Patch Area and Connectivity Promote Biodiversity for Birds in Urban Landscapes

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1 Marissa Simpson 4/29/15 Patch Area and Connectivity Promote Biodiversity for Birds in Urban Landscapes The majority of the world s population lives in the city and it is expected that by 2050 around 70% of the world s population will occupy cities (Fontana et al., 2011). The creation of urban areas results in the fragmentation of natural areas due to the land undergoing construction of buildings and roads (Mortberg & Wallentinus, 2000). This fragmentation of the landscape creates areas within the urban areas known as greenspaces. Greenspace provides habitat and food sources for birds within the urban environment (Unfried et al., 2013). Another side effect of urbanization is that it reduces connectivity for organisms by reducing their movement, gene flow, and dispersal (Unfried et al., 2013). The combination of patch area and connectivity for greenspaces promote biodiversity for avifauna in urban environments. Landscape connectivity is the degree of the ability of landscape features to either positively or negatively affect movement among the fragmented landscape (Fernandez Juricic 2000). Connectivity is needed within urban environments because it allows the movement, gene flow and dispersal of birds. A result of a lack of connectivity can be seen in the Song Sparrow population in the greater Seattle area. Unfried et al. hypothesized that if urbanization limits connectivity then there would result in genetic differentiation between the populations (2013). Based on gene analysis, it was determined that there was a differentiation in the genes of the two populations, thus indicating that connectivity had been reduced (Unfried et al., 2013). In order to prevent other urban populations of birds from undergoing similar declines in gene flow connectivity has to be increased. One of the ways in which to increase connectivity in urban areas is to increase the number of greenspace in an urban area (Fontana et al., 2011).

2 One way of increasing connectivity is to have corridors connecting one patch area to another. Corridors, a linear strip that connects isolated habitats, can overcome some of the effects brought on by habitat fragmentation. Some of the benefits of an ecological corridor are that it reduces extinction rate, increases species diversity, and decrease the risk of inbreeding (Hong et al., 2013). An example of corridors that one might see in an urban setting is wooded streets. Madrid has many urban parks that are connected by wooded streets. The number of species in wooded streets was in the middle of the number of species in control areas and urban parks. The factors that effected the number of species in the greenspace was corridor placement, vegetation structure, and human disturbance (Fernandez Juricic, 2000). There are several methods that can be used in evaluating the connectivity of greenspaces within urban environments. The first step in every study was to perform a bird survey in order to evaluate species richness, species abundance, or presence or absence of a species (Carbo Ramirez & Zuria, 2011). Green areas are often identified through the use of Lidar data or Spot data (Qian et al., 2015). Spot satellite data was used to see the change in greenspace over time. This was done by performing land cover classification and then comparing the change in urban areas (Qian et al., 2015). Once the greenspaces were identified, the degree of connectivity between the greenspaces can be measured. After determining the abundance of birds in a green area, there are several different procedures that can be undertaken in order to measure the degree of connectivity. One of the ways connectivity can be measured is by performing the predicted movement path of birds. This method included selecting an indicator species and then determining their most likely path through the urban environment. An indicator species was chosen because literature showed that the indicator s movements would improve by ecological corridors and based on the criteria was selected if the indicator was a resident species and was a species that could inhabit an urban area. A path finding algorithm was used in order predict the potential movement paths that connected all of the locations that the species

3 was found. In the case of Hong et al. the indicator species chosen was the Great Tit (2013). Based on the predicted pathway, greenspaces could be created along the pathway in order to increase connectivity through the urban environment which in turn will create more biodiversity (Hong et al., 2013). Another method utilized to measure connectivity was through the use of Geographical Information Systems. Buffers were created surrounding the greenspaces and the degree of connectivity and the degree of isolation was calculated. Large park areas were determined to be the best indicator of species richness (Oliver et al., 2011). One other method that was used to measure connectivity was by creating a multi scale graph. Multi scale graphs are geometric features that have points and lines that connect the points. Habitat connections are connected when the patches are less than the threshold distance. The threshold distance depends on scale (Van Langeveld, 2000). The multi scale graph shows the linkages of greenspace exist because of the revegetation by the dispersal patterns of birds (Shanahan et al., 2001). The second main contributor of biodiversity in urban areas is patch area. Patch area in some studies is considered to be more vital to bird biodiversity than connectivity. Patterns of species composition confirm that park size determines the accumulation of species in urban parks (Fernandez Jurcic & Jokimäki, 2001). In several cities like Madrid and Oulu the distribution of urban birds is higher in larger parks than small parks areas. Large parks provide a large diversity of habitats that can support more bird species. Small parks can be used as stepping stones that could be temporarily used by different species through urban habitats (Fernandez Juricic & Jokimäki, 2001). Landscape connectivity had a greater influence than patch area on species richness while patch area in combination with connectivity enhanced bird abundance (Unfried et al., 2013). Large parks can support high amount of vegetation that provides habitats for birds. Even if a species can travel through an urban environment, some may not have the correct vegetation in order to support the species (Unfried et al., 2013). One of the main factors that determines species richness in greenspaces is the composition of vegetation. Woody plants composition is an important factor for bird richness and the most species richness occurs

