<P> The effects of overpopulation are compounded by overconsumption . According to Paul R. Ehrlich: </P> <P> Rich western countries are now siphoning up the planet's resources and destroying its ecosystems at an unprecedented rate . We want to build highways across the Serengeti to get more rare earth minerals for our cellphones . We grab all the fish from the sea, wreck the coral reefs and put carbon dioxide into the atmosphere . We have triggered a major extinction event...A world population of around a billion would have an overall pro-life effect . This could be supported for many millennia and sustain many more human lives in the long term compared with our current uncontrolled growth and prospect of sudden collapse...If everyone consumed resources at the US level--which is what the world aspires to--you will need another four or five Earths . We are wrecking our planet's life support systems . </P> <P> The applications of technology often result in unavoidable and unexpected environmental impacts, which according to the I = PAT equation is measured as resource use or pollution generated per unit GDP . Environmental impacts caused by the application of technology are often perceived as unavoidable for several reasons . First, given that the purpose of many technologies is to exploit, control, or otherwise "improve" upon nature for the perceived benefit of humanity while at the same time the myriad of processes in nature have been optimized and are continually adjusted by evolution, any disturbance of these natural processes by technology is likely to result in negative environmental consequences . Second, the conservation of mass principle and the first law of thermodynamics (i.e., conservation of energy) dictate that whenever material resources or energy are moved around or manipulated by technology, environmental consequences are inescapable . Third, according to the second law of thermodynamics, order can be increased within a system (such as the human economy) only by increasing disorder or entropy outside the system (i.e., the environment). Thus, technologies can create "order" in the human economy (i.e., order as manifested in buildings, factories, transportation networks, communication systems, etc .) only at the expense of increasing "disorder" in the environment . According to a number of studies, increased entropy is likely to be correlated to negative environmental impacts . </P> <P> The environmental impact of agriculture varies based on the wide variety of agricultural practices employed around the world . Ultimately, the environmental impact depends on the production practices of the system used by farmers . The connection between emissions into the environment and the farming system is indirect, as it also depends on other climate variables such as rainfall and temperature . </P>

The study of human populations and their impact on the natural world is called