When Stewart Udall passed away this spring, he left a legacy that filled the planet. As a leader in America's environmental awakening in the 1960s, he took Teddy Roosevelt's 19th-century conservation vision to protect natural resources and broadened it into the larger concept of environmentalism, emphasizing the interdependence of all life on Earth.

As Interior Secretary under Presidents Kennedy and Johnson, Stewart Udall promoted clean air, clean water, and preservation of wild lands and wildlife. And he was among the earliest to recognize that, because our habitat now spans the entire globe, our species had reached a critical

Santa Fe is fortunate in that, upon retiring here the 1990s, Stewart brought his lifetime of experience to bear on local environmental issues.

Serving the Santa Fe Conservation Trust as board member and chairman at the behest of his friend and our founding director Dale Ball, Stewart spearheaded the Santa Fe Rail Trail project, helped to protect Santa Fe's iconic backdrop, Atalaya Mountain, worked with political and opinion leaders to promote conservation, and never let our community lose sight of the importance of protecting what matters.

Stewart had the mind of a scientist: always curious, absorbing new knowledge, fearlessly exposing his ideas to critical thinking (including his own), and exhibiting a willingness to change when new facts came to light. His thoughts continued to evolve right up to his last days, and he was willing to share those thoughts with future generations in writings and interviews.

He told his children and grandchildren that they would face greater challenges than those of any past generation. To Stewart, the world's future threats included the sheer size and growth of the human population; global climate change; and the calamitous future day when petroleum extraction from underground would no longer meet the demand above ground.

Stewart Udall regretted that, as a young congressman in the 1950s, he had failed to challenge the proposed Interstate Highway System. Never anticipating its widespread negative consequences, in retrospect he saw with clarity the devastating impact of America's enshrinement of the automobile and the ensuing proliferation of highways and suburbs that create a bottleneck for our very survival. In his last years, Stewart continually emphasized that we must realize that smaller is better; must learn how to make do with less, not more; and must understand that there would be no technological silver bullet to save us. We have to save ourselves.

Deeply inspired by Stewart's vision, the Santa Fe Conservation Trust has itself evolved since its beginning in the 1990s. We've always helped landowners create voluntary land protection agreements to preserve wildlife habitat and prevent suburban sprawl.

Now, in response to global climate destabilization, we also focus on working farms and ranches — our only source of fresh local foods — and provide options for modest-income landowners who wish to ensure their traditional family lands will never be lost to development.

In our own evolution, we take Stewart Udall's life as an inspiration. He taught us that we are a part of, not apart from, nature, and that our survival as a species depends on our ability to learn and adapt. The Santa Fe Conservation Trust invites the community to join us in honoring Stewart Udall's legacy by investing in the health of the natural lands upon which we all depend.

Charlie O'Leary is executive director of the Santa Fe Conservation Trust.