Chill out man: climate change and the future of marijuana

Moving to California, I learned quickly that everyone smokes pot here.  Everywhere.  All the time.  People smoke openly on their porches, walking down the street, even pulling their cars onto the highway (a little scary).  Our favorite bar doesn’t have a reserved area for cigarette smokers outside (cigarettes are so bad for you!!), they have a reserved area for pot smoking (not official and not legal, of course).  Taking a bike ride through Oakland on a Friday afternoon takes you through one sweet smelling cloud to the next…to the next…to the next, for nearly 8 miles.  It has become as normalized here as a cup of morning coffee.

As a beloved plant, that society appears to worship, there is a wealth information out there about it.  Unfortunately, as a plant whose main side effects are the munchies and watching Adult Swim, the research is not so good.

So when I wanted to write a blog post on the effect of climate change on cannabis – plant growth, health and of course environmental effects on the development and strength of the psychotropic component THC – I was disappointed to find that rather than wading through scientific papers, I was buried under  webpages with dancing smoke plumes and industry newsletters.  For the most beloved plant in America, the research is extremely thin.

Though there is ample scientific literature on the effects of THC on mice (how many NIH grants does it take to figure out that mice get the munchies too?!?!) and a couple of interesting articles about the negative environmental effects of cultivation (Mexican drug cartels taking over pristine national park land (1) and indoor cultivation carbon footprints (2)), it is slim pickings when it comes to climate change.

I did find some literature dating back nearly 40 years suggesting that THC, like some other phenolic compounds, is used by plants as a defense against pests, and that temperature can have an effect on THC development (like with some other phenolic defensive compounds in other plants).  The sources though were so cringe-worthy I refused to include them in this post.  Let’s just say there is a gap in the literature that perhaps could be an interesting pursuit for a researcher.

However, I did find some information about the effect of increasing atmospheric carbon dioxide concentrations on the cannabis plant.   Now if you are a grower or spend a lot of time on those websites with the dancing bears, then you already know that sticking a tank of carbon dioxide in your grow house and running outside as you crank it open, will make those plants boom.  However, let’s pretend those people don’t read science blogs.

It turns out, that over the next 40 years, an increase of carbon dioxide concentrations to 545 ppm (what is expected by 2050) won’t have much effect on the cannabis plant (3).  However, when grown in carbon dioxide concentrations of 700 ppm (what is expected by 2100), plant growth takes off.  Both their photosynthesis and water-use efficiency go way up (i.e. more growth while needing less water, which is generally a good thing).  This is not unique to cannabis plants, as similar studies have found that other plants respond in a similar way.  A Duke University study, in which researchers pumped carbon dioxide into a temperate forest (your tax dollars at work), found that poison ivy took off in this carbon-rich environment and produced more allergenic compounds (awesome!)(4).   In California, a study at Stanford University found that the ever-prickly agricultural pest, the yellow star-thistle, will also do well in a high-carbon environment, out-competing other grassland plants and slowly driving farmers insane (5).

In a carbon-rich world 100 years from now, when our environment is over-run with poison ivy and star thistle; where rising sea levels will displace millions of people causing natural disaster refugees; where warmer temperatures will increase epidemic risks and famines globally; I think we’ll be very glad that the cannabis plant is doing so well.  We’ll probably need it.

Minda Berbeco has a PhD in Biology from Tufts University and is a science blogger in the Bay area.  Unlike everyone around her, she does not smoke, but she does enjoy the mellow scented cloud that descends on Berkeley every Friday afternoon and lasts through the weekend.  Some people say it’s the fog coming off the ocean.  This is California after all.

Future Reading for Your Enjoyment!

  1.  Marijuana National Forest: Encroachment on California Public Lands for Cannabis Cultivation
  2.  The carbon footprint of indoor Cannabis production
  3. Photosynthetic response of Cannabis sativa L., an important medicinal plant, to elevated levels of CO2
  4. Biomass and Toxicity Responses of Poison Ivy (Toxicodendron radicans) to Elevated Atmospheric CO₂
  5. Strong response of an invasive plant species (Centaurea solstitialis L.) to global environmental changes


1 thought on “Chill out man: climate change and the future of marijuana”

  1. CO2 concentrations of 700 ppm? Sure, cannabis might do okay, but isn’t doubling the amount of carbon dioxide ( in the air going to have direct chemical effects on animals? How much of it does it take before we start poisoning ourselves directly?


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