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Calcimator

Invasive Species Impact Calculator

Project invasive species population growth and spatial spread over time. Estimate area occupied and time to full invasion.

Inputs

km/yr
years
km²

Results

Projected Population

1,101,323

Area Occupied

5,000 km²

Habitat Occupied100%
Time to Full Invasion7.7 years
Population Doubling Time1.39 years
Spread Front Velocity13.7 m/day
Peak Population1,101,323
How to Use This Calculator
  1. Enter the Initial Population size and Intrinsic Growth Rate (r) for the invasive species.
  2. Set the Radial Spread Rate (m/year) from field measurements or literature.
  3. Enter the Projection Period (years) and Total Habitat Area available.
  4. Review Projected Population, Area Occupied (ha), and Habitat Occupied (%).
  5. Use Time to Full Invasion and Population Doubling Time to prioritize control timelines.

How the result changes with Intrinsic Growth Rate (r)

Intrinsic Growth Rate (r)Projected PopulationArea Occupied
0.511,318,5235,000 km²
1.765,000,0005,000 km²
3.255,000,0005,000 km²
4.55,000,0005,000 km²

What each input means

Initial Population
Number of invasive individuals at the start of the projection (e.g., founding population).
Intrinsic Growth Rate (r)
Per-capita growth rate per year. Invasive species often have high r values (0.3-2.0+).
Radial Spread Rate
Rate of range expansion as radial distance per year. Varies from <1 km/yr (plants) to 50+ km/yr (insects).
Projection Period
Number of years to project the invasion forward.
Total Habitat Area
Total available habitat area that the species could potentially occupy in km².

What each result means

Time to Full Invasion
-1 indicates spread rate is zero.
Population Doubling Time
-1 if growth rate is zero or negative.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Initial Population = 50, Intrinsic Growth Rate (r) = 0.5, Radial Spread Rate = 5, Projection Period = 20 = 5 input(s) provided
  2. Calculate Projected Population
    Projected Population
    1101323 = 1101323
  3. Calculate Area Occupied
    Area Occupied
    5000 = 5000
  4. Calculate Habitat Occupied
    Habitat Occupied
    100 = 100
  5. Calculate Time to Full Invasion
    7.7 = 7.7

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