Rat Poison Is the New DDT, and Marijuana Is the Problem

An illegal marijuana grow site in Six Rivers National Forest in Northern California. | Photo: USFS Region 5/Flickr/Creative Commons License

Rachel Carson was right: everything is connected.

Writing 51 years ago in Silent Spring, with language that is as lyrical as it is lacerating, she probed the impact of toxins in watersheds and bloodstreams, and wondered how it came to be that these lethal substances were sprayed, dusted, and dumped into nature, only to work their way inevitably, irrevocably through water, air, and food into flora and fauna, including humans.

"Who has made the decision that sets in motion these chains of poisonings, this ever-widening wave of death that spreads out, like ripples when a pebble is dropped into a still pond?" Her chilling question came with another every bit as unsettling: "Who has decided -- who has the right to decide -- for the countless legions of people who were not consulted that the supreme value is a world without insects, even though it is also a sterile world ungraced by the curving wing of a bird in flight?"

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Carson's anger would be as blunt today knowing that for all the impact her book had -- and historians credit it with the banning of DDT in the United States and propelling such critical environmental legislation as the Clean Water Act into law -- its dire warnings have not fully penetrated the American consciousness.

That's what is revealed in the recent (and devastating) news about how deeply rodenticides, or rat poisons, have percolated into Northern California's biota. The reason for this is that illegal marijuana growers are scattering rodenticide pellets by the shovelful around their secret plantations tucked away on national forests throughout the state's mountainous regions. A particularly virulent poison, it is laid down like berms around the high-value cash crop itself, parallels irrigation infrastructure in thick lines, and, as if a stout fence, is applied liberally around the lean-tos, tents, and shacks where the "farmers" rest their weary heads.

San Joaquin kit fox. | Photo: courtesy USFWS
San Joaquin kit fox. | Photo: courtesy USFWS

Follow, then, the "elixirs of death," as Carson styled them. Animals drawn to the rough camps in search of food or water consume the super toxin or eat other animals that have done so. Because it is a second-generation anticoagulant, which has been developed precisely because some species have become resistant to earlier rodenticides, this new version is so powerful that if ingested at high enough levels it can lead to death by bleeding out.

So prevalent has rodenticide use become that wildlife biologists have launched scientific investigations of its pathway through various ecosystems. In the past couple of years or so, researchers have identified high concentrations of the murderous poison in more than 25 species, including falcons, owls, raccoons and bobcats, and such endangered species as the San Joaquin kit fox and the Pacific fisher.

A Pacific Fisher. | Photo: Courtesy Washington Dept. of Fish and Wildlife
A Pacific Fisher. | Photo: Courtesy Washington Dept. of Fish and Wildlife

The fisher is of particular interest. Despite its name, the furry mammal does not live in or near the coast but instead occupies remote, closed-canopy forests, sites that are prime landscapes for illegal marijuana grows. Akin to a weasel, it pursues a wide diet ranging from fruits to small mammals to birds, and has been known to take on the most bristly of forest creatures. It is the "only animal tough and clever enough to prey regularly on porcupines," observes the Center for Biological Diversity -- "no easy feat."

However skilled a killer it might be, the fisher is not able to discern whether its dinner is laced with rodenticide. This has led to a spike in its mortality, further diminishing its already declining population. That's the word from scientists working for the Sierra Nevada Adaptive Management Project, out the College of Natural Resources at UC-Berkeley; they have launched the first in-depth analysis of the threats this toxin poses to this rare species. Of the 58 fisher carcasses they autopsied, the data revealed some troubling patterns:

The lethality of the chemicals listed is only part of the picture. Another facet is the spatial distribution of the dead Pacific fishers; their bodies were widely distributed across northwestern California and in the southern Sierra Mountains. The fact that there was no clustering of deaths by specific location "indicates that fishers are encountering these poisons in remote, natural forest regions within their home ranges."

As to the source of these killer toxins, the study but hints: "irresponsible use of ARs is continuing despite recent regulatory changes. Further study is needed to identify sources of ARs in the forest, including illegal grow sites."

Others are less reticent about pointing the finger at pot farmers who, according to Ann Lombardo writing for UCB's Green Blog, are the sole source of the toxins. "Considering the hundreds of marijuana grow sites found every year on public lands, the scale of the damage to California's natural resources may be unprecedented," she writes. "Grow sites are also found containing massive amounts of fertilizers, herbicides and pesticides, all of which are being used without concern for run off or aquatic species nearby."

Lombardo's insight, which confirms the assessments of law enforcement officials at all levels of government, raises the specter of serious and persistent harm to many interlinked species -- not least those that already are threatened or endangered -- throughout the Golden State.

It reminds too of Rachel Carson's brilliant declaration about the severity of the problem she identified in 1962 and the need for a swift political response: "if the Bill of Rights contains no guarantee that a citizen shall be secure against lethal poisons distributed either by private individuals or public officials, it is surely only because our forefathers, despite their considerable wisdom and foresight, could conceive of no such problems."

Now we can. It is high time that the state legislature to pass a bill banning the use of these deadly rodenticides, for the governor to sign it into law, and for the California Department of Pesticide Regulation to enforce it rigorously. This action, when combined with a vigorous and unrelenting campaign to uproot illegal marijuana plantations on the national forests, will give the Pacific fisher, and the national forests, a fighting chance.

Their health, as Carson might have said, is bound up with our own.

For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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