As I hike mountains, valleys, and deserts, I’m often amazed at the complex beauty of the world and its creatures. I often forget that the most diverse animals, birds, insects, amphibians, and more need something quite basic: H 2 O.

Hikers like me often think about water, of course, at least in terms of our needing to drink it. As a light-weight backpacker, I’m always trying to guess how little water I need to carry before I can get a refill. And as a photographer, I’m often thinking about how I might include water in my art.

A photo like this one—Jackson Lake near Grand Teton National Park—might make us think water is readily available. But water supplies are decreasing, and clean water is not available to many on this planet.

On the issue of water, my mind goes to a controversial subject: population growth. We live on a planet with many more people using much more water than ever before. Human population growth is exponential.

At what point will the majority of people decide we need to conserve water? When will the majority think population growth must be slowed? Or will famine, wars, disease, and other catastrophes—directly or indirectly caused by lack of water—be the population reduction mechanism? As I see it, love demands that we make difficult choices to reduce as much suffering as possible.