4 when there is an equal ratio of both coniferous and deciduous plants (Fontana et al., 2011). The amount of vegetation that exists in a patch limits the population size and the reduced connectivity can limit dispersal. In order to try to conserve species, revegetation is an important tool in conservation management (Shanahan et al., 2011). The conservation of greenspaces is important for bird populations and there are varying opinions on whether connectivity or patch area is more important. One of the options is increasing the area of the vegetation patch or increasing connectivity by joining patches together. When there is a small amount of habitat available, connectivity is more important. As habitat increases the importance of connectivity will decline (Unfried et al., 2013). Small built up patches maintain urban bird communities because the patches provide shelter and food. When species like the song sparrow cannot locate large patches, they will utilize smaller patches that can act as stepping stones to larger patches (Fernandez Juricic & Jokimäki, 2001). In order to conserve bird populations it was recommended that urban planners create ecological corridors that connect the fragmented green areas in urban landscapes (Unfried et al., 2013). An example of the implementation of connecting greenspace by corridors can be seen in Stockholm. Stockholm has implemented a region wide effort to maintain a system of greenspace corridors. Many green areas have been determined to be necessary for nature conservation and these areas have been outlined as large core areas with buffers and linked together with corridors. The purpose of this system was to maintain biodiversity of birds in the urban area (Mortberg & Wallentinus, 2000). Urban planners need more information regarding the factors affecting the avifauna in order to create greenspaces that can support a large biodiversity. For general management, there are some actions that can be taken including considering greenspaces as a priority in development for citizens and wildlife conservation, greenspaces should have the largest possible areas and complex vegetation cover to support a diverse biodiversity of birds. Lastly, the amount of vegetation cover and connectivity

5 between sites should be maximized. Not only will this help the biodiversity of birds but also create a healthier area for the humans (Carbo Ramirez & Zuria, 2011). There are some studies that indicate not all greenspaces are good for all different types of bird species. Therefore, it not only important to have greenspace but to have the right composition of factors. Chong et al. asserts that not all greenspaces are good because they are mosaic leftovers that cannot be utilized by all bird species. Natural greenery tends to promote alpha diversity but not all types of greenery will enhance alpha diversity. For example bird richness will decrease when cultivated turf cover increases (Chong et al., 2014). This idea of that there is not a cookie cutter type of vegetation for all bird species is important when trying to conserve species within urban areas. This topic is of particular interest to me because I enjoy urban ecology and I think that it is an emerging topic in landscape ecology. Having the knowledge that biodiversity is enhanced in urban areas by the connectivity and patch size of greenspaces, can hopefully help if I am ever involved in the restoration of greenspaces. In the next fifty or so years, as urbanization increases, I believe that this will be a prominent issue in cities. Having the knowledge to act now in cities will hopefully help to keep biodiversity within urban areas in the future. In addition some of the methods including the GIS method and the potential movement paths could be used in future job opportunities. In the future, I would like to be employed as a GIS analyst and having the knowledge of different methods of measuring connectivity could be helpful if I have an opportunity to analyze urban landscapes. Greenspaces are the most positively influencing factor on bird species richness and is an integral part of supporting bird populations in urban areas. The factors that the greenspaces are dependent on in order to support these bird species are patch area and connectivity. In some scenarios patch size or connectivity may be more important than the other. However, it is the combination of both that allows for there to be a large amount of bird biodiversity within an urban environment.

