American farmers and ranchers are facing increasing risks to their livelihoods as a result of climate change, according to a recent report from the U.S. Department of Agriculture.

“Climate change poses unprecedented challenges to U.S. agriculture because of the sensitivity of agricultural productivity and costs to changing climate conditions,” the report said.

According to the report, increases in greenhouse gases in the atmosphere resulting from human activity are raising average global temperatures, which in turn can alter weather patterns and cause both prolonged droughts and severe downpours and increase stress on both crops and animals.

The USDA anticipates that these factors will have a negative impact on agricultural productivity in the near future if adaptive farming measures are not taken, and if greenhouse gas emissions are not curbed.

The report points out that U.S. agriculture has demonstrated the capacity to adapt to a variety of challenges in the past 150 years, but that it was done during a period of “relative climatic stability.”

The USDA emphasizes that adaptive measures alone will not necessarily mitigate the consequences of climate change and that substantive action must also be taken to address the greenhouse gas emissions that are driving it.

“Continued increases in greenhouse gas emissions will increase the amount of climate change the United States will experience in the next 100 years,” the report said. “Limiting the increase in greenhouse gas emissions will reduce the rate and amount of climate change during this period.”

The report does not mention, however, the contribution of the U.S. agricultural industry itself to climate change.

In 2010, the Environmental Protection Agency found that the agriculture sector accounted for 7 percent of U.S. greenhouse gas emissions, primarily from large-scale industrial cattle ranching.

Electricity production through the burning fossil fuels such as coal, oil and natural gas remains the largest source of greenhouse gas emissions, accounting for 34 percent, followed by transportation (27 percent), industrial activity (20 percent) and commercial and residential activity (11 percent).

Globally, however, industrial agriculture accounts for 14 percent of all greenhouse gas emissions, surpassing transportation (13 percent), according to the U.N. Intergovernmental Panel on Climate Change.