Biosphere and Conservation
Life on a Planetary Scale
Biomes and Global Patterns
The biosphere is divided into major biomes — large-scale ecological areas determined by climate (temperature + precipitation):
- Tropical rainforest: highest biodiversity, constant warm temperatures, high rainfall
- Temperate deciduous forest: seasonal, deciduous trees
- Grassland/savanna: grasses dominate, seasonal rainfall, large herbivores
- Desert: extreme temperature fluctuation, minimal rainfall
- Taiga (boreal forest): coniferous forest, cold winters
- Tundra: permafrost, treeless, extreme cold
- Aquatic biomes: marine (oceans, coral reefs) and freshwater (lakes, rivers)
Biome boundaries shift with climate change, threatening species that cannot migrate fast enough.
Biodiversity Loss and Conservation
We are in the 6th mass extinction — species extinction rates are 100–1,000× the background rate, primarily due to: Habitat destruction (deforestation, urbanisation), invasive species, climate change, pollution, and overexploitation.
Conservation strategies:
- In situ: protected areas (national parks, marine reserves), habitat corridors
- Ex situ: zoos, seed banks, captive breeding programmes
- Ecosystem restoration: rewilding, reforestation
- International agreements: CITES (trade), CBD (biodiversity convention), Paris Agreement (climate)
The 6th Mass Extinction
Current extinction rates are estimated at 1,000× background levels. The IUCN Red List (2024) has >44,000 species threatened with extinction out of >157,000 assessed. Unlike past mass extinctions, this one is caused primarily by one species: Homo sapiens.
Which factor is considered the GREATEST immediate cause of global biodiversity loss?
Habitat destruction (especially tropical deforestation) is the primary driver of species extinction. Loss and fragmentation of habitat eliminates species directly and reduces gene flow.
Correct answer: Habitat destruction and fragmentation
A Seed Bank (like the Svalbard Global Seed Vault) is an example of:
Seed banks preserve genetic diversity of plant species outside their natural habitat (ex situ = 'off-site'). In situ conservation = protecting species in their natural environment.
Correct answer: Ex situ conservation
Explain why habitat corridors are considered an important conservation tool for fragmented populations.
Corridors counter fragmentation effects by restoring connectivity.
Correct answer: Habitat fragmentation isolates populations in 'islands' of suitable habitat. Small, isolated populations suffer inbreeding, loss of genetic diversity, and vulnerability to local extinction (demographic stochasticity). Corridors connect patches, allowing gene flow between populations, recolonisation after local extinction, and migration with climate change — all of which improve long-term population viability.