Weed Biology and Climate Change

Homeowners detest dandelions, and hikers abhor poison ivy. However, as pesky and unwanted as they often are, weeds’ stubborn resilience makes them well worth studying, especially as climate change affects plant life around the world.

To find out more, we interviewed Dr. Lewis Ziska and Dr. Jeffrey Dukes, two authors who worked on the recently released Weed Biology and Climate Change.

• What defines a “weed” from any other type of plant?

  DUKES: Somebody doesn’t like it where it is. One person’s weed can be another person’s wildflower, or salad ingredient. It’s an entirely subjective thing. But the plants that make the lists of “noxious” weeds can cause serious economic or environmental damage, so there’s real benefit to controlling them.

• In a nutshell, what are the most significant ways climate change is affecting weed biology?

  ZISKA: Weeds are supremely adapted to change; they thrive on environmental disturbance. Therefore, sudden changes in temperature, CO2, drought, floods . . . in short, all of what we anticipate with global climate change, increase ecological “opportunities” for weed seed dispersal, initiation, and biological success.
  

  DUKES: In terms of the atmosphere, we’re creating conditions that plants have never seen before – the atmosphere has nearly 25% more carbon dioxide than it did just 50 years ago. This is a big deal to plants, since they slurp up carbon dioxide and use it to grow. It changes the landscape for them, and some plants are going to benefit more than others.

  From the research that’s been done so far, Lew and I think that there are a lot of cases in which the weeds are going to benefit from the new conditions, with some important downsides for people and other species.

• Everyone hates seeing dandelions sprouting up in their yards, but do you think that weeds get a bad rap? How can they be useful? Do we already use weeds that we simply do not recognize?

  ZISKA: There are some weeds that are universally recognized as being harmful in almost all circumstances (e.g. puncture vine, nightshades, poison ivy). That being said, there are many plants that are undesirable simply because we haven’t found a use for them. For example, wild or red rice is an acknowledged weed in rice production, but may also have unique genes that will allow it to survive in extreme environments—genes that may be very useful in adapting cultivated rice to climate change.

• Do you anticipate that climate change will impact all growing environments, even down to amateur gardens? If so, what sort of advice would you give to non-scientists for dealing with this issue?

  DUKES: Yes, it already has. I was in England a few years ago and got to visit some gardens where Robert Marsham and his ancestors had been tracking the flowering dates of a variety of plant species since 1736. Keeping track of flowering times and the timing of “signs of spring” is a pretty common hobby there. Plants in that region are now flowering, on average, something like a week or two earlier than they ever did before over that time span.
  

  So, yes, climate change has already altered growing environments in lots of ways. But it’s not something that would be obvious to anyone over a period of a decade; there’s too much year-to-year variability for people to notice trends over that sort of timespan. And it won’t change peoples’ day-to-day activities much, but they may be able to consider planting some species now that they wouldn’t have considered a few decades ago.

  ZISKA: If you want to see, in a simple way, how climate change has altered amateur gardening, just look at how plant hardiness zones (the different colors on the back of a package of seeds) have changed since 1990.

  Few people notice plants; most of us are hard wired to notice immediate, moving things like deer, birds, a charging rhino. Plants take patience, and they require you to be outdoors. The best advice I can give is to get a sense of what is around you and observe how it has—and will—continue to change as the environment changes.

• What inspired you to study plant physiology?

  ZISKA: The ability to plant a seed and watch it grow has, since my earliest recollections, been nothing short of miraculous to me. I wanted to know how plants could do things that no other living organism could do. I was very fortunate to have good instructors who encouraged me to continue my interests.

  DUKES: I’m more of a plant ecologist; I started down my line of work when a class in college got me thinking about how the thinning of the ozone layer above our planet could affect plants, and how anything that affected plants would affect lots of animals and people.

• What is the most unusual thing you have done in your line of work?

  DUKES: Boy, there are lots of things. Most people don’t go around collecting weed seeds on purpose, for instance. But I guess getting up in the middle of the night in Mexican deserts and Utah wilderness to wander around cutting off plant leaves and pressurizing them in a special chamber has to rank up there. This isn’t just a scientist’s idea of a wild night, of course – the idea is to get a sense for how much water the plants have access to.

  ZISKA: Working and handling poison ivy is always fun.

• What would you say has been the most significant scientific discovery in your lifetime?

  DUKES: I think the series of discoveries that led to the realization that chlorofluorocarbons were depleting the ozone layer has to rank pretty high.

  ZISKA: The Keeling Curve.1

• What do you enjoy doing in your spare time?

  ZISKA: Painting and gardening.

  DUKES: Playing with my kids, going on hikes with my family, and when I get the chance, playing ultimate frisbee.

• What are you reading at the moment?

  DUKES: Mostly news and work stuff. Right now I’m rereading Spencer Weart’s The Discovery of Global Warming for a class I’m teaching.

  ZISKA: Denialism by Michael Specter.

  Related work from these authors
  	“Chapter 2. Plant Responses to Rising Atmospheric Carbon Dioxide” James I.L. Morison, Michael D. Morecroft, Lewis H. Ziska, & James A. Bunce. Plant Growth and Climate Change, (2007). DOI: 10.1002/9780470988695.ch2
  	26. Responses of Invasive Species to a Changing Climate and Atmosphere David M. Richardson, & Jeffrey S. Dukes. Fifty Years of Invasion Ecology: The Legacy of Charles Elton, (2010). DOI: 10.1002/9781444329988.ch26

  
  1. Keeling, C. (1960). The Concentration and Isotopic Abundances of Carbon Dioxide in the Atmosphere Tellus, 12 (2), 200-203 DOI: 10.1111/j.2153-3490.1960.tb01300.x

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