“An invasive species is defined as a species that is: 1) non-native (or alien) to the ecosystem under consideration and, 2) whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”
– USDA legal definition
“A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise.”
– Aldo Leopold
In a geological time frame there is little meaning to the terms alien or invasive. The vast majority of species on Earth have some degree of vicariance, i.e., mobility through time and space. Our perspective on species is often limited by our four score lifespan and our flawed concept of what constitutes an intact ecosystem. The sciences of ecology and evolutionary biology have largely been written by white boys that speak the King’s English. These founders believed that species and ecosystems changed only very slowly over relatively long time frames. Their concepts of alien and invasive species as dictated by this absurd notion have hindered science for decades.
Since the late 20th century the dominance of these fields by relatively comfortable white males from England and the US has begun to crumble. This change has resulted in new perspectives on the definitions of ecosystem form and function. Especially welcome are the views of women and scientists from Latin America and Asia. African Americans with tenured positions in ecology are vanishingly rare. The number of Asian and Latin American ecologists on key papers has increased significantly over the last twenty years. China, Japan, Brazil, Colombia, Mexico, and other countries host internationally renown scholars who publish critical papers that address the very survival of civilization.
Nevertheless, ecology textbooks and journals are too frequently devoted to reciting and expanding the theories and often poorly reproducible studies from the white-boy founders and their progeny. Many modern practitioners can trace their understanding of ecosystems to the Ivies of the East and West Coast, and to England. I cut my academic teeth at the University of Pennsylvania reading venerated papers by Robert MacArthur, Harold Mooney, W. D. Billings, John Krebs, Robert May, and other similarly esteemed white men. My pedigree is rooted in founding fathers from Stanford, Duke, and Princeton, who in turn attribute their upbringing to British schools of thought, primarily Oxford.
The relatively young field of conservation biology depends on the theories and constructs developed by this intellectually inbred group of scientists and their narrow view of nature. It is long overdue to rethink the terms invasive and alien in the context of the widespread profound ecological change now underway. Throughout my career, papers and conference talks have warned me of the the horrors of invasive species and how these aliens disrupt putatively stable ecosystems. Well intentioned ecologists have raised the alarm, insisting that invasive species must be controlled and eradicated. The metaphor of command and control by annihilating invaders is deeply embedded in the psych of Western males. Maintaining these insidious white-boy definitions in a science as crucial as conservation is a losing proposition.
Climate change, massive human migrations, extreme weather events, pandemics, and wholesale habitat disruption by humans have foreshortened the time frame for ecological and evolutionary change to less, often much less, than that of a human lifespan. For the first time these fields are faced with the gratuitous anthropocentric nature of the definitions of such fundamental units as species, ecosystems, ecological communities, and biomes. Any ecologist will tell you that the distinction between an ecosystem and an ecological community is vague at best, and mostly meaningless. Yet these terms are memorized by generations of undergraduates who generally have not a clue how they apply to the real world. In fact their professors don’t understand their meaning because they too were taught that these terms must be learned because they are somehow important.
Among thousands to choose from, a case in point is the Amazon and its complex of forest ecosystems. The traditions of my training at Penn and my associations with the Ecological Society of America taught me that the forests of the Amazon Basin are ancient climax communities unlikely to change in any significant way during my lifetime. Anthropologists enthralled by certain thinkers within the academic hierarchy were immovably convinced that the Amazon Basin could not have supported widespread agriculture and thus human populations were small. Even today college textbooks chart the growth of human numbers by leaving uncounted the indigenous populations of the Americas and the mass mortality that followed contact with Europe. Of course this is utter bullshit and we should have acknowledged this decades ago.
Pre-Columbian Amazonia supported a human population of up to 30 million. Agriculture and trade were widespread. The form of agriculture used was considered impossible because it did not conform to Western anthropological notions of how crops should be farmed. It was the Americas depopulated by European diseases that early settlers encountered. Long before Europeans arrived the forest ecosystem complexes of the Amazon had been hugely transformed by human hands. Just this month researchers discovered that indigenous peoples of South America had contact, trade, and reproduced with Polynesians about 1230 AD.
It is likely that the Basin will transform within 5 years to become a global carbon source rather than a sink. In 20 years much of the southern half will become savanna. Much of this change now seems attributable to climate change. There has also been ongoing widespread industrial scale slashing and burning of forest for conversion to pastureland and crops. Once-in-a-century drought now occurs every 3–5 years resulting in forest ecosystems without the capacity to recover positive carbon gain before the next drought hits. Across the forests of the Amazon the frequency of fire has increased at least 200 percent in the last 30 years.
Many of the changes underway are unstoppable and we must give up on the fantasy that the Amazon can be maintained in anything approximating our absurd notion of virgin tropical forest. The most that we can hope for is to manage the transformed ecosystems for maximum biodiversity and carbon sequestration. The tropical forest where I worked for two decades during my early professional days is effectively gone forever. We did this. We own it. Now we must manage it or, like COVID-19, it will follow its own path of destruction.
Mass human migration is also unstoppable. Even attempted annihilation of migrants through the massive disruption of their families as implemented by the Trump administration is doomed to failure. Borders will never be truly closed and no wall can ever completely prevent migration of humans, nor can it completely stop plants and animals moving from one geopolitical space to another. As climate change drives more and more refugees and economic human migrants, so it also drives global shifts in plant and animal distributions. That said, while not stopping it, Trump’s wall is disrupting animal migration and reproduction, resulting in unknown changes in ecosystem structure on both sides.
Common meanings of the terms alien or invasive are useless. There are no alien species, except perhaps those from another planet, and there is certainly no such thing as an illegal human, alien or otherwise. This is especially apparent in the eyes of children brutally separated from their parents at the US southern border. The immigration policy of the Trump administration is an abomination. Like Germany after WWII, the harm inflicted by these policies on an entire generation may never be assuaged and it is a guilt that we must live with for a very long time.
This is not to say that introduced novel species cannot disrupt an ecosystem. The examples of this are manifold. Instead, I am suggesting that we acknowledge that ecosystems have always been changing and now many are changing within decades rather than over the course of hundreds or thousands of years. As species go extinct because they cannot maintain reproduction in regions where climate has shifted, we are left with little choice but to manage intentional introductions if we hope to maintain ecosystem form and function. This new reality means that we must quickly learn how to holistically manage ecosystems. Our present understanding of how to maintain ecosystem services as ecosystems transform is rudimentary at best.
Management of ecosystems based on narrow old-school concepts of eradicating alien and invasive species is not only doomed to failure, it will produce long-lasting consequences. These consequences will often preclude appropriate management actions over the remainder of this century and beyond. The practice of conservation biology is rife with mistakes, stupid assumptions, and trivial arguments that are now moot in the face of climate change. It is time that we develop modern working definitions of ecosystem form and function based on the true dynamic nature of species vicariance. How we treat human and non-human migrants and the ecosystems we all inhabit will literally determine the fate of humanity.