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The purpose of this project is to see the possible effects of building a dike through Philip Flat, where the Patrick’s marsh wren is found. The common marsh wren, Cistothorus palustris dawsoni is an isolated population that lives in wetland reed and grasses. There are four subpopulation sites for Patrick’s marsh wren, which include the three mile marsh composed of Philip Flat, Castleton Creek, and Delinger Meadow. This bird migrates during the winter and returns to the Central Valley in spring; they return to the same nesting sites.
Green Valley Ranch, Inc.
owns the land around the habitat of Patrick’s marsh wren and they want “more pasture to allow them to graze”. Since a semi-permanent wetland, which can be created by intense seasonal flooding, is not suitable for pasture to graze, Green Valley Ranch wants to build a dike through Philip Flat to prevent seasonal flooding. Moreover, they are willing to remove the aging dike around Delinger Meadow.
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The problem of building a dike can destroy the Philip Flat and it can have a significant influence on the overall wren population.
By applying analytical techniques, Philip flat was found to be not that crucial to the persistence of the metapopulation because Philip Flat might be a degrading habitat, and the extinction of Patrick’s marsh wren has already happened in Philip Flat. In the Models of potential scenarios for Patrick’s marsh wren, translocation of individual birds from Philip Flat to Delinger Meadow has less extinction rate compared to an unaltered degrading habitat (U(-1), U(-2)), where U(-1) is the Unaltered degrading habitat model.
This model, which is Philip Flat, is assumed to be mildly degrading.
Carrying capacity is reduced by 1 individual per year. U(-2) is the unaltered degrading habitat model in which Philip Flat is assumed to be severely degrading. Carrying capacity is reduced by 2 individuals per year. A( R ) is an altered habitat, a remediation performed model. This proposed model in which Philip Flat is destroyed after half of its population is translocated to Delinger Meadow. The carrying capacity of Delinger Meadow thereby increases from 100 to 157 due to removal of the aging dike. Methods There are five types of models of potential scenarios for Patrick’s Marsh Wren, which are U(0), U(-1), U(-2), A(NR) and A(R).
As you can see in Table 1, U (0) is an unaltered habitat with constant carrying capacity and 400 individuals of total initial population size. In the three mile marsh, the figures are as follows: 125 Abundance, 150 Carrying Capacity, 1. 05 Growth Rate, 50km Average Dispersal Distance, and 0. 1 Correlation of Environment. In Phillip Flat, the findings are: 95 Abundance, 105 Carrying Capacity, 1. 05 Growth Rate, 50km Average Dispersal Distance and 0. 1 Correlation of Environment. In Castleton Creek, the table shows: 100 Abundance, 120 Carrying Capacity, 1. 05 Growth Rate, 50km Average Dispersal Distance and 0. 1 Correlation of Environment.
In Castleton, there are 100 Abundance, 120 Carrying Capacity, and Growth rate, Average Dispersal Distance, Correlation of Environment Values are the same as other regions. In Delinger Meadow, Growth rate, Average Dispersal Distance, Correlation of Environment Values are the same as other regions. The only differences are 80 Abundance and 100 Carrying Capacity. U (-1) is an unaltered degrading habitat model, which Philip Flat is assumed to be mildly degrading. The carrying capacity is decreased by 2 individuals per year, which means temporal carrying capacity is -1 with the 400 individuals total initial population size.
Everything else’s values are the same as U (0). U (-2) is also an unaltered degrading habitat model, which Phillip Flat is assumed to be severely degrading. The carrying capacity is reduced by 2 individuals per year which means temporal carrying capacity is -2 with 400 individuals of the total initial population size. Furthermore, other values are the same as U (0) and U (-1). A (NR) is a proposed model, which Philip Flat is destroyed with total initial population size of 305 individuals. It removes Phillip Flat which means Phillip Flat is destroyed.
Other regions values are the same as U (0,-1,-2). A(R) is also a proposed model in which Phillip Flat is destroyed after half of its population, 47 individuals, is translocated to Delinger Meadow. As mentioned earlier, the carrying capacity of Delinger meadow increases from 100 to 157 due to removal of the aging dike. The total initial population size is 352 individuals. Other regions are the same as A (NR). To know how the extinction risks rate changes, we changed numbers of translocated birds from Phillip Flat region to Delinger Meadow by 47, 50, 55, 60, 65, 70, and 75. Results
The extinction risk of falling below 100 of U (0), which is an unaltered habitat, is 0. 4525. The extinction risk falling below 100 of U (-1), which is an unaltered degrading habitat, is 0. 4925. The same of U (-2), A (NR) and A (R) are 0. 6, 0. 5967 and 0. 5057. As you can see the Table. 2, U (-2) model has the highest extinction risk of falling below 100. A (R) model has a less extinction risk than A (NR) model and U (-1) model. Because U (0), A (NR) and A (R) don’t have the values of temporal trend in K, the Carrying Capacities of these models don’t change. As you can see in Figure.
