I am a global change scientist. I’ll admit we are a bit of a mythical beast. Most people have never met one. We don’t show up on TV or radio much. People assume we are all like Al Gore. Some people like to tell us we are wrong.
What’s important (and why I’m writing here) is that global change scientists have learned some interesting things over the years.
I, for one, have learned a lot about grass.
Everyone who reads this depends on grass for their income in one way or another.
Yet, grass still holds mysteries.There are over ten thousand species of grass in the world. Why so many?
Most grasses do not taste bad. Almost all plant leaves have chemicals that deter animals, but most grasses do not. Why not?
Grasses were around during the age of dinosaurs, but grasslands are a relatively recent phenomenon. What caused grasslands to suddenly expand?
It turns out that the history of grasses** cannot be separated from CO2 concentrations in the air. Neither can its future.
**Global change scientists spend about as much time thinking about the past as the future. Understanding how things used to work helps us understand how things are going to work.
When ice sheets were at their greatest extent 20,000 years ago, the CO2 concentration of the atmosphere was about 180 parts per million (ppm). When we first brought cattle to the Great Plains, it was about 280 ppm. Today it’s 400 ppm. By 2100 it likely could be 700 ppm.
What does all this mean for grasslands and the world’s 1 billion cattle? How different were the grasslands of the settlers compared to today? What are they going to be like at the turn of the next century?
One way we start to answer this question is to run experiments. One clever experiment was in Texas, funded by the USDA and the Department of Energy. Global change scientists constructed long linear chambers that looked like hoop houses used for growing plants in winter. Air was blown through the chambers and plants scrubbed the CO2 out of the air. At one end, CO2 concentrations were elevated to 550 ppm. At the other end, they were 200 ppm. So the experiment simulated grasslands growing in atmospheres from 60 years in the future to 20,000 years ago.
If you had to choose, which grassland would you want your cattle to graze? The grassland of the mammoths? Of the settlers? Or your grandkids?
In this experiment, your grandkids’ grasslands produced about 50 percent more plant biomass aboveground than the mammoth’s.
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