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What Pesticides Showed Me About Protecting Our Future

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In the spring of 2020, as my planned summer of glorious sunshine-y fieldwork disintegrated under the sudden and crushing weight of a global pandemic, I flew home to Singapore. An ocean away from Stanford University, I took classes and attended meetings after my family had gone to sleep, wandering through the days in a sleep-deprived haze of whiplash. Weeks before, I’d been in college and the future seemed clear: I was going to work in conservation and protect nature and biodiversity. Now? I was searching for certainty, for an answer to what it meant to keep learning as the world fell apart, to how I could be a good student and citizen of the planet. 

At the very least I wanted another research project. And so, my lab at college tasked me with answering a simple question: what biocides were used for mosquito control at Searsville Reservoir, a marshy water body at Stanford’s Jasper Ridge Biological Preserve in the Santa Cruz mountains about five miles from campus. 

Searsville Lake and Dam on a sunny day in the middle of February Photo by Jorge Ramos

I figured I’d have an answer — a neat spreadsheet and timelines — in a month, if not sooner. I emailed the county vector control district for their records. They sent me several spreadsheets, as well as a stack of historical documents from the 1960s and 70s discussing the decisions to use different kinds of mosquito control at Searsville. 

I started clicking through the old reports at night before my online lab meetings. I’d never been to Searsville or Jasper Ridge. In those first few months of the pandemic, it was difficult to believe I ever would see the place the reports described. The headlines accumulated — describing grounded container ships and disappearing jungles, people migrating in long dusty chains across continents, crops withering in fields, wildfires sparking like stars on the map — and I was afraid to step out of my house. I didn’t know how to answer what it meant to live as a citizen of the world when I had no idea how to interact with it.

At first I thought the history of biocide development would be an escape from the very present uncertainty. But I soon saw a bigger picture emerge, of how our endless battle against mosquitoes speaks to what it means to live with nature. In the reports that tracked the pros and cons of various insecticides in meticulous detail, I encountered one of the largest issues of the 1970s. The United States Food and Drug Administration was on the verge of banning most popular insect controls after the 1962 publication of Silent Spring, a book by well-known nature writer, biologist and conservationist Rachel Carson. Carson’s book fired a watershed salvo against the primary weapons — specifically, organophosphates like dichloryldiphenyltrichloroethane, better known as DDT — in humanity’s war with insects.  

Rachel Carson — writer, scientist and lyrical ocean advocate — holds 
copy of her most famous book, Silent Spring 

Carson’s writing inspired the creation of a generation of new insecticides as the then-standard methods of managing insect populations crumbled under the pressure of her meticulously collected research. Stanford professor Carl Djerassi saw a social and financial opportunity in Carson’s legacy. Djerassi was already known for his work synthesizing the chemicals that formed the basis of the first oral contraceptive. But, past the peak of his career, he decided to turn his attention to insect control. 

In 1968 — the year marking the end for DDT and the beginning for the National Environmental Protection Act — Djerassi started a new chemical company. Within a few years, its first product was on the market. Its technology drew directly from Djerassi’s hormonal work on birth control. The new product, Altosid, was an insecticide inspired by organic chemical research on hormones that worked to interrupt biological development and prevent the maturation of juvenile animals. Altosid would become the first of what Djerassi named “biorational” chemical agents. The name combined the words biology and rational to express Djerassi’s vision for a new generation of insecticides based on biological mechanisms with more targeted impacts.

But he also implied something else with his chosen term. Djerassi suggested these chemicals were the rational choice, founded in reasoning and evidence, tied therefore to the scientific rationality of humanity’s future. This approach would be based on understanding nature and extending that understanding into a fine tightrope balanced between human needs and the broader world. More than mastery, Djerassi described something with both the “virtues of scientific glamor and responsiveness to social need.” He decided that the world was ready “for a new approach to mosquito control.”

Carl Djerassi, the chemist who synthesized the main component of birth control and later invented 
Altosid, a hormone-based biocide that became the first biorational biocide 

What surprised me the most when I started learning about pesticide development in the 70s was how familiar it sounded. That conversation — about how to decide what and what not to control — remains the conversation today. The biggest difference since Djerassi’s time is that we have had more opportunities in the last 50 years to discover how skewed that attempt at balance has become. We reckon today with a world tipped out of balance entirely. Daily we confront climate catastrophes; pathogens and the rise of disease; the disappearance of insects across the world; the militarization of institutionalized biases; economic disparity; broken education systems; and the industrialization of everything — from our news to our crops. 

As I read more and more, I saw an age-old question spin out around me: how do we save ourselves without killing everything else? As I went into the history of Jasper Ridge and biocide development, I realized I could learn more than a list of names. There might be an answer here: not a formula, but rather a framework for how to work toward harmony, what it means to go in with curiosity and the best intentions, how to make science matter and how to navigate the gray areas. 

