Missing the Forest for the Trees

It’s late October, and I keep finding myself wanting to go outside. I spend a while at the window, looking at the trees, wanting to be covered by them. Thinking about what they do.

I try to think about what the climate even is. What happens to the junk we put into the air? I remember phrases from documentaries and YouTube videos, ones I understand well enough until I try picturing them happening in front of me. I can’t picture the methane sink.

Forest soil takes methane out of the atmosphere. Somewhere below the surface, organisms eat it. Cool. I can follow that. But looking outside, I just see trees. The organisms doing the work are out of sight, living under conditions I mostly know through someone else’s measurements.

Eventually, I go outside.

The air is cool, and I’m in no hurry. As I walk toward the trees, I think about how much of a forest I leave out of the picture. My eyes follow what grows above ground. Below it is another part of the place that I rarely think to look at.

I think back to when I first read about declining methane uptake. Researchers had been measuring forest soils around Baltimore and at Hubbard Brook in New Hampshire for years, and the soils were taking less methane out of the air than they used to. I wanted to look back through those years and understand what had changed down there.

The explanation I kept finding was rainfall. Water fills the spaces in the soil and makes it harder for gases to move through, so less methane reaches the organisms that eat it. Got it. It connected the rain above ground to something happening below it.

But I’d been reading about insect losses and pollution, and the ways we disturb these places. I wondered how those changes might show up underground. Rain could be part of the story. I wanted to know what else had been happening.

The ground keeps drawing my attention as I get closer. I imagine the gaps in the soil and the routes methane and oxygen take through them. Those spaces have a history. Roots grow through them. Animals walk over them and dig through them.

And earthworms, which I’d started to read about, don’t all work the same way. Some pull leaves down into deep burrows. Others work through the topsoil, mixing as they go. If the mix of worms changes, the routes through the ground might change with it. I wanted to see whether the worm records lined up with the methane measurements.

I was still carrying those ideas when I went back to the rainfall explanation. There were 27 years of Baltimore data to go through, alongside the Hubbard Brook record. I could ask when uptake changed and how much of that change rainfall accounted for. Following that question eventually became a paper.

Rainfall helped explain some of the changes from year to year. But after I accounted for it, the decline was still there.

So what had been changing beneath those trees, across all those years, that the rain couldn’t account for?

The city forests seemed to have settled into taking up less methane, while uptake in the rural forests kept falling. I wondered whether the city soils could ever take up as much again, and whether the organisms were still there to do it.

But I’d been taking those earlier years for granted. What had made uptake so high back then? I was thinking about getting “it” back before I understood what all was lost.

I’m among the trees now. My eyes drift from one to the next. Even the trees have become part of the question. I’d read that methane can be produced inside living wood, and I’d spent so long trying to look past the trees that I’d almost forgotten to look at them.

I stop and look around.

The air is still cool. No bugs around. Leaves rustle overhead and drift down in the breeze. The ones already on the ground crunch beneath my feet.

I crouch and press into them. On top, they’re loose and crushed, broken into pieces where I’ve walked. I work my fingers underneath. The leaves are damper there, then wet and clumped together. Then I reach the soil.

I try to process the layer I’ve just pushed through. Leaves have been falling here, and others have been rotting. I can feel what’s left between my fingers. I can’t tell how much arrived, or how much has already gone.

I’d been looking at the methane measurements the same way. Methane was being made and methane was being eaten. The net balance had changed. But now, I wanted to know how much was being made, and how much was being eaten.

I stay crouched a while, the wind moving through the branches above me, a handful of leaves in my palm.

Eventually, I’ll take those questions back inside.

For now, I’ll stay outside a little longer.