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

cold temperate (USDA zones 4–6), boreal (USDA zones 2–3), and arctic (USDA zone 1). Rain- fall categories are humid (1000+mm rainfall/yr), semi-arid (250-1000mm rainfall/yr), arid (0- 250mm rainfaal/yr), and aquatic. Shade tolerance was also assessed. Carbon sequestration In order to assess the potential carbon sequestration potential of PVs, we must first estimate per-hectare sequestration rates, adoption rates, and total potential adoption. Existing data are sparse for all aspects of this question. Despite this, an approach based on available data and a range of plausible scenarios is useful for exploring the and defining the boundaries of the solu- tion space for these critical questions. In order to model potential impact, we therefore devel- oped twelve scenarios built around estimates for carbon sequestration rate, and a range of plausible values for rate of adoption, potential (maximum) scale of adoption, and the ratio of adoption between woody and herbaceous PVs. We consulted the research literature for the available data on per-hectare carbon sequestra- tion impacts of individual PVs, as well as sequestration rates for relevant farming systems (Table 1), categorized by a three-level classification scheme: a broad top-level dichotomy of (1) woody perennials and (2) perennial vines and herbs, and then production system and sample species or system. The average rate for woody PVs is 3.7 tC/ha/yr, while that of perennial vines and herbs is 0.43 tC/ha/yr/. Carbon sequestration rates of PVs, where known, are shown here. Rates for farming sys-

tems that match PV production systems are shown as well. The ratio of Mha in woody to non-woody PVs is important to scenario development, as woody PVs have much higher sequestration rates. Currently there at 1.7 Mha of woody Pvs and 1.6 Mha of herbaceous perennial PVs [16]. The scenarios assume that 25%, 50%, and 75% of new adoption is woody. The potential scale of adoption of PVs is also necessary to calculate climate impact. One set of scenarios assumes that total global vegetable production area remains constant at 58.2 Mha. A second set of scenarios assume that world vegetable production area triples to 174.5 Mha, in Table 1. Carbon sequestration rates of PVs. PV Category PV production system type Sample species or system Sequestration rate MgC/ ha/yr Source Woody perennial crops Orchard and plantation; full-sized woody plants for flowers, fruits, and unripe seeds Convert cropland to orchard 3.5 [54] Olea europaea 2.6 [55] Bactris gasipaes 5.1 [56] Dacryodes edulis 7.8 [57] Tree crops–temperate 2.1 [58] Tree crops–tropical 1.8–10.0 [58] Bamboo for shoot production Bamboo plantations 6.0–13.0 [59] Coppiced woody plants for edible leaves Fodder tree blocks 0.1–0.5 [54] Short rotation coppice 1.18 [60] Average sequestration rate 3.71 Perennial vines and herbaceous crops Perennial vines Vitis vinifera 0.3–0.8 [61] Robust perennial herbs (over 2m height) Giant biomass grasses 1 [62] Perennial grains 0.3–0.5 [63] Ordinary perennial herbs (under 2m height) Residential landscape with herbaceous perennials 0.0–0.1 [64]

Average sequestration rate 0.43 https://doi.org/10.1371/journal.pone.0234611.t001 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 5 / 19