Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: April 12, 1999
Publication Date: N/A
Interpretive Summary: While the reality of global warming is yet to be determined, our assessments indicate substantial direct effects on ruminant livestock can result, both in the United States and globally. This is contrary to the belief of some that such impacts are not expected to be great. Current summer weather already reduces production of high-producing dairy cows and beef animals in feedlots. With predicted global warming, our analyses sho additional declines in summertime milk production of dairy cows in the U.S., with largest losses in southern areas. Extremely hot conditions also can result in death losses; the predicted increased frequency of heat waves and other extreme events will increase such losses. Countermeasures, such as shades, sprinkling, and fans to provide relief, or shifting production locations, can be costly. However, the ability of livestock managers in the U.S. to adopt and keep up with projected rates of change in global temperature appears quite good.
Technical Abstract: If the perceived risks of global warming materialize, our assessments of the direct effects suggest substantial summer season impacts on key areas of ruminant livestock production in the United States and globally, contrary to a statement in the literature that "direct impacts on [livestock] are not expected to be great." High-producing dairy cows, beef animals in feedlots (particularly new entrants and those nearing market weight), and animals in early or late stages of gestation are strongly affected by hot weather, while sheep are generally affected less by adverse conditions. Our analyses have indicated additional 5-14% declines in June 1-September 30 milk production for dairy cows normally producing 32 kg/cow-day in southern areas of the U.S. as a result of projected global warming. Our recent development of environmental profiles for heat waves resulting in substantial death losses in commercial feedlots suggest that predicted increased frequency of extreme events (e.g., heat waves) and higher nighttime temperatures associated with global warming also will exacerbate death losses. Countermeasures for adverse effects can incur significant costs, such as environmental modification technologies and dislocation costs in some areas. Possible benefits of global warming during cooler seasons are not well documented, but are likely to be less than adverse effects during hot weather. However, the ability of livestock managers to adapt and keep up with projected rates of change in global temperature appears quite good, especially if the low to "best" IPCC estimate of change (1 to 2 deg C) over the next century is correct.