It’s Spring in our garden and everything is starting to grow – everything of the non native plants, that is, most of our native plants are winter growers and have been growing for a while – especially the Oxalis. We have two kinds of Oxalis in our backyard, one that hitchhiked in and one that I brought in on purpose. Both of them are trying to take over my potted plants. The hitchhiker probably came in as seeds in a succulent that I bought. Once it got here, the Oxalis went nuts, and it seems that 50% of my gardening time in spent pulling little Oxalis plants from between more desirable plants, like the Gasteria in the picture. I have no excuse for actually buying an Oxalis plant but I did have a reason. My thinking was that the new plant, Oxalis callosa, is a beautiful little South African bulb, I like South African bulbs, and, because it is a bulb, I assumed it would just stay in its pot. It hasn’t.
O. callosa, the South African bulb, is doing so well because it has no natural predators. Well, that is not true, the deer probably like it, but the local bacteria and local bugs don’t, so, when I say it has no predators, I am not talking about large mammals that will eat almost anything, I am really talking about the basic predators at the most basic level.
A story that most of us have heard is that of rabbits taking over Australia. In the late 16th century, English sailors brought rabbits to Australia for food. They were kept in cages and weren’t, apparently, a problem. Then in 1857, Thomas Austin released 24 rabbits into the countryside, saying “The introduction of a few rabbits could do little harm and might provide a touch of home, in addition to a spot of hunting.” The rabbits went wild, just like my Oxalis and for the same reason. There was nothing in Australia to make them sick, there were no germs that loved rabbits, there were no parasites to slow them down, Yes, there were larger animals that could and did eat the rabbits but that is usually not a big enough problem to destroy a population. Ten years later, the millions of rabbits had become a major problem and they are still a problem.
Humans, or more accurately proto-humans, have been leaving Africa for millions of years, even before we became what we now call human. The current thinking is that H. sapiens, modern humans, us in other words, crossed from Ethiopia to Yemen sometime around 75,000 years ago. We did run into some of the proto-humans that had populated Western Asia earlier and they must have fought and killed each other, but there were no germs waiting for us, there was no bacteria to prey on us, there was no malaria or parasitic disease like flatworms, no typhoid or dengue fever.
We evolved in Africa during the last 4 to 8 million years and lots of organisms that like to live off of people evolved right along with us. But Greater Asia didn’t have the African diseases or parasites. Our new Eden was a much easier place to live in than our birthplace and we were are worse than the rabbits; we are explorers and we have spread everywhere.
