Sheep: The new weapon against invasive plants

What’s better than spraying herbicides on a field full of non-native weeds? Setting a herd of sheep loose on it to chow down.

That’s what they’re doing in Missoula, Montana, where 1,000 acres of public lands above the Missoula Valley have been invaded by non-native weeds such as leafy spurge and knapweed.

The sheep feast on the weeds all summer and part of the fall, then are rounded up and chased home to a local ranch before the winter snows begin. The New York Times featured a story about these sheep yesterday.

I’ve heard of people using goats to keep their lawns cropped, but I’ve never seen sheep employed in a plant management role. Apparently grazing sheep for weed control has also caught on at Civil War battlefields and ski slopes, among other places.

I love the idea! As the article mentions, sheep are a low-cost, non-toxic way to get rid of weeds. Much better than spraying loads of herbicides. Plus they provide a bucolic look — and allow sheep farmers to get a return on their investment (or in this case, allow a rancher to afford to keep his ranch).

One plant ecologist at the University of Montana, however, notes that there’s no data to show whether they sheep are having a positive or negative impact on the environment. They could be causing erosion and moving invasive weed seeds to new places.

It’s probably worth studying these sheep more, but call me a romantic — I prefer the sheep weed-eating strategy to spraying 1,000 acres with herbicide.

What do you think? Post your comments here!