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Human Ecological Sustainability
1.1 Introduction
It is important to study and understand the complex relationships between
the many changing factors that affect human ecological sustainability. These
include, but are not limited to, human population P, freshwater supplies W,
energy supplies E (including fossil fuels and renewable sources), food sup-
plies F, natural resources N (metal ores, cement, wood, etc.), the economy
[using gross domestic product (GDP) as a measure], emerging diseases D
(human, animal, and plant), and pollution C (atmospheric: greenhouse gas-
ses, volatile organic compounds (VOCs); water and land: insecticides, fert ...