A couple of times, my ex and I bouldered (that’s rock climbing, but without ropes and harnesses) in the Berkeley hills. His little Honda Civic didn’t have power steering—he’d work up a sweat as he hauled the steering wheel this way and that. I’d peer wide-eyed over the edge as we rounded hairpin curves mounting up and up narrow residential roads, past classic convertibles parked in front of mansions tucked behind giant rhododendrons.

The house-sized rocks had soft powdery red dirt round them, tamped down. We hung, our fingers grasping sharp holds in the stones, our toes wedged into cracks. We worked quietly, shaded by tall eucalyptus trees growing furiously in foreign soil.

Both the rhododendrons and the eucalyptus were exotics imported to California. As an immigrant to the Bay Area it was all intensely exotic to me. The shingled mansions with deep porches, the wealth, the sunshiney days.

The cultured and cultivated gardens of the wealthy of centuries past have always been filled with exotics, a show of colonial power. How many species from across the globe can I collect into this space around which I’ve built my fence. How much of the wild world can I bottle up, send back, own and exert my dominion over, at least in symbolic ways.

Everything is invasive, if you look at it on the right time scale.

Humans certainly are. Life itself has been forever invasive, blossoming anew after each of the five massive extinction events that we’ve learned about so far. After each mass death life moved once more across the globe from environment to environment if it proved to be possible.