodiversity is NOT just about the NUMBER of species — it also includes the RELATIVE ABUNDANCE of each species. An ecosystem with 100 species but 99% of the biomass belonging to just one species has LOW biodiversity in practice. High biodiversity means many species AND reasonable numbers of each.
📌 Key Note
Biodiversity = species diversity + genetic diversity. Importance: ecosystem services (food, medicine, clean water, pollination), stability, ethical reasons. Threats: habitat loss, pollution, invasive species, overexploitation, climate change. Conservation: protected areas, captive breeding, seed banks, legislation.