Aliens in Our Backyard

Canada doesn’t have any Brazilian fire ants, which is fine with me. Given a chance, fire ants will swarm a newborn calf before it gets a chance to stand; they go for the eyes. In the warmer parts of the United States, fire ants have been doing just fine ever since the 1930s when somebody – either unwittingly or with a terrible sense of humour – introduced them. In their native country they’re held pretty much in check by other species, but in the US they’re aggressive and highly successful, an import nobody wants.

I was introduced to fire ants in a stifling field station in the Brazilian state of Mato Grosso do Sul, by a wispy American graduate student who spent the last three years hiking into the Pantanal scrub and observing the creature in its rightful place. He seemed credible enough, and I tend to believe people who are prepared to spend six months of the year hunkered down in alligator country in forty-degree heat.

The next day, I went on a field trip of my own, to the place on the Miranda River where, a few weeks earlier, two tucunaré had been caught.

What’s the connection? Well, tucunaré (too-coo-na-RAY) is a fish – a sizable and attractive one – and like the fire ant it’s emigrated to places where it has no business. It belongs in the Amazon basin, not the Parana, and although the sport fishermen love it, tucunaré outcompetes the local species. This particular pair (and let’s face it, if two were caught it means there are thousands in the river now) escaped from a fish farm upriver; the rains came, the dike broke, and off they went, kids in a candy store.

Brazil is the perfect place to contemplate escapes and colonizations. The slavers who brought Africans from Dahomey were themselves transplants from Portugal; Germans and Italians populated the south, and a wave of Japanese immigrants began in 1908. The local indigenous people, of course, didn’t stand a chance. But out of this genetic cauldron, a couple of hundred years later, has come a society with some of the most beautiful people on Earth, and it’s a remarkably tolerant one.

So perhaps, at least for Brazil, colonization and assimilation have been good things. But fish and fire ants are like people: if there aren’t any barriers to reproduction, they’ll jump in and assimilate their brains out. You can build all the containers you like, but everything that lives – people and plants and animals and fish – will eventually find ways to jump out. Dikes break, nets tear, seeds stick to tourists’ socks, cockroaches crawl out of suitcases and the world’s shipping lines distribute whole aquaria of marine stowaways in their ballast tanks.

So, is mixing bad? Should we try and stop it? Can we? These are tough questions, especially for me, a biologist who has spent his career trying to preserve the genetic diversity of fish. When you run a dip net through a little two-bit lagoon in the Pantanal, as I did recently, and come up with a dozen different species of fish that any hobbyist would die for, emotions take over and it’s hard to condone the loss of even a single species.

A visit to a place like Brazil can be subversive. The whole world is genetically leaky, but maybe it’s just more obvious here. If escapes and colonization are inevitable, what does that mean for conservation? Should we just lie back and enjoy it? For me, the answer is still an emotional one, with the huge caveat that, maybe, diversity doesn’t have always to be static. The face of life in Brazil changed forever when the Europeans and the Africans and the Asians came, and the fire ants and the tucunaré and the farmed Atlantic salmon in the photo above and thousands of others like them are going to keep escaping. I don’t much like it, but you have to be realistic about how much you can change it. Maybe that’s just evolution.


A version of this article was originally published in Waters Magazine
Photo of Atlantic salmon on a farm in British Columbia by Monica MacIsaac