 The SPI includes all these different issues affecting the environment.A total area Atot which would be needed to embed human activities into ecosphere can so be aggregated.Atot = AR + AE + AI + AS + AP [m2] (1)
AR = ARR + ARF + ARN [m2] (2)
AI = AID + AII [m2] (3)
The sum for the total area is the sum of all partial areas (Formel 1).