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 opefully you had the good fortune to spend time in the Canyon during this year's astonishing spring bloom. Tiny, purple-flowered daleas (Dalea spp.) carpeted the ground alongside the Tanner Trail. Mariposa lilies (Calochortus flexuosus) abounded on the Tonto Plateau, gloriously swaying in the wind. The graceful seedheads of the annual, dandelion-like silverpuffs (Uropappus lindleyi) were a fun surprise to backcountry travelers. A favorite of many, the vividly-colored and phenomenally fragrant purple sage (Salvii dorii) displayed themselves proudly on Bright Angel shale slopes, a treat to the passerby. Many of these species had been patiently awaiting the winter rains which arrived in an abundance that we have not experienced in many, many years in the Grand Canyon region.
While the winter rains brought these friends out of hiding, they also set the stage for exotic plant species (aka non-native, alien) to dominate the landscape. In fact, the verdant green slopes that enthralled many canyon wanderers this spring, actually paint a very different picture than what we saw just a few decades ago. A quick stop near Eminence to take a closer look at the slopes reveals a near dominance of red brome (Bromus rubens), cheatgrass (Bromus tectorum), ripgut brome (Bromus rigidus), and mustards (Descaurania spp.-some native, some exotic). The first bromes you probably know since almost all of us who have taken a walk in Grand Canyon have painstakingly pulled their seeds from our socks. Cheatgrass is now more abundant in the west than the large native bunchgrasses and annual forbs that are relished by wildlife. Red brome is one of the most dominant species in the inner canyon, and you have to wonder-what native species have been crowded out by this aggressive little annual? The third brome you may not know yet. Ripgut brome used to only be seen near a few campsites and developed areas (Indian Garden, Phantom Ranch), but it has now spread far beyond those disturbed areas. I remember only five years ago when there were just a few small patches of ripgut brome along the Bright Angel Trail, and I regret not having the foresight to pull them. With their long, barbed awns, the seeds cling to fur and clothing, allowing the plant to cast its progeny far and wide, which it has.
While it may be too late to address some of the more widespread species, we would be remiss not to take notice of a new species that is just now knocking at the park's door-Sahara mustard (Brassica tournefortii). Sahara mustard is native to Mediterranean area, thriving in the broad desert belt from northwestern Africa to the Saudi Arabian peninsula and possessing a fondness for sandy and gravelly soils. This means it is fully adapted to arid regions, in fact, the southwestern u.s. might just remind this plant of home, allowing it to settle in and feel very comfortable. So how did it get here? Like camelthorn (Alhagi maurorum), another of our spiny invaders, Sahara mustard was likely brought over, unintentionally, with imported date palm (Phoenix dactylifera) trees. It was first found in California in 1927 and within ten years it was commonly seen along roadsides and fields. Despite its presence in California for almost eighty years, this year it earned the name “tsunami mustard” as it has blanketed whole valleys, hillsides and ecosystems.
Sahara mustard takes many shapes and forms-growing from only five inches to up to four feet tall and almost a broad. It often has enormous basal leaves that can smother surrounding plants and rob the early spring moisture from winter annuals. It also has another crazy adaptation for survival-it coats its seeds with a sticky gel that helps them to cling to animals. As these giants die back in early spring, their large, dry bodies act like tumbleweeds, acrobatically roaming across the landscape and providing tinder for future fires. Rodents, and likely many other creatures, eat and cache the seeds, which are know to remain viable long periods of time. The seeds can actually stay viable for many weeks on floating plants-imagine what that could mean. This plant has superb survival strategies, loves the desert and riparian areas of the Southwest, and is in our neighborhood. In fact, it now forms a dense blanket around portions of Glen Canyon, and at Lake Mead, Sahara mustard is threatening the habitat of rare dune plants. We know it is upriver and downriver, but what about Grand Canyon?
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If you were at Lees Ferry this spring, you more than likely saw this plant. The alarming news is that if you were at Lees Ferry last spring, you might not have noticed it. In just two years, Sahara mustard went from growing in just a few manageable patches, to being one of the most dominant plants, found along the mouth of the Paria River, spreading up the slopes, and literally surrounding the campground. In 2004 at the Guides Training Seminar (gts), I introduced you to this plant and showed a few photographs. Some river guides even got to know this plant up close and personal by pulling over 9,000 individuals from the Paria Beach area and along the roadsides. This year, volunteers removed almost 30,000 plants in just two days, and to be quite honest, there were probably about another 500,000 that we did not pull due to lack of time, money and people. And that's just Lees Ferry! During spring surveys we found Sahara mustard at Indian Garden and along Pipe Creek, and the CanX crew pulled it at North Canyon, Buckfarm beach, Silver Grotto, and a few other places on the upper half of their spring training trip.
Ecologists in California are loudly sounding the alarm about this exotic mustard worrying that entire ecosystems are at risk. Some believe that this plant could easily destroy the native vegetation of several National Parks within our lifetimes. Dr. Libby Powell, the botanist at Lake Mead National Recreation Area, posted a report about their efforts to date and says, “We have a disaster on our hands that a great deal of manpower will be needed-just to keep at bay… It is time to act, not study this menace-in my opinion-or say goodbye to our favorite desert places as we have known them. It is definitely easier and more fun to create experiments rather than start pulling plants-but pull we better start doing-soon-or we can forget finding an answer otherwise, in my opinion.”
This is an alarm that we should be hearing loud and clear. The truth is that we don't actually know the current distribution of this species in the park. We do know that seeds from the Glen Canyon plants are floating down the river this year. We do know that the plants we did not get at Lees Ferry will be spreading downstream. Is it possible that the amazing biodiversity found within Grand Canyon which brings such joy to humans and is critical to wildlife, is more threatened than we imagine? The answer is probably yes. But, it is also probable that the community of people that call Grand Canyon home, will continue to educate themselves as they always do, and in doing so, will be willing to join in and lend a hand. We will be looking for volunteers to spend time at Lees Ferry next February and March-the plan is to pull all of the Sahara mustard plants before they produce seed. That is the least we can do and it will take a massive commitment on our part, to be thorough, vigilant and timely. We will also be looking for folks to keep an eye out for this plant downriver next year-and we will have laminated handouts about this species along with postcards so that you can write down location and control information and send it back to me. I feel confident that we have learned enough lessons in the past to now fully embrace the need to act quickly and cohesively in the present. I can also envision the long days of pulling plants, and I know they will end with songs, stories, and an excellent meal shared with friends, so I invite you to join the “over the edge veg” team!
Lori Makarick
lori_makarik@nps.gov
Over the Edge Vegetation Program Manager
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