If you ever get a chance to hike a  stretch of the Appalachian Trail, you’ll find that the shelters all have “trail registers”. These are cheap notebooks where people mark down when they were at the shelter, and leave relevant notes. Sometimes you’ll see warnings of a bear that’s been showing up, or a Kevin Bacon sighting. Sometimes thru-hikers will leave notes for friends or acquaintances who’re behind them on the trail, and sometimes people get creative. I met one woman who would perform a rap at most shelters, and write the whole thing in the trail register.

Sometimes you come across something that seems a little… worrying.

Picture the scene, if you will. It’s early evening, and you’ve been hiking for several hours. The sun’s starting to get a bit lower in the sky, and the golden light is shimmering on the Housatonic to your right. Ahead to the left, you see a sign for the Stewart Hollow Brook lean-to, and you take the turn, glad you reached your day’s destination with plenty of daylight left.

You heave your pack into the lean-to, and sit on the edge, eating a mint-chocolate food bar, and listening to the wind and the birds. You wash your snack down with a swig of water, and lean over to grab the trail register.

Someone who passed you a week ago is now just a day ahead. There’s a liquor store that’ll give through hikers a free beer not too far away. And there’s –

-WARNING – DO NOT SLEEP ON THE GROUND HERE! Seriously don’t. There are these huge bugs that come out at night! Check your shoes!

-Holy shit I thought the other entries were joking but they’re not! They’re like some kind of alien bugs or something? They’ve got spikes and stuff all over them and pincers!

-Ridgerunner here – yes there are scary bugs, but they won’t hurt you. They’re just hellgramites

“Hellgramites”?

Like that doesn’t sound like some kind of alien parasite? Well, it’s just a name, so let’s see what they actually look like.

Oh.

Well.

And not just one or two – in the evening and through the night, there’s a never-ending march of these things up from the river.

So, dear readers – what’s going on here?

Well, lots of things, but when I saw this phenomenon as a ridgerunner back in my college days, it put me in mind of a high school environmental science class I took. It was a well-designed course, looking back. We learned about stuff like water quality, industrial runoff, and so on, and we learned it by going out and testing the water, and visiting sewage treatment plants and papermills.

And we learned how to use benthic macroinvertebrates as pollution bioindicators. In plain speech, we learned how to learn about water quality by looking at the bugs that lived in the riverbed. There are many kinds of bugs and worms that live under the rocks and in the sand at the bottom of any river, and as with any community, they have different specializations, preferences, and chemical tolerances.

Hellgramites – also known as dobsonfly larvae – were one of the species we studied, and I have them lodged in my head as being “pollution tolerant”. I believe that assessment is an exaggeration – it’s probably better to say that compared to some other fly larvae that live on riverbeds, they’re more tolerant of moderate levels of pollution. We’re talking the kind of water rivers that have people fishing for food, but also have signs warning everyone not to eat more than one fish per month from that water.

The Housatonic, as I remember it, is a shallow and somewhat murky river that can smell a bit off on a hot day, and has a lot of brown algal growth over its stones. It was pretty, but I think I only swam in it on a couple occasions when the heat got to be too much. Like most rivers in the U.S., it suffered from various forms of runoff, and while I never actually studied its invertebrate community, I’m willing to bet it would have been possible to gauge where the river was at even without the ability to measure for specific chemicals.

A couple years later, I had graduated, and was working as property manager for the Earlham College biology department. The job involved a number of tasks, but one of them was helping with a turtle population survey for a nearby pond. The pond was located between a couple industrial parks, and had had a major fish kill in recent years. The biology and chemistry departments had a grant to investigate, and my end involved catching, measuring, and marking as close to every turtle in that pond as I could get. I never saw the final reports, but there was one finding that jumped out at us right away – we caught dozens of turtles, of three or four different species, but not a single one of them was younger than six years old.

Sure, you can guesstimate pollution levels by what bugs are or aren’t thriving, but in this case reproduction had just ended in that pond. That’s another level.

During my work as a curriculum writer, the team I was on spent a good amount of time on the idea of bioindicators, because we had students studying how climate change is affecting things like leaf-out and flowering times in plants.

All of these things – the bugs, the turtles, the plants – they’re like looking at a person’s skin to assess their health. How does the color compare to their normal complexion? Do they have wounds? Blisters? A rash? Are they clammy, or is their skin too dry? None of the symptoms are the underlying problem, but they’re all useful ways to get an idea for what’s going on.

