Poison Frogs and Super-Weeds: Controlling the Uncontrollable

Should we start thinking of GMOs as invasive species?

When the infamous cane toads were introduced to Australia in 1935 to try to control the population of the pestilent sugar cane beetle, there were only 102 of them – at first. The scientists bred the amphibians in the lab and released 2,400 hoppers into the wild in the hopes that they would eat the cane beetle. But the plan backfired. Today, the cane toad population is estimated to be in the billions and their habitat is expanding by 55 kilometers every year. Not only are they a giant nuisance that has cost the Australian government millions, but their poison is toxic to other animals, affecting many of the native species.

For thousands of years, biology evolved in silos—habitats separated by oceans, rivers, mountain ranges, and different climates—creating the diversity we know and love. These isolated ecosystems reached a cautious equilibrium over millennia of trial and error, and established their own rules of co-existence. Although this process was not deliberate, it may seem like there is an intelligent design to it: as if Nature (or God) carefully created these real-world terrariums. And today, humans are acting as gods— or, perhaps, more like pollinators—spreading the seeds of life from faraway lands wherever we go.

Whether accidental or deliberate, the introduction of non-native animals, plants, fungi, and even bacteria or viruses, can cause profound changes to the environment. In the absence of natural predators or immunity, introduced species can wreak havoc on the local flora and fauna. The Australian frogs are only one of the many examples. It is a striking one: you can literally see the animals taking over the land that does not belong to them. However, the spread of biological material is not always apparent. And we are just starting to realize that it’s happening a lot more often than we think.

Horizontally, not vertically

The accepted view is that genetic information is passed down in the form of DNA from parent to offspring. With each generation, DNA gradually accumulates mistakes, which leads to the emergence of different species that don’t look anything like their distant relatives. This process takes place over millions of years. But that simplistic view of the propagation of genetic information has been challenged since Darwin formulated his theory of evolution. Since the 1980s, scientists have known that DNA can be shared between bacteria outside of the act of reproduction. Skipping the long and tiresome process of evolution through inheritance, genes can be passed along to unrelated species—friend-to-friend—in a process called “horizontal gene transfer”.

Think of DNA as a script for carrying out instructions inside a cell. One bacterium, swimming in a lake or pool of water, dies and its cell falls apart, releasing its DNA script into the environment. The long ribbon of DNA breaks up into smaller pieces, small enough to where they can get inside other bacteria swimming in the same pool through the pores in their cellular membranes. If the new script proves to be useful to the cell, it gets incorporated into its own DNA and passed down to future generations.

Of course, this is a very simplified (and not entirely accurate) way to describe the complex process of horizontal gene transfer—but it gives you an idea. Turns out, horizontal gene transfer happens not only between bacteria that swim in the same water. Since we started sequencing the DNA from the world around us, scientists have discovered that genes can jump between different kingdoms of life: from fungi to plants, bacteria to insects, fungi to nematodes, plants to plants, fish to fish – and everything in between. There is a gene-sharing fest going on out there in nature.

And the crazy thing is—we don’t really know how it happens. How does a plant growing in solid dirt, with its DNA enclosed inside a nucleus and protected by a durable cell wall, share its genes with another, unrelated plant? Horizontal gene transfer happens in the dark. We only know that it happens AFTER the fact. Environmental DNA sequencing is only now beginning to illuminate just how common horizontal gene transfer is in nature. And it makes scientists question everything we thought we knew about evolution.

Speeding up evolution

We are living in the era of biology when we can dramatically speed up evolution. What used to take thousands of years to evolve, can now be designed and created in a lab in a matter of months. Of course, scientists take into consideration the potential consequences of the genetic manipulation of bacteria and plants and put mechanisms in place to make sure that those organisms cannot replicate uncontrollably outside of the lab and to avoid the accidental release of synthetic genes into the environment.

But things could go wrong. And things HAVE gone wrong already. One example is the antibiotic resistance crisis the healthcare system is currently facing. Antibiotic-resistant infections happen when a microbe acquires a trait that allows it to survive antibiotic treatment. It has been shown that antibiotic resistance traits can be acquired by horizontal gene transfer from other organisms—ones that have been previously exposed to antibiotics and survived. Those microbes can pass on their “wisdom” in the form of genes, creating an army of “super-bugs” that are super hard to get rid of. And we are running out of ammunition to fight them.

This analogy can be applied to glyphosate-resistant Roundup-Ready crops that Monsanto peddles to farmers. They are the “super-crops” that survive being sprayed with toxic chemicals that kill everything around them. But how long until the Monsanto canola shares its herbicide resistance genes with the weeds it is supposed to outcompete? How long until the “super-weeds” that already grow like – well, weeds – begin to be impossible to destroy with the existing arsenal of herbicides we have?

(By the way, there is already ongoing speculation that the escape of transgenes into the wild populations could become a real problem.)

There are a lot of things we still don’t know about biology, and it is important to think about the worst-case scenarios before they occur. For example, the potential unintended consequences of supposedly “safe” practices, such as planting GMO crops in biologically diverse areas that we want to preserve and protect. If an invasive species can spread through a country and change its ecology in just a few decades, so can individual genes, including genes made in the lab.

To put it in perspective, I’ll leave you with something to think about that is at once really cool and potentially terrifying. A California company called Living Carbon has created genetically engineered trees that grow much faster than normal. The idea is that these trees can be farmed as super-workers that suck out carbon dioxide from our atmosphere and slow down global warming. In theory, this is fool-proof technology: trees are non-mobile and can be destroyed by cutting down at any point in time.

But what if those super-trees manage to pass down their rapid-growth genes to surrounding plants or animals? They could suffocate the native flora—and potentially even overtake farmland, taking away our food sources.

It would be ironic if we were outcompeted by an invasive species of our own creation. If these plants actually reclaimed the forests which were cut down by humans in the brief few hundred years of our reign, the air would finally be fresh and crisp from the cool temperature of the “crisis-averted” Earth. Except – we might not be there to appreciate it.

If you enjoyed this article, you may also like this one that discusses the not-so-simple topic of how we should treat invasive species. Click to read below!