3.1 LULC analysis.
Figure 3 shows the land uses for the year 2022 on a general scale of the entire basin, indicating a level of intensive land use and a highly anthropic landscape that has functional effects on ecosystems and their capacity to provide services [51].
(Fig. 3. Land Use in the Yuna River Basin 2022)
A complex mosaic in which intensive use of the land prevails, including the ecosystem services related to agriculture and intensive livestock, represented by rice (52,055.28 ha), cocoa (58,388.80 ha), and pasture plantations (168,046.69 ha). These agricultural uses together represent 52.9% of the surface area of the basin, thus determining the configuration of its general landscape [52]. Table 2 summarizes the primary land uses of the Yuna River basin.
Table 2
Land Use in the Yuna Basin 2022
Land use | Hectares | % |
Coniferous forest | 17,430.45 | 3.31 |
Broadleaf forest | 122,086.52 | 23.19 |
Dry Forest | 277.93 | 0.05 |
Mangrove forest | 251.29 | 0.05 |
Rice crops | 52,055.28 | 9.89 |
Cocoa crops | 58,388.80 | 11.09 |
African palm (Oil palm) | 29.97 | 0.01 |
Musaceae | 19,307.59 | 3.67 |
Fruit crops (pineapple, orange, coconut, others) | 2,229.23 | 0.42 |
Subsistence agriculture (dispersed crops) | 2,649.46 | 0.50 |
Coffee crops | 5,225.66 | 0.99 |
Pastures | 168,046.69 | 31.92 |
Bodies of water | 5,114.87 | 0.97 |
Built-up land | 11,900.04 | 2.26 |
Mining | 1,825.29 | 0.35 |
Bushes | 59,708.27 | 11.34 |
Total | 526,527.34 | 100.0 |
Source: Own elaboration |
Table 2. Land use statistics in the Yuna Basin 2022
Rice and cocoa crops (52,055.28 and 58,388.80 hectares, respectively) demand ecosystem services such as intensive water use for the former or soil quality, pollination, or the benefits derived from biodiversity and climate regulation for the latter [53]. Concerning pastures (168,046.69 ha), it is necessary to assert that livestock farming interacts with the heterogeneity of the landscape in a multi-scale process related to the biodiversity of the grasslands, thus contributing to ecosystem services such as soil fertility and erosion control, which this economic activity is related to regulatory services and cultural services such as scenic beauty and its contribution to the Functional diversity of the landscape [54].
Considering the findings in Table 2, about 62% of the land use is anthropogenic (about 326 thousand ha), which includes activities such as agriculture, livestock (pastures), urbanized soils, artificial water bodies, and mining, among other uses. Conservation-oriented uses represent about 26.6% of the basin's surface area (about 140,000 ha), including coniferous forests, broadleaf forests, dry forests, and mangroves in coastal areas. In the same way, land uses related to the agroecosystems of the basin, in this case, giving priority to cocoa and coffee [53, 55], represent some 63,614 hectares, which would mean that the area of the basin intended for the development of an eventual PES program would be about 203,660 hectares, which represents 38.6% of its total area of the basin. When taken together, anthropogenic uses account for just over two-thirds of the basin's surface, which is an indicator of an economically intensive watershed that depends on ecosystem services such as water supply, soil conservation, erosion control, nutrient recycling, pest control or pollination, the latter a key element to the yield of crops such as fruit trees, cocoa or coffee, which predominate in the basin [5].
Regarding the LULC analysis comparing 2012 and 2022, Fig. 4 and Table 3 show the significant changes experienced throughout the decade. The intertemporal analysis of land use can approximate an answer to the question related to the situation of the basin's critical ecosystems.
