20th century

=== Energy and the environment ===
[[File:Oilfields California.jpg|thumb|[[Oil field]] in California, 1938.

The first modern oil well was drilled in 1848 by Russian engineer F.N. Semyonov, on the [[Apsheron Peninsula]] north-east of [[Baku]].]]
* [[Fossil fuels]] and [[nuclear power]] were the dominant forms of energy sources.
* Widespread use of petroleum in industry—both as a chemical precursor to plastics and as a fuel for the automobile and airplane—led to the geopolitical importance of petroleum resources. The Middle East, home to many of the world's oil deposits, became a center of geopolitical and military tension throughout the latter half of the century. (For example, oil was a factor in Japan's decision to go to war against the United States in 1941, and the oil cartel, [[OPEC]], used an oil embargo of sorts in the wake of the [[Yom Kippur War]] in the 1970s).
* The increase in [[fossil fuel]] consumption also fueled a major scientific controversy over its effect on air pollution, [[global warming]], and global [[climate change]].
* [[Pesticide]]s, [[herbicide]]s and other [[toxicity|toxic]] [[chemical substance|chemicals]] accumulated in the environment, including in the bodies of humans and other animals.
* [[Population growth]] and worldwide [[deforestation]] diminished the [[environmental quality|quality of the environment]].
* In the last third of the century, concern about humankind's impact on the Earth's [[environment (biophysical)|environment]] made environmentalism popular. In many countries, especially in Europe, the movement was channeled into politics through [[Green party|Green parties]]. Increasing awareness of [[global warming]] began in the 1980s, commencing decades of social and political debate.