The Farm Bill makes sequestration possible.

Agriculture generates only 11 percent of total U.S. greenhouse-gas emissions, so reducing emissions from the farm sector, important as it is, can go only so far toward driving total U.S. emissions toward zero quickly and steeply. However, unlike other sectors of the economy, farming also has the potential to help mitigate climate change by absorbing carbon dioxide from the atmosphere through nature’s preferred method of carbon sequestration: photosynthesis.

To use U.S. farmlands and forests as reservoirs for atmospheric carbon would help to reverse a massive loss of soil carbon that began long before the age of mechanized agriculture. In the 19th and early 20th centuries, native grasslands and forestlands across North America were plowed up to make way for corn, wheat, cotton, and other annual crops—replacing vast, biodiverse, perennial ecosystems with plantings of annual monocultures. Extensive root systems, alive year-round, were killed off across hundreds of millions of acres, to be replaced by the sparser, ephemeral root systems of crops that had to be resown with every growing season. For much of the year, there were now only spindly seedling roots or no living roots at all to support the soil ecosystems that had thrived before the arrival of the plow. Consequently, over subsequent decades, countless tons of carbon that had been captured by plants over millions of years went back up into the atmosphere.

Accumulating enough carbon in the soil to mitigate climate change effectively will require switching from annual to perennial crops across most of U.S. farm country, to get soils even part way back to their robust state. Fortunately, the necessity for perennial agriculture is being expressed more widely in this year’s Farm Bill discussion than in previous years, with both the scientific community and grassroots climate and sustainable-agriculture groups calling for more perennial farming systems.