Seeing as how this is supposedly a blog about invasive management, and seeing as how there are some divergent ideas about whether invasives are actually a “problem,” or whether one should even use the term “invasive” because of possible issues of pejorative objectification and/or nativist bias, I thought I’d have a go at my rationale why invasive plant management is actually important. I’m not going to recite in comprehensive detail the degradative effects of invasives on native landscapes; there are many, many local, state, federal, and conservation websites that cover this. I’ve also previously addressed my take on this issue here. My intention now is to answer some things I’ve heard and read that question the necessity, efficacy, and/or reasoning behind invasive plant management, remembering that by definition the difference between “invasive” organisms, and “non-native” or “introduced,” is the tendency to do ecological and/or economic harm.
One argument I’ve heard goes along these lines: Do we have the right or obligation - practical, moral, ethical, or otherwise - to interfere with natural processes? Haven’t we done enough damage? Nature will (eventually) sort it out; the best thing we can do is to leave nature alone. By managing invasives we’re just continuing the process of “command and control” that got us here to begin with. We know through decades of study and experience that natural ecosystems are unknowably complex and beyond our capacity to replicate; the best thing we can do is let the system sort itself out in its own way and in its own time.
My answer goes something like this: Yes, nature will always sort itself out eventually, but this is a tautological argument. The issue is not whether the biosphere can compensate for imbalances; given enough time of course it can. The key word is time, as in we don’t have any to spare. Landscape ecologist Tom Wessels estimates coevolutionary processes as operating on millennial timescales; at a minimum it will take hundreds of years for these processes to even begin to stabilize at any level. We don’t have hundreds, let alone thousands of years to wait for this. Global warming is worse than predicted and accelerating, resulting in extreme heat, drought, flooding, reduced snowpack, and extreme weather of all kinds which leads to stress, reduced resiliency, and mortality in ecosystems on multiple dimensions. A multitude of invasive insects and pathogens are killing and threaten to destroy entire tree species and large swaths of forested ecosystems (i.e., northeastern forests). Forest cover is shrinking yearly from human development; rural sprawl is cutting into and fragmenting large areas of formerly intact forestland; deer browse is crippling forest regeneration throughout the northeast; we even have invasive jumping worms destroying the duff layer necessary for native forests to survive as functional ecosystems. This is only a partial catalogue of the novel threats facing northeastern forests, which in addition to historically extant stressors like spongy moth and large scale intensive weather events (hurricanes, etc) are all subject to the force multiplying effects of global warming.
While regions of well established, relatively undisturbed, older native ecosystems are generally resistant to invasive takeover, anything outside these conditions is at risk or already impacted. Invasives famously thrive on disturbance; it’s the foot in the door for these vigorous, opportunistic, fast growing species. What happens if and when areas - possibly large areas - of the northeast forest open up from forces as outlined above? Given the multitude of potentially existential threats that face northeastern forests, to my mind the achievable management of invasive plants takes on a note of urgency in order to increase as much as possible the area, resilience, and connectivity of forested (and other) ecosystems. Invasive pressure on ecosystems, and the ability to rapidly form monocultures, both lead to radically simplified systems with low resiliency, reduced carbon uptake and storage, minimal support for wildlife, degraded soils and soil development, and so on. Perhaps a little closer to home, current infestations act as vectors for local and regional incursion; the choices we make for our landscapes lead to impacts beyond parcel boundaries.
But the ultimate and for me crucial reason why it matters to remove invasives and steward native establishment, especially in regions of endemic infestation, is insects. Insects, the other half of ecosystem coevolution, do not and cannot eat non-native flora. The dramatic decline in insect numbers and species worldwide has been well documented, for a number of reasons including global and cumulatively immense swaths of non-native plant establishment and incursion, from suburban lawnscapes to agriculture to wild invasive monocultures. This amounts to what are essentially insect food deserts; instead of starving individuals, though, we’re starving entire populations. If the change from native to non-native were happening at geological timescales, or if the change were not overwhelmingly pervasive, or if there were no human induced pressures and stressors, would “invasives” be a problem? No. But that’s not our reality.
Invasive flora are here to stay. Noone I know or know of thinks in terms of eradication. The task before us is to return as much of our degraded landscapes as reasonably possible to native ecosystems in order to offset the pace and extent of change as outlined above. Barring some kind of unforeseen forcing, non-native species of all kinds - plant, animal, insect, fungal, microbial - will on a century to millennium timescale coevolve with native ecosystems and achieve functional parity. In the meantime, my job as I see it is to do everything possible to mitigate the worst effects of one of the five drivers of global ecosystem and biodiversity loss, and to help offset and prevent the decline and potential collapse of local and regional forested, arthropod, and insect ecosystems and the tiers of life these support.
Invasives aren’t evil, they’re just plants. But we brought them here, and we created the conditions for what Tom Wessels calls an evolutionary “bottleneck,” i.e., an extinction event. We can’t turn back the clock, but we can - like the First Peoples who preceded us - steward the land for the greater good, including our own. Others may feel differently, but for me this is a responsibility I feel obligated and compelled to assume. Finally, this is not a hopeless Sisyphean task doomed to failure. I have seen multiple parcels change in real time from invasive choked and barely functional to exploding with life; this is not an exaggeration. Is it work? Yes. It’s hard work, but it’s worth it. And that’s why I do what I do.
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