übertool: web applications for ecological risk assessment (beta version)
Cloud-based environmental models used by the USEPA for evaluating pesticide risks to ecosystems under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Endangered Species Act (ESA).
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Logistic Model Overview


Developed by Belgian mathematician Pierre Verhulst (1804-1849), logistic model assumes that population change rate (rt) is not a constant. It is related to the maximum population growth rate (r0), carrying capacity (K), and current population (Nt), which follows the following relationship:



  • Population growth rate (rt) declines with the increase of population size (Nt)
  • Population growth rate (rt) is 0 when the population (Nt) reaches carrying capacity (K)
  • If population size (Nt) exceeds carrying capacity (K), then population declines