Species Population Viability Calculator — Formula
## Population Viability Analysis
Population viability analysis (PVA) projects whether a species can sustain itself over time. The simplest model uses exponential growth.
### Formula
**N(t) = N0 x e^(r x t)**
Where N0 is the current population, r is the net growth rate (birth rate minus death rate), and t is time in years. A positive r indicates growth; negative r indicates decline. The minimum viable population for most mammals is estimated at 500-5,000 individuals.
Population viability analysis (PVA) projects whether a species can sustain itself over time. The simplest model uses exponential growth.
### Formula
**N(t) = N0 x e^(r x t)**
Where N0 is the current population, r is the net growth rate (birth rate minus death rate), and t is time in years. A positive r indicates growth; negative r indicates decline. The minimum viable population for most mammals is estimated at 500-5,000 individuals.
Esempio Risolto
500 individuals with a 12% birth rate and 10% death rate, projected 50 years.
- Net growth rate = 0.12 - 0.10 = 0.02 (2%/year)
- Projected = 500 x e^(0.02 x 50) = 500 x e^1.0 = 500 x 2.718 = 1,359
- Doubling time = ln(2) / 0.02 = 34.7 years