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Invasive weeds contribute to fire threat

By Bureau of Land Management Director Kathleen Clarke

WASHINGTON, D.C. – They come with benign names like June Grass, Foxtail Chess, and bufflegrass, or the soft-sounding Downy Brome. Though pretty sounding, these insidious invasive weeds are continuing to expand their range and dominate native plant communities across large portions of our Western landscape.

Unfortunately, these grasses are also extremely flammable and largely responsible for carrying fire into once healthy vegetative communities. While fire is a natural, even beneficial element in fire-adapted ecosystems such as pine forests, it can have devastating effects in areas less accustomed to flame. We're seeing some of those effects this summer in the Southwest and Great Basin.

The Sonoran Desert, for example, home of large saguaro cactuses and other native desert species, has evolved for hundreds, if not thousands of years without fire. The vegetation has not adapted defenses against flames.

Naturally spaced apart to maximize sparse rainfall, the vegetation would not carry flames. Until recent decades, that is, when Foxtail Chess, a friendly name for the invasive Red Brome, established a foothold and began to fill in between the native plants. That foothold created a pathway for fire.

In the 1970s, wildfires began to follow those pathways into the desert. This year's Cave Creek Complex, a 250,000-acre fire in Arizona, burned through areas of the Sonoran Desert where there was no recorded history of fire occurring. The impact from fire on the native vegetation has been immediate and severe, and it may be three to five years before the mortality rate of the large saguaros is fully known.

It remains to be seen what the long-term impacts of this year's fires will be on the land and vital habitats. The climate, vegetation types, and soils make rehabilitating these desert areas difficult at best.

Typically these types of non-native, invasive grasses reinvade with even more force following a fire. And they will continue to expand into new areas, creating more fire pathways in the desert to repeat this burn-spread-burn cycle.

This cycle has disabled once healthy landscapes, turning them into flammable monocultures of invasive weeds. Although we continue to seek ways to break this cycle, so far we've had only varying degrees of success.

This year, the expansion of these weeds has been exacerbated by heavy winter and spring moisture. The moisture did provide some relief from years of drought and delay the onset of fire season at higher elevations. But at lower elevations, it created landscapes laden with record-breaking volatile fuels.

Across the West, the invasive grasses range from two to five times the amount seen in an average year. Once ignited, these grasses will spread fire rapidly and erratically.

Already this year we have seen severe impacts on both land and humans. Nearly 100 homes and more than 200 other structures have been lost to wildfires. We've also seen hundreds of thousands of acres scorched, and we have weeks, if not months of fire season ahead.

As of early August, we have experienced 14,800 fewer fires than average, but the fires we've had have burned in excess of two million acres more than average. As we move into the peak fire season in the West, these trends are likely to continue.

All of this serves to heighten our awareness this summer and to remind us how quickly these light fuels ignite and rapidly spread fire. You cannot outrun one of these fast moving fires. As always, I encourage you to enjoy our public lands, but please be careful with anything that may ignite a fire.

You can also help stem the spread of these invasive and flammable weeds. For instance, use weed-free hay when riding or packing with livestock, and wash your four-wheelers to remove weed seed before trekking off to enjoy the public lands.

Enjoy the summer, but be safe.