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The long view of science turns out to be both reassuring and daunting. Life on Earth turns out to be remarkably resilient. Within the story of our 13.5-billion-year-old universe, our own lives — so crucial to us and to our families and dear friends — look fleeting, gossamer. These paradoxes overwhelm me.

For five years, I've immersed myself in geologic time while writing exhibit text for the new Natural History Museum of Utah. Again and again, mass extinctions sweep away millions of years of diversity, and we start anew.

One time period produces 6-foot-long arthropods that look like centipedes in a child's nightmare. Another evolutionary interval yields a flightless, 6-foot-high bird whose head mostly consists of formidable jaws, a predator that may have hunted in packs. The Mesozoic landscape teems with dinosaurs the size of commuter jets — and then the strange animals are gone.

Evolution proves relentlessly inventive as life forms come and go. I recognize that humans appear as just one more entry in the evolutionary spiral. But now we don't just live within this geologic story, we shape it. With that power comes responsibility.

Geologists think of the last 65 million years as recent, and so all the epochs in our era end with -cene, from the Greek for "recent." Pleistocene. Eocene. Holocene. The prefix changes, but the "-cenes" mark "recent" developments in evolutionary and tectonic cycles, even when the time line for these epochs reaches back tens of millions of years.

Many scientists now believe that we have entered the Anthropocene. In just two centuries of this "human-dominated recent time period," beginning with the Industrial Revolution, we have transformed half of the Earth's land surface, changed global climates and triggered losses in biodiversity. Animals slip away as we destroy their habitat, at extinction rates 45 times greater than the long-term average (for mammals) and 270 times greater than average (for rain forest species).

In the Anthropocene, 7 billion people everywhere insert themselves into delicately interwoven systems. Bio-crusts carpet the soil in dry country. Disturb that living crust in the redrock canyons of the Four Corners with a careless boot print, too numerous livestock, or a freewheeling all-terrain vehicle, and you liberate dust to blow onto the snowpack in the Rockies.

Dark snow melts faster than clean snow, and the spring runoff now comes 50 days earlier in the Colorado River Basin, with stark consequences downstream.

We've constructed a desert civilization in the American Southwest that depends on water from elsewhere. When climate change drains the delivery system, will Phoenix and Las Vegas (let alone small towns like Hanksville and Needles) dry up and blow away?

And so I've become obsessed with fragility. We can take nothing for granted, from the air we breathe, to the value of our homes, to the well-being of our loved ones.

In one recent week, I saw this tenuousness shatter four exceptional people. I attended memorial services for two friends, one who died in a freak accident at 41, a second who died of a disease with no treatment and no cure, at 63. In between, I visited a mentor living with the debilitating aftermath of a stroke and a legendary teacher paralyzed in a bike accident and fighting for breath, year after year.

Watch your step. On this day-to-day level, live every moment fully. Nurture resilience.

When we can define geologic time by our actions, we must think hard about consequences.

When we have become connected to one-third of the people of the planet through our computers, our effects multiply; politics and social justice and human rights are no longer local issues. In the Internet-driven Anthropocene, we mightily affect our generation and those who come after us.

We can deal with the Anthropocene with hubris — why conserve when in a million years we will move on to a new evolutionary world? This might explain the Utah Legislature's selfish attempt to turn over fragile public lands to the state for development, for management by the few and for the few, even though all Americans own the federal lands in question. Or the fossil-fuel industry, intent on maximizing profits until we've drilled the last drop of oil, without regard for the people who live nearby.

Or we can deal with the extraordinary opportunity of our few decades on Earth with restraint, blessed by the fragile miracles of our health and acutely aware that we must act with care if our natural world is to flourish.

Stephen Trimble is a contributor to Writers on the Range, a service of High Country News (hcn.org). He is a writer and photographer in Salt Lake City and was the lead writer for the new Natural History Museum of Utah.