The Casper Star Tribune highlights an important threat to wildlife habitat – weeds:
The article gives a pretty good indication of the extent to which different weeds threaten wildlife habitat and are an economic scourge – but I will take issue with one statement made in the article :
Native plants have no built-in defense mechanisms against noxious weeds, which spread like a slow wildfire, squeezing out native plants one by one.
This statement is just not true – and it’s a pretty neat thing why it’s not true :
If you frequent this site much and have read through some of my commenting in the past – you know – I am passionate about soil science (if you don’t know anyone passionate about soil science, you’re really missing out – us folk are apt to grow a tasty salad and/or a huge pumpkin ! ) – it’s fascinating the expansive life/biology of dirt !
Living soil crusts
Many native plant communities do have defenses against weed incursion – living soil crusts ~ mosses, lichens, bacteria, fungus, insects, bugs etc. – the life of the soil evolved in symbiosis with the natives above the ground.
Many bacteria and fungi love plant roots. That’s because plants, in photosynthesizing the sun’s energy, discharge resulting carbohydrates (sugars) into the soil via their roots. These sugars feed the microbes in the soil – in fact, many microbes in the soil cross the cell walls of roots and join to become one with the plant.
Why do plants expend/pump energy into the dirt ?
In exchange for the energy/sugar, some microbes extend into the soil profile bringing back water and breaking down other micro-nutrients that would not be soluble/available to plants if not for the metabolizing effect of these other life forms ! Other bacterium even fix nitrogen from the atmosphere into the soil while others taper it out at just the right rate for particular native plant species.
This living activity in the soil can also serve to break up hard and compacted soil – and because there is so much of it around roots (sugar valves) soil gets broken up and aggregated enough to ease along vigorous root growth – another benefit of the relationship ! Aggregated soils hold water longer, hold enough space for the right amount of oxygen, and the decaying microbes (humus) are perfectly charged for storing nutrients (otherwise it might leach down beyond the roots).
The living soil can also act as mulch, covering the ground in arid and semi-arid systems keeping the soil moist and cooler longer into the dry spells of the season. When drought or extreme heat hits – every moist day matters, especially when considering wildfire.
Likewise, the living mulch acts much as any mulch works in your garden – it can keep weed seeds from germinating while promoting natives seed germination and helping fragile seedlings get their start..
When allowed to co-exist in equilibrium, the relationships between the life of the soil and native plant communities promote vibrancy and health.
In short – living soil regulates the optimal conditions (chemistry/nutrient/micronutrient, moisture, loose soil, temperature, mulch, biological community, etc.) for natives !
The best defense against non-native incursion is strong, established native plant communities themselves.
When a plant community is diverse, vibrant, and established natives will have a fighting chance of out-competing non-natives – after all, natives did evolve in conjunction with these perfect conditions.
But non-native plants evolved under different conditions – thus are apt to respond more favorably to a different range of conditions. When external influences (drought, livestock grazing, extreme fire, soil disturbance, etc.) put stress on these communities – alter these native conditions – and non-natives have established populations nearby, weeds will exploit the opportunity as the conditions fall more directly into their range of viability.
The bottom line: Weeds exploit stressed plant communities and disturbed soils that are robbed the benefit of the living soils which regulate that fine balance of native conditions necessary to promote native plant communities.
Unfortunately, once disturbed – especially in arid and semi-arid landscapes – these conditions can take decades to recover to optimal native ranges. Less water = slower response time.
A costly “War on Weeds”
As the original article demonstrates, the millions/billions of dollars that non-native infestations incur on the economy and the incredible toll the incursion is taking on wildlife and wildlife habitat is staggering. We must do something to stop the spread. But what ?
The vast majority of the resources spent on this “war” are spent spraying weeds with herbicides. In fact, the BLM is planning on aerially crop-dusting your public lands (to the tune of 1 million acres annually) with toxic herbicides ~ and for all the claims of these chemical agents being “selective”, the fact remains that these toxic chemicals end up lacing our (including wildlife’s) sources of water and subjecting native plant communities to hormonal treatments that alter the chemistry and health of entire biological systems – all with very little understanding of the ‘big-picture’ effect that these “treatments” will have into the future. Chemicals can’t restore the original/optimal range of conditions favorable to native plant communities – especially when agencies/people refuse to mitigate the disrupting land uses that threw the conditions off balance in the first place.
Let’s be honest – what success have chemicals had at restoring our public landscapes ? For all of the heavy handed management and large sums of public resources and “treatments” inflicted with this “war” the weeds are still winning – the cost increases every year – and our wildlife and wildlife habitat is diminishing.
These treatments – this approach – contributes to the very stress that is the precursor to weed incursion in the first place
Unfortunately, we do not have the political will to take the steps necessary to address and mitigate the fundamental causes of the widespread advancement of weeds across our most cherished wild places.
At an initial public meeting concerning the BLM’s Vegetation Treatments Using Herbicides Draft Environmental Impact Statement (DEIS) a question was asked:
Why does the BLM refuse to consider an alternative which includes the passive restoration of landscapes ? The removal or reduction of agitating uses of land that contribute to the spread of weeds (livestock grazing, ORV use, road blading, chaining, etc.) ? The prevention of weed establishment in the first place ?
Brian Amme, EIS project manager, responded:
‘Prevention’ does not fit into the management action of ‘treatment.’
BLM refused to consider preventative measures off-hand casting aside the Restore Native Ecosystems Alernative.
Weeds as Industrial bio-pollutants
Imagine a lung-cancer patient who undergoes radiation treatment after radiation treatment with a doctor too beholden to the tobacco and pharmaceutical industries to tell him to quit smoking. Our public lands, wildlife habitat, regard for fiscal responsibility, and economic condition are subjected to the same. This government’s ability to confront and effectively mitigate the industrial abuses of our public domain are stifled.
The most pervasive land use that has promoted the spread of weeds is livestock grazing. Livestock are spread across wide swaths/acreage of public lands, compel the most disturbance of soil, alter the chemical make-up of soils and water, act as vectors for weed-seed, alter fire-regimes, denude native plant vigor, break-up soil crusts diminishing the regulation of optimal conditions for natives, etc. etc.
Instead of bringing a rational end to this particular land use that denudes our public lands and wildlife in any diverse number of ways (wolves, bison, bighorn, pygmy rabbit, weeds, watersheds/systems, global warming, sage grouse, desert tortoise, pygmy owl, slickspot peppergrass, etc. etc. etc.) – we add to the mound of public subsidy the cost of cloaking their industrial bio-pollutants, subsidizing another industry in the process, with chemicals that render the consequences of these disturbing land uses less conspicuous than leafy spurge or cheat – but no less dire. Because these chemicals keep the systems stressed and keep the land uses that alter the native conditions afloat – managers become dependent on the “treatment” if keeping the symptoms of abusive land uses are to remain hidden from public view.
I love soil science. It fascinates and fills me with wonder to imagine the miniature universe – the micro-biology, soil chemistry and intricate systems that take place within the soil. These relationships among life only visible under a microscope or while huddled against the ground, support the more visible systems above them in ways that we’re just beginning to understand. Soil – dirt – might not be as charismatic as large wildlife or predators – but it is as important to the proper balance of functioning ecosystems as any other member of living communities that we can see – and if we let it – it might well be our strongest and best defense against the now pronounced “waging war on weeds.”