> The cows were left to roam free I think they mean that a farmer had a herd and let it roam free over a vast area. Then he sent some cowboys to take the herd

> The cows were left to roam free I think they mean that a farmer had a herd and let it roam free over a vast area. Then he sent some cowboys to take the herd to the city / town with a train and sell them. Just like in Red River movie ;) > It doesn't clarify which species shouldn't have been introduced It may be the cows 150 years ago. Now the species mix would be probably different, with similar effects on the marine ecosystems. Does it really matter if the river of urine and excrements is from cow, pigs or chickens? I don't know.