Over the next months, I dove into the intricacies of Jasper Ridge’s pesticide decisions. The timeline I began to develop for how pesticides had been used filled with color codes as I tracked how different chemicals came in and out of favor. It wasn’t as easy as picking the pesticide that had the least non-target impacts. Jasper Ridge Biological Preserve, as the name implies, was intended to be preserved, held in an ecological stasis where researchers could go to observe the “natural progression of plant communities” for generations. The preserve management had a vested interest in minimizing chemical pollutants at the Ridge. 

But the preserve did not exist out of time, or space. Its 1,200 acres in the Santa Cruz Mountains lay 45 minutes from the skyscrapers of San Francisco, with housing on three sides of its boundaries. People could not be taken out of the equation. The San Mateo Mosquito Vector Control District was in charge of protecting the health of surrounding communities, not the natural progression of plant communities, and they wanted the pesticide that removed mosquito populations as efficiently and permanently as possible.


Excerpt from a brochure advertising biocide products in the 1970s

The Jasper Ridge management proposed the new biorational pesticides as a compromise. They petitioned the San Mateo County Mosquito Abatement District and got them to transfer control of mosquito management to Stanford itself for “research in mosquito control.” For the next two years, from 1976 through 1977, they launched everything they could at the lake. In addition to Altosid, they used parasites, machines to alter lake vegetation and other methods to see if there was any non-chemical way of controlling mosquitoes. But mosquito populations continued to grow. 

Finally, the Abatement District stepped in: the experiment was over, they said. Clearly Stanford hadn’t succeeded in pioneering any of the sustainable, environmentally friendly mosquito management strategies they had promised. But before the final handover back to the District, the Jasper Ridge management did succeed in signing a memorandum with the District promising that only biorational pesticides would be used at the lake. 

For the next five decades, through two different directors, the program remained largely unchanged. Biorational pesticides eventually replaced the Abatement District’s old approach everywhere in the county. This marked a sea change as the world shifted toward biorational pesticides, which FDA studies promised were the good, safe and above all easy replacement for the non-discriminate pesticides that killed all arthropods in reach.


As I moved from the reports on DDT to today’s science on insect control, the parallels became clearer — horror at pesticide dangers, the search for a solution, faith in technology and the gradual emergence of flaws. In the last few years, as researchers have had the opportunity to look at ecosystems over time, a different narrative about biorational pesticides has begun to emerge. For the most part, decades of studies have shown few, if any, immediate deleterious effects from Altosid and their biorational counterparts. Most reviews and FDA documents still list these pesticides as having no effect on nontarget species, although broad swathes of known insect species have never been studied. 

However, a recent study linked Altosid to colony collapse disorder in honeybees after it was fed to bee larvae. They found that Altosid-fed larvae died at significantly higher rates, even though it was supposed to be nontoxic to anything other than mosquitoes. Research on other popular pesticides like Bti, a parasitic pesticide, has also revealed impacts on midge and other nontarget insect populations — with potential knock-on implications for the rest of the ecosystem. 

This narrative might need decades more research to crystallize into a definitive answer one way or the other. Most likely, rather than Altosid being uniformly horrible, it’ll end up somewhere in between: working sometimes, not working other times and, through it all, wending its way through the ecosystem in strange, small and largely unknown ways.

Reading through the studies, I was reminded of what the scientists I’d interviewed about the 1970s told me: 15 years before Silent Spring was published, they had studied how DDT resistance developed in houseflies. The media and legislators ignored the research because DDT still had too much financial and political clout. For these scientists, Silent Spring was a welcome moment of validation. Finally, someone had said clearly what needed to be said: that humans and nature need to give and take, and that we need to find ways of harmonizing conservation with development. That the solution was just around the corner. That it had to be.

Mosquito control associations have argued otherwise. At an EPA hearing in 1988, the head of the California Mosquito and Vector Control Association asserted an “inherent conflict” between mosquito control and the Endangered Species Protection Act. Every successive generation of scientists has tried to resolve that conflict and promised an ultimate balanced solution to insect control — almost within reach, just a few years away. 

But the solution keeps slipping away. Biorational pesticides were trialed on my international school campus, Singapore American School, for the first time seven years ago. The school administration ultimately rejected it as a permanent solution for the dengue-carrying mosquitoes that infest the neighborhood. Instead, every Wednesday evening, my school undergoes “fogging” and becomes blanketed in a thick white curtain of aerosolized pesticide, most often a pyrethroid, a chrysanthemum-based cousin of DDT. There are never as many butterflies after fogging.

