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In recent years, the relationship between the economy and the environment has begun to boom. Scientific research is beginning to focus on quantifying the value of environmental components. Although some natural resources, such as livestock productions, have a price in the market, this does not contemplate in most cases, the wide variety of environmental functions that add a greater economic value. Generally, this environmental component is disregarded when making decisions related to its management (Rangel et al. 2013 and Ferro et al. 2016).
Silvopastoral systems (SSP), as a form of livestock production, appear as a sustainable alternative with high economic value, mainly due to the optimal use that is achieved from the strata that make up its vegetation. In addition, they constitute a natural reservoir of high biomass productions, which not only allows the creation of carbon sump in the form of trees and timber products, but also promotes an increase of the biodiversity in the agroecosystem. This favors the conservation of existing natural resources, as well as increasing food availability for livestock production (Miranda et al. 2008 and López-Vigoa et al. 2017).
It is necessary to economically value the different environmental functions of the agroecosystem under study, as a basis to enhance its integral management and achieve its sustainability. The objective of this study was to determine the environmental economic value of a typical dairy farm in Mayabeque province, based on the exploitation of a silvopastoral system (SSP) with Leucaena leucocephala, after 20 years of continuous production.
Materials and Methods
The study was carried out in Genético 3 dairy farm, a typical tropical dairy, which belongs to the Dirección de Innovación y Tecnologías Aplicadas (DITA) of the Institute of Animal Science (ICA), in Mayabeque province, Cuba.
This facility is located at 22°93 North and 82°01 longitude west, at an altitude of 80 m a.s.l. (National Atlas of Cuba 1989) and has 53 ha of soils, mainly hydrated red ferralitic type (ferralsol). It is based on an SSP with 20 years of exploitation with Megathyrsus maximus Jacq (guinea) grass and the shrub legume Leucaena leucocephala (Lam.) De Wit cv. Peru. Early leucaena population was 9,014 trees per hectare. In the 10th year of establishment, a pruming was carried out, so the legume population decreased by approximately 20%. In the studied year, trees were taller than 2 m, so they were not a food source for livestock, although the SSP continue to provide the rest of the associated environmental benefits. Cattle was composed by Holstein, Siboney and mestizo breed cows. Mean stocking rate was 1.8 LAU ha-1 in the last five years. Animals received a concentrate starting at 3 L milk/d to meet their requirements and achieve the desired milk production. Rotation time was every 57 and 28 d on average, in dry and rainy season, respectively.
In this research, different environmental economic valuation techniques were applied in the SSP. The theory of total economic value (TEV) was the methodological approach used for identifying the environmental goods and services provided by the livestock ecosystem and for evaluating them economically, based on already recognized techniques in the references. This allowed to separate the valuation of environmental goods and services according to their use. Dixon and Pagiola (1998) have reviewed this theory and Ferro et al. (2016) have carried out the economic evaluation of the environmental impacts of an ecological reserve in Havana. Ripka de Almeida et al. (2018) discussed on different methods of environmental economic valuation used in four countries, and Alonso Vázquez et al. (2020) determined the total economic value of a dairy farm in Pinar del Río province.
The TEV is composed of the use value (UV) and the non-use value (NUV) (equation 1). The use value is divided into the direct use value (DUV), which refers to the resource obtained by the development of a certain activity; indirect use value (IUV), which are those benefits derived from the functioning of ecosystems, and option value (VO), which has to do with the possibility of using or not using the environmental resource in the future (equation 2). In turn, the DUV is divided into consumptive, which refers to goods that can be extracted, consumed or enjoyed directly; and non-consumptive, which includes those values derived from recreation and science. Non-use value is divided into bequest value (BV) and existence value (EV) (equation 3). The first refers to the possibility that the resource will be consumed by future generations, and the second refers to the value given to a certain resource, just by knowing that it exists (Pearce and Moran 1994 and Dixon and Pagiola 1998).
For the environmental function of milk production, gross profit technique was used (Rangel et al. 2013 and Ferro et al. 2016). Economic and productive efficiency data, registered by DITA during the year 2020, were used, such as income and expenses of the dairy farm in the period of interest, percentage of milking cows and liters of milk per cow per day.
