Why do you think some groups are highlighted and others are mostly ingored?

Depends on the subject, but some are highlight due to having back up evidence for their importance. Those groups that are ignored don't usually offer enough good claim to back themselves up on what they support.

Hopefully this is the kind of answer you needed.

b) to encourage free trade

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.