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Humans have always used wild plants for various purposes, such as firewood, food, clothing, medicine, and construction (Rapoport et al. 2009). Uses related to edible and medicinal purposes have always been of importance, as they are fundamental to human survival (Toledo et al. 2009). Even today, wild edible plants (WEPs hereafter) help to diversify and enrich modern diets by providing vitamins, minerals, carbohydrates, fiber, proteins, and fatty acids, as well as other compounds beneficial to human health (Pereira et al. 2011, Sánchez-Mata et al. 2012, Romojaro et al. 2013). Wild medicinal plants (WMPs hereafter) can represent an effective and low-cost complement to modern medicine. They may be used to cover the basic health needs of people as they contain biologically active compounds that can prevent and treat physical and mental diseases (Bakkali et al. 2008, Delbanco et al. 2017, Moore et al. 2017). For these reasons, the conservation of traditional knowledge about WEPs and WMPs is not only critical to the livelihood security of human cultures worldwide, but also has a role to play in preserving cultures in modern societies in developed countries (Cunningham 2001).
In the last few decades, knowledge of traditional practices has progressively declined as a result of different processes which occur on a global scale (Rajbhandary & Ranjitkar 2006). Several factors have been identified as causes of this, such as cultural homogenization, consumerism, modernization, and a general fading of interest in and negative perceptions of wild plants, especially among younger generations (Pilgrim et al. 2008, Rana et al. 2012, Turreira-García et al. 2015). Nevertheless, the use of wild plants is determined not only by sociocultural but also by ecological factors (Barreau et al. 2016). The abundance, diversity and productivity of wild plants are usually related to the intensity of the gathering and use of wild plants (Albuquerque & Lucena 2005, Molina et al. 2014, Bortolotto et al. 2015). Furthermore, the direct interaction of people with local environments is one of the most significant ways of traditional knowledge acquisition (Turreira-García et al. 2015, Pardo de Santayana et al. 2017).
Urbanization has been recognized as an important factor behind the decrease of traditional practices (Ahmad et al. 2013). Urban development causes environmental degradation mainly due to changes in land-use and deforestation (Goddard et al. 2009), which directly impacts the quantity and quality of wild vegetation available to be gathered (Ahmad et al. 2013). These changes result in a loss of plant diversity and consequently in a loss of knowledge of plant use (Teklehaymanot et al. 2007).
Since natural landscapes are fragmented or reduced in urban areas, wild plants are only available to be gathered from a few types of environments, mainly anthropogenic disturbed sites, such as vacant lots, pathways, planting strips, railroad tracks, and streets (Díaz-Betancourt et al. 1999, Tardío 2010, Turner et al. 2011, McLain et al. 2014). Conversely, in rural areas natural environments are often well preserved and tend to contain a greater diversity of vegetation, facilitating the gathering of wild plants, a common practice maintained over time by local populations (Bortolotto et al. 2015, Kujawska & Luczaj 2015). Due to the restrictions in resource availability, as well as the sociocultural factors mentioned above, people in cities usually know and use fewer wild plants than those living in rural areas (Sogbohossou et al. 2015).
To maintain the integrity of natural environments and to preserve traditional knowledge and the security of livelihoods, it is necessary to develop strategies for biodiversity conservation (Berkes 2003, Bortolotto et al. 2015). This is particularly important in urban areas because they are subject to greater threats to their biological and cultural diversity (Joos-Vanderwalle 2015). The presence of open green spaces in cities, such as urban forests, has been shown to encourage the use of wild plants for medicinal and food purposes, since they facilitate the interaction of urban inhabitants with nature (Poe et al. 2013).
We explored how the access to natural environments in urban populations contributes to the preservation of traditional practices, reducing the gap in knowledge with rural populations about the use of wild plants. We hypothesize that under a landscape conservation scenario, characterized by the abundance of wild vegetation without restriction of access to natural environments from rural and urban areas, both urban and rural populations would tend to share similar plant knowledge and use similar plants species. To assess our hypothesis, we compared the use of WEPs and WMPs by urban and rural populations and identified the most important gathering environments in Curarrehue. In addition, we looked into the mechanisms of traditional knowledge transmission.
