Saturday, February 27, 2016

Contaminants in our Environment, Biomagnification, and Science Literature


The Dissemination of Useful Knowledge in the Struggle for Modern Life

According to the Canadian Museum of Nature, belugas (Dephinapterus leucas) and killer whales (Orcinus orca) may be considered toxic waste in some places when they die. I'm going to do my best in this post to explain how and why.

So there's this thing I'm gonna introduce as background, called an Ecological Pyramid. This is a simple graphic representation of biomass at multiple trophic levels. Trophic levels being, of course, position on the food chain, from plants to bacteria and little buggies that decompose dead plant matter, to the larger buggies that prey on those, to the grazers that eat the grass that grows in the decomposing material, to the megafauna predators that prey on the grazers. Biomass, being simply the sheer amount of matter that is living, for this purpose categorized by trophic level.

The idea in an Ecological Pyramid is that only about 10% of the energy in all the biomass of one trophic level gets transferred/used to the next trophic level, so the apex predators need a ton of biomass and a large territory to support them. Now, this is simplified because it doesn't show food web interactions, so there are a number of reasons it doesn't work out for all situations, and there are a ton of exceptions and inconsistencies, but toss that aside a moment and imagine this:

So think about this as a way that nature might process some heinous contaminants. DDT, for example. Lead. PCBs. Mercury. Hydrocarbons from petroleum products or oil spills. This stuff gets picked up and processed a little bit at a time by the primary producers, bioaccumulated into that trophic level, but as a ton of primary producers get consumed by the next step up the pyramid, the contaminants don't dilute out. They aren't ever broken down because of how enduring they are, so they biomagnify. That means that a lot of contaminants sucked up out of the environment by the primary producers then end up in the bodies of each herbivore, because the structure of the food web and the biomass pyramid means a LOT of the primary producers are required to support herbivores. The concentration of the contaminant doesn't necessarily actually harm organisms at lower trophic levels, but because it gets more concentrated at each successive level, it can be really harmful to larger animals.

So if a chemical is mobile in the environment, long lived, and doesn't break down easily, if it is soluble in fats and/or can be considered "bio-available" for uptake by the primary producers, it can biomagnify. DDT was the beginning of our understanding of this phenomenon.

See, DDT is a nasty chemical, but the broader effects of it aren't immediately apparent. As far as we knew, it was just a really, really effective pesticide. It didn't just kill a few pests, though, it killed the broadest array of insects we'd ever seen. And like whaling or ocean dumping or logging or any number of other natural resource issues, we went overboard. Seriously, kids got hosed down with it in the streets, it was put on food crops everywhere, sprayed over whole forests and ornamental trees in residential neighborhood. We were spraying the stuff like it was going out of style.

“By their very nature chemical controls are self-defeating, for they have been devised and applied without taking into account the complex biological systems against which they have been blindly hurled” -- Rachel Carson, Silent Spring

The more pesticides got sprayed into our environment, the more made their way into the food web, the more it impacted species that had nothing to do with the intended use of the pesticides, particularly apex predators (which, as you know from previous posts, are vital to the health of an ecosystem). Bald eagles, for example, were impacted by DDT in such a way as to reduce the hardness of the shells of the eggs they laid, so they were severely impacted, and put on the endangered species list. They were only removed from the list in 2007 after enough time had passed without ongoing continued exposure so that their population could recover.

Hang in there, I'll get back to whale carcasses in a minute. See where this is going, though?

Anyway, part of the problem was that the people making decisions to spray were typically pest control officials, largely bureaucrats who found it a cheap way to get a ton of land cleared of pests in a hurry or agricultural producers advised by those bureaucrats on how to dramatically increase their yield in a single season, and not the underfunded wildlife biologists who were seeing the impacts on the rest of nature or the public health specialists who eventually started to see impacts on people. Even otherwise fully healthy people, years after use and exposure.

See, the problem with a lot of pesticides is that they are fat soluble. Which meant that not only do they get into mammary tissue and breastmilk and harm the most vulnerable of our population, they can accumulate and be stored in fat for years, seemingly harmlessly, until one day a person might lose weight due to illness or injury or even an attempt at improved exercise lifestyle and find their system suddenly overloaded with more pesticide than they could handle, suddenly released from those tissues as their fat cells got used for energy. People can drop like flies, kinda literally, years after any exposure to pesticides.

