What is a duty or task to be fulfilled?

forty niners migrated west due to gold discovery in california and it the west was a new place for hope this : )

explanation:

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.