(Fig. 4. Land Use Change 2012–2022)
Table 3
Inter-temporal Land Use Dynamics 2012–2022
Land use | 2012 | 2022 | Change | % of variation | Direction |
Hectares | % | Hectares | % |
Coniferous forest | 28,155.83 | 5.35 | 17,430.45 | 3.31 | -10,725.38 | -38.09% | ↓ |
Broadleaf forest | 129,184.27 | 24.54 | 122,086.52 | 23.19 | -7,097.75 | -5.49% | ↓ |
Dry Forest | 823.29 | 0.16 | 277.93 | 0.05 | -545.36 | -66.24% | ↓ |
Mangrove forest | 3,324.36 | 0.63 | 251.29 | 0.05 | -3,073.07 | -92.44% | ↓ |
Rice crops | 52,302.86 | 9.93 | 52,055.28 | 9.89 | -247.58 | -0.47% | ↓ |
Cocoa crops | 56,049.21 | 10.65 | 58,388.80 | 11.09 | 2,339.59 | 4.17% | ↑ |
African palm (Oil palm) | 0.00 | 0.00 | 29.97 | 0.01 | 29.97 | 100.00% | ↑ |
Musaceae | 26,220.73 | 4.98 | 19,307.59 | 3.67 | -6,913.14 | -26.37% | ↓ |
Fruit trees (pineapple, orange, coconut, others) | 4,507.89 | 0.86 | 2,229.23 | 0.42 | -2,278.66 | -50.55% | ↓ |
Coffee crops | 3,733.49 | 0.71 | 5,225.66 | 0.99 | 1,492.17 | 39.97% | ↑ |
Subsistence agriculture | 4,079.98 | 0.77 | 2,649.46 | 0.50 | -1,430.52 | -35.06% | ↓ |
Pastures | 192,345.16 | 36.53 | 168,046.69 | 31.92 | -24,298.47 | -12.63% | ↓ |
Body of waters | 3,364.90 | 0.64 | 5,114.87 | 0.97 | 1,749.97 | 52.01% | ↑ |
Built-up land | 13,264.55 | 2.52 | 11,900.04 | 2.26 | -1,364.51 | -10.29% | ↓ |
Mining | 561.92 | 0.11 | 1,825.29 | 0.35 | 1,263.37 | 224.83% | ↑ |
Bushes | 8,608.90 | 1.64 | 59,708.27 | 11.34 | 51,099.37 | 593.56% | ↑ |
Total | 526,527.34 | 100.00 | 526,527.34 | 100.00 | |
Source: Own Elaboration |
Table 3. Inter-temporal Land Use Dynamics 2012–2022
Figure 5 summarizes the findings of Table 3, indicating a trend of land use change in which decreased ecosystems such as coniferous forests or traditional agriculture have led to a dramatic increase in shrubland. This indicates a possible trend towards landscape deterioration.
(Fig. 5. Land Use Statistics 2012–2022)
The coniferous forest in the upper sub-basin shrank by 38% in the analyzed period, the broadleaf forest shrank by 5.4%, and the already meager dry forest lost 66% of cover. In the case of mangroves in the lower sub-basin, the impact over the decade reduced it by 92%. The most affected ecosystems have been the ones indicated, but when we look at the land uses with a vocation for conservation, the affected ecosystems went from covering an area of just over 161 thousand hectares in 2012 to 140 thousand hectares for an overall reduction equivalent to 13% of the area covered (coniferous forest, broadleaf forest, dry forest, and mangrove).
Regarding intensive agriculture, the area cultivated with rice was almost unchanged (just a decrease of 0.47% between 2012 and 2022). On the other hand, the areas dedicated to cocoa and coffee cultivation experienced an increase of 4.17% and 39.97%, respectively. Fruit crops (pineapple, orange, and others.) fell by around 50% between 2012 and 2022. The area dedicated to pasture was reduced by 12.6%, as well as subsistence agriculture in the basin, which experienced a reduction of 35% from 2012 to 2022, possibly related to the diversification of productive activities in the basin and the process of demographic decline that has been experienced for several decades in the Dominican countryside. Over the decade, urban land use fell by 10%, while water bodies (dams, dams, reservoirs) increased by 52% along with mining, which expanded by more than 200%. The most striking change can be seen in the increase in shrubland, whose cover has grown by nearly 600%.
In a very preliminary way and without data to confirm it, the possibility can be raised that this change may indicate a landscape degradation process as a response to the pressure of socioeconomic factors and environmental stress in the basin that affects ecosystems and the services they provide [51]. Suppose it adds up the losses of coniferous, broadleaf, grasslands (pastures), and other essential losses. In that case, the total resembles the increase in shrubland in the basin, which could indicate a trend toward deforestation. For now, there is a lack of firmer evidence to support this idea, and more research needs to be done on the matter. As indicated, it has been possible to estimate the dynamics of land use change to 2030 by using Markov chains and cellular automata, as shown in Fig. 6.
(Fig. 6. Markov chain-based simulation 2022–2030).
