Database used

Since very little published information was found related to backyards in Tlaxcala, it was decided to use El Padrón de Productores Agropecuarios del estado de Tlaxcala, carried out by the National Institute of Statistics and Geography (INEGI) in 2004 at the request of the State Government; its objective was to obtain basic information on the agricultural and forestry sector, as well as to generate sample frames through which specific studies could be carried out by having a state inventory of land (social, public and common use property) (^{INEGI, 2004}), as is the case of this research; as a member of the work team, a copy of the original database was obtained informally, which consisted of a total of 53 968 basic information cards.

Data used and backyard

The data from the basic information questionnaires was obtained from ejidatarios, communal landholders, small landowners, representatives of agricultural or forestry production groups or any person responsible for land adjacent to the dwelling with agricultural or forestry activity. Given that the complete database consists of 53 967 census Rural Production Units (RPUs), in order to analyze only those that corresponded to the backyard, we considered, first, the definition of Trabanino (2018), which states that "the family garden in Mesoamerica is an agroforestry system with an antiquity of more than 11 000 years; it is located in the surroundings of the domestic unit, it facilitates the care and access to plants without having to travel to the most distant mountains" (p.87); then, from the section land of the responsible person's dwelling, the first question was taken into account that says: between February and August last year, in the land where this dwelling is located, did you have or plant fruit trees or did you plant any crop? Thus, only those RPUs that reported any fruit tree or crop in the area planted next to their dwelling were considered as backyard. This is because both plant and animal species of commercial value are mostly found in backyard conditions, for safety reasons.

Plant and animal species

The reagent applied to find out if the farmer had a backyard area is shown in Figure 1. It was assumed that if the respondent answered yes to P0010101 and P0010202, for example, then he (her) had one or two plant species in the field, respectively.

Figure 1: Reagent to know if you have backyard surface area. Source: ^{INEGI (2004)}.  

In the case of animal species, the item that indicated whether there were animal species in the backyard was: 7 Do you have or raise animals that sleep on the land where this dwelling is located? (P0070001), marking the answer with yes or no. As for other species, these were identified with item 18: On the land where this house is located, on January 31, did you have: 1. hens or chickens, 2. beehives, 3. other animals. This last item is important because working animals were found there.

Class intervals

To calculate the class intervals, the recommendation of ^{Gorgas, Cardiel, and Zamorano (2011)} was followed, "when the number of different values taken by the statistical variable is very large or the variable is continuous... the data are grouped into intervals and a count is made of the number of observations that fall into each interval". The lower and upper limits of the class intervals are shown in hectares.

Size of agricultural crop production units

According to the proposed methodology, 17 131 basic information forms (Rural Production Units, RPU) were used. In a first approximation of backyard size, class values were grouped from 1000 to 1000 m²; Table 1 shows that 93.6% have 1 to 10 000 m² of backyard with crop production. This shows that more than 90% of the backyards in Tlaxcala are less than one hectare in size.

Taking into account that Góngora and Pastrana (quoted by ^{Castañeda, Lope, and Ordóñez, 2018}), stated that the size of the orchards analyzed in the literature ranges from 48 m² in Chemblas, Campeche, to 20 000 m² in Catmís, Tzucacab, Yucatán, as well as ^{Olvera, Álvarez, Aceves, and Guerrero (2017)} reported for three communities in Puebla a backyard size between 300 to 20 000 m², with an average of 2195 m², taking into account the results shown in Table 1, the surface between 1 and 1000 m² was analyzed with intervals of 100 to 100 m between classes.; the results are pointed out in Table 2.

It is observed in Table 2 that the backyard of up to 400 m² corresponds to 85.61% of the RPU, concerning 13 061 RPU out of 15 257 counted. When the average value of the range 0.0001 to 0.1000 hectares is obtained, the average area of the backyard is 0.0215 ha, it is, 215 m²; this is consistent with the 200 m² size reported by ^{CEDRSSA (2018)} for backyard livestock in Mexico.

Plant species in agricultural crop production units

A total of 74 different plant species were detected in 17 131 backyards in Tlaxcala, when the responses referred to the first option. When they mentioned up to two different types of plants, or second option, 10 484 backyards were counted, when there were three species this was in 6 498; when four species were 3404 backyards and up to five species of plants, it was in 1586 backyards; clearly it is observed that the greatest diversity of plants is found in the least amount of these production units. Nine were the most common species: corn, peach, plum, pear, pecan nut, apple, lemon, apricot and fig. Their relative importance is related to the number of species in the backyard. Thus, when only one species was mentioned, corn was the most reported plant (33.67%, followed by peach with 20.29%). When two, three or four types of plants were mentioned, the most important were plum and peach (19.52 and 17.85%, respectively); when up to five species were mentioned, the most important were again maize and peach (13.38 and 12.93%, respectively). However, this does not mean that medicinal and ritual plant species are not found in the backyards; there was just a lack of interest in recording them. It is also important to clarify that agricultural crops are mainly established in rainfed conditions, both in the main plots and in the backyards. Figure 2 shows the main plant species present in Tlaxcala's backyard.

