The Age of the Lion Fish
“Pest” is a very subjective term. To it’s victim, a pest is an unwanted species. It is an organism that has overstepped a critical boundary and become a nuisance. When we use the word “pest”, we usually refer to a species that has migrated to a new environment. The term “invasive” is often used to more specifically denote species that have come from somewhere else, yet somehow have become even more successful in their new home, despite evolving over millions of years often in a completely different ecosystem. They surprisingly now find themselves even better adapted to their new surroundings, something of an evolutionary paradox, given what we learn in biology. We learn that although mutations happen by accident, they are not selected by accident. New genes are rigorously “test-driven” in the real environment, over millions of years, through a painstakingly slow process that may seem impossibly slow, but is reality-proof: those genes that represent successful adaptations are passed on to the next generation, while those that pose a risk are eliminated. In the end, species are uniquely adapted to their specific surroundings, and this is why we see such a tremendous genetic variation of the same type of animal or plant across different terrains. Speciation is an active process that never stops, as organisms try to develop new and improved “gadgets” that will help them survive.
If evolution is then driven 100% by environmental factors, and goes through such a rigorous and specific process, how can it be that a species may find itself better adapted in a different environment? We often think of invasive species as “lucky”. Did nature somehow make a mistake, and their “tools” were accidentally better suited for another ecosystem?
Nature never makes a mistake. The missing insight here is our definition of what “environment” means. Because species do not only evolve to adapt to temperature, types of terrain, or availability of food. Most of all, they adapt to other organisms. One of the most important category of traits that they develop is those that help them escape their predators and successfully compete with other species. In almost all cases, an invasive species did not come across more food or better survival conditions in its new home. More often than not, it has discovered a new niche where its key predator was absent. Or even better, it discovered new prey. Almost overnight, it has transformed itself from prey to pest. From a food source, to a predator. And yet this is the same exact organism, 100% genetically identical to what it was before, contrary to our popular sci-fi culture where we like to see giant mice chasing after cats or massive squid lifting ships out of the ocean as part of their morning work-out.
This demonstrates how important predator-prey relationships are in our various ecosystems. These relationships control everything. Once disturbed, anything is possible. The 20th century saw the greatest proliferation of invasive species across the world: from a range of Japanese plants brought over to America, to camels in Australia, to the now infamous lion fish that escaped pet acquariums and is now plaguing large parts of the world in an unstoppable rage of destruction. In almost all cases, the human species is involved in bringing these species to their new homes: but it is also a super-predator itself, that ticks all the boxes in the pest definition. Yet just like the lion fish, it has no sense of its parasitic nature. It sees a different “truth” than the species it parasitizes. But as with all truths, there is only one version of it: bitter to those who accept it, and inflammatory to those who deny it.
David Attenborough recently remarked that “Humans have overrun the planet”. I would go a step further to say that humans have become an invasive species to the entire planet, hostile to all ecosystems. The population explosion that followed the industrial revolution was a direct result of our ability to maximise our competitive advantage in exploiting our resources, and continuing to defeat our biggest predators: deadly infectious diseases that used to decimate millions of humans.
But nature always has the last word. And it even has solutions for persistent, invasive species, thanks to the paradox of overpopulation: the more a species multiplies and occupies new niches, the more it comes in contact with other organisms it never encountered before, organisms that may be its new predators. The larger the pest population, the greatest this risk becomes, as eventually the pest comes in contact with the entirety of the vast genetic library of the planet, which is not to be underestimated . Somewhere inside that library, there is a key. There is the solution nature has been looking for. There is a weapon against this pest.
COVID-19 is a textbook demonstration of this exact principle. Nature is trying to cull humans before they destroy too many other species. Unless we realise that we are the lion fish, the camel, the Japanese honeysuckle, our end will be even more spectacular. Because just like any other parasite, we are nothing without our host. Once we kill it, we die with it.
To be continued…(or not)
George is a chemist, molecular biologist and food scientist. You can follow him on Twitter @99blackbaloons , read his books or join his mailing list
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George Tsakraklides 
My first reaction to “pest” was humans. But of course.
I’ve often thought of this “paradox” wondering how these invaders could do even better here than in the environment they specifically evolved for. Then as soon as I read your first sentence the answer hit me. We tend to think of “natural predators” as wolves or mountain lions or something large and furry, but in reality they include the whole panoply of microorganisms, flora and fauna, living their own lives. It’s often said humans have no natural predators, but we know that’s ridiculous. If nothing else, we are our own natural predators.