Invasive Species

According to the Western Governors Association, species like the Canada thistle and common carp aren’t just nuisances -- they’re a matter of western biosecurity.

In an open field in Longmont, Colorado, about a dozen people crouched in the tall grass, moving slowly and deliberately through mud that squelched underfoot. Some carried huge, serrated knives called hori-hori, a Japanese tool made specifically for gutting weeds. Others wielded gardening shears, saws or chemical sprays as their weapons of choice.

The tamarisk plant, also called saltcedar, is infesting waterways across the West. The scaly-leafed shrub can grow taller than a person. It sucks up a lot of water and spits out salt, making the soil around it too salty for other plants to grow.

“It’s very bad, yes,” says Alex Gaffke, a graduate student in land resources and environmental science at Montana State University.