Jasper Ridge hasn’t stopped trying to find a sustainable solution. In 2012, Phillippe Cohen asked the San Mateo County Abatement District to stop using Altosid at Searsville Reservoir; they agreed, and replaced it with more applications of Lysinibacillus sphaericus, a recently discovered bacterium that parasitizes mosquito larvaeAfter the West Nile Virus scare in 2004, the Jasper Ridge management asked the San Mateo County Mosquito Vector Control District to transition to aerial applications. For a decade they used a helicopter, which flew over the lake to dump payloads of the stuff three times a year; this year, the district transitioned to using a drone, which can deposit the biocides with far more precision. Still, the idea of tons of pesticide descending on Searsville Reservoir can feel incongruous with a biological preserve, especially for many researchers at Jasper Ridge, for whom the chemical control of mosquitoes carries chilling associations. 

And maybe it’s fine. Maybe these new pesticides do work exactly as promised — just controlling the mosquitoes, leaving all else alone, breaking apart harmlessly in the water. Maybe we can pick and choose like that. Maybe it did just take that little bit of development — the researchers after Djerassi who went digging through murky ponds in the desert and stared at microscopes for years trying to figure out what they’d found and then going on to show it to the world.

Or maybe not. We can’t know for sure. But the questioning, I have learned, is one of the most important parts. The further I got into my reading, the more difficult I found it to explain to my friends and family what I was doing. Studying mosquito control? Why? Most people I talked to believed mosquitoes should be eradicated as thoroughly and as soon as possible. Years ago, I watched my grandfather fight malaria in our guest bedroom, wracked with shivering fevers every few hours as we tried to figure out what was wrong. My friend recovered from dengue as a teenager and remains terrified of getting the disease again. The second infection strikes twice as hard and leaves you shaking.

When we talk about protecting nature, we do not necessarily think of mosquitoes. We imagine beautiful forests, elegant tigers, glistening butterflies. Mosquitoes — biting and beady and angular — do not fit the image. Unlike much of the rest of nature, they are annoying and dangerous. Unlike our relationship to the hills, the mountain lions, the butterflies and the birds, we cannot pretend everything works out best if we leave it all alone. We cannot leave mosquitoes alone. Our survival and health depend on intervention. 

But we also can’t pretend we can pluck them neatly from the ecosystem, hone our chemistry into a scalpel that extracts only them and leaves everything else whole. We are still crude creatures. And the mosquitoes are not so disconnected as to be carved out so neatly. We cannot make them merely our enemy to be destroyed, because they are intrinsically connected to the human world and the entire web of life. 

As I was going through the archives, I also began helping with a project at the preserve based on several bat detectors that have listened every night for bat calls as they fly over. My co-authors and I compared the acoustic data with the number of mosquitoes collected by the Abatement District and found dramatic correlations, especially for the small Myotis bats that form the majority of the bat population at Searsville. These bats rely on the mosquitoes. And bats here, like everywhere else, are critical to the ecosystem: they pollinate flowers, fertilize the ground with their nitrogen-rich guano and eat an incredible biomass of insects every night, ensuring no insect population grows too large.


Students explore Jasper Ridge as the sun sets. Photo by Jorge Ramos.

And so the web keeps spinning outward.

Sometimes I think longingly of the techno-optimism of the post-World War II era. I wish I could believe that a single technology could save us all today — carbon capture, battery storage, a pesticide that neutralizes just the disease-carrying mosquito and nothing more. I am trying to build my own path forward. I want there to be a simple, clear line to walk. There never will be. But I think of the 1970s scientists and writers dreaming of a new approach to mosquito control, of a different way for humans to relate to nature, and how that dream brought us a little further along.

I still haven’t been to Jasper Ridge, and it remains a place I know only through others’ stories. I think often about when I first heard about it, long before I arrived at university — in the forests of southern India, where I was helping a friend with a field research project. The two of us met a couple who had driven up to go birding and, late in the evenings, they told us of where they’d come from, a land far away from the sticky, leech-filled monsoon hills. 

They had taken a class at Jasper Ridge to become docents for the preserve. The docent program began when Jasper Ridge was founded in 1973, and expanded in later years to invest local community members in the space many had been excluded from when Stanford took over. Access to the preserve is not universal. Many people who live next door still cannot reach Jasper Ridge, for want of transportation, knowledge or resources — but more people learn from this land every year. Bit by bit, it teaches them the most fundamental skills: how to bird, yes, but also how to be caretakers of the ground, how to take people around and guide them through the paths and how the Muwekma-Ohlone people, the Indigenous inhabitants of the area, continue to call this place home, and return to gather and celebrate the land as it has been for centuries. 

As we sat at dusk in southern India, the couple described what Jasper Ridge looked like: Searsville Lake in the sunlight and the trees twined like old men, the golden grasslands. As the night came, they held before us a picture of everything that could be. I watched it gleam. 

Author’s note: A month after finishing this essay, I visited Jasper Ridge for the first time. I left the preserve, satiated with laughter and conversation, at sunset. Below is how it looked. It was everything I dreamed. 

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