5 Results
5.3 Scenario 2 – Conservation
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Figure 5.17 Comparison in fish abundance (left) and the number of fish species (right) for the baseline and conservation scenario
Because the fish population has the capacity to grow many herbivorous fish species also increase. These herbivorous fish species forage on algae and can now regulate their abundance. This is apparent when looking at Figure 5.18. Algae cover decreases the first ten years and levels out at around the same moment when the fish abundance reaches it maximum. A decrease in algae cover provides more space for corals to expand. At first coral cover continues to decrease, but after 5 years the decline halters and eventually corals have the space to expand. Coral cover finally reaches a maximum of 27% cover after 25 years, almost recovering to initial values. Algae cover still
remains because of high ambient nutrient conditions.
Figure 5.18 Variation in benthic cover for the conservation scenario
The effects of fencing the free roaming livestock are most apparent when looking at the forest cover (Figure 5.19). The results of the simulation show that in this scenario, the amount of mature forest cover reaches high numbers. Goat removal was
implemented in stages in the model, hence there first is a small decline forest cover as 0
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goat numbers decrease to such a level that forests have the chance to mature. From 2017 and onwards, the mature forest cover keeps on increasing. After 30 years mature forest cover amounts to 7,500 hectare.
Figure 5.19 Amount of mature forest cover for the baseline and conservation scenario Removing free roaming livestock not only affects the terrestrial environment but also the marine environment. An increase in more mature forest cover causes a decrease in sediment runoff. This means that the overall stress experienced by the corals
decrease. This is visible in Figure 5.20. Coral diversity still decreases, yet at a slower rate compared to the baseline scenario.
Figure 5.20 Number of coral species present for the baseline and conservation scenario
All the aforementioned changes in the environment result in a higher marine and terrestrial indicator. After 10 years the marine indicator levels out at a value of 0.5.
The terrestrial indicator experiences a rapid growth the first 5 years and levels out at 0.74. In this scenario the interventions had a very positive effect on the environment.
For both environments it can now be said that they are no longer in a degraded state.
The effects of which are also apparent in the economical model.
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5.3.2 Economic model
Despite an increase in the quality of the terrestrial and marine ecosystem, there is still a visible decline in the amount of stay over tourists. The reduction in stay over tourist can be attributed to the vast expansion of the cruise tourists. The negative feedback mechanism in the model presumes that as cruise tourists increase, stay over tourists are less likely to visit. After 30 years the cruise tourists reach a level of 547,000 visitors (Figure 5.21). The stay over tourist group reaches a minimum of 7,500 visitors per year after 30 years.
Figure 5.21 Change in the number of tourists for the conservation scenario Although only the cruise tourists increase in numbers, there is a contrast in the recreational value between the conservation scenario and the baseline scenario (see Figure 5.22). At first, the two scenarios follow the same trend, i.e. a steady and slow decline. However, as the cruise tourists continue to increase in numbers, the
recreational value diverges from its path. Eventually the value even starts to increase ending at a value of $18.5 million.
Figure 5.22 Comparison of the recreational value for the baseline and conservation scenario
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effort increases. This is reflected in the fact that the fisheries value increases substantially. After a period of 30 years, the value of fisheries levels out at $1.8 million.
Since the coral cover is increasing and the amount of mature forest is expanding the chances of encountering medicinal plants or extracting substances that can be of medicinal use, the biodiversity value increases. The model simulates that after 30 years the value in the conservation scenario will be $2.47 million.
Another value that differs substantially from the baseline scenario is the non-use value.
The WTP of Dutch and Bonairean depends on the qualitative state of the environment.
In the baseline scenario the Non-use value drops by more than $30 million. In the conservation scenario, however, the value stabilises at $44 million (see Figure 5.23).
Figure 5.23 Comparison of the Non-Use value for the baseline and conservation scenario
The interventions in the conservation scenario have a substantial positive influence on the different ecosystem services. As a result the TEV increases compared to the baseline scenario: the TEV decreases just as in the baseline scenario, however in the conservation scenario the trend diverges. After 30 years the value reaches $70 million, compared to a TEV of $38 million after 30 years in the baseline scenario (Figure 5.15).
As a result higher NPV is also emerging (Figure 5.24). The difference between the scenarios decreases as the discount rate increase, but there remains to be a pronounced difference.
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Figure 5.24 Comparison of the NPV for the baseline and conservation scenario Finally the benefit cost ratio is a good indicator whether or not the interventions were worth the investment. The most expensive part of the interventions are catching and fencing the goats. It is presumed that this costs $231,000 the first 10 years and
$10,000 per year for maintenance for the remaining period. Removal of the lionfish is
$40,000 for the first 3 years and $10,000 per year for the remaining period. At its highest the cost benefit ratio is 227 at its lowest 26. Despite the discount rate, the investment has a very high yield.