The Biology of Climate Change

Introduction

Photo by billy barr
Photo by billy barr

Most climate scientists are now in agreement that earth’s climate is changing because of enormous and rapid additions of greenhouse gases, such as carbon dioxide, methane, and nitrous oxide, to the atmosphere due to the consumption patterns of humans. Predicted outcomes of this warming include rising sea levels, more extreme weather events, and changes in precipitation and temperature patterns globally, but it is less clear exactly how climate will change at any one location and even less clear how organisms and ecosystems will respond to the predicted changes.

 

07060005
A marmot family in the spring. Photo by Nickolas Waser

In the high elevations of the Rocky Mountains, snow covers the ground for most of the year – summer is short. Organisms that live here or just visit for the summer have a lot of work to do to complete their life cycle in a very short period of time. For example, marmots emerge from hibernation in late April to early May and retire to their burrows by late August to early September. In that span of time, they need to mate, raise pups, and put on enough weight to survive hibernation during the long high country winter. (They can lose up to half of their summer weight during hibernation.)

How will climate change affect organisms and ecosystems around the RMBL? Will all effects of climate change be negative or could some organisms actually benefit from the change?

The Climate of Central Colorado

“Climate is what you expect, weather is what you get.” Mark Twain

Climate can be thought of as the average weather conditions for a location. Because of high elevations in central Colorado, temperatures are cool and the thin, dry atmosphere allows relatively high levels of ultraviolet (UV) radiation to reach the surface. Highest elevations generally receive more precipitation than lower elevations with most precipitation accumulating during the winter as snow.

High elevation and extreme relief are major factors in the average climate of central Colorado, including the lab. For example, the Rocky Mountain Biological Laboratory sits at roughly 9500 feet (2920 m) above sea level (asl). The surrounding mountains are roughly 12,000 feet asl or 3000 ft (915 m) higher than the lab. Avery Peak, about 3 miles north of the lab is 12644 ft (3854 m) asl. Summer afternoon temperatures decrease about 4-5 degrees Fahrenheit for every 1000 feet of elevation gain. That means that the top of Avery Peak is usually 16 degrees Fahrenheit, or 9 degrees Celsius, cooler than down in Gothic!

Major Climate Drivers for Ecosystems around RMBL

There are two particularly important climate-related occurrences for organisms and ecological systems in the high country. The first important event is the day that snow cover is reduced to zero, the snow melt date, which as you can imagine, doesn’t happen at the same time in all locations. The snow melt date is really the beginning of the short growing season.

Another very important climate variable is the amount of water available to plants during the growing season. This variable can directly reflect the amount of precipitation received, but can also be influenced indirectly by temperature. For example, during a year with normal rainfall, plants could still be stressed by lack of soil moisture if temperatures are higher than normal, resulting in higher than normal rates of evapotranspiration and lower than normal soil moisture.

RMBL Climate Records

billy barr
billy barr

Fortunately for us, climate observations at the RMBL extend back to shortly after billy barr arrived in Gothic. Since 1974, billy has kept a running tally of temperature, precipitation, and total snow pack near his off-the-grid house north of the field station. billy also records the first day of the year that he sees local animals that hibernate, like marmots, emerge from their burrows as well as the first day he sees animals that migrate to higher elevations for the summer months, such as hummingbirds. These incredible four-decade long records from a remote sub-alpine to montane environment are invaluable to scientists that study the effects of climate change on organisms and ecosystem functioning. For more about billy barr and his observations, download a short Rocky Mountain News article here. Is a 40-year record of observations a long-term data set?

Phenology

The timing of important life cycle events, such as emergence from hibernation, is called phenology. Many behaviors change with changing environmental conditions. Because of billy’s detailed daily observations, we can ask certain questions about certain phenological events around the RMBL field station. For example, is there evidence for changing climatic conditions at the Rocky Mountain Biological Laboratory? How does the timing of life cycle events of high-country organisms change with changing environmental conditions?

Next step – learn about RMBL Phenology Research.

Glossary

evapotranspiration – the sum of evaporation and plant transpiration from the Earth’s surface to the atmosphere.

phenology – the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate. Examples include the date of emergence of leaves and flowers, the first flight of butterflies and the first appearance of migratory birds, etc. Because many such phenomena are very sensitive to small variations in climate, phenological records can be a useful climate proxy for temperature in historical climatology, especially in the study of climate change and global warming.

relief the vertical difference in elevation between the summits and the lowlands of a given region. Rough country has high relief; and flat country has low relief.

transpiration – a process similar to evaporation. It is the loss of water vapor from parts of plants (similar to sweating), especially in leaves but also in stems, flowers and roots. Leaf surfaces are dotted with openings called, collectively, stomata, and in most plants they are more numerous on the undersides of the foliage. The stoma are bordered by guard cells that open and close the pore. Leaf transpiration occurs through stomata, and can be thought of as a necessary “cost” associated with the opening of the stomata to allow the diffusion of carbon dioxide gas from the air for photosynthesis. Transpiration also cools plants and enables mass flow of mineral nutrients and water from roots to shoots.