Materials and methods
Study area. The study was conducted in Curarrehue, a province located in southern Chile (La Araucanía region, Figure 1). Curarrehue covers a surface of 1,170 km2 (INE 2019) and is part of the Chilean Winter Rainfall-Valdivian Forest hotspot (Myers 2000). The climate is warm temperate with a dry season of less than 4 months. The mean annual rainfall exceeds 2,000 mm and the mean annual temperature is about 12 °C (PLADECO 2009). Two protected areas surround the study area, Villarrica National Park and Villarrica National Reserve, which combined cover 74 % of the Curarrehue surface (MMA 2011). Primary forest is the dominant vegetation type, mainly composed of Aextoxicon punctatum Ruiz & Pav., Araucaria araucana (Molina) K. Koch, Gevuina avellana Molina, Laurelia sempervirens (Ruiz & Pav.) Tul., Lomatia hirsuta (Lam.) Diels ex J.F.Macbr., Luma apiculata (DC.) Burret, Nothofagus alpina (Poepp. & Endl.) Oerst., Nothofagus dombeyi (Mirb.) Oerst., Nothofagus obliqua (Mirb.) Oerst., and Weinmannia trichosperma Cav. Also, Curarrehue has several bodies of water, such as the Trancura, Maichin and Pucón rivers, and lakes such as the Huesquefilo, Los Patos, Huenfuica, Hualalafquen and Quillelgue (PLADECO 2009). Since these are not private lands and local government programs promote regular visits, the inhabitants of Curarrehue can easily access them and gathering wild plants, especially during the seedfall periods for the pehuén (A. araucana).
Figure 1 Study area in La Araucanía, an administrative region of southern Chile. We included the urban area and the rural area, as well as wild protected areas of the state.
The population of Curarrehue is about 6,784 inhabitants (52.6 % men and 47.4 % women) (INE 2019). About 50.6 % of the population identifies themselves with the Mapuche culture (PLADECO 2009). The economy is based mainly on tertiary industry, such as retail, education, public administration, and domestic services. Primary and secondary industries make up a smaller proportion of the economy and include activities such as agriculture, hunting, and the production and manufacture of wood and cork products (PLADECO 2009).
Data collection. Field research was conducted during the summer of 2017 through semi-structured interviews with 121 participants, using open-ended questions. The interviewees were split into two groups, based on the type of area where they live: rural and urban. The rural area was defined based on functional and demographic features: low population density and non-urbanized land used mainly for agricultural, agro-industrial, extractive, forestry and environmental conservation activities, and non-concentrated dwellings. Conversely, the urban area was defined based on characteristic population features: high population density and the presence of all types of infrastructure; as well as by functional characteristics: activity and employment concentrated in the secondary and tertiary sectors, with a lower participation of the primary sector. From these definitions, our rural population included people living in a non-urbanized area at least 5 km away from the urban core, and consisted of 57 interviewees (54.4 % men and 45.6 % women) whose age was 48.4 years ± 2.4 (mean ± standard error; range: 19 to 86). On the other hand, our urban population considered people living in the urban center and consisted of 64 interviewees (46.9 % men and 53.1 % women), which age was 49.7 years ± 1.9 (range: 19 to 82). For the urban group, the interviewees were approached from public spaces within the urban core (squares, bus stops, shopping centers), asking to confirm if they permanently reside in the urban area of Curarrehue or if they were just visiting the urban center. Also, we knocked on the front doors of houses distanced by at least 125 m and then interviewed those who were willing to take part in the study. For the rural group, we knocked on the front doors of houses in the rural area, selecting houses at least 1 km apart to cover the largest rural surface. Interviewees were asked to provide a list of WEPs and WMPs they usually gather. Wild plants were defined as “plants gathered from the wild that are not grown in gardens or agricultural systems but grow without human intervention”, requiring confirmation for controversial species that occur spontaneously but are also usually cultivated. For each species we asked: which plant part they used, the mode of use (preparation or application), and the type of environment from which the plant is gathered (forest, riparian and disturbed areas). In addition, we asked about the sources of knowledge through which interviewees learned about the uses of WEPs and WMPs (e.g., parents, grandparents, local people).
