If I didn’t know better, and I had to bet whether a flaccid
grass could outcompete a blackberry capable of flinging its spine-studded canes
20 feet up into the crowns of trees, I’d have bet on the blackberry. I probably
wouldn’t have thought about either invasive species, honestly, living as I do
in the lush belt of coastal forest in western Oregon, whose understory used to
be dominated by shiny Oregon grape, shaggy ninebark, and the sturdy upflung
arms of the sword fern. But I turned around in the last five years and the
ferns were gone.
In fact, the grass wins, by exuding chemicals from its roots
that cut off its competition far below the knees. If the enemy of my enemy is
my friend, I should love the grass that overwhelms the blackberry. Instead,
there is an army marching in on the forests of my home, one that might well
bring down even the massive trees. We know that invasive species can utterly
overwhelm native vegetation, change ecosystem dynamics, and thus alter entire
landscapes. They can be plants, insects, fungi, viruses, or even birds or
mammals or snakes. Think kudzu, gypsy months, white-nose syndrome or sudden oak
death, the starling, the wild pig, or the python in the Everglades. It’s the
sort of overwhelming problem that might make you think that somebody,
somewhere, must surely be doing something about it.
By and large, we are not. In fact, we rarely track the
spread of even the most egregious invasive species, as a quick visit to the
various state databases revealed to me. A glance out my window revealed the
gaps, as the mass of invasive ox-eye daisies offered up a white-mouthed hoot of
derision at the scanty occurrence map on my computer. They aren’t even in my
county, according to the Authorities. Yet here they are, drifting thickly
across my pasture. Almost none of the invasive species on my small farm are
documented to be here.
Worse, we know even less about the consequences,
particularly in a world facing climate change as well as the rapidly spreading
army of non-native species. My colleagues and I reviewed hundreds of scientific
papers dealing with climate change and invasive species. Almost none of them
were based on hard experimental data. Instead, they were mostly limited to
computer projections of climate models, themselves subject to considerable
revision as more data are obtained. In sum, we have no idea how climate change
will interact with and affect the rapid spread of invasive plants, animals,
insects, and disease. The little data that do exist suggest that native species
and habitats will not be favored. How this extraordinary, reckless experiment
in shifting biota and climate will play out is not a matter of academic
interest only; everything from food and fiber, fire and rainfall, ecosystem
services from nitrification to pollination, hang in the balance.
Yet our efforts are at best perfunctory, dealing only with
the most egregious invaders in a rear-guard action that can only fail. Boats
carrying zebra mussels are frequently found just before they are lowered down
the boat ramp. You can buy an incredible array of invasive species on the
internet, and release them, undetected, when you tire of them. Entire
neighborhoods of Oregon’s largest city are being subjected to mandatory
chemical treatment for an infestation of Japanese beetles, whose spread was
facilitated by a regrettable cut in funding for monitoring. It goes without
saying that treating the infestation is costing orders of magnitude more than
was saved. Each day, more cargo unloaded from ships and planes that have
traveled from all parts of the globe may carry new invaders. At some point,
we’ll have to ask ourselves just how addicted we are to this high-stakes game
of biological substitution speeding in on the wings of cheap and easy
transportation, globalization, and free trade, unfettered by any considerations
of collateral damage.
I spent the winter cutting blackberry along the creek. I
uncovered trees and light-starved stands of snowberry, freed the branches of
ninebark and Indian plum. But there were no more ferns, and along the newly
revealed stream banks, the forward scouts of false brome are infiltrating the
cow parsnip. The enemy of my enemy is still my enemy. I can’t begin to know how
all the shifting balance of species and processes will affect even this small
bit of creek bank, let alone what the occupying armies will create out of the
wreckage of the world we knew. But we need to start asking the questions, and
seeking the answers as quickly as we can.