The Markov-based prediction model has limitations and should be taken as an indication of the change in the trend of land use in 2030. Table 4 summarizes the results of the Markov-chain simulation:
Table 4
Land use change statistics 2022–2030
Land use | Hectares | Win/losses | % of variation | Direction |
2022 | 2030 |
Coniferous forest | 17,391.00 | 13,605.00 | -3,786.00 | -22% | ↓ |
Broadleaf forest | 118,195.00 | 119,857.00 | 1,662.00 | 1% | ↑ |
Dry forest | 309.00 | 308.00 | -1.00 | 0% | n/a |
Mangrove forest | 157.00 | 99.00 | -58.00 | -37% | ↓ |
Rice crops | 51,365.00 | 51,363.00 | -2.00 | 0% | n/a |
Cocoa crops | 56,339.00 | 56,333.00 | -6.00 | 0% | n/a |
Fruit crops (pineapple, orange, coconut, Musaceae, oil palm, others) | 21,496.00 | 21,496.00 | 0.00 | 0% | n/a |
Subsistence agriculture | 2,645.00 | 2,642.00 | -3.00 | 0% | n/a |
Pastures | 161,879.00 | 152,599.00 | -9,280.00 | -6% | ↓ |
Body of waters | 5,077.00 | 5,077.00 | 0.00 | 0% | n/a |
Built-up land | 11,687.00 | 11,683.00 | -4.00 | 0% | n/a |
Mining | 1,761.00 | 1,721.00 | -40.00 | -2% | ↓ |
Bushes | 71,347.00 | 82,695.00 | 11,348.00 | 16% | ↑ |
Source: Own elaboration |
Table 4. Land use change statistics 2022–2030
The findings in Table 4 are consistent with the land use change between 2012 and 2022. By 2030, the trend continues, significantly affecting coniferous forests in the upper sub-basin (projected decrease of 22% of the area) and mangrove forests in the lower sub-basin (projected reduction of 37%). Despite their limitations, these scenarios clearly show the urgency of an intervention that ensures the capacities of the identified critical ecosystems to provide services. Figure 7 gives a more unambiguous indication of the projected dynamics for 2030.
(Fig. 7. Land Use Statistics for 2030)
As shown in Fig. 7, the big losers in the coming years are land uses related to the conservation of ecosystems. The coniferous forest in the upper basin, essential for the water supply service for consumptive and non-consumptive uses, will be reduced by more than 20% compared to 2022, having already experienced a loss of 38% compared to 2012. This situation will undoubtedly put much more stress on the basin and its ability to meet the demand for surface water for the coming decades, considering that by 2040, the market is expected to reach 2,540.22 million cubic meters per year, not to mention the adverse effects on support and regulation services that the trend of landscape degradation marked by the simulation would have Performed. The trend of the mangrove in the lower basin is just as dramatic, so it is very likely that if the simulated scenario continues, the mangrove will tend to disappear from the areas in which it was found in 2022. The efforts of organizations such as CEBSE will likely contribute to reversing this trend in the lower Yuna basin. The trend of change and possible landscape deterioration continues with the increase in shrublands by more than 15% compared to 2022, having already experienced an increase of more than 500% compared to 2012. The impact of reducing the area occupied by these ecosystems can be varied. In the case of the ecosystems of the upper basin, it can be translated, on the one hand, into the decrease of the water balance of the basin, specifically in the amount of water stored in its aquifers, and on the other hand, in the increase in the rates of soil erosion and sediment entrainment to hydroelectric reservoirs will decrease its lifespan and reducing its efficiency. Without counting, ecosystem services regulation would no longer capture carbon [56].
In the case of mangrove ecosystems, their reduction has several implications from the point of view of the provision of a wide vector of ecosystem services, ranging from a decrease in net biomass productivity to an increase in the risk of flooding as a result of increased exposure to the eventual tropical storms that regularly hit the Caribbean [57]. The dramatic reduction of the mangrove forest already experienced between 2012 and 2022 is a powerful wake-up call as the income generated by fishing is affected, and protection is diminished, among other services [57]. It is worth saying that mangroves are one of the most productive and dynamic ecosystems for decomposing and recycling nutrients and carbon sequestration [58], contributing to waste assimilation. However, it is also an ecosystem that serves as a refuge for around 239 species of birds (native, migratory, and endemic) in the surroundings of the Samaná Bay at the mouth of the Yuna River [8]. How does the destruction of the mangrove affect Samaná Bay's ability to receive a population of around 1000 humpback whales from the North Atlantic during the boreal winter? We cannot answer this question in the context of this report. However, a PES intervention is undoubtedly required to protect and restore a critically threatened ecosystem in the lower Yuna sub-basin. Therefore, the landscape along the altitudinal gradient over the next decade is proposed to be managed from a multifunctional landscape perspective [59].