In order to identify the mentioned taxa, pictures and herbarium specimens were shown to interviewees and in some cases, short walks through the locality were carried out to identify and collect samples. The collected specimens of plant species were deposited in the herbarium at the Pontificia Universidad Católica de Valparaíso (UCVA). To standardize scientific names, the plant inventory was compared with The Plant List (www.theplantlist.org/), the most comprehensive working list of all plant species (Kalwij 2012).
Data analysis. Based on the collected information, we compared the mean number of WEPs and WMPs used per interviewee in rural and urban populations using the Mann-Whitney test. Also, we built a quantitative “interviews x species” matrix to assess the richness and diversity of WEPs and WMPs used by rural and urban populations. Richness was estimated as the number of species mentioned by each population. Diversity was evaluated as a measure of the heterogeneity of the number of reports of the species (frequency of use) by using the Shannon-Weiner index, an index used in ecology modified for ethnobotanical studies according to Begossi (1996) as:
Both richness and diversity were calculated from rarefaction curves using 999 randomizations and sampling without replacement by using iNEXT (Hsieh et al. 2016). To make comparable observations between populations with different numbers of interviewees, extrapolations were performed to end 150 interviews, and then we compared both estimators to 100 interviews. Differences were considered to be statistically significant when 95 % confidence intervals did not overlap. In order to evaluate the similarity of WEPs and WMPs used between both groups of populations, we conducted a one-way analysis of similarities (ANOSIM) based on Bray-Curtis distance and using 999 permutations. Then, a similarity percentage (SIMPER) analysis was used to identify the main species responsible for the differences observed between the populations. Furthermore, we evaluated the most important environments for collection by comparing the mean number of WEPs and WMPs gathered from each type, using the Kruskal-Wallis test with post hoc Dunn test.
Finally, to highlight the differences and similarities in the patterns of use of wild plants by the studied populations, we grouped plants based on categories related to the illnesses, conditions or disorders they are used to treat (illness category for WMPs) and the mode they are consumed (edible category for WEPs). Illness category was subcategorized as: articulatory system diseases and traumatic injuries (articular degeneration or traumatism), circulatory system diseases (diseases that affect the heart or blood vessels), dermatology diseases and skin injuries (diseases and conditions that affect the skin, hair, and nails), digestive system diseases (diseases and disorders of the digestive tract), metabolic disorders (deficiencies in enzymes involved in the metabolism), respiratory system diseases (conditions that affect organs and tissues making breathing difficult), urogenital system diseases (problems that affect the urinary and genital tracts), and others (including headache, fever, sleep disorders, and depression). On the other hand, edible category was subcategorized according to the way of consumption of wild plants as: beverages (plants used to elaborate cold or hot herbal infusions due to their pleasant taste, without medicinal purposes), condiments (plants used for flavoring beverages), flours (plants whose seeds are ground into powder and used as flour for making bread and others), fruits (plants whose fruits are eaten raw or cooked), green vegetables (plants with shoots eaten raw or cooked), seeds (plants whose seeds are eaten raw or cooked), and others (plants who are used as preservatives). These categories allowed us to identify the most commons purposes for which plants were used.
All statistical analyses were conducted using the software R version 3.4.2 (R Development Core Team 2017), except ANOSIM and SIMPER, for which we used the software PAST version 3.14 (Hammer et al. 2001).
