Perennial vegetables: A neglected resource for biodiversity, carbon sequestration, and nutrition

It is also a goal of this study to identify standout species with superabundant levels of individual key nutrients. To this end, the vegetables were ranked in order of concentration from highest to lowest for each nutrient. This enabled the development of “top ten” lists for each nutrient, showing the ten crops with the highest levels of the nutrient in descending order. Results Biodiversity PVs are a large and diverse group. They represent a third to half of vegetable crop species and over 7% of all cultivated crops. Most are herbaceous perennials, but over a third are woody plants. Leaves are the most widely used part. There are species suited to virtually all climates where crops are grown. A literature search was conducted for this study with the aim of compiling a comprehensive list of cultivated PVs. This search found 613 cultivated species of PVs. Further analysis broke down these species by cultivation status, form and part used, and climate suitability. The full list is included as supplemental document “Cultivated Perennial Vegetable Species” as an Excel spreadsheet. We approached the goal of assessing the extent of PV cultivation in several ways. Our analy- sis of [25], a reference which is limited exclusively to cultivated vegetables, found 63 fully perennial crops out of a total of 180 vegetable crops, including 37 perennials sometimes grown as annuals. PVs represent 35–56% of the cultivated vegetable species profiled in this source. This study also sought to determine the percentage of all crops which are PVs. Of the 6,000

crop species and subspecies profiled in [26], 470 are perennials cultivated as vegetables, includ- ing 45 perennials sometimes grown as annuals, suggesting that 7.7% of all cultivated crop spe- cies are PVs. Cultivated PV species were broken down by form and part used. Woody plants comprised 36.5%, vines 11.7%, and perennial herbs 50.9%. Of these, 114 (18.5%) are perennials often grown as annuals. Fig 1 shows the part used for woody, vine, and herbaceous perennial PVs. Note that some species have more than one part used. While 80% of global crop production comes from only 14 botanical families [10], this study found that cultivated PVs represent 107 botanical families. The level of domestication of these 613 cultivated PV species was also assessed (see Fig 2). Eighteen (2.9%) are global crops, with over $1 billion USD in sales [6]. Minor global crops, which are cultivated outside of their continent of origin but with sales under $1 billion, account for 30.7% of cultivated PVs. Regional crops, which though cultivated have never been taken up outside of their region of origin, make up 61.0% of cultivated PVs. Historic crops, which are formerly cultivated but now abandoned, are 1.5%. New and experimental crops account for the remaining 2.6% of cultivated PVs. In order to assess the geographic variability of PV crops, we analyzed the full list of culti- vated species to determine climate suitability. While PV species are suited to virtually every cli- mate where crops are grown, diversity follows a familiar latitudinal gradient: increasing with

humidity and temperature, from the poles toward the equator. Fig 3 shows the distribution of PV species for climate types. Many PVs can be, in some cases must be, cultivated in shade. Nine percent of the 613 culti- vated species identified in the study are suited to full shade, and 46% to partial shade. PLOS ONE Perennial vegetables: A neglected resource for biodiversity, carbon sequestration, and nutrition PLOS ONE | https://doi.org/10.1371/journal.pone.0234611 July 10, 2020 8 / 19