ne of the most serious problems affecting natural ecosystems globally is the invasion of nonnative, exotic plants and animals. Some of the most intractable, damaging, and widespread exotics, such as cheatgrass (bromus sp.) and tamarisk, are well known. Cheatgrass, for example, competes with native plants for water and nutrients, an often critical factor in the arid southwest. Even more significant, however, is the resulting foreign fire regime that now threatens desert archetypes such as the Joshua tree and saguaro cactus, not to mention hundreds of other species dependent upon natural ecosystems. The effect of tamarisk has been especially damaging, displacing native vegetation and drying up critical water sources for native wildlife. There are literally hundreds of other nonnative plants and animals which collectively imperil native biodiversity by damaging the ecological balance of plants, animals, soil and water achieved over many thousands of years. As native plants are displaced, animal populations that rely on the plants for food and shelter also decline. This directly and adversely affects the creatures dependent on complex food web relationships.
Exotic seeds and plant parts are introduced by wildlife, wind, water and humans. The National Park Service is required by law to keep the parks as unaltered by human activities as possible, and has a clear policy on protecting natural processes within its natural areas, such as the 1.1 million acre proposed wilderness of Grand Canyon. The NPS defines nonnative species as any animal or plant species that occurs in a given location as a result of direct, indirect, deliberate, or accidental actions by humans. This definition allows the NPS to recognize and distinguish between changes to park resources caused by natural processes of animals and plants, such as natural range expansions, and those changes caused by animals and plants introduced by humans.
In its Preserving Our Natural Heritage: A Strategic Plan for Managing Invasive Nonnative Plants on National Park System Lands, the NPS has developed management strategies to address the problem of ecosystem alteration due to nonnative invasion. The first line of defense, the most economical and efficient means of management, is to prevent introduction. The introduction of nonnative plant and animals into natural zones is not permitted, except in rare cases where they are the nearest living relatives of extirpated native species, where they are improved varieties of native species that cannot survive current environmental conditions, where they may be used to control established exotic species, or when directed by law or expressed legislative intent.
Obviously, the best time to attempt control is when the population of exotics is relatively low, such as for Russian olive or ravenna grass. These two species are potentially extremely damaging to natural riparian areas and both were deliberately introduced to areas immediately adjacent to Grand Canyon. The park, as well as a small group of dedicated volunteers operating on a shoestring budget are effectively controlling these two species.

These folks are investigating the feasibility of controlling camelthorn in limited areas such as campsites. Control or eradication of widespread species, such as tamarisk and camelthorn lies beyond the realm of possibilities, at least for now. Such large scale restoration efforts require considerable research and funding, and could actually adversely impact the natural environment in unforeseen ways.
Other park restoration programs include control of the Himalayan blackberry (also deliberately planted), a tasty but damaging exotic that has taken control of an entire drainage off the South Rim. A variety of introduced plants plague the urbanized environment of the North and South Rim developed areas. Again, a dedicated cadre of volunteers lead by a few NPS revegetation crew leaders has made impressive inroads in controlling many of these problem plants.
Palm trees, a tenacious, some would say beautiful exotic, first appeared along the river in Grand Canyon toward the end of the 1970s. The first one actually removed once happily thrived near Mile 103 at the “Shady Grove” camp. It took a lot of digging, but ultimately the palm, or most of it, perished. Since this deed occurred in 1982, the year before the 90,000+ flood flows, no one knows if in fact it would not regenerate from remnant parts hidden beneath the sand since most of the sand ended up in Lake Mead anyway. Since then, no less than ten palms have appeared throughout the park (Hermit Creek, Bright Angel Creek, Havasu, Thunder River, and at Christmas Tree Cave). It is interesting to note that at least two of the Havasu palms survived the great flash floods that removed much of the native velvet ash population. The odd distribution of trees suggest either avian, human, or divine intervention contributed to the modest proliferation of this species. I always thought it was a dory boatman.
For 20 years I would pass Christmas Tree Cave and think of the exquisite stalagmite and dust loaded with bat droppings that characterized the cavern. On the 21st I noticed another palm tree. Given the difficulty of removing them, another 5 years or so passed before an approved herbicide with a qualified applicator (human) accompanied a resource river trip. On that trip we removed (killed, murdered, or whatever) a dozen Russian olives, scores of ravenna grass, a few hundred camelthorns, and one palm tree. Rain prevented the crew from working up Thunder River, Havasu, and Hermit Creek.
There was nothing vindictive about the palm's slaughter. Another nonnative plant, probably planted as an ornamental in what should be a wilderness setting, was removed. But, as is often the case involving killing an attractive, living organism, more than a few caring, very sane people are quite upset about it. For that I am sorry.

Kim Crumbo