The Yao people know and eat more WEPs compared with local people from other ethnic groups such as Zhuang and Han. For historical reasons, the Yao people live at higher altitudes in the mountains than other ethnic groups. The Yao people also have a reputation of ‘mountain people’, who live on mountains, depend on mountains, and eat on mountains [32]. Historically, the Yao people moved from one mountain to another from year to year, because of the depletion of natural resources [32]. From the long-term interaction with nature, the Yao people developed their own knowledge about natural environment and resources [31]. In contrast, the Zhuang and Han people live in the plateaus, running a rice-based agricultural system, with more cultivated vegetables and fruits, and less access to wild species [32].

On the contrary, in Jiangcheng, a boundary county between China, Laos and Vietnam in south-west China, the WEPs collected by Yao people share great similarity with other neighboring ethnic groups like Dai and Hani, which might because of their long-term interaction at the similar geographic environment [27]. While most of the WEPs were also herbaceous, the most used parts were tender stem and leaf as a potherb, rather than fruits. Fruit and rhizome were also among the topmost used parts. Another difference was that Yao people in Jiangcheng also use WEPs as sour condiment, which was not recorded in Jianghua [27]. This might result from the regional variance of environment, as Jiangcheng is located in the tropics while Jianghua is subtropical. People from the same ethnic group but have lived in different areas have developed different uses and knowledge of plants accordingly, which also contribute to the differentiation of different branch groups among the same ethnicity.

Many other studies on WEPs have been done using similar ethnobotanical methods in other areas in China. Though study areas were different, the results share similarities in many aspects such as that the majority of WEPs were herbaceous; most frequently consumed plant parts were fruits, young leaves, and stems; the most common way of consumption was eating freshly or cooking as vegetables; WEPs have multiple uses except food, like medicine, fodder, ornamental etc.; plant family with most species were among Rosaceae, Asteraceae, Fabaceae, Poaceae, Liliaceae etc. This phenomenon is consistent with the study of useful vascular plants in China [45]. Differences lie in the total number of species gathered as WEPS, fewer in Northern China and areas with higher altitude compared with Southern China in general, e.g. inner Mongolia [26], Qinling [46] and Tibet [23, 47] V.S. Yunnan [24, 27, 28, 30, 48, 49], Sichuan [25], Guangdong [50], Guangxi [51], Guizhou [29], Hunan [52]. This might be because of biogeographical reasons. In Southern China, the climate is much warmer and more humid, and plant species are more diverse. Relatedly, cultural diversity is also richer in Southern China, such as the number of ethnic groups within one province might be much higher in the south than in the north, a typical example is Yunnan, where there are more than 30 different ethnic groups. Specific ethnic groups also have unique patterns in the use of WEPs, such as in Tibet, WEPs were also used for religious ceremonies [47].

One main target in collecting WEPs is for starch, mostly rhizomes and tubers, which have served as famine food and saved people through tough times. The Yao people collect Canna edulis, Pueraria lobata, wild yams (Dioscorea cirrhosa and Dioscorea polystachya), and ferns like Cibotium barometz and Pteridium aquilinum var. latiusculum (Table 2). After collecting, the starch from WEPs is mixed with sticky rice powder into diverse cakes, called baba in local language (Fig. 7), to support them through starvation. The elderly think baba from WEPs is much more delicious than those made from cultivated grains today, even though it demands more time and labor. The modern baba sold in local farmers’ markets are made from Oryza sativa, Zea mays and Sorghum bicolor in Jianghua (Fig. 7). Culturally, the Yao people consume baba on a daily basis. The first author participated in the process of making baba from pumpkin (Cucurbita moschata), taro (Colocasia esculenta) and rice (Oryza sativa) in an interviewer’s house in October, 2018 (Fig. 7). Additionally, the Yao people will also make aibaba by adding tender leaves of Artemisia argyi to control intestinal parasites. Zongzi, a wrapped baba, is viewed as a cultural food for Chinese symbolism [53]. As a special form of baba, zongzi is also very common and popular in Jianghua (Fig. 7), especially during the Dragon Boat Festival. Baba can be regarded as a cultural identity food for the Yao [54].

Baba—a cultural identity food. a Gaoliang baba (Sorghum bicolor (L.) Moench). b Undyed (in white) and dyed baba (in yellow, dyed by Gardenia jasminoides Ellis). c Fried pumpkin baba (Cucurbita moschata Duchesne). d Two major forms of zongzi (Wrapped baba) named by their shapes (triangle zongzi and pillow zongzi). e Triangle zongzi sold on local market. f Traditional way of cooking pillow-like zongzi

WEPs are of vital importance to indigenous communities in providing nutrients, increasing dietary diversity, promoting social interaction, reducing economic pressure, and enhancing cultural identity. Yao people in Jianghua gather WEPs because: (1) WEPs are more delicious and flavorsome than cultivated market plants; (2) WEPs are healthier, without artificial fertilizers and pesticide; (3) WEPs are diverse, supermarket selections are too limited to satisfy needs for diverse materials and different recipes; (4) some WEPs have desired medicinal functions; (5) WEP collection is more interesting, e.g., the possibility to find rare but valuable plants; 6) WEP collection is a good way to socialize, e.g., meet other collectors, and to share and cook collected WEPs with families and friends. Some city residents forage WEPs when returning to the countryside home, as a way of recreating childhood experiences. There is a new trend among local Yao people of sharing their unique daily life on social media such as Tik Tok. Similarly, studies in Europe also showed that people harvest WEPs not only to satisfy physical needs but also for cultural needs such as recreation and social purposes [1, 4].