To determine the carbon stored in soil (CSS), the method used by Miranda et al. (2007, 2008) was applied, based on the area, apparent density, sampling depth and organic matter contained in soil. According to the international literature, CSS is obtained by dividing the percentage of organic matter (% OM) by 1.7 (McVay and Rice 2002). To determine the organic matter, four samplings were carried out, in which two diagonals of the area were selected, and a homogeneous sample was taken in five points, from 0 to 20 cm deep in each, according to Henríquez and Cabalceta (1999). In this way, the CSS in t C ha-1 was obtained from the area (ha), apparent density (t/m3), soil sampling depth (m) and its carbon fraction (% CS / 100). For the economic valuation of this function, the carbon stored in soil in the entire area was multiplied by the average price of a carbon ton in the international market. Ferro et al. (2016) suggested that this price ranges between 5 and 10 USD. In a study developed by Miranda et al. (2008) was 10 USD. Portela Peñalver et al. (2019) took the value of 5 USD, reported by the World Bank, as well as Rodríguez Córdova et al. (2017). This study takes into account the price of 8 USD, since it is an average value of those reported in the references.
Nitrogen fixation and soil fertility were determined from the study of agrochemical indicators of the silvopastoral grassland of the dairy farm. Total nitrogen percentage and pH values were taken into account. Its economic value was obtained from the avoided costs for maintenance inorganic fertilization, as recommended by Milera et al. (2017) for guinea grass.
For soil quality function, visual soil assessment (VSA) was seasonally determined each year, according to Shepherd (2008). Five representative points were taken for the visual determination of texture, structure and consistence, porosity, color, earthworm content, depth of root penetration, ponding, surface coverage and soil erosion. In addition, an undisturbed reference point was taken to have greater precision to determine the natural coloration of that soil, without the effects of cultivation, as well as to compare structure and porosity. The test was always carried out in soils with adequate humidity (between 60 and 80%), for which the “worm test” was carried out. This consists of taking soil in the palm of the hand and rolling it to make a small “worm” that is 5 cm long and 0.4 cm in diameter. If the soil cracks and breaks before finishing, it means that it has adequate humidity. On the contrary, if the soil acquires a “worm” shape, it is because it has too much moisture. Each sampling point was taken in a square 20 cm wide by 20 cm long by 30 cm deep. An index higher than 30 indicates that soil conditions are good, which is due to an adequate management of the system, and this allows rehabilitation labors to be stopped. Its economic value was obtained from the avoided costs for grassland rehabilitation, based on what was reported by Padilla et al. (2009).
In the case of the function of obtaining renewable energies, feasibility of building a biodigester was studied. With it, it is possible to obtain the electric energy, necessary for the daily work at the dairy farm, from the collected excreta. For this, indicators for electric energy production in biodigesters with bovine excretions were used, reported for Cuba by Suárez-Hernández et al. (2018). Savings of the dairy farm, thanks to the payment of electric energy, if the biodigester is built, constitutes an environmental benefit and, therefore, a part of the economic value of this function.
To calculate plant biodiversity of the dairy ecosystem, Shannon (H) index was taken into account, according to the methodology indicated by Shannon and Weaver (1949). The economic value was obtained from the avoided costs, attributable to that environmental service. These were calculated as the product of days necessary to control weeds in the studied area and the cost of mean salary of a worker, for which the research of Miranda et al. (2008) was taken as a reference.
Results and Discussion
In the livestock agroecosystem, six environmental functions were identified, which were grouped by their value category, according to the TEV theory (figure 1). They were, then, economically evaluated, and their VET was determined.
