Now, listen to part of a lecture on the topic you just read about. Russian thistle does offer some benefits, but it's not as helpful as the reading suggests and can actually cause problems. Now, it's true, farmers have sometimes helped their animals during droughts by feeding them Russian thistle. But this can be very dangerous. You see, under certain conditions, Russian thistle can absorb high levels of nitrogen from the soil and store it in the form of nitrate. Even fairly small amounts of nitrate can be very poisonous to certain animals such as cows, killing them within just a few hours. So feeding Russian thistle to farm animals is not always safe. Second, Russian thistle probably destroys more habitat than it creates. That's because tumbleweed helps spread wildfires. Natural fires are common in dry areas of the United States. Normally, empty areas of land, places where there is no vegetation to burn or natural barriers that stop the spread of wildfires. But tumbleweeds can catch fire and be blown by the wind across natural barriers, start new fires in other areas. Many habitats are destroyed by these fires, and very few animals can live where the vegetation has burned away. Finally, the fungus that infects Russian thistle can sometimes improve damaged soil for native plants, but this is rare. You see, the fungus is only found in the upper most part of the soil. Now, in areas where lots of Russian thistle grows, the upper part of the soil often dries out and is blown away in the wind. This happens because Russian thistle is very efficient at taking water out of the soil. So when there's a lot of Russian thistle, the soil will become very dry and blow away easily. And when the dry soil gets blown away by the wind, the fungus get blown away, too. So the soil remains damaged and unable to support native plants.