By Ben Ikenson

COLFAX COUNTY, New Mexico--At Maxwell National Wildlife Refuge here in the northeastern part of the state, sandhill cranes sail gracefully over wide-open valleys. Eagles glide above the rolling, wind-swept prairie, searching for prey. Ducks and geese drift across the surface of scattered lakes, in which a bounty of yellow perch swim.

And through the middle of this seemingly picture-perfect scenery, a perturbed-looking man slowly drives an ATV with his gaze attentively fixed to the ground. What looks like another day in paradise is, to Dan Dinkler, another day in a botanical hell.

As manager of the 3,000-acre wildlife refuge, Dinkler has officially declared war on the prolific musk thistle, the bull thistle, the hoary cress, and the tenacious and control-resistant Russian knapweed and Canada thistle. These plants represent a growing threat to wildlife habitat on the refuge as well as to the ecological integrity of the region.

By degrees, non-native plants can literally take over a landscape and dramatically alter the ecology. Freed from the diseases, insects, and other controls found in their native habitats, these plants use their energy to grow larger and faster; to put down deeper roots; and to produce more seeds. Uncontrolled, they quickly outcompete and replace native plants.

In the past, exotic seeds traveled across the continent as freight in covered wagons. Some were planted as ornamentals by settlers; some were introduced as cost-efficient forage for livestock; others arrived as "hitchikers" along with food crop seed supplies. Settlement, which increased dramatically in the West in the late 1800s, altered both the landscape and the ecosystem. Through the years, non-native plants such as Russian thistle and musk thistle have gained a foothold and invaded the range. Some plants, such as toadflax, which form solid stands, do not adequately hold the soil, and have thereby increased erosion significantly.

Today, wildlife will not forage on most of the non-native weeds that are invading northern New Mexico; and some of the invaders, such as yellow starthistle and Russian knapweed, are toxic to livestock and, if eaten, can cause a slow, horrible death.

Straddled atop his four-wheeler, Dinkler rides in slow search of the enemy. "Invasive plants must be detected before they flower or else they will produce seeds," he said, without lifting his earthbound glance.

Dinkler uses Global Positioning System (GPS) and Geographic Information System (GIS) equipment to locate, map, relocate, and monitor weed infestation sites as part of an integrated weed management program. To fight these tenacious invaders, he must select from an arsenal of weaponry and defense tactics, which includes hand removal; mechanical cultivation; low impact, selective herbicide applications; and planting of competitive grasses. Control methods vary with species.

"While the annual crop of new plants can be controlled," Dinkler warned," it's necessary to follow up for several years to manage each year's crop of new plants that sprout from the abundant seed bed and perennial root systems." Some musk thistle seeds, for example, can survive 15 years, though the majority will emerge within five years.

That is why Dinkler is a strict believer in the 3:1 rule: For every year you delay controlling an infestation, it will take three years to regain control. "This rule may vary with locations, species, and environmental conditions," said Dinkler, "but as a general rule of thumb, it demonstrates why it is important to jump on weed problems as early as possible!"

But jumping on weed problems is a constant challenge, especially because infestations can spread so easily and so unpredictably--on the wind, through wildlife migration, and other ways. Today, seeds are no longer transported across the country in slow-moving wagons; they crisscross the continent on interstate highways, in the tracks of tires.

In fact, experts estimate that invasive plants already infest well over 100 million acres and continue to increase by 8 to 20 percent annually, causing billions of dollars in lost revenue and control costs. As for public wild lands, 4,600 acres are lost each day to invasive weeds, according to the Interagency Committee for Management of Noxious and Exotic Weeds. Much of this land will never be recovered. If invasions are allowed to spread, wildlife populations will decrease proportionately, and some plant species are likely to become extinct.

Though it poses serious management issues at Maxwell, the weed infestation problem does not begin or end at the refuge boundary. Quite possibly, Dinkler's most powerful weapon of defense is outreach. "We all share, or will share, the same invasive weeds eventually, so it is vital to get as many land owners and agencies on board as possible."

In Colfax County New Mexico, the refuge is just one of several entities that are developing a systematic plan of attack on invasive weeds. "Trying to control non-native invasive weeds is like fighting fire or waging war," Dinkler said. "You have to know your enemy, plan and implement an effective, science-based strategy, and stick with it."

Dinkler's battle cry echoes across the nation, where invasions by alien species--animal as well as plant--are rampant: In the Southwest, salt cedar continues to spread over the riverbanks to the detriment of native cottonwoods and willows and the species that depend on them;

Giant salvinia--a floating fern that quickly colonizes, shades water, and depletes oxygen--is rapidly infesting the bayous of the Texas Gulf Coast and threatens to blanket all open, quiet water; (see related article);

Similarly, the aggressive hydrilla (some call it "devil grass") is choking the life out of Louisiana swamps;

In the Great Lakes, the parasitic sea lamprey--with its outlandish sucking disk and razor sharp teeth--has wreaked havoc on the native trout population, and zebra mussels are destroying native mussel populations while they clog up industrial and municipal water delivery systems. And, in Guam, the brown tree snakes has decimated several bird species on the tiny U.S. territory.

According to a U.S. Fish and Wildlife Service report, the number of invasive non-native plants and animals in the United States is over 6,300, with new invasions occurring on a weekly basis. That is why the Service has made it a priority to address and resolve the multitudinous problems that stem from the spread of invasive species. Where possible, the source of those problems should be removed by the roots, so to speak. Consequently, an army of land managers, with warriors such as Dinkler, is fighting the invaders and striving to restore health to their respective landscapes.

As Dinkler said, while grubbing a clump of musk thistle from the earth, "all that is green is not good."