Invasive species

Shawn Pollard
Tue, 04 Aug 2009 07:42:37 PDT
Dear all,

The plants of Satan here in the Arizona desert, outside of the riparian areas, are buffelgrass (Pennisetum ciliare) and Sahara mustard (Brassica tournefortii).  Buffelgrass has the potential to change the ecology of the Sonoran Desert because fire is not part of its environment. The native grasses need around 15" of yearly rain to form a grassland environment, but the South African buffelgrass will thrive on half that and is thus making inroads into the desert, especially where the desert has been disturbed.  The Tucson chapter of the Arizona Native Plant Society has a group of "Weed Whackers" who primarily combat buffelgrass.  It was introduced in the USA by national and state agriculture departments, but it is in northern Mexico where its effects have been the most devastating.  As early as the 1980s in Sonora, acre upon acre of old growth cactus forest (mostly Stenocereus, Pachycereus, and Carnegiea) was being bladed to plant buffelgrass for ranching.
  The rumor is that much of this devastation is financed by drug profits being invested and laundered in local enterprises.

The annual Sahara mustard is a problem in the low desert where it smothers the native ephemeral wildflowers during years of abundant winter rainfall.  For example, in the Mohawk Valley east of Yuma, where one would see vast expanses of desert lilies, sand verbenas, evening primroses, etc. after rains, all there is now is solid Sahara mustard.  This is what our local "Weed Whackers" focus upon.

Shawn Pollard
Yuma, AZ


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