Final answer:
The author considers the ecological and health risks of pesticide use as a significant threat to civilization, on par with weapons of mass destruction. The dangers include the disruption of ecosystems, health issues in humans and wildlife, and the global spread of persistent chemicals.
Step-by-step explanation:
The "last and greatest danger to our civilization" proposed by the author concerning the effects of pesticides is likely the existential threat that these chemicals pose to ecological systems and thus, indirectly, to human survival. As explored in Rachel Carson's renowned work, Silent Spring, pesticides such as DDT have caused significant ecological damage through bioaccumulation, contributing to the decline of predator species like birds. Furthermore, the widespread use of these chemicals has led to health issues in humans and wildlife, the evolution of pesticide-resistant pests, and environmental pollution that reaches even the most remote areas of the planet.
Studies highlight that pesticides contribute not only to the immediate poisoning and chronic health conditions in agricultural workers, especially in developing countries but also create long-term risks by undermining the natural pest control by predators and parasites. The indiscriminate and heavy use of pesticides can consequently destabilize ecosystems, with the potential to cause an ecological collapse that would be detrimental to human society. Additionally, the chemicals have been found globally, even in organisms and regions far removed from agricultural sites, due to their persistence and ability to travel through atmospheric transport.
The author might then be underscoring the interconnectedness of human actions and the environment, suggesting that the unintended consequences of pesticide use are a profound and pervasive danger that competes with the threat of weapons of mass destruction. By disrupting ecological balance, threatening biodiversity, and impacting human health, the ongoing reliance on harmful pesticides is presented as a significant risk to the future of our civilization.