To top it off, for quite a while, it seemed like the only way we could find to deal with pests developing resistances to pesticides (a natural evolutionary consequence of pesticide application) was to spray at higher concentrations, and more frequently. This served the interests of the chemical manufacturers quite nicely, and they had armies of lobbyists pushing their product on Congress and on agencies like the USDA. They sold their products as "cheap and easy!" until it wasn't, and then it was just all we knew for a while.

However, there are alternatives out there. Selective application of pesticides rather than wholesale spraying at incautious concentrations as used to be common is one way. If you use just a little of just the right pesticide at just the right time in a particular pest's lifecycle, you can get away with applying a lot less pesticide, at way less cost, to much greater effect. We've also had great results by selectively importing predators and microbial enemies and other biological controls of pest species, after very careful testing in controlled lab and field tests to find what would work.

Collectively, these practices are called Integrated Pest Management, or IPM. My state, along many others including probably yours, has tons of information and resources on it available for the public (that's you!), for yardwork and gardening hobbyists, for agricultural producers, and for anyone who might be interested. I have vague memories of what my dad did to our yard and house to control an absurdly huge infestation of our dog's fleas when I was a kid, and I wonder what the concentration of those chemicals is in our own fat cells to this day as a result. It's a tough thing to think about, because nobody knew better. To this day, many people don't know better, and still over apply pesticides because they think simply that more is better and don't realize they can be causing problems that won't be seen for years, whether in the health of their family or in increased resistance by the pests to those chemicals.

Eventually, the voices of biologists like Rachel Carson started to get heard, even over the character assassination attempts of the well financed chemical industry and the politicians who served them. Rachel's 1962 book, Silent Spring, laid out all the evidence and made a convincing case for the application of alternatives and reduction of the use of pesticides. Her book, a labor of love she wrote while fighting cancer in the last days of her life, raised such a ruckus that DDT got banned, and the environment was raised for the first time to the status of a major political issue of interest to all of us. She basically started a major branch of the modern environmental movement singlehandedly.

I'd encourage you to read it, though I'd understand if you never picked it up, dear reader. I only got around to reading Silent Spring last year, in part just because I was embarrassed that I, an actual ecologist, had never read such an important work. Oh, don't get me wrong, I knew the information it held, and had taken classes that presented the same information with more recent updates to the science, but had never really fully appreciated the grace of Rachel's prose, or the effort she put into her work.

And that's why I (too rarely, I know) write about this stuff. Not because I consider myself a writer or scientist anywhere near Rachel Carson's eloquence or brilliance, but because so many people don't know this stuff, and sometimes someone might pick up a little knowledge from me. This is all just background information I'm fully aware of as a person with a career in natural resources, but many of my friends and family know almost nothing about it, and I feel like I have to honor the works of Rachel Carson and Bill Nye and Edward O. Wilson and Charles Darwin and Mary Roach and all the rest of the fascinating and entertaining science literature out there from ages past and present . . . by sharing it. We all benefit from this knowledge, because our neighbors overapplying pesticides in their yards, ignorant through no real fault of their own, affects us and the rest of the world we live in, too. Lots of issues are like that.

Maybe I'll get back into writing here more just by taking the time to read more, and sharing the experiences I get from my favorite new and classic science writing. Let me know if you like that idea, and encourage me once in a while, and you'll see more submissions from me, I promise. Gimme prompts! If there are questions about ecology or the broader sciences that you've wondered about, let me know. I'll be happy to share my knowledge, and go searching for it if I don't already have it.

Now: Confession time! I tricked you. Whale carcasses were really just a silly excuse to get me writing, and are hazardous not for the bioaccumulated environmental contaminants, but because Brobdingnagian sized rotting carcasses are a hazard to public health. Also, they have been known to explode without warning as gasses build up within them while they decompose from the inside out. But you learned some cool stuff, didn't you?

So without further ado, I'm really happy to have created an opportunity to share the following grossness. Enjoy. Oh, and, uh . . . viewer discretion is advised.

A few Rachel Carson quotes to leave you with:

“But man is a part of nature, and his war against nature is inevitably a war against himself.”

“Those who contemplate the beauty of the earth find reserves of strength that will endure as long as life lasts. There is something infinitely healing in the repeated refrains of nature -- the assurance that dawn comes after night, and spring after winter.”

“The winds, the sea, and the moving tides are what they are. If there is wonder and beauty and majesty in them, science will discover these qualities... If there is poetry in my book about the sea, it is not because I deliberately put it there, but because no one could write truthfully about the sea and leave out the poetry.”

(She was primarily a Marine Biologist, FYI)