Buffelgrass (Pennisetum ciliare, Cenchrus ciliaris), is the archenemy of the Sonoran Desert, the invasive grass most likely to cause significant damage to the native ecosystem. Buffelgrass is native to Africa, Asia, and the Middle East. This grass was intentionally brought to arid portions of the U.S. in the 1930s and was planted for cattle forage because of its drought tolerance.
In dry climates throughout the world, buffelgrass escaped from where it was planted and has established in places where it is unwanted -- natural areas, city parks, roadsides, and vacant lots. In the U.S., buffelgrass has been recorded in California, Arizona, New Mexico, Texas, Oklahoma, Missouri, Louisiana, Florida, New York, Hawai'i, Puerto Rico, and the Virgin Islands. In some areas, such as the Sonoran Desert of Arizona, buffelgrass is a highly invasive non-native weed and is officially listed and regulated as a noxious weed.
Buffelgrass pastures were planted in and around Tucson in the late 1930s for cattle forage and erosion control. Since then, it has become established in both disturbed and undisturbed desert environments and is now recognized as a top threat to the Sonoran Desert ecosystem. Here at Saguaro National Park, buffelgrass was first detected in 1989 and is widely distributed throughout the desert portion of both districts.
Buffelgrass plants are prolific seeders and its seeds are easily transported by wind and water. Additionally, each seed has little bristles which allow it to easily hitch a ride on animals, people, bicycles, and vehicles.
What is the threat?
The greatest threat that buffelgrass poses is that it can fuel wildfire; however, buffelgrass is able to severely and irreversibly alter that desert ecosystem even without fire. Buffelgrass grows in dense patches, crowding out and competing with native plants for nutrients, water, and sunshine. Open spaces between native vegetation fill with buffelgrass, occupying areas where one typically sees wildflowers bloom. Dense bufflegrass patches alter the habitat for desert animals and inhibit the growth of native plant forage. With increases in buffelgrass, we stand to lose plant and animal diversity, including some of our Sonoran Desert signature species.
The threat of fire is very real, with habitat, homes, and lives at risk. Our desert plants and animals did not evolve with fire and therefore, are not adapted to it. Fire can kill or severely damage much of the Sonoran Desert vegetation upon which animals depend on for food and shelter. Typical desert vegetation is sparse, so a fire would not spread and would quickly extinguish itself because of the lack of fuel. Natural desert fires are often caused by dry lightning strikes during our summer monsoon season. In a natural ecosystem severe impacts are unlikely during this time due to high humidity and probable rainfall.
With buffelgrass filling in the spaces between native plants, fire can carry over a continuous stand of vegetation. Buffelgrass evolved with fire and thrives under repeated burning. In the event of a desert fire, native plants would be killed or injured, while buffelgrass would survive and resprout. Such an event would result in additional buffelgrass plants replacing native plants, thus producing more fuel for another fire. This is termed a grass-fire cycle which increased the frequency, size, and intensity of fires over time.
How bad are buffelgrass fires? We decided to find out. Saguaro National Park and the University of Arizona performed several bufflegrass test burns in Avra Valley, Arizona. These test burns taught ecologists about buffelgrass fire behavior to help them develop models predicting how buffelgrass would burn in the park. Some of the observations and results from the fire include:
Peak temperatures reached over 1600° F.
Average temperature was between 1300-1400° F.
Tallest flame height was 25 feet.
Average flame heights were 8.5 to 11 feet.
Rate of fire spread was 1.4-3.0 mph (with wind speeds of 4-9 mph).
Fuel loads (biomass of buffelgrass) varied from 1 to 6 tons per acre.
These experimental burns provided an excellent opportunity for firefighters to experience firsthand how quickly the fire could move and how hot it could burn; hot enough to melt tin, zinc, and aluminum. While the fire did not spread at an alarming rate on the flat ground, a buffelgrass fire in the mountain foothills would move much faster. This has many firefighters concerned. Outrunning such a fire would not be an option. Watch a video clip of the test burn below.
Outside the park, buffelgrass threatens homes, property, and lives. It now grows in urban and suburban areas, roadsides, empty fields, washes, creosote flats, and other natural areas. Establishing itself particularly in subdivisions in the foothills of the Santa Catalina Mountains, buffelgrass presents a greater threat to safety, structures, utility poles, and other improvements.
Homes and buildings that are embedded in buffelgrass or near dense patches of buffelgrass are at high risk. Tucson's Rural Metro Fire Department has been urging resident to remove buffelgrass from around their homes to create a defensible space.
