Everything is spreading. We're a large interconnected world, and we'll inherit everyone's problems eventually. There are better alternatives, but it's not something people will seriously consider.
A system that prices in cost of negative externalities is better than what we have now. A system that caps how much wealth a person can have is a better system that what we now have. A system that prevents the exportation of pollution is a better system than what we have now.
These are opinions and I understand not everyone has these same beliefs.
Do you live in the American continent? Look at the skin tone of most people you find in the streets. Go to a library and try to find out what was the average skin tone in your region 600 years ago. Compare both.
Thinks have been spreading for quite a while. Migratory species are older than ourselves. Jet stream can carry spores over oceans. World commerce is older than you think. Wars and migratory movements has always been a part of our civilization.
Not the OP, and this is probably not what they were thinking of, but from the point of view of the planet's ecosystem, eliminating the humans that keep introducing species where they don't belong (or at least drastically reducing their population) would be the most effective measure.
Also, what is that babble about "the planet's ecosystem" being better off by eliminating humans? If you really want to see it as a whole - the Gaia hypothesis - then humans are part of it just like flies and ticks and mosquitos and birds and whales. All play a role, some spread diseases to others while they feed yet again others. Removing humans from the equation is just like Mao's decision to get rid of the sparrows which ate some of the harvest in that the balance will shift until a new equilibrium has been reached. In Mao's case it killed tens of millions of humans, removing humans will result in the death of hundreds of millions of other species.
We are in the midst of a great extinction event. It’s the only extinction event caused by one species. We are quite bad for the planet’s ecosystem and things like factory farming of cows and pigs cause great suffering. Having far fewer humans on the planet would be a great benefit to other species and to humanity.
There's no such thing as introducing species where they don't belong. Ecosystem are dynamic, several other animals serve as vectors for transporting species from a place to another.
There's no such thing as a long term static equilibria where godess gaia looks like a Jehova's witnesses book illustration. This is an incredibly cultish and misanthropic position.