outline reasons for the need to maintain biodiversity

Conservation – Why Maintaining Biodiversity Is Essential (Cambridge 9700 – Topic 18)

Learning Outcomes (AO1, AO2, AO3)

1. Classification – Foundations for Biodiversity Assessment (AO1)

• Three levels of biodiversity (as required by the syllabus):
  1. Genetic diversity – variation of alleles within and between populations.
  2. Species diversity – number of species and their relative abundances.
  3. Ecosystem diversity – variety of habitats, biotic communities and ecological processes.
• Taxonomic hierarchy: species → genus → family → order → class → phylum → kingdom.
• Phylogenetic relationships reveal common ancestry; they help identify:
  • Keystone species – whose impact on ecosystem function is disproportionate to their abundance.
  • Umbrella/flagship species – whose protection benefits many other taxa.

2. Reasons for Maintaining Biodiversity (AO1)

These reasons map directly onto the four ecosystem‑service categories (see Table 1). Where a quantitative expectation is set in the exam, students should be able to calculate percentages, rates of change or indices.

• Ecological stability & resilience – diverse communities recover more quickly from disturbances (e.g., disease, extreme weather, invasive species).
• Provision of ecosystem services – food, water, timber, medicines, climate regulation, pollination, cultural enjoyment, soil formation, etc.
• Genetic resources for agriculture, medicine and industry – a wide gene pool underpins crop improvement, livestock breeding and biotechnological innovation.
• Economic value – sectors such as agriculture, fisheries, forestry and tourism generate billions of pounds annually; loss of biodiversity raises production costs.
• Moral/ethical considerations – intrinsic value of all living organisms and a duty of stewardship.
• Scientific and educational value – biodiversity provides a living laboratory for research and learning.

Table 1 – Ecosystem Services Linked to Biodiversity (AO1)

3. Species‑Level vs. Ecosystem‑Level Conservation (AO1)

• Species‑level approaches – focus on individual taxa (e.g., flagship, umbrella, keystone species).
• Ecosystem‑level approaches – protect habitats and ecological processes (e.g., protected areas, restoration, ecosystem corridors).
• Both levels are required because:
  • Species‑level actions can act as surrogates for broader biodiversity (umbrella effect).
  • Ecosystem‑level actions maintain the conditions needed for multiple species to thrive.

4. Main Threats to Biodiversity (AO1)

• Habitat loss & fragmentation – urban expansion, intensive agriculture, infrastructure.
• Invasive alien species – competition, predation, disease transmission.
• Over‑exploitation – unsustainable fishing, hunting, logging, plant collection.
• Pollution – nutrient run‑off, plastics, heavy metals, pesticides.
• Climate change – altered temperature/precipitation, range shifts, phenological mismatches.

5. Conservation Strategies & Tools (AO1)

• In‑situ conservation
  • Protected areas (national parks, nature reserves, marine protected areas).
  • Habitat restoration & creation (re‑forestation, wetland creation, ecological corridors).
  • Legal protection of species (Wildlife Acts, Species Protection Orders).
• Ex‑situ conservation
  • Seed banks, gene banks, cryopreservation.
  • Botanical gardens, zoological parks, captive‑breeding programmes.
• International frameworks & legislation
  • Convention on Biological Diversity (CBD) – sustainable use & fair benefit‑sharing.
  • CITES – regulation of international trade in threatened species.
  • IUCN Red List – assessment of extinction risk and priority setting.
• Monitoring & assessment techniques
  • Population surveys (transect counts, mark‑recapture).
  • Remote sensing & GIS for habitat mapping.
  • DNA bar‑coding & environmental DNA (eDNA) for species detection.
  • Bio‑indicators (e.g., lichen diversity for air quality).

6. Case Study – Decline of Pollinators in the United Kingdom (AO2)

Background – Between 1990 and 2020 UK bumble‑bee (Bombus spp.) and solitary‑bee numbers fell by ~30 %. Main drivers: habitat loss, neonicotinoid pesticides and climate‑driven phenological mismatches.

6.1 Data Set for Interpretation (Exam‑style)

Quantitative expectations: students should be able to:

1. Calculate the percentage decline in nest density between 1990 and 2020.
2. Calculate the percentage decline in oilseed‑rape yield over the same period.
3. Discuss the likely causal link between the two trends.

