<span>They act like dams or form long ridges of land.</span>
A line has one dimension, length.
A plane consists of an infinite set of lines.
In Russia, after the global financial crisis in 1998, Russia became a major exporter of grain after 2001.
One way in which the study of populations ( human populations - I assume) affects us is that they can help predict the population size in the future and prepare us for it. For example, if we see that the population is decreasing, a country might want to consider supporting child-bearing or immigration to avoid the problem of too many people receiving pensions but not paying taxes.
