One of the perks of being a field geologist is that they often get to spend time outside! Follow along with a geologist as he spends a day mapping rocks in the Jemez Mountains, and then try your own hand at observing rocks and mapping soils
Click the links below to take a virtual geology field trip!
Twenty years ago, the Cerro Grande Fire permanently altered Los Alamos. The devastation brought on by this fire is something so many people had to live through. I’m too young to have experienced life pre-Cerro Grande, so I can only imagine how hard it was for people to see the once densely forested Jemez completely decimated.
I did live through the Las Conchas fire in 2011. It was difficult for me to revisit the areas of wilderness I spent so much of my life exploring after they had been destroyed. I, like so many other New Mexicans, am incredibly fond of our ponderosa pine and aspen forests, and hope for their preservation. Unfortunately, these ecosystems are currently under threat.
Compared to places that have been ravaged by wildfire, any well-forested area in the Jemez might outwardly appear healthy. However, there are many factors acting against our forests that make them great vectors for megafires — a scientific term used to categorize forest fires that burn over 150,000 acres, which is an unnatural occurrence. Both the Cerro Grande and Las Conchas Fires fall into this category.
In order to fully explain why megafires like these happened, and understand why the forests of the Jemez are still at risk today, it is necessary to examine the historical environment of the area, and what the forest looked like before people first settled here.
The truly undisturbed environment of the Jemez dates back before the 1900s. Back then, forest fires in the Southwest were categorized as low-intensity, surface fires that mostly burned through grassy undergrowth. Frequent, but small and slow-burning fires were beneficial for healthy forest conditions by maintaining an open understory and maintaining large stands of coniferous trees.
The balanced forest structure between mature and old-growth trees, aspen, and openings with understory grasses, flowering plants, and shrubs prevented uncharacteristically high-intensity and severe fires. When severe fires did occur, they were a result of prolonged drought and lightning strikes during the summer months. These patterns are evidenced in fire scars in old-growth trees, however these fires were rare and typically burned in small patches.
Then, when railroads connected New Mexico to the rest of the country in the 1880s, people settled in the Jemez and human activity started to impact the environment. Activities such as overgrazing cattle, logging, and fire suppression all had detrimental effects on the ecosystem that have made it more susceptible to fires.
What proves to be the biggest threat to Jemez’s forest ecosystems is the same factor jeopardizing all at-risk ecosystems across the globe — climate change. On top of human activity dramatically shifting the natural state of the forest for over a century, climate change has brought increasing temperatures, drought, less available water (due to increasing demand for it), and extreme weather to the Jemez. All of which contribute to more severe fires that burn hotter and are harder to contain.
Today, the forest ecosystem of the Jemez looks a lot different than what it would be if left undisturbed by people and climate change. The natural forest structure of the Jemez should be groups of trees of different ages and sizes. Instead, there is a dense, continuous canopy of young and mid-age trees. Additionally, continual fire suppression has also allowed conifers to invade once naturally-occuring meadows, shrinking them down.
Climate change and human activity have shifted the forest structure in the Jemez, and the Cerro Grande and Las Conchas fires have dramatically damaged the environment. Not only have the trees and meadows been affected, but riparian and aquatic systems also have been degraded. Watershed areas without meadows or big trees allow more sediment to pass into stream banks and stream-road crossings, harming both plant and animal life. Streams have also become straighter and narrower due to shrinking meadows, reducing quality habitat for fish.
Beyond the watersheds and aquatic environments, the aftermath of megafires in the Jemez has led to habitat loss for important species like the Jemez Mountain salamander and the Mexican Spotted Owl. Non-native and invasive species introduced by humans have decreased biodiversity and weakened ecological communities in the Jemez environment. Examples of invasive plant species currently growing in this area include Pigweed, Ragweed, and False Tarragon.
On a more positive note, there are many ongoing efforts to restore the environment in the Jemez back to a healthy state and repair some of the areas that have been ravaged by megafires. Some examples of current ecological repair are:
Using herbicides to help eliminate non-native plant species.
Using machinery to create pools and channels in rivers to improve aquatic habitats.
Even still, the threat of climate change is on the global scale. I cannot help but continue to worry about the future of the forests surrounding Los Alamos, and if they will still be here for future generations to enjoy — as I have been so lucky to. My greatest hope is that New Mexicans will continue to support efforts to understand and help alleviate climate change, and that we continue to support agencies that are working to repair our forests so that they are less susceptible to megafires.
By Siobhan Niklasson, based on a conversation with Bob Parmenter of the Valles Caldera
The forests of the American West look much different today from how they looked 150 years ago. Around that time, a handful of large and destructive fires in the United States convinced land managers and the public that fires should be stopped as soon as possible in order to protect natural resources.
Without fire to clear the landscape, many more trees were able to take root, increasing the tree density from around 40 – 60 trees per acre to 1,000 – 2,000 trees per acre in some cases. It’s painful just to think about trying to ride a horse through such a dense forest!
So many trees in the forest meant that each tree had to compete for water and nutrients with all its neighbors, surface water running in streams was reduced, sunlight was largely blocked from the ground level, leading to a dearth of grasses and other understory plants, and animals that depended on these small plants for grazing were squeezed out. Crucially, for fires, the increase in fuel in the forest turned what would once have been healthy ground fires into raging infernos that could wipe out an entire forest, and get so hot that the soil was sterilized.
Today, we have a better understanding of the importance of fire in our forest ecosystems. But the 150 years of fire suppression policy left a legacy of overgrown forests that must be returned to a healthy state, both to restore healthy ecosystems, and to reduce the risk of severe megafires.
In the Jemez Mountains, agencies have joined forces in a collaborative forest landscape restoration program to undertake this work. The first step is to thin the forest using mechanical means or cutting by hand to reduce the density from 1,000+ trees per acre to about 100 trees per acre. This means potentially cutting out 90% of the trees in the area! Once the trees are cut, they can either be removed and used for wood products, or they can piled and burned. This work is expected to be completed in the southwestern Jemez Mountains within another two to three years.
Once the forests are thinned, natural mortality will further reduce the number of surviving trees. The idea is that after another 100 – 200 years, we will end up with a mature forest with about 40 – 60 trees per acre.
With the first thinning completed, natural and prescribed fire can be used to manage the forest. It’s much cheaper and safer to manage fire in a thinned forest than it is to bring in helicopters and air crews to battle high-intensity fires that threaten lives and neighborhoods. For example, the 2011 Las Conchas fire burned over 150,000 acres, and cost almost $50 million to control.
In 2019, a lightning strike in the Valles Caldera started a low-intensity ground fire that burned through thinned forests. Firefighters saw an opportunity to use this fire to maintain some forested areas that needed to be burned. With the cooperation of local residents, they managed to safely allow the fire to burn right up to the boundary between the preserve and the Sulfur Flats neighborhood.
For the trees, thinning makes it easier for each individual tree to secure the resources (water and nutrients) it needs to survive. This should help the trees be more resilient to rising temperatures due to climate change.
A tree can live for several hundred years. Even if we are able to reverse the trend in our greenhouse gas emissions by 2050, we can expect temperatures to keep rising for another 50 years after that, and it could be an additional 50 years before temperatures cool off again.
So while that timescale of around 150 years is a long time in human terms, it means that the trees that are living now could potentially see the other side of the climate change curve, if we can help them survive fires and beetle infestations now.
Next time you’re out, see if you can find signs of forest thinning and prescribed burns. This is important work that’s keeping our forest ecosystems healthy for everything, including us, that depends on them.