University of Minnesota
University of Minnesota
College of Biological Sciences

BAC Experiment


Naturally-occurring greenhouse gasses are responsible for the hospitable climate of our planet. Of the light energy entering earth’s atmosphere, about 30% usually bounces back into the solar system. Greenhouse gasses trap a small percentage of this energy, warming global temperatures an average of 33 °C (59 °F). Without this greenhouse effect, the global average temperature on this planet would be below freezing. However, artificially large amounts of four of the longest-living greenhouse gasses (carbon dioxide, methane, nitrous oxide, and halocarbons) have been released into the atmosphere since 1750 as a result of technological advancements in industry and agriculture. This increased concentration of greenhouse gasses is trapping an increased amount of energy, contributing to the phenomenon known as global warming.

The Intergovernmental Panel on Climate Change (IPCC), an apolitical, nonprofit organization comprised of over 2500 scientists from over 130 countries, released their latest report in 2007 stating that “warming of the climate system is unequivocal”. Consensus of this magnitude among scholars is increasingly rare in today’s world of hot-button topics. The overwhelming evidence in support of global warming has convinced the vast majority of the scientific community, with dissenters few and far between.
While several global models exist to project future trends, no one is certain exactly what will happen as a result of climate change or precisely how much temperatures will rise. Long-term data shows that, in the past 65 years, the average daily minimum temperature at Cedar Creek has increased by 2.0 °C (3.6 °F) and the average daily maximum temperature has increased by 1.2 °C (2.2 °F). Best estimates suggest that within the next 70 years, Minnesota’s temperatures will rise another 2-7 °C (4-13 °F). Elevated temperatures affect many parts of an ecosystem, including soil moisture, plant phenology and distributions, biomass production, and decomposition processes. Initial conditions, such as biodiversity or nutrient availability, will influence the nature of any changes. Complex ecosystem interactions may lead to other unexpected effects.

The BAC (biodiversity and climate) experiment examines the interactive effects of global warming and biodiversity on prairie ecosystems. The experiment consists of 38 plots containing varying levels of biodiversity (1, 4, 16, or 32 prairie species). The plots are divided into three areas, each receiving a different warming treatment: a temperature increase of 1-3 °C (2-5 °F), a temperature increase of 3-5 °C (5-9 °F), and a control (no increase). Warming treatments occur from March to November.
Biotic factors to be monitored include any changes in plant phenology, such as budding time; and possibly an analysis of the microbial community. Abiotic factors to be tested include soil flux, which is the amount of CO2 being released from plant roots and underground microbial activity, and soil moisture. The results of this experiment will be analyzed in the hope of forming better models and management strategies about climate change in prairies.


Funding for the BAC experiment was contributed by the National Science Foundation and Conexus Energy.