If I had to pick my top two topics of the last year, they would probably be air pollution, and covering our cities with plants. With that as context, please understand that todays post is difficult for me, because it’s time I came clean about something. It’s not just us – plants also cause air pollution. The reality is that this little biosphere of ours is a messy place, and was messy well before we started getting clever with things like fire and pressure. I think it’s pretty clear that air pollution from traffic and industry is a bigger problem than air pollution from plants, but that doesn’t mean that plants are just nature’s perfect air filtering machines. It’s not just pollen either – plants emit all sorts of interesting stuff:

All plants produce chemicals called biogenic volatile organic compounds, or BVOCs. “The smell of a just-mowed lawn, or the sweetness of a ripe strawberry, those are BVOCs. Plants are constantly emitting them,” Gomez said.

On their own, BVOCs are benign. However, once they react with oxygen, they produce organic aerosols. As they’re inhaled, these aerosols can cause infant mortality and childhood asthma, as well as heart disease and lung cancer in adults.

Put in stark terms like that, it can be pretty alarming, and as I said, I absolutely think that we should be accounting for this stuff. It also doesn’t remove the various benefits to having plants around that I’ve discussed in the past, it just complicates the story a little. Unfortunately, as with the air pollution we humans make, air pollution from plants is getting worse, not just from the rising temperature, but also from the rising CO₂ levels:

There are two reasons plants increase BVOC production: increases in atmospheric carbon dioxide and increases in temperatures. Both of these factors are projected to continue increasing.

To be clear, growing plants is a net positive for the environment. They reduce the amount of carbon dioxide in the atmosphere, which helps control global warming. BVOCs from small gardens will not harm people.

“Your lawn, for example, won’t produce enough BVOCs to make you sick,” Gomez explained. “It’s the large-scale increase in carbon dioxide that contributes to the biosphere increasing BVOCs, and then organic aerosols.”

See, increasing plant life as we decrease our own pollution will not only make our lives better, it will also create something of a feedback loop. By reducing CO₂ levels, we will also be reducing both of the things causing air pollution from plants to get worse. Even so, the temperature’s going to keep rising for a while to come, so it’s good to be aware of this aspect of that problem.

The other thing this paper mentions is dust. I talked the other day about the danger of toxic dust from the drying Great Salt Lake, but these researchers were taking more of a global perspective, and at that scale, it’s the Sahara that has them worried:

The second-largest contributor to future air pollution is likely to be dust from the Saharan desert. “In our models, an increase in winds is projected to loft more dust into the atmosphere,” said Robert Allen, associate professor of Earth and Planetary Sciences at UCR and co-author of the study.

As the climate warms, increased Saharan dust is likely to get blown around the globe, with higher levels of dust in Africa, the eastern U.S., and the Caribbean. Dust over Northern Africa, including the Sahel and the Sahara, is likely to increase due to more intense West African monsoons.

Both organic aerosols and dust, as well as sea salt, black carbon, and sulfate, fall into a category of airborne pollutants known as PM2.5, because they have a diameter of 2.5 micrometers or less. The increase in naturally sourced PM2.5 pollution increased, in this study, in direct proportion to CO2 levels.

“The more we increase CO2, the more PM2.5 we see being put into the atmosphere, and the inverse is also true. The more we reduce, the better the air quality gets,” Gomez said.

For example, if the climate warms only 2 degrees Celsius, the study found only a 7% increase in PM2.5. All of these results only apply to changes found in air quality over land, as the study is focused on human health impacts.

The researchers hope the potential to improve air quality will inspire swift and decisive action to decrease CO2 emissions. Without it, temperatures may increase 4 degrees C by the end of this century, though it’s possible for the increase to happen sooner.

Gomez warns that CO2 emissions will have to decrease sharply to have a positive effect on future air quality.

“The results of this experiment may even be a bit conservative because we did not include climate-dependent changes in wildfire emissions as a factor,” Gomez said. “In the future, make sure you get an air purifier.”

 Though be careful about what kind of purifier you get, since the good ol’ profit motive has done anything but clear the air on what makes for a good product.

I think I should mention – the particles we’re discussing here are not just the ultrafine particles I’ve discussed in the past. A lot of them are much bigger, which means that masks are going to be much more effective than they would be for freeway and airport pollution. That said, none of us are getting out of this life alive, and air pollution has played a role in that throughout our species’ existence.

That’s why it’s so important to have universal healthcare as part of our response to global warming.

The grim reality is that as temperatures continue to rise, the world will become more dangerous in a number of ways, and under a private healthcare system (or a public one that has been deliberately under-funded to discredit it), that will inevitably translate to shorter lives, with more suffering and disease. As much as I enjoy cyberpunk as a genre, I’m not thrilled about the part of it where all of us cyberserfs are constantly ill because of pollution and poverty. Kinda seems like the workers of the world oughta unite…

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