Wild edible and medicinal plants definition. There is not a single definition for wild edible and medicinal plants. However, the treatment for wild plants in our study derives from Heywood’s definition (Heywood 1999), which has been modified as: “plants species, native or exotic, that grow spontaneously in self-sufficient populations in natural or disturbed ecosystems and can exist independently of direct human action”. This definition also considers those plants that probably escaped cultivation but can grow without human intervention. Thus, WEPs were considered as those wild plants that can be used as food and WMPs as wild plants that can be used to treat or prevent some illness.
Results
Wild edible and medicinal plants used in Curarrehue. We recorded a total of 61 species of vascular plants used in Curarrehue. Of these, 55 species were WMPs and 27 species were WEPs (21 species were used both as food and medicine) (see Appendix 1). The patterns of use for WEPs and WMPs were similar between the rural area and the urban area, showing that people from both population types use local plants for the same purposes and with a similar frequency of use (Tables 2, 3).
Digestive system diseases and urogenital system diseases were identified as the illness categories with the greatest number of reports in the two studied areas (rural: 113 and 30, respectively; urban: 113 and 35) (Table 1). Most of the WMPs were used because of their digestive properties as herbal infusions after meals, which was indicated as a common practice in Curarrehue. However, other uses of WMPs were mentioned as circumstantial or infrequent, except for interviewees who use plants to treat a permanent medical condition (e.g., diabetes). The most used WMPs by the interviewees was menta (Mentha suaveolens Ehrh.) (rural and urban: 25 reports), followed by manzanilla (Matricaria chamomilla L.) and matico (Buddleja globosa Hope) in rural (13), and maqui (Aristotelia chilensis Stuntz) in urban (18).
Table 1 Illness categories of WMPs used in Curarrehue by rural and urban populations.
| Rural population | Urban population | |||
|---|---|---|---|---|
| Illness categorya | No. used species | No. of reports | No. used species | No. of reports |
| Articulatory system diseases and traumatic injuries | 4 | 14 | 5 | 8 |
| Circulatory system diseases | 4 | 9 | 3 | 15 |
| Dermatology diseases and skin injuries | 7 | 13 | 6 | 12 |
| Digestive system diseases | 18 | 113 | 13 | 113 |
| Metabolic disorders | 7 | 15 | 2 | 3 |
| Respiratory system diseases | 13 | 19 | 8 | 16 |
| Urogenital system diseases | 13 | 30 | 10 | 35 |
| Othersb | 15 | 25 | 8 | 19 |
a Several species were mentioned to be used to treat more than one illness
b Including headache, fever, sleep disorderes, and depression
Fruits and seeds were the food categories with the greatest number of reports in both areas (rural: 172 and 66, respectively; urban: 140 and 60) (Table 2). In general, species with edible fruits and seeds were highly valued by rural and urban inhabitants. Fruits were perceived as being nutritious and seeds as a key resource for obtaining flour and derived products. In both the rural and the urban area, the most mentioned edible species were maqui (A. chilensis; 33 and 39 reports, respectively) and pehuén (A. araucana; 33 and 32), which were also gathered to be commercialized in local and non-local markets, mainly by rural inhabitants. Beverages category was also important for both populations (rural: 12 used species and 40 reports; urban: 8 and 31), being Mentha pulegium L. and M. suaveolens the most widely used species, employed as herbal infusion because of their pleasant taste and smell. On the other hand, the least important categories were green vegetables with only three species used and others, with a single species mentioned by a rural interviewee who used Ribes magellanicum Poir. to curdle milk.
Table 2 Edible categories of WEPs used in Curarrehue by rural and urban populations.
| Rural population | Urban population | |||
|---|---|---|---|---|
| Edible categorya | No. used species | No. of reports | No. used species | No. of reports |
| Beverages | 12 | 40 | 8 | 31 |
| Condiment | 5 | 8 | 7 | 23 |
| Flours | 2 | 12 | 2 | 8 |
| Fruits | 15 | 172 | 11 | 140 |
| Green vegetables | 3 | 26 | 3 | 7 |
| Seeds | 2 | 66 | 2 | 70 |
| Othersb | 1 | 1 | 0 | 0 |
a Several species were mentioned to be used for different purposes
b Including preservatives
Overall, interviewees of both the rural and the urban area more frequently cited species that are used as both food and medicine.
