The greatest impact individuals can have in fighting climate change is choosing not to reproduce.
A carbon-footprint study of people in the wealthier nations of North America, Europe and Japan concluded that having one less child would reduce carbon emissions 20.2 times as much as living car-free, 39.9 times as much as switching to renewable energy and 71.5 times as much as eating a plant-based diet.
We are experiencing the sixth mass extinction of animal species due to human ecological impact. Humanity has killed off about 60% of the global wildlife population of mammals, birds, reptiles, amphibians and fish since 1970. During that time, the human population increased from 3.7 billion to 7.7 billion.
About 83% of all wildlife mammals have died off since the dawn of agriculture. Farmed poultry now accounts for 70% of birds worldwide. Mammal life is now 60% livestock, 36% people and 4% wildlife.
Climate change is a consequence of ecological overshoot. Too many people consume and pollute too much.
If the average person on Earth consumed as wastefully as the average resident of the United States does today, the Earth could not sustain a human population of more than 1.5 billion people.
Meanwhile, 815 million people suffer from chronic hunger.
The number of people that is “sustainable” depends upon the average standard of living. More people means more widespread poverty.
Sustaining life on Earth means reducing both human birth rates and per capita ecological footprints.