Current Threats

by Francesca Gentile

Although Organ Pipe Cactus National Monument seems a doubtful place for abundant vegetation to exist several species have habituated to this area. Along with the native species there are seventy two non-natives which plagued the land of the monument. Some of the invasive species include buffelgrass, red brome, and Sahara Mustard. When these species were introduced to the land they created problems of dominating the space and strangling the soil of the already existing plants.

Buffelgrass is one of the most pervasive non-native plants in Organ Pipe Cactus National Monument. Like many of the other invasive species of grass, buffelgrass came from another part of the world. This particular species of grass is native to Africa and the Middle East.[1] Buffelgrass traveled to the New World when people ventured from distant lands. First appearing in areas of California then introduced to this region of Southern Arizona during the mid-1930s. The grass can range in size being “as short as a few inches, or as tall as three to four feet.[2]” Buffelgrass produces a small flower which develops into a fruit that has a “fluffy appearance,[3]” allowing it to spread easily and withstand extreme conditions. This plant can be seen along the road side as well as throughout the monument. The dense grass competes with larger native plants for water, often weakening and killing off natives.[4] The anatomy of buffelgrass has allowed the plant to adapt in the dry and arid climate of this region. The native species are not adapted to the non-native plants that take over, causing competition over water, nutrients and space. Buffelgrass is also fire resistant and this adaptation is particularly vital in this area of the United States, where temperatures often climb into the hundreds. Once an area is infiltrated by this species, it may never recover; however, manual labor of pulling the grass and herbicides may help prevent future growth.[5]

Another invasive plant attacking the Organ Pipe Cactus National Monument is Sahara mustard, a plant that resembles a shrub. The Sahara mustard plant has a “nearly leafless flowering stem[6]” that resembles a shrub bush.  With the flower, the seeds of the plant are easily distributed. This plant is also able to disperse by rolling like a tumbleweed at high speeds when the climate is dry thereby exacerbating the threat of Sahara mustard. The plant grows best in sandy soil making the desert an ideal habitat.[7] Even though the plant travels best during a wet year, dry years cause problems as well, a because this plant catches fires easily heightening the threat of desert fire in Organ Pipe Cactus National   Monument, which receives very little rain per year. Most desert plants cannot sustain in fire therefore creating issue when sparks begin. The first recorded occurrence of Sahara mustard in California was in 1927, but the plant first disturbed the Sonoran Desert in 1957.[8] Some prevention measures can be taken, but the large spread of the plant creates prevents halting its growth completely. Because the seed can survive in sun or shade, the plant must be completely removed from the site when weeded.[9] Some herbicides can also be used to eradicate small areas ofSahara mustard, although the problem will probably never be completely ameliorated; measures are being taken to control the damage.

Red Brome is a third threatening plant found in Organ Pipe Cactus National Monument. This plant come from the Mediterranean and is a winter grass[10].  Another grass that creates problems in the area is a species classified as bunchgrass. Numerous stems sprout from the base and can reach heights of twenty inches[11]. Due to the high seed content of the plant, it spreads effortlessly throughout the region. Red brome also survives fires unlike most desert vegetation creating an even higher cause for concern.

Even though there are several threats among the area of the Sonoran desert the ecological threats have become overlooked. Understanding these issues will allow for the preservation of these unique lands.

[1] Rutman, Sue.OrganPipeCactusNational Monument Invasive Plant Species. National Park ServiceU.S. Department of the Interior.

[2] Ibid

[3] Ibid

[4] Invaders Citizen Scientists Combat Invasive Species. Buffelgrass (Pennisetum ciliare). Buffelgrass.

[5] Ibid

[6] Invaders Citizen Scientists Combat Invasive Species. Sahara Mustard (Brassica tournefortii). Natal grass.

[7] Ibid

[8] Invaders Citizen Scientists Combat Invasive Species. Sahara Mustard (Brassica tournefortii). Natal grass.

[9] Ibid

[10] Biogeography of red brome (Bromus madritensis subsp. rubens) in theSonoranDesert.

[11]Red Brome. Bromus rubens.

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