Red Deer Rising

By Robert C. Balling Jr., Ph.D.
Arizona State University

We listen for their hoofbeats on our rooftops. But come Christmas morning, we don’t give them another thought. Where do they go? What do they eat? Is there enough to go around? How will elevated carbon dioxide (CO₂) levels affect where and how they live?

All year long, Santa’s reindeer and their Northern Hemispheric colleagues must forage for food, battling low temperatures in their struggle to survive. Happily, the scientific literature consistently reveals that, whether temperatures warm or not, elevated CO₂ will have a direct, positive effect on the high latitude ecosystems and, consequently, their inhabitants.

Consider, for example, this comforting news about one of our favorite holiday-season animals—the famed red deer of Norway. In a recent issue of Oecologia, scientists at the Norwegian Institute for Nature Research reveal the benefits of the changing ecosystem’s affect on these elegant animals.

To begin, the authors note that red deer populations have increased steadily over the last few decades for a variety of reasons. Thanks to a rather aggressive capture-mark-recapture strategy in Norway, a unique database is emerging on these wondrous animals, allowing for analyses of many factors impacting their health and survival.

In this investigation, data for 678 individual animals were used to assess growth and survival rates and their association with winter and spring weather, as well as sex, age, population size, body condition, and body weight (in the world of red deer, as in the world of automobiles, small is dangerous, whereas big may ensure your survival.) Using statistical techniques, the authors were able to isolate the influence of each variable on the red deer population.

One thing they discovered is that red deer simply cannot warm up to those cold winters of northern Norway! Winter harshness acts as a limiting factor on population growth: In the short-term, it limits first-year survival. In the long-term, it diminishes body weight and condition.

Global climate change, then, bodes well for the red deer. As WCR readers are aware, winter temperatures may indeed be increasing over selected land areas of the Northern Hemisphere. From what we learn in this study, the red deer in Norway can be thrilled about the trend!

Obviously, more high-latitude deer mean more demand for plants to eat—something the northern latitude animal population can count on, as two recent articles prove.

Tjoelker and colleagues examined seedlings of five boreal tree species (quaking aspen, paper birch, tamarack, black spruce and jack pine) grown in controlled-environment chambers for three months at 370 parts per million (ppm) and 580 ppm atmospheric CO₂. This 57 percent elevation of CO₂ increased the seedlings’ photosynthesis by about 28 percent, while water-use efficiencies increased by 40 percent to 80 percent. The jack pine seedlings, too, showed a further increase in photosynthesis when the day/night temperatures were raised by a few degrees. Increased CO₂, and to a lesser extent increased temperature, combined to enhance the biomass production of all five species. And that’s good eatin’ if you’re a hungry red deer hoping to bulk up for safety.

A second study, by four German scientists, appeared in a recent issue of Arctic and Alpine Research that will have high latitude animals shouting from the rooftops (if there were any rooftops up there, that is). In it, Lange and colleagues examined seven lichen species in Alaska, and they measured in-field CO₂ exchanges and photosynthetic rates (did you know that 8 percent of the earth’s terrestrial surface has lichens as the dominant life form?).

Among many other interesting findings, the scientists tracked a strong linear relationship between net photosynthesis rates and carbon uptake in the lichens. Although not a focus of their study, the results show us that increased atmospheric CO₂ should lead to increased photosynthesis and increased lichen biomass in the future.

So the red deer will thrive. CO₂ increases will stimulate growth in a variety of species, including those high-latitude plant varieties of special interest to these Norwegian icons. Slightly higher temperatures only compound the benefits.

Somehow, it seems a shame that up the red deer of Norway, the five boreal tree species, and the seven types of lichen cannot vote on international policies aimed at reducing emission of CO₂. Perhaps they, more than any of us, understand what’s at stake here.

References:

Lange, O.L., at al. 1998, Upland tundra in the foothills of the Brooks Range, Alaska, U.S.A.: Lichen long-term photosynthetic CO₂ uptake and net carbon gain. Arctic and Alpine Research, 30, 252–261.

Loison, A. and R. Langvatn, 1998, Short- and long-term effects of winter and spring weather on growth and survival or red deer in Norway. Oecologia, 116, 489–500.