Agroecosystem restoration through strategic integration of perennials

A dominant trend in arable farming systems worldwide is the replacement of large areas of perennial vegetation with a small number of annual crops (Green et al., 2005). Some of this change occurs as native vegetation is replaced by annual crops, but change in the latter half of the 20th Century has also occurred through the simplification of diverse systems that formerly included perennial forages and annual crops (Bullock, 1992). Extreme examples of these processes can be seen over the last century in the U.S. Midwest, where prairies, savannas, forests, and wetlands have been almost completely replaced by corn and soybean (Figure 1). Landscape simplification and the expansion of annual crops have been accompanied, and to a large extent driven, by the broad scale use of synthetic pesticides and fertilizers, new cultivars and machinery, and soil drainage and irrigation. The resulting increases in yields and farm labor productivity are well documented (e.g., Cochrane, 1993). Less well documented but increasingly evident are the unintended consequences of simplified, intensive farming systems, including contamination of drinking water sources and coastal areas by soil sediment, pesticides, nitrates, and phosphates; threats to human health and non-target plant and animal species resulting from …