by Tyler Kokjohn
Over 60 years have passed since Rachel Carson published Silent Spring(1) and alerted the world to the dangers of environmentally-persistent chemical pesticides. Despite repeated warnings and sad experiences, a similar situation is unfolding around us today.
The new problems involve second generation rodenticides. Arizona is home to a diverse collection of rodents and, as many residents discover, some of them may become destructive nuisances. While new rodenticides are effective, they also threaten untargeted wildlife(2). By feeding on rodents that have consumed these slow-acting, longlived poisons, predators, scavengers, and birds of prey become accidental victims of rodent control efforts.
These persistent poisons have seeped deeply into food webs and are present in an alarming range of untargeted animals(2)...measures have big gaps(2). The irony of using second-generation rodenticides is that they may also decimate key rodent-controlling species and ultimately make bad situations worse–permanently.
The widespread use of the anti-inflammatory drug diclofenac for veterinary medicine purposes in India(3) offers an example of consequence cascades following the introduction of a potent chemical into an ecosystem. An extreme sensitivity to diclofenac contamination inadvertently turned many animal carcass food sources deadly to several species of vultures and caused their mass die-off(3, 4). The loss of vultures, keystone animal carcass-scavenging species, set the stage for more problems. When vultures vanished, the increased food available to other scavengers allowed feral dog populations to increase, contributing to an upsurge in deadly rabies infections in humans(4). No longer quickly and cleanly scavenged by vultures, the fast-growing volume of animal carcasses forced disposal of dead livestock in waterways, which facilitated the spread of other infectious diseases. Figuring out why vultures vanished and comprehending the full consequences was complicated and time-consuming(4). It is believed the summed impacts resulted in a half-million human deaths between 2000–2005 and enormous economic losses (3, 4).
Masters of test tube organic chemistry, we consistently overlook the dangers of polluting our living world with persistent chemical poisons. As Rachel Carson warned, unless we act judiciously, we may discover the under-appreciated cycles of life essential to human wellbeing are being unwittingly transformed into deadly, vicious circles.
by Taylor Kokjohn -- an active member of the Grand Canyon Chapter of the Sierra Club
(1). Rachel Carson. 1962. Silent Spring. Houghton Mifflin Company, Boston.
(2). Dina Fine Maron. 2024. Rat Poison’s Long Reach. Science, 10 July 2024. https://www.science.org/content/article/ really-scary-rat-poisons-wreaking-havoc-raptors-wildlife
(3). Vivian La. 2024. Loss of India’s Vultures May Have Led to Deaths of Half a Million People. Science, 15 July 2024. https://www.science.org/ content/article/loss-india-s-vultures-may-have-led-deaths-half-million-people
(4). Prerna Singh Bindra. 2018. Declining Vulture Population Can Cause a Health Crisis. Mongabay, 5 February 2018. https://india.mongabay. com/2018/02/declining-vulture-population-can-cause-a-health-crisis/