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Figure 1: Human population growth over the last 10,000 years.

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Figure 2: Population projections for human populations through 2050.

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Figure 3: Current and projected rates of annual nitrogen fixation due to human activities [1]

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Figure 4: The human footprint index reflects human population density, land transformation, access, and electrical power infrastructure [4]

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Figure 5: The human footprint index clearly shows metropolitan areas in the northeastern United States. In addition to Boston and New York, which are labeled, it's easy to pick out Providence, RI, Hartford, CT, Springfield, MA, Worcester, MA, and Portland, ME. If you know the freeways in the area, it's not hard to pick out I-95, I-91, I-90, and others.

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