Agriculture can be made far more sustainable by transitioning many annual agricultural systems to perennials. Perennial crops are crops which are alive year-round and are harvested multiple times before dying. Perennial plants are not new to agriculture; plants such as apples and alfalfa are perennials that are already commercially grown and harvested. However, most farmland is devoted to annual agriculture. Cereals, oilseeds, and legumes – all annuals – occupy 69 percent of global croplands. Many of these staple crops can be replaced by perennials by hybridization and other genetic engineering techniques. According to Glover and Reganold (2010), ten of the thirteen most grown cereals and oilseeds can be hybridized with perennial plants.
Conversion of annual fields into perennial fields offers many biodiversity-friendly benefits. One of these benefits is reduced soil erosion. Annual farming leaves fields fallow in between growing seasons and offers less root mass throughout the growth cycle. This leaves fields vulnerable to wind and water erosion. This erosion destroys topsoil which then pressures microbial and plant populations. Perennial plants develop much greater root mass and protect the soil year-round. Perennial farming can reduce erosion rates by up to 50 percent (Pimentel et al., 1997).
Another benefit of conversion to perennial is reduced chemical runoff. Farming chemicals such as fertilizers and pesticides are not completely absorbed by crops and the excess migrates into waters. Agriculture is responsible for 70 percent of water pollution in the United States. This water pollution is harmful to biodiversity in numerous ways. One of the most significant is the creation of ocean dead zones which cover thousands of square kilometers (Dewar, 2007). Perennials can reduce agricultural chemical runoff because their extensive root systems are more efficient at absorbing chemicals. For example, annual crops have been shown to lose up to 35 times more nitrogen than their perennial counterparts (Glover et al., 2010).
Perennial plants also conserve freshwater better than annuals plants. Annual crops lose up to five times more water than perennials (Glover et al., 2010). This means that annual fields require more irrigation which threatens fresh water sources and consequently biodiversity in certain ecosystems.
Finally, perennial agriculture uses less fossil fuel than annual agriculture. Annual systems require fields to be tilled and replanted more often than perennial systems. This incurs a higher fuel usage due to farm machinery. For example, perennial corn farming would reduce fuel usage by 300 million USD of diesel fuel in the United States as opposed to annual corn (Pimentel et al., 1997).
Glover and Reganold (2010) and The Land Institute (2009) show that conversion of significant portions of annual farmland into perennial farmland is an achievable goal. The primary obstacle to the usage of perennial cereals, oilseeds, and legumes are the lack of economically viable plant strains. Advances in genetics and molecular biology in recent years make the development of favorable perennial strains. Research is ongoing to create perennial strains of wheat, sunflowers, sorghum, legumes, maize, rice, and mustard (Glover & Reganold, 2010). Governments need to take initiative to fund this research. A framework for implementation of perennial research is discussed in the implementation section of the website.
Replacing annual crops with perennials holds many benefits for both developed and developing countries (Dewar, J. A., 2007). However, perennial crops are not ready to replace annuals. Genetic development is needed for perennials to compete with the output of annual crops. Engineers need to modify perennial strains to express certain characteristics such as large seed size, palatability, strong stems, and high seed yield (Glover & Reganold, 2010). Developed nations have better capacity for genetically engineering crops so the burden of research and development falls upon them.
The Land Institute, a United States non-profit group devoted to sustainable agriculture, offers a plan for efficiently and effectively converting annual plantings to perennials in the United States (The Land Institutem 2009). The Land Institute’s plan is a 50 year farm bill that aims to convert U.S. farmlands to 70 percent perennial crops from their current state of 25 percent perennials within 50 years. Their approach is two-fold. The first aspect is the development of desirable perennial strains. The Land Institute estimates that the work of 80 plant breeders and geneticists coupled with 30 agricultural and economic scientists would be sufficient to develop the necessary strains and agricultural practices. They estimate that research costs will be 400,000 USD per scientist per year. This equates to a cost of nearly 50 million USD annually. For perspective, the USDA’s FY 2012 budget devotes 1.138 billion USD in discretionary spending towards research (United States Department of Agriculture, 2011). The second aspect of the Land Institute’s plan is a readjustment of farm subsidies. Federal subsidies are designed to work with a predominately annual system. Perennial agriculture can be promoted by reworking subsidies to accommodate, and eventually, encourage perennials.
The Land Institute’s plan can be adapted to any developed government with centralized research and agriculture support. Once perennial strains and agriculture practices are established, they can be spread to developing countries using the current framework of philanthropic organizations.