March 8 - IPAT as a method of assessing human impacts on...

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IPAT 1. What is it? A. Developed by Harte's full version of IPAT IPAT should be thought as I = f (P, A, T) rather than I = α PAT Increasing function of all 3 variables; impacts are not multiplicative nor are they linear Impact = Population (size) x Affluence x Technology - Affluence & Technology can be measured in many different ways Impact usually is not simply proportional to the products of these three Problems? - B. Not increased as much as affluence P increased 3.86x A (world per capita GDP) increased 27.5x Rate of patent applications has increased over 1000x; but relevant quantity is the impact of a unit increase in affluence Technology impossible to measure There is bigger impact on what people are doing rather than number Since 1990, - Countries with high affluence has low rates of population growth (except Gulf Oil states with low population size) No country with high birthrate has greatly increased affluence (except Gulf Oil states) Rapid population growth leads to large poor people and burden on infrastructure Technological innovation is more rapid if there is lower change in population size P,A and T are not independent of each other / or their rates of change - Why are we interested in IPAT? We want to achieve human impact to be sustainable. Sustainability means that impact does not excee regenerative ability C. Study by Wackernagel et al (2002) - Tried to estimate the amount of land required for growing crops, grazing animals, infrastructure, timber, etc. IPAT as a method of assessing human impacts on ecosystems March-12-11 11:05 PM March 8 Page 1
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Growing crops Grazing animals Harvesting timber Fishing Infrastructure for all activities Burning fossil fuel We are 20% above what we can sustain; this was 3 years before the publication. Estimated number of Earth required to sustain 2000 level average per capita impact If population size and affluence goes up, it will surpass the sustainable level by the planet Assumes sustainability (CO2 inputs and uptake balance) Calculates land required Biggest changes in land required to support energy use (top gray area) What are some of the complexities in calculating impacts using IPAT? ( Harte) D. "feedbacks, thresholds and synergies greatly amplify risk, causing degradation to grow disportionately faster than growth in population size" Non - linear phenomena are involved in human impact on systems; they cause phenomena or degradation to grow disproportionately faster than growth of population size Summary: - Density dependence Amount of prey eaten by a predator Impact of a toxin on the physiological functioning of an organism… + many other examples Nonlinear relationship between PAT & Impact - A brief diversion about nonlinear phenomena in the ecology of non-human organisms (why expect non-linear to happen?) 2.
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March 8 - IPAT as a method of assessing human impacts on...

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