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

Regarding the top ten species for each key nutrient, the superior performance of perennial species is notable, particularly woody perennials. It is also noteworthy that, of the crops tracked by FAO, only cassava leaf makes it onto these lists. It would appear that the vegetables which are most widely grown and marketed are not those best suited to addressing nutrient deficien- cies. An exception is folate, for which few vegetables, annual or perennial, exceeded the set of reference vegetables. Folate, however, is also the least-reported nutrient of the nine nutrients we examined (81 data points, compared with 221 for calcium). Some species are found on the multi-nutrient tables for both traditional malnutrition and industrial diet deficiencies. These species represent extremely powerful tools to address nutri- ent deficiencies. They include the woody plants Cnidoscolus aconitifolius, Manihot esculenta, Moringa oleifera, Morus alba, Senna obtusifolia, S. sophera, and Toona sinensis, the perennial vines Momordica cochinchinensis and Vitis vinifera, and the perennial herb Solanum aethiopicum. The meta-analysis approach taken in this study does not account for differences between variety, climate, farming system and practice, and soils, all of which can impact nutritional composition. [67]. Further research should account for and determine the reasons for varia- tion within species. Data on sequestration rates of PV species, in various production systems, are needed. This would allow improved climate impact projections. Conclusions

Perennial vegetables represent a very large and neglected group of crops. They have potential to increase carbon sequestration in vegetable production and address nutrient deficiencies affecting over 2 billion people. They offer an important set of tools to tackle some of the key challenges of the 21st century. This study found that the vegetables which are most widely grown and marketed are not those best able to address nutrient deficiencies, with a few exceptions. As world vegetable pro- duction needs to be tripled to provide healthy diets for all, efforts should be made to incorpo- rate PVs in the new production areas. It is especially good news that tree vegetables are among the most nutritious, feature high sequestration rates, and represent over a quarter of PV species. Note that tree vegetables are not confined to the tropics, with multiple species for colder climates, even including cold drylands. The identification of species with high levels of multiple key nutrients offers to potential to highlight these crops in development and nutrition campaigns. Regional programs could iden- tify species suited to the climate and targeted to the specific nutrient needs of the population. Given the wide distribution of PVs, species native to a given region can be prioritized. Perennial vegetables can play a role in the perennialization of agriculture to increase carbon sequestration in soil and perennial biomass. Their potential for use in agroforestry systems, especially given the abundance of shade-tolerant PV species, is notable given the high seques-

tration rates of agroforestry systems. It should be noted that some PVs sequester far more car- bon than others, notably the full-sized woody plants like trees, palms, and bamboos. Time and time, again around the world, over the course of thousands of years, farmers and gardeners have taken these species into cultivation. Their highly desirable biodiversity, carbon sequestration, and nutrition impacts should be a major motivation to research, cultivate, and promote PV crops. This study is intended as a launching point for initiatives to increase the adoption and utilization of these remarkable crops. 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 14 / 19