If you have a frightening experience immediately after hearing a strange sound, your fear may be aroused when you hear that sound again. this best illustrates:

depends on what they need

the invasive species was introduced due to commercial purpouses, as there was a demand for fur clothes and hence, a business opportunity connected to this product. actually, it was when the nutrias scaped, causing harm to the us ecosystems when they acquired the status of invasive species. in this case they have caused an environmental problem, but it could have affected also economic interests or even human health.