Despite the benefits of WEPs there are doubts and concerns about safety, particularly concerning toxicity. Studies have reported the risks of consuming toxic plants [5, 7]. Illness from consuming wild harvested plants can result from failure in plant identification by confusing similar edible and non-edible plants, or lack of knowledge in processing. Bitterness in plants generally indicates toxicity [7], while the Yao people view bitterness as medicinal and therefore consume many bitter plants. Of the 130 WEPs recorded, five are known to be bitter, reflected in the nomenclature, such as bitter sow-thistle (Ixeris polycephala), bitter bamboo shoot (Pleioblastus amarus), bitter chestnut (Castanopsis sclerophylla), bitter tea (a variety of Camellia sinensis) and man’s bitter vegetables (Patrinia villosa). By eating bitter food, Yao people memorialize their tough history, reminding them that life is not easy, and hard work is necessary for survival. It is believed in Yao medicine that bitterness is good for the liver, and detoxifying, clearing extra heat and reducing blood pressure [32]. Therefore, the reasons and risks/benefits of eating bitter WEPs and other risks such as toxicity merit further investigation.

According to Chinese folk wisdom, for enhancing body function, medicine is good, but food is better. In our study, 54.5% WEPs were also used as medicine (Table 2), and Yao folk doctors commonly prescribe these plants. In China, some recipes use specific combinations of food and medicine, cooked together to enhance healthy function. Research on Hakka revealed 42 medicinal herbs were used in soup in Fujian for health benefits [55]. Another common medical use of wild plants by the Yao was taking herbal baths. Similarly, former studies also showed Yao people in Guangxi and Yunnan made use of various wild plants in medical herbal bath, especially after giving birth [34]. Previous studies showed that one popular way to consume WEPs was as recreational beverages such as tea, tea substitute and alcohol [5, 27, 37]. WEPs were either brewed into or infused in alcohol by Yao people. In Jianghua, the three most welcome “tea” (or “cha” in Chinese) varieties are Tengcha, Kucha, and Gunguncha, consumed frequently for their potential medicinal functions and served to visitors. Compared to normal tea (Camellia chinensis), tengcha (vine tea) is a tea substitute made from a wild climbing plant, Ampelopsis grossedentata. The special white powder on surface after fermenting is thought to be beneficial to health by Yao people. The major antioxidant compound in vine tea is dihydromyricetin [56]. Studies suggested tengcha has multiple physiological functions such as anti-inflammatory [57], anti-bacterial [58], anti-tumor and anticancer effects [59]. Unlike Camellia sinensis, and despite the multiple functions and potential uses of tengcha, it is not yet cultivated. If local government can develop planting tengcha at scale, combined with cultural tourism, it will be helpful to provide job opportunities, increase incomes, and enhance cultural confidence.

As the younger generation moves to urban areas for better jobs, education and more convenient life, they lose touch with traditional lifestyle, and become more ‘plant blind’, ignoring or overlooking plants in society and daily life [60]. Some lose interest in old-fashioned traditions, others doubt the safety, hygiene, or nutritional value of WEPs. Compared with collecting WEPs, buying food from markets is much more timesaving and convenient. However, mankind relies on a narrow range of foods, which is problematic in feeding the growing population and providing all necessary nutrients [61]. WEPs can have high nutritional values, providing diverse sources of fiber, vitamins, proteins, carbohydrates, fatty acids, and bioactive compounds [62, 63]. WEPs provide ingredients to diversify people’s diets [64], and improve diversity and resistance of food ecosystems under climate change [5, 6]. A Norwegian study indicated that the ethical motivation driving vegetarianism is environmental and animal rights [65], and WEPs are an ideal option to reduce consumption of animal products.

Ecologically, there is a risk of over-harvesting especially for species with high socio-economic value. Harvesting amounts are not effectively controlled, which may threaten slow-growing species, such as those foraged for underground parts, e.g., Cibotium barometz, Dioscorea alata, Smilax glabra, and etc. Digging for collection of such parts causes much disturbance to the microenvironment and may greatly impact the habitat and local ecosystem. Nevertheless, there is a Yao folk consensus concerning protection of wild gathered plants such as ‘collecting bigger plants and leaving smaller plants’ and ‘harvesting older plants while leaving the root system’. Similar folk wisdom occurs in Norway, which was assessed as having sustainable foraging [1]. Study among the Yao people in Vietnam also indicated TEK would enhance resiliency to climate change if better integrated and applied into adoption of new plans and policies [66].

With the building of the Centian River Dam, the local environment has been going through huge changes in recent years. The river had historically bred rich diversity. However, the new dam has lifted the waterline by more than 50 m, submerging ecosystems that used to be a great source of wild food. Meanwhile, the local government has tried hard to develop touristic villages for poverty alleviation, which destroyed some agricultural systems and landscapes. Local villagers changed from farmers and foragers into businessmen or performers, abandoning much of their traditional way of life. Similarly, an ethnobotanical study on traditional medicinal plants used by the Mien (Yao people) in Thailand found the erosion of traditional knowledge and practice among young generations due to transition of lifestyle and also moving away from mountains [67]. Studies show that land use change, urbanization, overexploitation and climate change are major threats to the conservation of WEPs and related TEK [6, 68]; these are also affecting the Yao people in Jianghua.