Gathering environments. Both rural and urban populations gather WEPs and WMPs from three types of environments in Curarrehue: (i) forest, (ii) anthropogenic disturbed areas and (iii) riparian areas. In the case of WEPs, no differences in the preference patterns of gathering environments by urban and rural populations were observed. Comparisons of the number of WEPs gathered per respondent from the different environments showed statistical differences between the rural area (KW: χ2 = 50.995, df = 2, p < 0.001) and the urban area (KW: χ2 = 69.895, df = 2, p < 0.001). In both cases, forest was identified as the main environment from which WEPs are gathered, followed by disturbed areas and riparian areas as the least used, with significant differences between each of the pairs (Dunn test: p < 0.05; Table 3).
Table 3 Number of WEPs and WMPs gathered by rural and urban populations from different environments of Curarrehue (forest, disturbed and riparian areas).
| Gathering environments | Number of WEPs gathered per respondent (mean ± standard error) | Number of WEPs gathered | Number of WMPs gathered per respondent (mean ± standard error) | Number of WMPs gathered |
|---|---|---|---|---|
| Rural population | ||||
| Forest | 2.09 ± 0.2a | 17 | 1.67 ± 0.2a | 24 |
| Disturbed areas | 1.26 ± 0.2b | 6 | 1.44 ± 0.2a | 21 |
| Riparian areas | 0.30 ± 0.06c | 2 | 0.44 ± 0.08b | 4 |
| Urban population | ||||
| Forest | 1.98 ± 0.2a | 16 | 1.17 ± 0.2a | 17 |
| Disturbed areas | 0.70 ± 0.1b | 4 | 1.33 ± 0.2a | 17 |
| Riparian areas | 0.13 ± 0.04c | 2 | 0.27 ± 0.06b | 3 |
Different letters represent significant differences (p < 0.05)
No differences were observed for WMPs between the two populations in terms of the preference patterns of gathering environments. However, significant differences in the number of species gathered from the environments were found between the rural area (KW: χ2 = 19.498, df = 2, p < 0.001) and the urban area (KW: χ2 = 24.402, df = 2, p < 0.001). In both cases, disturbed areas and forest were preferred for gathering WMPs, which showed no significant differences between them (p > 0.05) but differed significantly from riparian areas (Dunn test: p < 0.05; Table 3).
Traditional knowledge acquisition. In Curarrehue, traditional knowledge about WEPs and WMPs was transmitted from different sources (on several occasions through more than one), but mainly from relatives. In both populations, the vast majority of interviewees mentioned that they had learned it from their parents (rural: 61.4 % of the cases; urban: 60.9 % of the cases) or grandparents (rural: 31.6 % of the cases; urban: 14.1 % of the cases) during their childhood. In addition, the main activities involved in the process of knowledge acquisition were participating in the gathering of WEPs and WMPs mainly from the forest for both populations, and drinking “yerba mate” infusion (Ilex paraguariensis A.St-Hil.) in the case of the rural population. A small proportion of the interviewees from the rural population (15.8 %) indicated that they acquired the knowledge from other sources, such as educational regional programs of rural development and from ñañas and machis (old grandmothers and female herbalists belonging to the Mapuche people, respectively, in Mapuzungun language). On the other hand, 12.5 % of the interviewees from the urban population affirmed it was by reading digital books on the internet. Finally, 8.8 % of the rural population and 12.5 % of the urban population mentioned that they learned it through conversations with elderly rural people of Curarrehue and by watching them gathering WEPs and WMPs from different environments that often are subsequently sold in local markets.