6.2 Model Answer Outline (AO2)

1. Percentage decline in nests:
   Δ % = [(12 – 5) / 12] × 100 ≈ 58 % decline.
2. Percentage decline in yield:
   Δ % = [(4.2 – 3.0) / 4.2] × 100 ≈ 29 % decline.
3. Interpretation:
   • Pollinators are a key regulating service (pollination). Fewer bees → reduced pollination efficiency → lower seed set → lower crop yield.
   • The larger proportional decline in nests than in yield suggests that other pollinators (e.g., flies, wind) partially compensate, but not enough to prevent a measurable loss.
   • Economic impact: if UK oilseed‑rape production is worth £X million, a 29 % fall translates to a loss of approximately £0.29 X million per year.

6.3 Additional Data Set (Trend‑graph practice)

Students may also be asked to plot a biodiversity index (e.g., Shannon‑Wiener) for a local grassland from 2000–2020:

Task: draw a line graph, calculate the overall % change, and comment on the implication for ecosystem‑supporting services (e.g., soil formation, nutrient cycling).

7. Evaluation Prompt – Monetary Valuation of Biodiversity (AO2)

“While ecosystem‑service valuation provides a useful economic argument for conservation, what are the limitations of assigning monetary values to biodiversity? Discuss at least two limitations and suggest how they might be addressed in policy making.”

8. Practical Investigation – Measuring Species Richness (AO3)

Investigation title: “Estimating species richness and Simpson’s Diversity Index in a local park using quadrat sampling.”

1. Objective – To assess the impact of habitat management (e.g., mowing frequency) on plant diversity.
2. Method
   • Lay out a 5 m × 5 m quadrat at three different management zones (frequently mowed, moderately mowed, unmowed).
   • Identify and record all vascular plant species within each quadrat (repeat for 5 replicates per zone).
   • Calculate:
     • Species richness (S).
     • Simpson’s Diversity Index: D = ∑(nᵢ/N)², where nᵢ = number of individuals of species i, N = total individuals.
3. Evaluation (AO3 – 20 % of total mark)
   • Sources of error – mis‑identification, seasonal variation, edge effects.
   • Improvements – larger sample size, use of permanent plots, repeat surveys across seasons.
   • Link to syllabus – demonstrates understanding of species‑level biodiversity, data handling and statistical analysis.

9. Consequences of Biodiversity Loss (AO1)

1. Reduced ecosystem resilience – higher probability of collapse after disturbance.
2. Loss of potential food, fibre and medicinal resources.
3. Decline in ecosystem services → increased costs for water treatment, flood defence, pollination, etc.
4. Economic losses in agriculture, fisheries, forestry and tourism.
5. Weaker climate‑change mitigation (e.g., lower carbon sequestration in degraded forests).
6. Limited evolutionary potential – populations become less able to adapt to new stresses.

10. Link to Other Syllabus Topics (Key Concepts)

• Genetic diversity ↔ Evolution & Natural Selection – a larger gene pool provides material for adaptation, a core idea in the “Cellular biology” and “Genetics” sections.
• Pollinator decline ↔ Plant reproduction – affects photosynthesis rates, seed set and ultimately food‑web dynamics covered in “Photosynthesis & Respiration”.
• Soil‑forming organisms ↔ Nutrient cycling – connects to “Cellular respiration” and “Energy transfer in ecosystems”.
• Pathogen regulation ↔ Disease dynamics – biodiversity can dilute disease transmission, linking to the “Human health & disease” topic.

Suggested Diagram

Summary (AO1)

Maintaining biodiversity is central to the Cambridge 9700 syllabus. It underpins ecological stability, supplies the full range of ecosystem services, provides genetic resources for food, medicine and industry, supports economies, fulfills moral responsibilities and fuels scientific discovery. Students must be able to describe classification, identify key threats, evaluate both species‑level and ecosystem‑level conservation strategies, interpret quantitative data, and design practical investigations that measure biodiversity. Linking biodiversity to other biological concepts (evolution, photosynthesis, disease) reinforces its relevance across the entire A‑Level programme.