Calculated Results
Review turnover, dissimilarity, gains, losses, and annualized change for your ecological comparison.
Interpretation
Summary
Calculator Inputs
Enter richness values and overlap between two surveys, seasons, years, or locations.
Example Data Table
This example shows how species richness and overlap can change across repeated biological surveys.
| Scenario | Survey 1 Species | Survey 2 Species | Shared Species | Gained | Lost | Turnover % |
|---|---|---|---|---|---|---|
| Wetland Spring to Summer | 48 | 55 | 36 | 19 | 12 | 30.10% |
| Forest Edge Year 1 to Year 2 | 62 | 58 | 44 | 14 | 18 | 26.67% |
| Grassland Plot A to Plot B | 39 | 46 | 28 | 18 | 11 | 34.12% |
Formula Used
Losses = S₁ − C
Union = S₁ + S₂ − C
Turnover Rate (%) = ((Gains + Losses) ÷ (S₁ + S₂)) × 100
Jaccard Dissimilarity (%) = 100 − Jaccard Similarity
Sørensen Similarity (%) = (2C ÷ (S₁ + S₂)) × 100
Annualized Turnover = Turnover Rate ÷ Interval in Years
Here, S₁ is species richness in the first survey, S₂ is richness in the second survey, and C is the number of shared species. The standard turnover formula expresses total compositional replacement relative to combined richness across both observations.
How to Use This Calculator
- Enter the names of the two surveys, seasons, years, or sites you want to compare.
- Input species counts for each survey and then enter the number of species shared by both.
- Add the time interval if your comparison is temporal and you want annualized turnover.
- Choose decimal places, add a site name, and optionally include notes for reporting.
- Press Calculate Turnover to display results above the form under the page header.
- Use the download buttons to export the resulting ecological summary as CSV or PDF.
Frequently Asked Questions
1. What does species turnover rate measure?
It measures how much species composition changes between two surveys or sites. Higher turnover means more replacement, gains, or losses in the observed biological community.
2. Can I use this for site comparisons instead of time comparisons?
Yes. Species turnover can compare habitats, plots, elevations, islands, or any two ecological samples. Annualized turnover is mainly useful for temporal comparisons.
3. Why must shared species be less than both totals?
Shared species cannot exceed the richness in either survey. If it does, the overlap is mathematically impossible and the turnover result becomes invalid.
4. What is the difference between turnover and Jaccard dissimilarity?
Turnover uses total gains and losses over combined richness. Jaccard dissimilarity focuses on nonshared species relative to the union of species across both observations.
5. When should I use annualized turnover?
Use annualized turnover when two surveys are separated by a known time interval. It standardizes compositional change per year for easier comparison across studies.
6. Does this calculator handle abundance or only richness?
This version uses presence and richness counts, not abundance. For abundance-sensitive comparisons, use Bray-Curtis, dissimilarity decomposition, or other community metrics.
7. Can this help with conservation monitoring?
Yes. Repeated turnover tracking can reveal habitat disturbance, restoration response, seasonal succession, or community instability in monitoring programs and biodiversity audits.
8. Is a higher turnover rate always bad?
Not always. High turnover can reflect disturbance, but it may also indicate seasonal migration, natural succession, or strong habitat heterogeneity depending on context.