Richness, diversity and similarity of the species used by rural and urban populations. We observed that the mean number of WEPs and WMPs used per respondent was greater in the rural area (WEPs: 3.65 ± 0.3; WMPs: 3.54 ± 0.4; mean ± standard error) than in the urban area (WEPs: 2.81 ± 0.3; WMPs: 2.77 ± 0.3). Nevertheless, no statistically significant differences between populations were found, neither for WEPs, nor for WMPs (p < 0.05). On the other hand, rarefaction curves showed that the rural population use a greater richness of WEPs species than the urban one (Rural: SRAR100 = 26.28 ± 5.0; Urban: SRAR100 = 24.57 ± 5.7), as well as WMPs species (Rural: SRAR100 = 60.82 ± 11.1; Urban SRAR100 = 40.91 ± 5.6), although significant differences were observed only for WMPs (Figure 2 A, B). Furthermore, the diversity of used WEPs species was also greater in the rural area (Rural: HRAR100 = 1.32 ± 0.2; Urban: HRAR100 = 1.26 ± 0.2), as well as the diversity of WMPs species (Rural: HRAR100 = 3.38 ± 0.5; Urban: HRAR100 = 2.40 ± 0.3), but statistically different only in the last case (Figure 2 C, D).
Figure 2 Rarefaction curves: A: Richness of WMPs; B: Richness of WEPs; C: Diversity of WMPs; D: Diversity of WEPs. Curves represent rural population (circles), urban population (triangles), interpolations (entire lines) and extrapolations (discontinuous lines).
Finally, with regard to the similarity of the species used in the rural and the urban area, an ANOSIM test revealed no significant differences, neither for WEPs (R = 0.0068; p = 0.245), nor for WMPs (R = -0.0024; p = 0.512). The plants with the greatest contributions to the dissimilarity of used species between populations were pehuén (A. araucana; 22.0 %), maqui (A. chilensis; 17.0 %) and murra (Rubus ulmifolius Schott; 14.2 %) in the case of WEPs, and menta (M. suaveolens; 11.4 %), manzanilla (M. chamomilla; 8.3 %) and matico (B. globosa; 7.5 %) in the case of WMPs, according to the SIMPER test.
Discussion
In Curarrehue, both rural and urban populations gather WEPs mainly from primary forests because these areas contain several species with highly valuable edible fruits and seeds. The remarkable prevalence of forest areas being used for gathering wild foods in Curarrehue supports the notion that protecting this type of environment is important to the conservation of traditional practices in both urban and rural contexts. This idea is presumably applicable to other Chilean regions because several ethnobotanical studies have shown that most WEPs belong to native species with edible fruits that inhabit forest areas (Cordero et al. 2017). However, forests in other regions of the world may contain less diversity of edible species, such as the sclerophyllous forests in central Chile (Cordero et al. 2017). Therefore, it is necessary to evaluate the role that forest areas play in maintaining traditional knowledge and practices of different cultures and in different geographic regions.
On the other hand, most WMPs in Curarrehue are gathered from disturbed areas and forests by rural and urban inhabitants. This pattern has also been observed in some studies (e.g.,Voeks 1996, Caniago & Siebert 1998, Frei et al. 2000) suggesting an explanation based on ecological aspects of WMPs: medicinal plants that inhabit disturbed habitats are predominantly exotic herbaceous species, while those that inhabit primary forests are mainly tree species (Stepp 2004, Albuquerque & Lucena 2005). Herbaceous plants tend to produce a wider variety of secondary compounds for diverse ecological functions, which can be useful as medicine for humans (Stepp & Moerman 2001). The preference for WMPs with short life-cycles shows that people are mostly attracted to plants that contain strongly bioactive compounds (Stepp 2004). Moreover, according to Stepp & Moerman (2001) plants that are closer to human settlements (e.g., disturbed areas) are preferred to be used for medicinal purposes. However, we observed in several cases that plants used to treat illnesses are gathered from forests, despite the proximity of disturbed areas to residential areas, which suggests that preferences in the selection of species between these types of environments are not so evident.