Figure 2: Plant species that are grown at tlaxcalteca backyard (%). 

Animal species in backyard production units in Tlaxcala

The main animal species that are produced in the backyard (mentioned as first option) are shown in Figure 3. It is observed that cattle and chickens, are the most produced, followed by sheep. It is important to mention that of 35 animal species, only 5 are not for human consumption (Figure 3). some species are companion such as dogs and birds. This result coincides with that reported by Castaños (quoted by ^{López, Damian, Álvarez, Parra, and Zuluaga, 2012}), in which the most abundant animal in the backyard are chickens. Also, according to the ^{OECD (2018)}, chicken meat is one of the main sources of protein for the Mexican population. Aditionally, the average number of heads or units per Rural Production Unit for the main species were: 11.89, 4.31, 5.11, 13.01, 11.19, 19.22 and 16.62 for chickens, cattle, pigs, sheep, goats, rabbits and beehives, respectively, for the RPUs that had them.

Figure 3: Animal species that are grown at tlaxcalteca backyard. 

Other animals also important in the backyard are working animals and the turkey (endemic species of Mesoamerica) and ducks; they are mentioned as second, third, fourth and fifth option (Table 3). Horses, donkeys and mules are work animals, while the other two are for human consumption. The percentage that is reported corresponds to the RPU that mention these animal species. Table 3 shows the importance of donkeys, standing out as the third, fourth and fifth option in the "other animals", despite the fact that it is a species at risk of extinction, as stated by Germán Flores (^{Velasco, 2018}). As for the turkey (huexolotl), ^{Pérez (2002)} calls it the king of the Mexican orchard.

It is also noteworthy that the greatest number of animal species is observed in the smaller backyards, i.e., their number and diversity decreases as the surface area of these agroecosystems increases; this was observed for the animal species shown in Figure 3.

Self-consumption-sales

Vegetable crops. It was found that 16 574 RPUs (95.23%) refused to sell the plant species or products produced, while 831 (4.77%) responded in the affirmative. This indicates, therefore, that approximately 5% of the RPUs that have a backyard sell plant species or products. (Table 4). It was also observed that in a backyard area of up to 1000 m², 33.05% sell vegetable species or products, while 66.95% of those who sell have more than 1000 m². This indicates that the smaller the surface area, the greater the self-consumption of agricultural production.

Animal products or species. Table 5 shows the Rural Production Units that sell animal products or species. It is observed that of the RPU that indicated they have a backyard surface and that have or raise animals, 12.93% sell products or species of animal origin, while 87.07% use it for self-consumption. It can be observed that unlike the RPUs that sell plant products, the RPUs that sell animal products are those with areas between 0.0001 and 0.1000 ha (73.7%). Note that 30.61% of Class 1 (0.0001 to 0.01 hectares) corresponds to 682 RPU out of a total of 2 228 RPU that sell products of animal origin. The low percentage of sales of vegetable and animal products, coincides with what was reported by ^{Martínez and Juan (2005)}, ^{López et al. (2012)}, ^{Aznar and Carmona (2014)}, ^{Covaleda, Paz, and Ranero (2016)} and ^{Suri (2020)}, in that backyard food production is mostly for self-consumption or survival.

Table 6 shows the animals or products of animal origin that are most commercialized from the backyard of Tlaxcala. It is observed that the highest percentage of what is sold (of the little that is sold) is related to cows, female pigs and sheep, showing the importance of these species in the backyard of Tlaxcala. Regarding the animal species produced in the backyard, the results found coincide with those of ^{García and Guzmán (2014)}, who found two types of livestock production units (producers), those of self-consumption (91%) whose production is for family sustenance and who also see backyard animals as a savings bank, and commercial units (9%) that sell the production obtained.

Final considerations

As ^{Rivera et al. (2013)} and ^{Ayala, Gutiérrez, and Zapata (2016)} said, climate change is one of the most urgent issues on the world agenda and can affect the productivity of plant and animal species, requiring countries to adopt public policies to mitigate its causes and effects; the backyard is a useful strategy in this regard, by improving energy efficiency, reducing water consumption, planting many trees, reducing the use of gasoline-powered machinery, incorporating native species and incorporating organic waste from the home into the soil (National Wildlife Federation, n.d.).