Intensive agriculture decreases the chemical complexity of dissolved organic matter in nearby rivers, suggests a paper online in Nature Geoscience. Simplification of organic material could affect the release of carbon dioxide from river systems.

Henry Wilson and colleagues examined the quality of organic matter dissolved in 34 rivers in Ontario, Canada, along a gradient of minimal-to-intensive agriculture. The researchers found that higher levels of cropland cultivation and usage resulted in a decrease in the structural complexity of the dissolved organic matter in the river. They suggest that the reduced complexity of organic matter could lead to elevated rates of microbial carbon-processing. As a result organic matter may be more readily removed from rivers ? either through storage in sediments or through release into the atmosphere as carbon dioxide.