In this study we reported 61 useful wild species, which inhabit mainly forest areas. This number may not be as great as those reported in other regions of South America, as in the case of WEPs used in the Bolivian tropical rainforest (102 species), the Peruvian tropical rainforest (98) or the Argentinian tropical rainforest (76) (Rapoport & Ladio 1999). However, the Chilean flora is quite smaller with only 5,471 species (Rodríguez et al. 2018) and the inhabitants of Curarrehue use a large proportion of the local wild resources available, based on the number of species reported as edible and medicinal in the studied region (Cordero et al. 2017). Regarding the patterns of use of wild plants, we observed similarities and differences with other regions of South America. Some studies have shown that WEPs used are mainly shrubs and trees with edible fruits that inhabit forest areas (e.g., the Andean Patagonian forest of Argentina, Rapoport & Ladio 1999; the Peruvian Amazonia, Lawrence et al. 2005). Other studies have reported patterns of WMPs use very similar to those shown in this work, as in the case of Begossi et al. (2002) for the Brazilian Atlantic forest, where plants were used mainly to treat digestive problems, respiratory diseases, and fever. Nevertheless, despite the similarities with some regions, there are also cases where wild plants gathered from forest areas are not primarily used for edible or medicinal purposes (e.g., firewood in the Bolivian Amazon, Reyes-García et al. 2005). Therefore, preferences for certain resources may be motivated by particular requirements of local populations or by the availability of some plant species. Thus, forest areas may not be relevant for medicinal or edible purposes, but to obtain firewood, construction materials or others.
Most ethnobotanical researches have shown that more species are used for medicinal purposes than for any other purpose (Bennett & Prance 2000), which is consistent with our results since the richness and diversity of species used by both populations were higher for WMPs than for WEPs. Knowledge about medicinal uses of plants is critical for health and human wellbeing, especially in rural populations (McCarter & Gavin 2015, World Health Organization 2013). In our study, the richness and diversity of WMPs were the only metrics compared between rural and urban populations that showed significant differences, being greater in rural than urban in both cases. It is possible that the existence of a great number of drugstores in the urban area of Curarrehue is causing a progressive abandonment of herbal medical systems by local inhabitants and, consequently, the decrease in the richness and diversity of used species. It has been documented that access to modern medicine by local populations can lead to the disappearance of traditional practices (Zank & Hanazaki 2012). However, in the urban area of Curarrehue these practices seem to have been maintained over time.
Knowledge on wild plants is generally acquired from parents (Somnasang & Moreno-Black 2000, Setalaphruk & Price 2007, Turreira-García et al. 2015), through familiarizing with the gathering environment, observing and helping other members of the community (Ohmagari & Berkes 1997, Zarger 2002). In our study, knowledge is acquired mainly from parents and grandparents, through direct observation and by helping them to gather wild plants. The socialization of the ecological knowledge within the family group it is also favored by drinking yerba mate, which is an important part of the cultural identity of many traditional communities from South America. The fact that plants gathering occurs mainly from the forest, confirms the importance of preserving natural landscapes to preserve traditional knowledge (Berkes 2003), because the interaction with the environment is fundamental in traditional knowledge acquisition (Turreira-García et al. 2015). The protection and easy access to natural environments in Curarrehue has contributed not only to improvements in the availability of useful wild vegetation, but also has increased the interaction of people with nature, resulting in effective traditional knowledge acquisition. However, it is possible that other factors not evaluated in this study have also influenced these processes. In some cases, cities develop around populations with a long history of living on that land and rich traditional ecological knowledge, which can cushion the effects of urbanization on traditional knowledge and practices, preventing its extinction (Emery & Hurley 2016). In our study area, some urban inhabitants told us that they learned from elderly rural inhabitants and from ñañas and machis. Even though half of the Curarrehue population has Mapuche ancestry, interviewees mentioned that they did not consider themselves as Mapuche when consulted. This can be explained by the fact that the Mapuche people live mainly in closed communities that we did not visit in this study. However, only a few interviewees mentioned that they have learned from them. According to several interviewees from both populations, Mapuche people usually do not share their knowledge with people outside of their culture, which may explain the reason why their participation in the process of knowledge acquisition is not so relevant for rural and urban populations. On the other hand, the urban center is relatively recent in Curarrehue with only a few decades of existence (PLADECO 2009). In this sense, it is possible that many interviewees migrated to the city at an early age from the rural area, or even that their relatives continue to live in them. Nevertheless, even though migration processes could explain why traditional knowledge has been preserved and transmitted in the last few decades in the urban area, there are no population censuses available that can confirm this idea. The censuses in Curarrehue only consider the area of residence of people in the last five years and were implemented relatively recently, thus it is not possible to assume a cause-effect relationship between historical rural-to-urban migration and traditional knowledge transmission in the urban area.
