Species Richness Calculator
Calculate expected species richness using rarefaction (Chao1, ACE estimators) or the species-area relationship (S = cA^z). Compare species counts between samples of different sizes.
🌳 Ecology📐 S = c·A^z (species-area)🧬 Biology
Known area A1 and species S1
S1 species count
New area A2 (find S2)
z value (typically 0.20-0.35)
Please enter valid values.
Formula & Reference
| Variable | Symbol | Formula | Units |
|---|---|---|---|
| Species Richness Calculator | — | S = c·A^z (species-area) | species count |
Step-by-Step Examples
Example 1
Island biogeography
Island 1: 100 ha, 50 species. Island 2: 400 ha (4x larger). z=0.25.
- c = 50/100^0.25 = 50/3.162 = 15.82
- S2 = 15.82×400^0.25 = 15.82×4.47 = 70.7
✓ S2 ≈ 71 species on 4x larger island
Example 2
Habitat loss
Forest fragment: 1000 ha, 80 species. 90% cleared → 100 ha remain. z=0.30.
- S_remain = 80×(100/1000)^0.30 = 80×0.1^0.30 = 80×0.501 = 40.1
- Lose ≈ 40 species (50%) from 90% area loss!
✓ 90% area loss → 50% species loss
Example 3
Tropical forest
Amazon: z=0.28. 10% of original area remains.
- S_remain = S_orig × 0.1^0.28 = S_orig × 0.525
- ~47.5% of species lost when 90% of habitat destroyed
✓ 52.5% of species remain with 10% of habitat
Real-World Applications
Habitat Conservation
Species-area relationship predicts extinction debt from habitat loss. Core tool in conservation planning.
Reserve Design
Larger reserves support more species. SLOSS debate: single large or several small reserves.
Marine Protected Areas
Size-species relationship guides MPA design for maximum species protection.
Biogeography
Island biogeography theory (MacArthur-Wilson) explains species richness on islands and habitat fragments.
Common Mistakes to Avoid
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z is typically 0.20-0.35 for mainland, 0.25-0.35 for islands
z is the slope of log S vs log A. Steeper slopes (higher z) mean species richness more sensitive to area changes.
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Habitat loss is not proportional to species loss
90% habitat loss does not mean 90% species loss (initially). Non-linear relationship. But extinction debt can be large.
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All species not equivalent
Some are area-sensitive specialists; others tolerate small fragments. SAR gives average expectation, not individual species outcome.
Frequently Asked Questions
What is the species-area relationship? ▾
S = cA^z. Species richness (S) increases with area (A) as a power function. c is a constant; z is typically 0.2-0.35.
What is the theory of island biogeography? ▾
MacArthur and Wilson (1967): Island species richness is equilibrium between immigration and extinction rates. Larger islands and closer to mainland: more species.
What is extinction debt? ▾
After habitat fragmentation, species expected to go extinct but not yet done so. Eventual extinctions > immediate ones because populations persist briefly before going locally extinct.
What are the SLOSS debates? ▾
Single Large Or Several Small reserves: does one large reserve contain more species than several small ones of equal total area? Generally: large is better, but depends on species and landscape.
What is rarefaction? ▾
Standardize species counts to same sample size. Compare communities fairly despite different sampling effort. Rarefaction curves show how species accumulate with sampling.