Noxious weeds alter the way these processes work. By increasing surface erosion, noxious weeds cause a loss of organic matter and nutrients that are normally concentrated in soil surface layers. The removal of organic matter also reduces infiltration capacity, thereby making water less available for plants. Because many noxious weeds have relatively sparse plant canopies, more water evaporates from the soil surface, which makes even less moisture available for plant growth. Protecting and conserving the surface soil are critical to the long-term sustain ability of healthy, functioning ecosystems.
Soil provides nutrients and moisture necessary for plant growth and is fundamental to all life.
When spotted knapweed invades range land dominated by native bunch grass, protection of soil and water resources is compromised. Loss of soil because of noxious weeds may have very serious consequences in the future. For most recreationists, the enjoyment of being outdoors is diminished in areas dominated by noxious weeds. Riding horseback through houndstongue promotes husbandry problems for horses when seeds attach to the hide. The invasion of spiny weeds, such as Canada thistle and musk thistle, limits river access and the sharp spines make walking difficult.