Voyager 2 is about 17 billion kilos away and has left the solar system. So solar system is about 34 billion kilos across. A light year is approx. 9 trillion kilos so the solar system is just less than .5% of a light year across.
Don’t you think it is irresponsible to introduce foreign fauna to an ecosystem and displace its current residents? I don’t see what is confounding about that. And what do the fauna of the region have to do with human cocaine use?
The article`s authors are enthusiastic about the hippos returning the ecosystem to a past state but I imagine that the current residents that are being displaced are not so sanguine about it.