3.2 The relative economic importance of ecosystem services
Given the available data and paper purpose, let’s focus only on provisioning (water supply) and regulatory (CO2 sequestration) ecosystem services [12, 14]. Supporting and cultural ecosystem services can be considered as assumed and should be estimated further on [14]. An example of the economic and social importance of the Yuna basin can be seen in the water supply service for consumptive (agricultural, industrial, and residential) and non-consumptive (hydroelectricity, recreation, and tourism) uses. The first thing to consider is that the Yuna basin produces about 15% of the available surface water in the DR, equivalent to about 3,600 million cubic meters per year (MCM/year) [60, 61]. Table 5 shows the participation of the Yuna basin in the generation of surface water supply.
Table 5
Surface water availability by hydrographic regions
Hydrographic regions | Millions of cubic meters | % |
Yaque del Norte river basin | 2,945.46 | 12.33 |
Atlantic region | 4,634.73 | 19.67 |
Yuna river basin | 3,600.96 | 15.28 |
East Region | 3,195.95 | 13.56 |
Ozama-Nizao region | 4,459.08 | 18.92 |
Yaque del Sur river basin | 4,771.51 | 20.25 |
Total | 23,567.69 | 100.00 |
Source: Own elaboration |
Table 5. Surface water availability by hydrographic regions
Combining different sources of information from public organizations, the basin's water demand for consumptive and non-consumptive uses could be estimated at 2,510.42 million MCM/year by 2020, of which 51.69% corresponds to consumptive uses (1,297.66 MCM/year) and 48.21% to non-consumptive uses (1,212.76) [4, 61–63]. The above demand is equivalent to 69.7% of the entire surface water supply of the basin estimated in the National Hydrological Plan [61]. The estimate of the projected demand for 2020 is slightly higher than that made in the framework of the INDRHI Trends and Scenarios Report [62], given that the estimated demand for turbine water for hydroelectricity generation in the Yuna basin has been added for more clarity [4, 63]. Based on the previous estimate, of the consumptive uses (1,297.66 MCM/year), 66.63% were dedicated to agriculture, 18.24% to livestock (combined agriculture represents 84.87% of consumptive uses), human consumption represented about 9.27%, and industry and mining 5.86%. Figure 8 shows the distribution of the consumptive uses and the number of millions of cubic meters per year of each activity.
(Fig. 8. Consumptive uses of water in the Yuna basin)
As indicated in Fig. 8, the demand for water for non-consumptive uses, especially for hydroelectricity generation, stood at around 1,212.76 MCM/year. The amount of water turbines used for hydroelectricity generation is equivalent to 48.21% of the surface water availability. Figure 9 shows the water demand and availability estimated by INDRHI [62].
(Fig. 9. Water supply and demand in the Yuna Basin)
Figure 9 shows that the basin is not a linear system. As can be seen, in the years 2001, 2002, 2003, 2007, 2009, 2010, 2016, 2018, 2019, and 2020, water availability was below demand, that is, for ten years of the series. The situation described in the graph is likely related to climate variability and the effects of droughts caused by events such as the Southern Oscillation, better known as El Niño, whose effects have been documented for the insular Caribbean [62, 64], shown, in this case, the environmental climate vulnerability of the basin, regardless of any projection scenario on demand and availability of its water balance. Assuming a conservative range of variability of around 10% between estimates of different future scenarios defined by INDRHI [62] and the projected demand for water for the basin made in this report (2,510.42 MCM/year), for the years 2040 and 2060 would be in ranges between 2,478.19 and 2,726.00 MCM/year and between 2,666.38 and 2,933.02 MCM/year, respectively. In other words, at the upper limits of the projected demand for the years 2040 and 2060, between 75.42% and 81.47% of the entire capacity of the surface water supply of the basin would be reached without adding these estimates, the ecological flow projected for 2040 and 2060 at 991.39 MCM/year [62]. Therefore, it can be said that the ecosystem services of the Yuna basin, such as the provision of water for consumptive and non-consumptive uses, not only for the present but also for the future, are under significant anthropic pressure that may jeopardize the ability of the basin's ecosystems to provide them sustainably in the medium-long term.