6 Annotated Bibliography Carbó Ramírez, P. and I. Zuria (2011). "The value of small urban greenspaces for birds in a Mexican city." Landscape and Urban Planning 100(3): Ramirez et al. demonstrates the value of greenspaces for birds within an urban area through the evaluation of vegetation and disturbance composition. The species richness was evaluated at each of the sites and species accumulation curves were made. Green space sites were divided into three types; gardens, parks, and road strip corridors. One problem that the study presents is that there is no control and rest of the urban areas were not utilized as a comparison. The study asserts that the greenspaces were the most important positively influenced bird species richness based on the results of the study. This supports the hypothesis in my own paper because green spaces are an integral part of supporting bird populations in urban areas. Migratory and resident species utilizes these greenspaces which could be important for refuel sites for migratory birds. The paper fails to expand on the concept of why these areas are particularly important for urban birds. However, this paper does provide evidence for the necessity of green spaces, and will be used in my paper to show some of the methods to evaluate the success of greenspaces. Chong, K. Y., Teo, S., Kurukulasuriya, B., Chung, Y.F., Rajathuri, S., Tan, H.T. (2014). "Not all Green is Good: Different effects of the Natural and Cultivated Components of Urban Vegetation on Bird and Butterfly Diversity." Biological Conservation 171: Chong et al. gives an alternate view to greenspaces. All of the other articles show the benefit of greenspaces, while this article shows a negative connotation of green spaces. The article asserts that not all greenspace is good because they are a mosaic leftovers of natural habitats. There were transects, bird surveys and greenery and traffic variables were accounted for. Natural greenery cover are important predictors of alpha diversity, however not all types of greenery will enhance alpha diversity. For example bird richness will decrease when cultivated turf cover increased. The main conclusion from this article was that in order to manage total biodiversity at both the alpha and beta diversity. This article will be used to show the negatives that can be caused by greenspaces. Fernández Juricic, E. (2000). "Avifaunal Use of Wooded Streets in an Urban Landscape." Conservation Biology 14(2): Fernandez Juricic studied the effects of street location, human disturbance, and vegetation structure on bird density in wooded areas. The methods included performing a bird survey, analysis of corridor placement, vegetation structure, and human disturbance. There was a gradient in the number of species in the urban parks, wooded areas, and control areas. The study showed that the wooded streets could potentially act as corridors and can enhance connectivity. This article was used for showing the usefulness and need for wooded streets because they promote connectivity. Fernández Juricic, E. and J. Jokimäki (2001). "A habitat island approach to conserving birds in urban landscapes: case studies from southern and northern Europe." Biodiversity & Conservation 10(12):

7 Fernandez Juricic et al. asserts that park size is one of the leading contributors to being able to support species and that wooded streets can increase connectivity because it provides an alternative habitat for nesting and feeding. Due to the fact that it is difficult to expand the size of parks in the city wooded streets may increase connectivity. This article assessed the main findings of a collection of other papers that examined urban park birds. Another interesting assertion from the paper is that when trying to plan corridors, it is important to maintain the existing diversity in the areas surrounding the corridors. This paper does however, fail to examine connectivity as a competing important factor. An important concept introduced in this paper was the idea that small parks, even though they could not support a large amount of biodiversity, but they are important to connectivity. The small parks act as stepping stones through the urban areas. This paper was used further support the idea about parks being crucial to connectivity. Fontana, S., Sattler, T., Bontadina, F., Moretti, M. (2011). "How to Manage the Urban Green to Improve Bird Diversity and Community Structure." Landscape and Urban Planning 101(3): Fontana et al. chooses to calculate model predictions for human influenced factors to sustain and enhance bird biodiversity despite the ever increasing urbanization. Some of the methods included bird surveys and the study sites included a variety of urban habitats including: private gardens, apartment buildings, public parks, and courtyards. The wide variety of sampling sites provide evidence for a wide range habitats. The model tested a wide variety of structural components. The results showed that the amount of trees is the most important factor in enhancing bird biodiversity. This is of particular importance for making greenspaces and ensuring that the corridors have the right factors to create a green space that is enhancing bird biodiversity. Human involvement is needed in order to make the greenspaces the most supportive that they can be. This article provides good management plans in order to make greenspaces that promote biodiversity and is one of the aspects that I included in my paper. The management plans involve re planting trees and also there needs to be a mixture of coniferous and deciduous trees. Fujita, M. and F. Koike (2007). "Birds Transport Nutrients to Fragmented Forest in an Urban Landscape." Ecological Applications 17(3): Some organism have actually increased in population due to the increase in urbanization. These types of species bring nutrients into the area through their excretory pathways. In this study the fecal samples were collected and analyzed for carbon, nitrogen, and phosphorus. The urban forest is highly fragmented and as a result nutrients in the surrounding area may concentrate in small evergreen forests and over enrich forest patches. This article will be used to show that some organism to thrive in urban setting and give nutrients back to their environment. Hong, S., Han, B., Choi, S., Sung, C., Lee, K. (2013). "Planning an ecological network using the predicted movement paths of urban birds." Landscape and Ecological Engineering 9(1): Hong et al. discussed the need for patches with high vegetation for bird movement through urban areas. The study looked at ecological corridors in order to link patch fragmentation despite the negative effects of corridors such as increasing predators and the dispersal of invasive species. The authors performed a bird survey and then selected the great tit as an

