Human Species Is the Most Successful Ecological Invader

The subject of invasive species always seems to raise hackles here in Delaware. We’re very loyal people and we want our local guys to have first dibs on habitat and to send the interlopers back where they came from, thank you. A closer look at the subject reveals it’s not all that simple, however, nor are all introduced species necessarily at war with native species. 

First of all, the most dangerous introduced species is Homo sapiens. Our presence everywhere on the planet is a sad tale of monoculture, predation, extinction and habitat destruction. Just wait until we get the hang of genetic manipulation.

We are all too familiar with recent and destructive introductions, from zebra mussels in the Great Lakes, through Japanese beetles, purple loosestrife, kudzu, Asian tiger mosquitoes and wetlands-destroying nutria. The list seems endless and provides what I think of as “standby worry,” which is worry you can bring to mind should you ever find yourself tending toward happiness about the state of things. The tale is told that there were repeated efforts to introduce the starling, a songbird in England, to America. Finally a batch released in New York City’s Central Park got a toehold, and now American skies are sometimes dark with them. 

This sentimental attraction to a species brought rabbits to Australia, whose marsupials were unready for the more canny placental mammals. Ruin followed, and the rabbits are still here, in spite of fortunes spent to control them.

Around the globe, intentionally-introduced goats and pigs have ruined island ecologies, not to mention the ubiquitous Norway rat, now rivaling humans as inordinately successful mammalian pests. The almost universal presence of rats brings to mind the mongooses imported to Hawaii to exterminate them. The diurnal mongooses turned to occasional and ineffective snacking on the nocturnal rats only after exterminating ground- dwelling birds and whatever native species evolution left unprepared to deal with the new kid on the block.

Another class of introduced species might be those aliens whose presence we no longer notice as being unnatural. The ubiquitous house sparrow undoubtedly displaced native species and did its share of damage, but its population is now somewhat stable and we’ve grown accustomed to its looks, as the song says.

Still further removed are species whose migrations were not a feature of human history, rather chance events of the distant past. The spread of coconut palms throughout the Pacific was probably accompanied by displacement, but its occurrence preceded our peregrinations and thus is accepted as natural. We find ourselves able to accept distant chaos associated with the spread of species, but lament the damage done on our watch. Admittedly, there is a lot more going on nowadays and our foolishness is giving native species no time for evolutionary response.

Still another alien category is the benign newcomer. These seem to me to be largely botanical, and few American yards are absent attractive and respectful foreigners – forsythia, black pines, red maple, tulips and most roses come to mind.

How will the intercourse of nations and the daily shuffling of the population deck afforded by air travel affect the future of the diversity of species? Look to southern Florida as a microcosm. From a would-be timberman seeding the Everglades with Australian eucalyptus to the unthinking release of dozens of alien species, both animal and vegetable, into Florida’s hospitable environment, that state is a large scale petri dish for species interaction, with human reaction ranging from concern to hysteria.

Most of us won’t be around to see it, but we human beings are going to homogenize our planet’s species in the habitats where they can survive, in a universal leavening of species, with the advantage going to aggressive, prolific and adaptable species. In the process, thousands, if not millions, of less agile exotics will be lost. Life on Earth will be less interesting, I think, but evolution, given time, will reassert its complexity on the well-mixed world of the future. In the meantime, let's fight the good fight for our local guys.

John A. Hughes
Secretary