Based on the hydrological relevance of the Yuna River basin for the Dominican Republic, the approach followed for the monetary estimation of the ecosystem services of the basin has been that of proximate markets [43]. For the values of water demand for consumptive and non-consumptive uses, the total volume of water used for consumptive purposes was considered to make it available for other uses. According to the data in this report, the demand for water for different uses (consumptive and non-consumptive) as of 2020 is 2,889.76 MCM/year per year, of which 37% corresponds to consumptive uses, that is, 1,069,211.2 and 1,820, 548 MCM/year for consumptive and no-consumptive uses, respectively. An average cost of US$0.60/m3 was assumed for effluent treatment (data provided by Barrick Gold) so that, directly, the value of water for consumptive purposes would be around US$ 641.5 million a year. The best proxy in the Yuna basin for non-consumptive water use is the production of hydroelectricity. Table 6 summarizes the available information on the average generation of hydroelectric plants in GW/year in 2020 of the basin and the volume of turbine water in MCM, i.e., the volume of water used to produce electricity [63].
Table 6
Hydroelectric production and turbine water
Hydroelectric | Production GW/year | Turbine water in MMC |
Hatillo complex | 82.32 | 740,560,426 |
Pinalito complex | 93.5 | 62,523,227 |
Rincón complex | 21.23 | 241,329,669 |
Rio Blanco complex | 113.5 | 168,347,503 |
Total | 310.6 | 1,212,760,825 |
Source: Own elaboration |
Table 6. Hydroelectric production and turbine water
The opportunity cost for hydroelectricity production for the wholesale market has been estimated at $DOP 0.82/m3, equivalent to US$0.014/m3 [4], so that the value of non-consumptive water use in the basin considering not only turbine water but the overall potential of water for available non-consumptive use (63% of the surface water supply indicated above), the value of water for non-consumptive use would be US$25.4 million/year. Based on the above estimates, the water supply service's value for consumptive use (US$ 641.5 million) and non-consumptive use (US$25 million) is around US$667.0 million/year. The value of the water supply service is about 3.2 times greater than that of cocoa exports and is only surpassed by the export of gold and silver in the basin. Regarding regulating ecosystem services (capturing and fixing CO2) [65–67], our findings indicate that the Yuna River captures about 3.17 million t/CO2/year, and the fixed carbon in trees is around 41.4 million t/CO2. The estimated social prices for CO2 in the DR range from US$31.00/tCO for carbon sequestration to US$17/tCO2 for fixed CO2 [46]. Thus, the value of regulating ecosystem services only considering CO2 sequestration is about US$98.2 million/year. In conclusion, the Yuna River basin provides ecosystem services for around US$765.2 million/year (see Table 7).
Table 7
Selected ecosystem services in Yuna river basin
Ecosystem services | Value US$ (mm) | % |
Provisioning services | | |
Consumptive use of water | 641.5 | 83.8 |
Non-consumptive use of water | 25.4 | 3.3 |
Regulating services | | |
Annual Carbon Sequestration | 98.2 | 12.8 |
Estimated Total Annual Value | 765.2 | 100.0 |
Source: Own elaboration |
It should be noted that coniferous ecosystems have suffered a significant loss in 2022 (38% compared to 2012), and mangrove ecosystems in the lower basin, which were reduced by 92%, or the already meager dry forest whose surface area was reduced by 66% compared to 2012. It points out a critical situation for ecosystem services in the coastal zone, especially considering the relevance of blue carbon sequestration for coastal ecosystem management [65, 66]. The possible trend of landscape degradation caused by a complex dynamic of land use change over a decade reduces the capacity of ecosystems to provide services and fulfill their ecological functions, and this translates directly into the reduction of the capacity of ecosystems to provide ecosystem services of regulation or support.
Table 7. Use values of the basin's ecosystem
As seen in Table 7, the weight of the use values of the basin's ecosystems falls on the water supply service for consumptive uses (83.8%). The most productive ecosystems in the basin, and at the same time the most threatened, are found in the upper basin in terms of water supply and regulation services (coniferous forest in the upper sub-basin, essential for water supply services and carbon sequestration and mangrove in the lower sub-basin).