8 indicator species. Hong et al. then predicted potential movement paths through the urban area. The methods utilized in this paper could be essential in planning where to place greenspaces. The problem with this is selecting an indicator species because not all species are going to take the same path through the urban areas. I used this paper to show the possible methods in selecting the location to greenspaces. Mortberg, U. & Wallentinus, H. (2000). "Red listed forest bird species in an Urban Environment Assessment of green space corridors." Landscape and Urban Planning 50(4): Mortberg & Wallentinus examined the fact that green space corridors could support red listed bird species. The findings of the study could be used to design new green space corridors. This study shows a different way to try an identify areas that could be used for green space corridors. The methods included performing a land use analysis and a bird survey. Models were then made based on landscape structure variables. This method is different than using pathway analysis and does not use GIS. Using the pathway analysis may be a more successful way to identify locations for greenspaces because it actually identifies location of the birds. The overall result of the study was that forest patch size was the main predictor of species richness. This article will be utilized as support for patch size and then another method in identifying locations for green space corridors. Oliver, A. J., Hong Wa, C., Devonshire, J., Olea, K.R., Rivas, G.F., Gahl, M.K. (2011). "Avifauna richness enhanced in Large, Isolated Urban Parks." Landscape and Urban Planning 102: This article looks at the fact that bird richness is larger by large urban parks. This article demonstrated another method to assess the urban park by using GIS methods. To begin with bird richness was performed by studying composite data from the sites over a nine year span. Using GIS isolation was measured by utilizing buffers. After extensive modelling it was determined that the best indicator for bird abundance was park area. A new idea that was introduced to me through this paper was that the birds may be funneled into the large park areas as a result of the urban matrix. This opens up an interesting idea because it is typically assumed that the vegetation factors drawn the birds in because it provides habitat and food rather than the birds being forced their and then surviving because of the food and habitat. Qian, Y., Zhou, W., Li, W., Han, L. (2015). "Understanding the dynamic of greenspace in the urbanized area of Beijing based on high resolution satellite images." Urban Forestry & Urban Greening 14(1): This article shows that there are other benefits to greenspace in urban areas for humans. Some of the other advantages is that they purify polluted air, alleviate urban heat islands, protect water from pollution and promote biodiversity. These factors could be used be used to promote stakeholder involvement in creating greenspaces. The main methods in this study was to utilize Lidar data to map the green spaces. New green space identified by the Lidar data was previously impervious surfaces and it was determined that these greenspaces are highly dynamic. When new patches were created they enhanced connectivity. While the article mentions connectivity was increased, it made no mention to how they determined that connectivity was increased. This article was used to show another method of determining greenspace and also to support the idea that biodiversity increases with an increase in greenspaces.

9 Shanahan, D. F., Miller, C., Possingham, H.P., Fuller, R.A. (2011). "The influence of patch area and connectivity on avian communities in urban revegetation." Biological Conservation 144(2): Shanahan et al. discusses revegetation sites in urban environments and examining the importance of patch size and connectivity. Bird surveys were performed, in order to determine the abundance of birds in the revegetation areas. Vegetation characteristics were taken into account. The article also provided an alternative way to determine connectivity. The method for measuring connectivity was they used a multi scale graph analysis which allowed for the linkage of revegetation sites through different dispersal patterns of organisms. In this study the results showed that landscape connectivity had a greater impact than patch area on bird abundance. This shows that there is a conflicting result between some of the other papers which suggest that patch area is a more important factor. Another important idea is that revegetation could be used as a conservation method. Unfried, T., et al. (2013). "Effects of urbanization on Song Sparrow (Melospiza melodia) population connectivity." Conservation Genetics 14(1): This paper is a prime example of the negative effects of urbanization can have on bird connectivity. Urbanization can negatively affect the gene flow, dispersal, and movement for different bird species. Therefore, over a period of time gene differentiation can occur between populations of the same species. Genetic analyses were run to test whether populations had a different genetic makeup. Based on their analysis, it was determined that the variation was high on a high number of loci. One of the problems that will occur as a result of the isolation is inbreeding. This paper gives good evidence to support the need to have connectivity in urban settings. One way in order to increase connectivity is to have greenspaces. I will utilize this article to support the need for connectivity within urban areas. Van Langevelde, F. (2000). "Scale of habitat connectivity and colonization in fragmented nuthatch populations." Ecography 23(5): This article focused on the nuthatch and how that its habitat is often fragmented into small patches. The colonization of unoccupied patches is not random and is dependent on the connectivity of the patches. This study measured the degree of connectivity between patches. The degree of connectivity was measured using mathematical graph theory, which is a network of points and lines that connect these points. The statistical analysis of the models indicates that there is a preference for larger patches. This supports the idea that large patches are can support more biodiversity. Overall this article showed a good technique for measuring connectivity when many of the other articles did not explain how connectivity is measured. This article was used for showing how large patches promote biodiversity and hoe to measure connectivity.