We live in a galactic sweet spot, on the Goldilocks planet that’s just right. So far as we know, this really is the best of all possible worlds.

The forces that make our situation so clement are complex, but the distance from the sun, the Earth’s size and spin, the shifting continents and ocean currents, even the stabilizing impact of the moon all combine to produce this liveable blue-green sphere. When you look at our neighbours – cold and dusty Mars, smoggy, hothouse Venus – we should be grateful.

Humans being what we are, though, we take a lot for granted. For centuries, maybe millennia, we’ve been conducting an unintentional experiment with our home, altering its atmosphere in ways that seem subtle, but have – and likely will have – planet-altering results. Now, with climate change projected to boost global average temperatures by roughly 1.5-4 degrees C by the end of the century, some are advocating planet-changing experiments that are intentional.

The concept is “geoengineering.” It’s a bit like the Old Lady of the children’s song – the one that swallows the spider (and so on) to get rid of the fly she initially ingested. In this case, we’re talking about slowing or reversing the warming we’ve already caused. Ideas include releasing sun-blocking sulphates from high-flying tanker aircraft; launching massive arrays of mirrors into space to block a small percentage of the sun’s incoming rays; or using ships to spray salt water into the air to whiten clouds and make them more reflective.

These ideas sound like something concocted in the lair of a James Bond villain. But with the atmosphere’s carbon dioxide levels continuing to climb, geoengineering is starting to look like a possible, (if risky) Plan B.

Consider, for example, the value of maintaining polar ice caps. Given their role in regulating global weather and climate, “the risks of doing nothing in the arctic are enormous,” says Hugh Hunt, engineering researcher and co-director of the University of Cambridge’s Centre for Climate Repair. The potential impact is dire enough that Mr. Hunt argues it’s time to investigate some of those “crazy ideas.” And not just in the lab, or through computer simulations. “We’re talking about going out in a ship and trying out ideas,” he says.

Tinkering with solar radiation is more than just fine-tuning the planetary thermostat. Along with potential impacts to rainfall patterns, weather and circulation – not to mention the feel of the sun on our own skin – sunshine fuels the food system.

Photosynthesis is a bit of a clumsy process (a topic worth covering in a future post,) but plants have spent millennia making it work. In the process they’ve remade the face of the Earth. Just one or two percent of all the solar energy reaching the earth falls in wavelengths plants can intercept, but that small fraction supplies the basic feedstock – the tissue and roots, the sugars, proteins, fats and amino acids – that virtually all life relies on.

Messing with that productivity, even in subtle ways, comes with obvious problems. If there’s less sun, won’t there be less plant growth, and ultimately less food for terrestrial insects, birds and animals? On the other hand, runaway warming imperils plant growth too, so how do we square these problems?

The answer, based on initial research into the impact of sulphates in the atmosphere, is unlikely to be clear-cut. When a major volcanic eruption lofts sun-blocking particles high into the atmosphere, those aerosols scatter and diffuse the light.

Perennial plants with lots of leaves take advantage of this diffuse, more evenly distributed light to crank up photosynthesis. After the 1991 eruption of the Philippine volcano Mount Pinatubo, leaves in the forest understory got more light than they otherwise would have. The result seems to have been more plant growth overall, and a temporary decline in the growth of atmospheric carbon dioxide.

That sounds good for a pasture farmer like me, because perennial grasses do a good job of soaking up this diffuse light. But my neighbour growing oats or barley might have a far different result, based on the findings of a 2018 paper. By modelling the Pinatubo effect on a global scale, the research team found the dimming triggered by the eruption reduced yields of crucial annual crops like corn by 9.3 per cent, and by 4.8 per cent for C3 crops, such as wheat or rice.

Why the difference? Plant architecture probably has something to do with it. Annuals put more effort into producing grain or fruit. After all, they have only one year to accomplish their life cycle. Perennials, on the other hand, are here for the long haul. It makes sense for them to invest more in roots, stems and leaves.

But even if grass and trees grow better under a geoengineering scenario, we’re a species that relies heavily on annual crops. With less corn, rice, tomatoes and pumpkins, our diet could change in an unwelcome way.

The authors of the 2018 Pinatubo modelling article study argue potential yield losses due to geoengineering cancel out any agricultural benefit from cooling the climate. As researcher Jonathon Proctor told The Atlantic’s Robinson Meyer, “the side effects of the treatment—the changes in sunlight—are kind of just as bad as the original disease.”

In a culture that is increasingly rootless (pun completely intended), it’s easy to overlook the fundamental value of plants. But as a farmer whose life is literally built on plants and soil, I worry our society’s “plant blindness” will lead to bad policy choices.

Before we turn down the dimmer switch on Sol, let’s start with no-regrets solutions that work with the botanical world, not against it. Throttling back on carbon emissions is the obvious first step, but there are “soft” geoengineering approaches too, including improving forest health. Or, in my case, working with better grazing techniques that not only help feed people, but put more carbon in the soil.

Because Earth isn’t just the best of all possible worlds. It’s our only option.

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