The scientists cite environmental impacts such as greenhouse gas emissions, soil degradation and pollution as reasons for the need to change practices.

"Quite frankly, we have to make this transition to sustainable agriculture," said Liz Carlisle of the University of California, Berkeley and corresponding author of the study.

"The question is: can we be proactive about it so that our institutions and economy are prepared to make the transition in a more intentional way and can we be sure that all rural communities will have access [to sustainably produced goods]."

To assess the level of political and economic support for sustainable agriculture, Ms Carlisle and her colleagues identified USDA-funded projects beginning in 2014 and searched key sections of project reports for major components emphasising sustainable agriculture.

Those components were grouped into four categories: improving system efficiency to reduce inputs including fertilisers and pesticides, substituting more sustainable inputs and practices into farming systems, redesigning agricultural systems based on ecological principles, or strengthening connections between producers and consumers.

The team searched 824 projects accounting for almost $300 million in funding. In many cases, sustainable agriculture was included in projects but not as the primary focus, which the researchers said suggested that significant improvements in sustainable agriculture could be made with additional investments and support.

"Prior to this, there was no clear accounting of how much funding had gone for agro-ecological research," Ms Carlisle's co-author Marcia DeLonge said. "We knew anecdotally that there was a need for more funding, but we needed to understand the numbers better and to understand what research areas might hold the most untapped potential."