We did not observe significant differences in the parameters compared between rural and urban populations, except for the richness and diversity of WMPs, which were greater in the rural area than in the urban area. The diversity of types of environments available determines the knowledge and use of wild plants by human populations (Bortolotto et al. 2015). A greater diversity of available vegetation tends to result in a greater diversity of wild plants used as food or medicine by surrounding populations (Ladio et al. 2007). For this reason, the use of wild plants in cities tends to be limited since natural environments have usually been reduced or destroyed, and the availability of vegetation is consequently reduced (Kujawska & Luczaj 2015). Conversely, the urban area in Curarrehue is surrounded by protected natural areas which allow the urban populations to access the natural environmental and therefore to gather a greater diversity of wild plants. Access to natural landscapes is critical to maintain local traditions since the physical environments of communities define the characteristics of their cultural identity (Vianna 2008). Furthermore, a high degree of similarity in terms of WEPs and WMPs use by urban and rural populations was observed, which could be explained by the fact that both populations have access to the same types of environments of Curarrehue. According to Saslis-Lagoudakis et al. (2015), communities surrounded by similar floristic environments tend to share similar plant knowledge and use similar plants species.
Due to the particular characteristics of Curarrehue in terms of size, it may be the case that the findings of this work cannot be extrapolated to large cities. In this sense, it is important to point out that Curarrehue should be classified as a town rather than a city. Since the degree of urbanization differs between towns and cities, its detrimental impact on traditional knowledge within the urban area of Curarrehue could be less severe, explaining the small differences observed between the urban area and the rural area. Furthermore, the rural area represents a great proportion of the total surface of Curarrehue, which as discussed above, could directly or indirectly influence the flow of traditional knowledge from rural to urban. In regions with larger cities and fewer rural areas, the interaction between urban and rural inhabitants may be less significant. Consequently, more industrialized cities with a smaller proportion of rural areas may not exhibit patterns of interaction patterns similar to those observed in this study. Nevertheless, green urban areas are considered to be spaces preferred for gathering by urban inhabitants (Poe et al. 2013), thus, protected areas within or around cities could have a more important role for the gatherers than parks or other public and private spaces, regardless of the extent of the city, especially if these are as easily accessible as in Curarrehue.
The protection of natural landscapes through strategies of public policy may contribute to avoiding the progression of the erosive process that traditional knowledge undergoes, especially in urban contexts. Nevertheless, more studies are still needed for a better understanding of the relevance of protected areas on the preservation of traditional knowledge and gathering practices, given the particular characteristics of the studied area and the varied sociocultural and ecological features of cities around the world.
Conclusion
In this work, we have shown that access to natural environments could have an important role to the maintenance of traditional practices in the urban area and the rural area from Curarrehue, as well as to reduce gaps in knowledge and use of wild plants between local populations. Forest areas contain a great diversity of wild resources, which are preferred for gathering by rural and urban inhabitants. However, disturbed areas have also great relevance for gathering practices in Curarrehue, since these provide a wide variety of medicinal resources used by both populations.
