Exhibits
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Changing Lands: the science and law of land management. |
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Noxious Weeds |
Noxious Weeds
| Wanted Dead (Not Alive): Noxious Weeds One of the most pervasive and dangerous problems facing public lands managers right now is how to control the deadly spread of noxious weeds. Legally, a noxious weed is any plant designated by a Federal, State or county government as injurious to public health, agriculture, recreation, wildlife or property. These weeds are often exotic species which threaten to choke out native plants, including many threatened and endangered species. Noxious weeds are threatening wildlife habitat, disrupting migratory bird routes, and reducing biological diversity-- in some places, noxious weeds create a monoculture where nothing else can survive. These weed invasions began a few centuries ago but in the mid-1800's many weeds arrived from other European and Asian countries (new invaders are still arriving). Unfortunately, they arrived without their natural enemies, such as insects and pathogens, that kept them in check in their country of origin. Consequently, these new plants are typically very aggressive and have the ability to dominate many wildland sites. For example, in its native habitat, purple loosestrife only comprises one to four percent of the native vegetation, but in North America densities of up to 80,000 stalks per acre have been recorded. In this way, the weeds force out native plants, reducing biological diversity. Plants are the crux of any ecosystem, stabilizing soils and providing food and shelter for animals. When a plant that is not adapted to an ecosystem invades, everyone suffers. The root systems of noxious weeds generally fail to stabilize soil, and the plants are often less nutritious than native plants, or are actually poisonous. Even worse, many weeds use more water than native plants, and dry up crucial watering holes and springs, or choke out riparian areas, driving out both birds and mammals. Some weeds even deposit poisons into the soil, preventing any other plant from ever growing there. In a recent summit conference on controlling weeds, the biologist from the BLM described the spread of weeds throughout the public domain as "a biological emergency" which is causing "the greatest permanent land degradation in recorded history." This environmental problem is fast becoming an economic problem. In 1996, the economic impact of leafy spurge along in the north central states (MT, WY, SD, ND) was about $129 million. Knapweed costs the state of Montana about $14 million every year, and other states are seeing similar impacts. Private land is also affected, reducing the market value of ranch land about 90%. How to address this problem? As every gardener knows, eradicating weeds is a laborious, painstaking, and lengthy process. Expand your backyard garden to some 600 million acres, and you begin to get an idea of the extent of this problem. For environmental reasons, herbicides are often not an option. Fires often exacerbate the problem, as the weeds can regenerate faster than the native plants. Cheatgrass is a particular problem on rangeland, as it not only spreads quickly after a fire, but it exponentially increases the risk of rangeland fire. Agencies, individuals, and state and local governments have all been working together to find solutions. Some areas are good candidates for spraying, and some land managers have had success using goats, which eat the weeds and digest them so thoroughly that the seeds are not excreted. In most cases, though, the only recourse is to dig up the weeds and plant native species in their place. This is costly, slow work, and programs suffer from lack of funding. Education plays a big role in weed control. Humans inadvertently contribute to the spread of weeds by carrying them out of infested sites on their shoes and the tires of their cars. You can help control this dire situation by learning to recognize noxious weeds in the wild & carefully cleaning the seeds off your clothes, boots, and cars before leaving the area. |
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) Russian olive. ) Tamarisk (salt cedar) are one of the greatest dangers to the West's native plants and watersheds. |
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