We may be surprised at how seemingly small decisions can make for a big impact. Pets are an excellent example. A pet is an animal kept for companionship or pleasure. They serve no purpose other than to help make us happy.

Apparently we need lots of joy. For example, we are enjoying an estimated 200 million to over 1 billion domesticated cats. Chances are good that you’ve encountered domestic cats so we won’t describe them. But do you know their effect? For one, a typical cat needs 250 to 300 food calories a day. Taking this as an average and assuming a median number of cats then these carnivores take about 2.5e+17 Joules of energy each year. That’s a lot of energy.

Also, while cats reportedly originated in Egypt, we’ve placed them everywhere except the Antarctic. And we’ve let some of them run wild. Thus, in the U.S. alone they are responsible for the deaths of about 2 billion birds and 15 billion small mammals annually; including the extinction of some.

Small decisions, such as having a pet, can lead to big consequences. A consequence of having cats as pets has led to them getting a much larger share of (autotrophic) energy than they would have naturally obtained. And through extinctions, they’ve eliminated future competition for this energy. How will other small decisions be affecting our future?