What I haven’t fully connected, until recently, is that the solidity of our knowledge about bioindicators and the sheer number of examples that exist both indicate that humanity’s traces can be found everywhere.

It’s easy to talk about indicators and trends, but even though one can spend an entire career teaching the same lessons over and over again, things don’t just start over. They continue happening. Chemicals continue building up, because they continue being released. Ecosystems take one hit after another, and bit by bit, cracks form in the foundations.

The study concludes that chemical pollution has crossed a “planetary boundary”, the point at which human-made changes to the Earth push it outside the stable environment of the last 10,000 years.

Chemical pollution threatens Earth’s systems by damaging the biological and physical processes that underpin all life. For example, pesticides wipe out many non-target insects, which are fundamental to all ecosystems and, therefore, to the provision of clean air, water and food.

“There has been a fiftyfold increase in the production of chemicals since 1950 and this is projected to triple again by 2050,” said Patricia Villarrubia-Gómez, a PhD candidate and research assistant at the Stockholm Resilience Centre (SRC) who was part of the study team. “The pace that societies are producing and releasing new chemicals into the environment is not consistent with staying within a safe operating space for humanity.”

Dr Sarah Cornell, an associate professor and principal researcher at SRC, said: “For a long time, people have known that chemical pollution is a bad thing. But they haven’t been thinking about it at the global level. This work brings chemical pollution, especially plastics, into the story of how people are changing the planet.”

Some threats have been tackled to a larger extent, the scientists said, such as the CFC chemicals that destroy the ozone layer and its protection from damaging ultraviolet rays.

Determining whether chemical pollution has crossed a planetary boundary is complex because there is no pre-human baseline, unlike with the climate crisis and the pre-industrial level of CO2 in the atmosphere. There are also a huge number of chemical compounds registered for use – about 350,000 – and only a tiny fraction of these have been assessed for safety.

So the research used a combination of measurements to assess the situation. These included the rate of production of chemicals, which is rising rapidly, and their release into the environment, which is happening much faster than the ability of authorities to track or investigate the impacts.

The well-known negative effects of some chemicals, from the extraction of fossil fuels to produce them to their leaking into the environment, were also part of the assessment. The scientists acknowledged the data was limited in many areas, but said the weight of evidence pointed to a breach of the planetary boundary.

“There’s evidence that things are pointing in the wrong direction every step of the way,” said Prof Bethanie Carney Almroth at the University of Gothenburg who was part of the team. “For example, the total mass of plastics now exceeds the total mass of all living mammals. That to me is a pretty clear indication that we’ve crossed a boundary. We’re in trouble, but there are things we can do to reverse some of this.”

Villarrubia-Gómez said: “Shifting to a circular economy is really important. That means changing materials and products so they can be reused, not wasted.”

The researchers said stronger regulation was needed and in the future a fixed cap on chemical production and release, in the same way carbon targets aim to end greenhouse gas emissions. Their study was published in the journal Environmental Science & Technology

There are growing calls for international action on chemicals and plastics, including the establishment of a global scientific body for chemical pollution akin to the Intergovernmental Panel on Climate Change.

Prof Sir Ian Boyd at the University of St Andrews, who was not part of the study, said: “The rise of the chemical burden in the environment is diffuse and insidious. Even if the toxic effects of individual chemicals can be hard to detect, this does not mean that the aggregate effect is likely to be insignificant.

“Diffuse and insidious” seems to apply to a lot of the problems we’re facing right now. In particular – and this will shock you – this makes me think of greenhouse gas pollution. The entire problem of global warming is diffuse and insidious. Instead of the attention-grabbing stuff, like causing cancer, greenhouse gases just… raise the temperature a little. So very little that it’s hard to measure, and then they do it again. And again. And again. Every hour, of every day, of every month, year round, for as long as they exist. We’ve known about it for well over a century now. We’ve been studying it for longer than that, and we’ve been watching as the numbers have gotten higher.

As the article says, we’ve crossed a number of thresholds recently, and there’s no real way to go back – we just have to find a different way forward.  As I will never stop repeating, we need systemic change. It’s not just the climate. It’s not just the chemical pollution. It’s not just the bigotry, and the greed, and the cruelty.

It’s everything. Plenty of parts of our society are good, and wonderful, and worth holding on to, but all parts of our society are sick. Because we are a self-aware collective organism, as a species, we have the ability to re-arrange the workings of our “body” to suit different wants and needs. That’s our greatest power, and it’s past time we did the learning and organizing required to put it to use for the good of all.

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