Our goal is to slow the spread of buffelgrass in order to protect native habitat and to manage fire risk in the park. At the present time, buffelgrass is so widespread throughout the park that complete eradication is not possible. Buffelgrass is here for now, but so is our determination to keep fighting. From our small successes, we have proven that buffelgrass can be controlled and native communities will recover, provided the infestations are removed in a consistent and timely manner.
Management of buffelgrass includes mapping and inventory, manual and chemical control, monitoring, research, prevention, and adaptive management strategies. Preventing buffelgrass from establishing in new locations within the park is a challenge because seeds can be dispersed by wind and travel long distances. We try to create a buffer between the park and established urban buffelgrass populations through cooperation with local departments of transportation and park neighbors.
We map and inventory buffelgrass to determine where it is and how fast the grass is spreading so that we can make informed decisions for applying resources to control the spread. Mapping and inventorying are ongoing tasks. Park staff and volunteers opportunistically map buffelgrass when they are hiking the trails and they also systematically map buffelgrass in a pre-established grid manner, covering large sections of the park's interior. The park conducted a second round of aerial mapping from a helicopter using digital sketch-mapping in 2012. All mapping efforts utilize global positioning systems (GPS) and geographic information systems (GIS).
We control buffelgrass either by hand pulling or by spraying the plants with herbicide. Buffelgrass is only susceptible to herbicide when it is over 50% green and growing, which is usually only a few weeks during the monsoon season and sporadically after winter rains. During this time, well-training, physically capable crews hike into rugged backcountry terrain to spray buffelgrass with glyphosate-based herbicides. They wear personal protective equipment and carry heavy back pack sprayers. We spray dense patches of buffelgrass that are too remote or too hazardous for people to reach on the ground with a helicopter.
Hand pulling can be done year-round. Digging bars, picks, and rock hammers are used to dig and lift the roots out with the plant, so that it will not later resprout from the roots.
Both methods of buffelgrass control are successful. However, repeat visits to the treated areas are necessary because of viable seed in the soil. We have found that it takes at least three years of biannual visits to eliminate buffelgrass from a particular site. We evaluate the success of our control efforts by measuring the change in the amount of buffelgrass coverage, before and after control efforts.
We started hand-pulling buffelgrass in the early 1990s, but our efforts could not keep pace with the rate at which buffelgrass spreads (our current estimates have roughly 1,800 acres of untreated buffelgrass within the park's boundaries). In 2005, we began using herbicide to control buffelgrass and increasingly found success. Each year we manage to knock back infestations in some areas, allowing for us to expand our treatments to new locations. In 2011, park staff and volunteers surveyed over 2,800 acres for invasive plants and treated a total of 140 acres using manual and chemical treatments. In 2014, we surveyed over 9,000 acres throughout all of our projects, treating invasive plants on 165 of those acres. After 4 to 6 years of annual treatments, sites are complete, but will require periodic monitoring for any new established plants. The hill to the east of Javelina Picnic Area in the Rincon Mountains (pictured on the left) is one area we call a success.
In 2014, after seeing buffelgrass increase unchecked in areas too remote or dangerous for people on foot to reach, the park began using a helicopter to spray buffelgrass infestations in these areas.
Volunteer efforts have contributed substantially to our successes in buffelgrass removal.
The second Saturday of every month (September through May), volunteers gather to remove patches of buffelgrass. One of many successes is the Freeman Homestead patch where 464 volunteeers contributed over 2,800 hours to remove an 11 acre patch.
Weed Free Trails volunteers monitor the trails below 5,000 feet elevation for several invasive plants that threaten the park, mapping and pulling as they encounter them. In 2013, volunteers monitored over 1,000 miles of trails.
Civic, social, work groups, and youth organizations also volunteer to assist in buffelgrass removal.
Our successes give us hope because, even though the task seems daunting, we have shown that we can effectively control localized buffelgrass populations.
The park participates in community events providing educational information about buffelgrass and other invasive species. Stop by a park booth to pick up some informational freebies. We also give presentations to homeowners associations and community, educational, and environmental groups.
Buffelgrass is a perennial grass that grows in dense messy-looking clumps. It sprouts new green (typically lime green) growth with adequate moisture and produces bottlebrush-like flowers. The flowers are red or purple when they are young and turn tan as they mature. White hairs can be seen at the base of a leaf blade, right where it diverges from stem (this area is called the ligule).
