Efficiency

A program that runs ten times slower, wastes at least ten times more power and more if CPU is multitasking.
Inefficient programs cost more to run.
Ten times more electricity is wasted, leading to ten times more coal and uranium consumed for nothing. The pollution and warming, are also significant factor due people making more "hardware to throw at the problem" rather than increasing efficiency. Each day millions of inefficient programs destroy world climate.

One way to save the planet is to live solely off the land. Hunt for your food using sticks and stones and forage for plants and seeds. Wear only a loincloth made either from shrubbery or animal skin.