Figure 1 Scheme of total economic value of the livestock agroecosystem, according to the main environmental functions identified
Milk production. The application of gross profit technique allowed to calculate, in 2020, an economic value of 17,669.60 USD as an average for this function. This is an acceptable value, considering that the dairy farm is composed by 87 cows, and 62.4% are under milking, and each one provides an average of eight milk liters per day. These values correspond to those reported in Cuba by del Pozo (2019), who registered between 6-12 L/cow/d. They are very close to those obtained by Iglesias et al. (2017), who reported between 6.7-10.1 L/cow/d in SSP with leucaena, also in Cuba. In this research, milk production per hectare in the year studied was 1,667 L/ha, which shows an adequate use of the land resource. A total of 88,348 liters were produced in that year and the price per liter of milk was 0.20 USD.
With respect to carbon sequestration, in this study values were found in the depth from 0 to 20 cm, which were between 33 and 40 t C ha-1, and an economic value of 292 USD/ha was recorded. The economic value of this function was estimated at 15,476 USD for the 53 ha under study. This figure is a small part of what carbon sequestration function actually represents in the studied ecosystem, since the carbon stored in the aerial and necrotic biomass was not considered. Miranda et al. (2008) stated that 75% of the carbon stored in soil is located between 20 and 80 cm deep, which was not the study object of this research. Alonso Vázquez et al. (2020) found CSS values in the first 14 cm deep, between 26-35 t C ha-1, with an economic value of 213.50 USD/ha, results that are inferior to those obtained in this study.
Regarding nitrogen fixation and soil fertility, it is known that L. leucocephala has high potential, as it is a rich source of protein for animal feed and because it fixes nitrogen to the soil. Studies carried out by Bueno and Camargo (2015) and Cubillos-Hinojosa et al. (2021) indicate nitrogen levels in the soil from 150 to 250 kg/ha/year, due to the effect of the presence of this tree that belongs to legume family. These plants generate symbiosis with soil microorganisms of Rhizobium genus, which create nodules in their roots and allow the symbiotic fixation of N in the soil.
In this study, values of 0.23% of total nitrogen were found in the 0-10 cm layer of the soil and 0.17% in the 10-20 cm layer. These values are quite adequate, since a value of 0.25% is recommended. Lok and Suárez (2014) found mean nitrogen values in ICA soils of 0.23%. This type of soil has medium fertility, as reported by Febles et al. (2015). The pH value was 6.69 and 6.37, at 0-10 cm and 10-20 cm deep, respectively. These figures are very close to 7, that is, to neutrality. This means that nutrients find favorable conditions in the soil to be available for plants, which contributes to the improvement of soil fertility, and brings with it, in that a long term, savings in the fertilization of the area.
In guinea grasslands, it is recommended to carry out a maintenance fertilization per year, of approximately 150 kg/ha of nitrogen, depending on the characteristics of the system (Milera et al. 2017 and Sánchez Hernández et al. 2019). For this, it is necessary to apply around 326 kg/ha of urea, since it contains 46% nitrogen, and it costs 0.27 USD per kilo. The economic value of this function was estimated at approximately 4,726 USD for the entire dairy farm, which is the cost avoided by maintenance fertilization in the 53 ha.
When analyzing soil quality, the VSA always showed values above 30 points during the 20 years of SSP production. This value was considered as good and indicated that SSP and its proper management allowed maintaining favorable conditions in soil quality. Therefore, rehabilitation labors in the system were not necessary during this entire period.
Padilla et al. (2009) reported the cost of various rehabilitation methods for different grasslands. In the case of guinea grasslands without fertilization, these authors reported a cost of 91.85 USD/ha. Therefore, the approximate total cost of a rehabilitation labor in the dairy farm under study would be 4,868.05 USD. This value is considered the avoided cost by rehabilitation labors that were not necessary in the dairy, thanks to the good soil conditions, which constitutes the economic value of soil quality as an environmental function.
Regarding the obtaining of renewable energy, livestock systems have potential for their production, from the excreta deposited by animals. With the construction of a biodigester, electrical energy can be generated, capable of self-supplying the consumption of the production unit. Each animal can excrete 10 kg per day (Crespo 2018) and the dairy farm is composed by 87 animals, which is equivalent to 870 kg per day, which would be 317,550 kg per year. The unit has a dung-heap and 45% of the excretions can be collected in the dairy barn, which is equivalent to 142,898 kg of excreta collected per year. From this amount, it is possible to generate up to 34 MW per year, and the cost price of a MW in Cuba is 260 USD, according to data from the National Electricity Union (Velázquez 2020). The economic value of generation from renewable energy sources is 8,840 USD.