3, these figures stay constant. In Figure. 1, U(-1) model has -1 value for temporal trend in K in Phillip Flat region, which means Carrying Capacity is reduced by 1 individual per year. Also in Figure. 2, U (-2) model has -2 for temporal trend in K in Phillip Flat area. This refers to the falling rates of Carrying Capacity which is decreased by 2 individuals per year. In the model U (-1) and U (-2), the Carrying Capacities are decreased over time. To compare the Trajectory Summary, which is the rise/fall of population over time, U (0) came out with a 106. 2 difference of average from 0 to 50 durations.
U (-1) has a 132. 7 difference of average from 0 to 50 time durations. U (-2) has 246. 1, A (NR) model has 76, and A(R) model has a 93 difference of average from 0 to 50 durations. Moreover, the extinction risk came out different each time when the more number of the birds tranlocated from Phillip Flat to Delinger Meadow. In Figure 4, when we translocated 50 birds, the extinction risk came out 0. 5057, and when we translocated 55 birds, the extinction risk was significantly lowered to 0. 484. When we translocated 60 birds, 65, 70, and 75 the extinction risk came out 0.
474, 0. 488, 0. 487, and 0. 489, respectively. In other words, the extinction risk was decreased as the numbers of birds that were translocated from Phillip Flat to Delinger Meadow were increased. Discussion Patrick’s marsh wrens have four subpopulation sites, which are Three Mile Marsh, Phillip Flat, Castleton Creek and Delinger Meadow. The problem is that Green Valley Ranch, Inc owns the land where includes Phillip Flat and Delinger Meadow, and Green Valley Ranch, Inc wants to build a dike through Phillip Flat because of the seasonal flooding.
In other words, Green Valley Ranch wants to destroy Phillip Flat to build a new dike, and Patrick’s marsh wrens which live in Phillip Flat will certainly lose their natural habitats. However, the California Fish and Game Department found that there was some indication that Phillip Flat might be a degrading habitat due to natural sedimentation. This might lead to a sink for the marsh wren population. In Table 2, U (-1) and U (-2) models are assumed to be mildly degrading and the Carrying Capacity is reduced by 1 individual per year and 2 individual per year.
U (-1) and U (-2) models’ extinction risks came out higher than U (0) model’s, which is the original model that has constant Carrying Capacity. The extinction can occur faster which will be dependent on how fast the land is degrading. In Figure 1 and Figure 2, because the land is getting smaller, the carrying capacity of the Patrick’s marsh wren is going to be smaller. Therefore there is still a possibility that Patrick’s marsh wren is going to be extinct even if the Phillip Flat region is not destroyed intentionally.
Moreover, if the Phillip Flat region stays constant like U(0) model, there is another possibility to have a high extinction risk of Patrick’s Marsh Wren because of unexpected seasonal disaster such as seasonal flooding. However, if we just destroy Phillip Flat region as Green Valley Ranch, Inc. to build a new dike to guard against seasonal flooding, in Table 2, A(NR) model, the extinction risk is higher than any other models’ except U(-2). Even though U(-2) model has the highest extinction risk, A(NR) model, which has the destroyed Phillip Flat region, almost has the same extinction risk as U(-2).
Therefore, I believe that the two ways, which is retaining Phillip Flat as it is or destroying it by building a new dike, cannot protect or keep the Patrick’s Marsh Wren in its natural habitat. However, since Green Valley Ranch, Inc. ’s property has Delinger Meadow, if they translocate some population of Patrick’s Marsh Wren from Phillip Flat to Delinger Meadow and increase the carrying capacity of Delinger Meadow like in Table 2 A(R) model, the extinction risk would become lower than A (NR) and A (R).
Moreover, as you can see in Figure 3, the greater the number of translocated Patrick’s Marsh Wren from Phillip Flat to Delinger Meadow, the less extinction risk until a certain point. In this case, the extinction risk dropped dramatically as the number of birds translocated was increased up to 60. After this point, it slightly increased again because of the Carrying Capacity. Therefore, we should make a dike through Phillip Flat and develop Delinger Meadow a little to raise the Carrying Capacity of Patrick’s Marsh Wren, then we can translocate Patrick’s Marsh Wren from Phillip Flat to Delinger Meadow.
Because we cannot avoid seasonal flooding, we might have a loss of lives and properties, which depends on how heavy the flooding is. Also, since we are already losing Patrick’s Marsh Wren’s habitat and they are ultimately going to be extinct by just leaving the land alone because of the degrading the habitat, we should translocate Patrick’s Marsh Wren to Delinger Meadow. This way we can protect the species and avoid the extinction of Patrick’s Marsh Wren. Additionally, Green Valley Ranch can be satisfied, and we don’t have to anticipate any more loss of lives and properties every time when the recurrent seasonal flooding occurs.
The Possible Effects of Building a Dike through Philip Flat. (2016, Aug 03). Retrieved from https://studymoose.com/the-possible-effects-of-building-a-dike-through-philip-flat-essay
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