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

Many PVs are suited to conditions where production of annual vegetables is difficult. For example, PV crops include numerous halophytes, desert species, aquatic species, and shade crops. The many shade tolerant PVs are particularly suited to multistrata agroforestry systems [4]. While many PVs are regional crops, of which little is known outside of the areas in which they are cultivated, a few are widely known and globally traded commodity crops. PVs are cur- rently cultivated on at least 3.3 Mha, 6% of the 52 Mha of world vegetable land. FAO [6] reports 1.1 Mha in table olives (Olea europaea, 10.6 Mha in global production, of which 10% is used for table olives, here defined as a vegetable use, [7]), 1.5 Mha in asparagus (Asparagus offi- cinalis), 0.6 Mha in avocado (Persea americana), and 0.1 Mha in globe artichoke (Cynara scoly- mus). Additionally, India has 38,000 ha in the tree vegetable moringa (Moringa oleifera, [8]). Note that these are only five of the over 600 cultivated species inventoried in this paper, though the area in cultivation of most PVs is surely very small. Greater adoption of a wider array of perennial vegetables could help to address some of the central, interlocking issues of the 21st century: climate change, biodiversity, and nutrition. The great diversity of PVs is a powerful tool to address the loss of crop biodiversity. As perennials, PVs sequester carbon, particularly the woody species. Many PVs are high in the key nutrients needed to remedy nutrient deficiencies that impact billions of people. Crop biodiversity

Crop biodiversity is essential to agroecological food production and multifunctional agricul- ture. However, globally, crop biodiversity is declining, in part driven by intensive, industrial- ized agriculture [9] Eighty percent of global crop production comes from 17 botanical families, just 4% of the total number of plant families [10]. Many benefits can come from increasing crop biodiversity. Increased cultivation of neglected and underutilized perennial crops can increase resilience to climate change impacts. This kind of crop diversification is an important risk-management strategy, especially in the context of the narrowing of crop diversity on which food security depends. Many perennial crops produce in seasons when other crops are not available [11]. Crop diversification at the family level can also reduce pest pressure, as many pests and diseases are family-specific [12]. Climate change mitigation Agricultural production is the source of 12.5% of anthropogenic emissions, yet the agriculture sector also has mitigation potential, including via carbon sequestration [13]. The perennializa- tion of agriculture is one way to sequester excess atmospheric carbon in soils and living bio- mass. This includes transition to reduced tillage perennial crops and use of agroforestry systems which incorporate perennial plants [14]. PVs are well-suited to no-till and agroforestry production systems as they do not require tillage after establishment, and many are shade-tol- erant, making them ideal for the understory of agroforestry systems. For example, in western

China, the PV species daylily (Hemerocallis fulva) is cultivated for its edible flowers in the understory of rows of jujube (Zizyphus jujuba), alternating with rows of annual crops [15]. Nutrition Recent research has shown that for all of the world’s people to consume a healthy portion of vegetables in their diet, global vegetable production would need to be tripled [16]. While underconsumption of vegetables is a global problem, economic and development context pro- duce distinct syndromes of nutrient deficiency: what is sometimes called “traditional” 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 2 / 19