For this function, the calculated value only represents a small portion of the income that can be generated from the biodigester construction. In addition to electrical energy, biogas and organic fertilizer can be obtained (Alonso et al. 2020), which means avoided costs for fuel used for cooking food and for the purchase and application of fertilizers, respectively. Despite the construction of the biodigester is a high investment, its recovery period is short due to economic benefits that can be obtained. Another element that must be considered is that this prevents solid waste accumulation, and it is an effective way to treat these wastes.
With regard to biodiversity, biodiversity index (H) of vegetation in the silvopastoral grassland was 1.07, on average. This indicated that SSP maintained stability in the soil-pasture system, which was evident in the high density of base pasture, decrease of weeds and gradual increase of soil fertility (Lok et al. 2015). This way, the number of weed control activities was reduced. This performance caused vegetation diversity to decrease, as a result of a correct management, which managed to maintain the grass-legume association in the proportions established by technology (Ruiz et al. 2019) to guarantee productivity, efficiency and persistence of the system.
According to the study by Miranda et al. (2008), under similar conditions, the number of days dedicated to weed control per hectare per year was reduced to 10. During 2020, mean daily wage of a worker in Cuba, converted to dollars, was obtained from the information provided by DITA. The economic value of the biodiversity function in the dairy rose to 609.50 USD. This is an acceptable figure, considering that only vegetation biodiversity was considered. For subsequent studies, fauna biodiversity associated with the system must be taken into account, which economic value can be calculated from subjective valuation techniques, such as the contingent valuation method or Delphi technique (Pérez Torres 2016).
The total economic value of the Genetic 3 dairy farm is 984.71 USD per hectare, so total economic contributed value by the livestock ecosystem during 2020 was 52,189.15 USD (table 1). The function that contributed the most to total value was milk production, which is the main objective of the dairy farm. It is followed by carbon sequestration function, which could have a higher value if it had been calculated in the rest of the strata of the agroecosystem. On the contrary, biodiversity function was the one with the lowest economic value. This can be explained because it was only possible to determine the value associated with plant diversity of the system, and it was not possible to calculate the value of the biodiversity associated with fauna. It is important to highlight the superiority of the total economic value of the system, with respect to if only the productive function of the dairy had been considered.
Table 1 Total economic value of Genético 3 dairy farm per environmental functions
| Environmental functions |
Total economic value (USD/ha/year) |
Total economic value (USD/year) |
|---|---|---|
| Milk production | 333.40 | 17,669.60 |
| Carbon sequestration | 292 | 15,476 |
| Nitrogen fixation and soil fertility | 89.17 | 4,726 |
| Soil quality | 91.85 | 4,868.05 |
| Obtaining of renewable energies | 166.79 | 8,840 |
| Biodiversity | 11.50 | 609.50 |
| Total | 984.71 | 52,189.15 |
This integrative analysis of the dairy farm allows managing the livestock activity from a multidimensional point of view. An ecosystem cannot be efficiently managed, if all the generated environmental functions are not taken into account. This way, it is possible to appreciate the different economic benefits that can be obtained from the environmental goods and services offered by these ecosystems, and, thereby, encourage farmers to promote their generation.
In recent years, environmental economic evaluation studies have increased in the Cuban livestock sector. However, these are not enough, considering the function of livestock farming for intensifying environmental problems and its potential for mitigating them (Báez Quiñones 2018).
This study is an approximation to the economic value provided by the Genético 3 dairy farm, taking into account the total of its functions. This research demonstrates the importance of considering environmental economic evaluation as an instrument to achieve sustainable management and reach resilience of livestock ecosystems. This type of exercise should be applied throughout Cuba, so as to promote the inclusion of environmental benefits and costs in the accounting of productive units. This does not mean that it is the only element to consider when making decisions, since it is important that cultural, social and political aspects are also taken into account.