When the plant is dormant, it turns golden and may appear dead (don't be fooled!). Another distinctive characteristic is that the stem the individual seeds are attached to (the rachis) is rough and zigzagged. Click here to see what a buffelgrass rachis looks like compared to the rachis of some common native grasses.
Please watch Welcome to the Buffelgrass Patch, our informational video where we take you to a small infestation in the park and talk about identification, removal, and the effects buffelgrass has on the landscape and the economy.
How you can help
In Saguaro National Park:
Volunteer to remove buffelgrass at a Second Saturday buffelgrass pull. You will be trained in how to identify buffelgrass and safely remove it. This is a great way to get outside and help protect the park.
Participate in our Weed Free Trails program. This is a wonderful opportunity to hike the trails and keep them free of buffelgrass and other invasive plants.
Please do not remove buffelgrass or other invasive plants in the park if you are not an official volunteer. To become a volunteer, email us.
To learn more about buffelgrass and how to get involved, schedule a buffelgrass presentation for your community group (neighborhood/homeowner association, civic or religious group, etc). Contact the Pima County Environmental Education Department or call (520) 615-7855.
Organize a neighborhood buffelgrass removal event.
Buffelgrass is native to Africa and countries in the Middle East and Asia, where it is part of savanna grasslands with sparse trees. Buffelgrass is not invasive in its native habitat because herbivores such as zebra and antelope graze on the grass and keep it in check. Frequent fires are part of the native savanna's natural ecosystem processes. The trees and grasses are adapted to withstand hot fires and will resprout.
Buffelgrass in the U.S. and Mexico
Buffelgrass was brought to the southwest by the U.S. Soil Conservation Service for cattle forage and erosion control. Several varieties of buffelgrass were planted in test fields in southern Arizona. It is the "common" variety or T-4464 that established the best and has since escaped from the test fields. Common buffelgrass can reproduce without pollination, so new offspring are genetically identical to the parent plant.
Until recently, Texas A&M University was conducting agricultural research on buffelgrass to develop more robust and cold-hearty strains. These varieties have been released in Texas and Mexico.
Because buffelgrass is able to grow in poor soils, withstand drought, and provide cattle forage, this grass can be an ideal plant in marginal agricultural areas. Buffelgrass has allowed many ranchers in Mexico to make a living on land that has been converted to buffelgrass pastures. In central Sonora, Mexico, over one million hectares of native desert thorn scrub have been converted to buffelgrass pastures for cattle and livestock. The benefit to individuals and the economy from beef sales make buffelgrass a friend in Mexico, though it is still ecologically devastating. Texas also uses buffelgrass for cattle forage.
Buffelgrass is considered an enemy to the Sonoran Desert in Arizona due to the threats to human life and the enviroment. Hawai'i and the Pacific Islands also consider buffelgrass to be a foe. For most buffelgrass-inhabited areas in the U.S., the threats outweigh the benefits, and efforts are made to control populations.
Buffelgrass in Australia
Buffelgrass has been in Australia longer that it has been in the Southwest, so we have an opportunity to learn from their experience. Buffelgrass was first introduced to Australia accidentally in the 1870s, originating from seeds in stuffing for camel saddles. Later, buffelgrass was harvested and seeds were sown for forage, but the establishment remained localized. In the mid-20th century, buffelgrass was introduced on a larger scale, providing cattle forage and reclamation of damaged grazing lands. Unfortunately, as in the U.S., bufflegrass escaped its plantings. Today there are tens of millions of hectares of buffelgrass in Australia, much of which were not intentionally planted.
While buffelgrass has improved livestock production and brought economic benefits to many parts of Australia, it is now considered to be a major environmental weed, a Category One species (a terrestrial species capable of destroying an ecosystem), with extensive continental distribution. Computer modeling shows that buffelgrass has the potential to expand across more than 60% of mainland Australia. The models show buffelgrass invading much of the arid north. There is more moisture in southern Australia, and buffelgrass does not appear to outcompete native plants in moister soils.
Some of the threats buffelgrass brings to Australia are similar to those in the Sonoran Desert. Australia is concerned with the loss of plant and animal biodiversity, loss of signature species, more frequent and intense fires, and the threat to lives and property. They expect negative economic impacts from loss of tourism and increases in buffelgrass management costs. There are also concerns in Australia that we might consider. Buffelgrass may change water infiltration into the soil as well as surface flow, blocking drainages and increasing flooding. It also threatens the traditional food plants of Aboriginal people.