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Fires Challenge the Resilience of Forest Ecosystems

Posted on Tuesday, April 11, 2023

Professor Donald Falk became interested in fire “because I saw fire as a big, powerful, scary process. If we get that wrong, we end up with a lot of degraded habitats,” he explains.  His career started with studying rare plant species but has evolved to a focus on ecosystem conditions, drought and fire, restoration ecology, and ecosystem resilience. “To me, there’s a very natural progression, trying to solve one problem, you unpack another problem. I think that’s very characteristic of science,” Falk says.  

At the University of Arizona, Falk is a professor in the Laboratory of Tree Ring Research, the School of Natural Resources and the Environment, and the Global Change Graduate Interdisciplinary Program. He was an ARCS Phoenix Chapter Scholar while pursuing his PhD at the University of Arizona.

Despite the challenges caused by the changing climate, Falk states “ecosystems, I would say, are remarkably resilient,” even though scientists don’t yet completely understand all the genetic complexity in ecosystems. “Ecosystems don’t have ethics, they just exist. For them, the turnover in species is just part of that natural process,” he says.

Forests are a prime example of an ecosystem reacting to change with gradual turnover and adaptation over years and decades, Falk says.  In the forest, established trees with big canopies “can tough it out over some pretty long periods” before they eventually die off.  Fires can happen almost overnight. Falk says “A high severity fire that reaches into the canopy of the tree can cause huge damage in a short time. And now you’re at a new starting point, you must rebuild the ecosystem from scratch,” he explains.

The gigantic fires that have been common in the west and southwest in recent years can be attributed to three things, Falk says. One is the climate itself. Climate changes like a diminished rainy season and higher temperatures “basically mean you have all the elements in place for a 12-month fire season” in the deep southwest of southern Arizona and New Mexico.

The second key factor to larger, major fires is land management. “When you exclude fire for, in much of the west, say a century roughly,” Falk says, “there is an enormous accumulation of fuel. The forests continue to produce fuel every year.” Prescribed burnings and mechanical thinning of forests is a multi-year or even multi-decade process to reduce fuel loads.

The third reason for huge fires is related to the second reason, Falk explains, and that is land use, such as building homes and new communities closer to nature and existing forests. Often that means when a fire does happen “it’s more severe than it would have been. You’re caught in this vicious cycle,” he says.

What ties all aspects of his work together, Falk explains, is “research and applied work that has the greatest payoff, in terms of protecting ecosystems from becoming further degraded.”

Falk says the ARCS Scholar Award he received while getting his PhD was “a real game changer” for him. “It came at a pivotal moment in my graduate studies. The ARCS funds gave me the intellectual freedom to explore ideas, just long enough to formulate a coherent plan” for choosing his graduate focus, he says. “It has paid off so many, many times.”