The Monsoon Jungle, for example, gives an additional nutrient to any squares located within it, and is thus a good place to build cities for fast growth. Rarely does everyone rise in power at the same time. One of the most important contributors to the bar chart's value is your faction's overall population. Population growth is determined by each city's nutrient total. Although building forests early in the game can help increase your production rate, forests reduce the nutrients you get from well-watered squares until you research Environmental Economics and Planetary Economics.
Every faction is more bloodthirsty and arrogant at the harder levels.
The only way to win is to rise to the top early and stay there. My strategy is to subjugate one of the weaker factions in the game as early as possible. Probe teams, similar to the Spies from the earlier Civilization game, become very useful in the harder settings. They can bribe units, steal technologies, send biological agents, and even convince cities to switch factions. The only defense against a Probe team is another Probe team.