CHAPTER OVERVIEW 21: Landscape Ecology and Island Biogeography Learning Objectives Understand the origins and aims of Landscape Ecology Learn some of the important terms used in Landscape Ecology Understand the basics of the Theory of Island Biogeography Make connections between the Theory of Island Biogeography and its application in Ecology Topic hierarchy 21.1: What is Landscape Ecology? 21.2: Important Terms in Landscape Ecology 21.3: Applications of Landscape Ecology 21.4: Island Biogeography Summary Landscape ecology is the science of studying and improving relationships between ecological processes in the environment and particular ecosystems. This is done within a variety of landscape scales, development spatial patterns, and organizational levels of research and policy. Landscape ecology often focuses on the composition of landscapes, and how the size, shape, and adjacency of different habitat patches affect ecological processes. The development of the Theory of Island Biogeography in the 1960s was fundamental to our understanding of how the size and isolation of habitat patches affect the life histories of species found within them. This, in turn, resulted in a strong focusses on habitat fragmentation within the subfield of Landscape Ecology. 21: Landscape Ecology and Island Biogeography is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.
Landscape Ecology Landscape ecology is the science of studying and improving relationships between ecological processes in the environment and particular ecosystems. This is done within a variety of landscape scales, development spatial patterns, and organizational levels of research and policy (Wu, 2006; Wu & Hobbs, 2007; Wu, 2008). Concisely, landscape ecology can be described as the science of landscape diversity as the synergetic result of biodiversity and geodiversity (Leser & Nagel, 2001). As a highly interdisciplinary field in systems science, landscape ecology integrates biophysical and analytical approaches with humanistic and holistic perspectives across the natural sciences and social sciences. Landscapes are spatially heterogeneous geographic areas characterized by diverse interacting patches or ecosystems, ranging from relatively natural terrestrial and aquatic systems such as forests, grasslands, and lakes to human-dominated environments including agricultural and urban settings (Wu & Hobbs, 2007; Turner et al., 2001; Forman, 1995). The most salient characteristics of landscape ecology are its emphasis on the relationship among pattern, process and scale, and its focus on broad-scale ecological and environmental issues. These necessitate the coupling between biophysical and socioeconomic sciences. Key research topics in landscape ecology include ecological flows in landscape mosaics, land use and land cover change, scaling, relating landscape pattern analysis with ecological processes, and landscape conservation and sustainability (Wu & Hobbs, 2002). Landscape ecology also studies the role of human impacts on landscape diversity in the development and spreading of new human pathogens that could trigger epidemics (Bloomfield et al., 2020; Bausch & Scwarz, 2014). Heterogeneity is the measure of how parts of a landscape differ from one another. Landscape ecology looks at how this spatial structure affects organism abundance at the landscape level, as well as the behavior and functioning of the landscape as a whole. This includes studying the influence of pattern, or the internal order of a landscape, on process, or the continuous operation of functions of organisms (Turner, 1989). Landscape ecology also includes geomorphology as applied to the design and architecture of landscapes (Allaby, 1998). Geomorphology is the study of how geological formations are responsible for the structure of a landscape.
Terminology The German term Landschaftsökologie-thus landscape ecology-was coined by German geographer Carl Troll in 1939 (1939). He developed this terminology and many early concepts of landscape ecology as part of his early work, which consisted of applying aerial photograph interpretation to studies of interactions between environment and vegetation.
One central landscape ecology theory originated from MacArthur & Wilson's The Theory of Island Biogeography (see 21.4: Island
Biogeography). This work considered the biodiversity on islands as the result of competing forces of colonization from a mainland
stock and stochastic extinction. The concepts of island biogeography were generalized from physical islands to abstract patches of
habitat by Levins' metapopulation model (which can be applied e.g. to forest islands in the agricultural landscape) (Banaszak,
2000). A metapopulation is a group of smaller populations of an organism in distinct habitat patches or islands which have
individuals moving between patches. This generalization spurred the growth of landscape ecology by providing conservation
biologists a new tool to assess how habitat fragmentation affects population viability. Recent growth of landscape ecology owes
much to the development of geographic information systems (GIS) and the availability of large-extent habitat data (e.g. remotely
: Land cover surrounding Madison, WI. Left: fields are colored yellow and brown, water is colored blue, and urban surfaces are colored red. Center: impervious surfaces. Right: canopy cover.
Development as a discipline Landscape ecology developed in Europe from historical planning on human-dominated landscapes. Concepts from general ecology theory were integrated in North America. While general ecology theory and its sub-disciplines focused on the study of more homogenous, discrete community units organized in a hierarchical structure (typically as ecosystems, populations, species, and communities), landscape ecology built upon heterogeneity in space and time. It frequently included anthropogenic (human-caused) landscape changes in theory and application of concepts (Sanderson & Harris, 2000). By 1980, landscape ecology was a discrete, established discipline. It was marked by the organization of the International Association for Landscape Ecology (IALE) in 1982. Landmark book publications defined the scope and goals of the discipline, including Naveh and Lieberman and Forman and Godron (1984; 1986). Forman wrote that although study of "the ecology of spatial configuration at the human scale" was barely a decade old, there was strong potential for theory development and application of the conceptual framework (1995).Today, the theory and application of landscape ecology continue to develop through a need for innovative applications in a changing landscape and environment. Landscape ecology relies on advanced technologies such as remote sensing, GIS, and models. There has been associated development of powerful quantitative methods to examine the interactions of patterns and processes (Turner et al., 2001). An example would be determining the amount of carbon present in the soil based on landform over a landscape, derived from GIS maps, vegetation types, and rainfall data for a region. Remote sensing work has been used to extend landscape ecology to the field of predictive vegetation mapping, for instance by Janet Franklin.
Sources Allaby, M. (1998). Oxford dictionary of ecology. Oxford University Press. Banaszak, J. (Ed.). (2000). Ecology of forest islands (p. 313). Bydgoszcz University Press. Bausch, D. G., & Schwarz, L. (2014). Outbreak of Ebola virus disease in Guinea: Where ecology meets economy. PLOS Neglected Tropical Diseases, 8(7), e3056. https://doi.org/10.1371/journal.pntd.0003056 Bloomfield, L. S., McIntosh, T. L., & Lambin, E. F. (2020). Habitat fragmentation, livelihood behaviors, and contact between people and nonhuman primates in Africa. Landscape Ecology, 35(4), 985-1000. https://doi.org/10.1007/s10980-020-00995-w Forman, R. T., & Godron, M. (1986). Landscape ecology. John Wiley and Sons, Inc. Forman, R. T. (1995). Land mosaics: The ecology of landscapes and regions. Cambridge University Press. Leser, H., & Nagel, P. (2001). Landscape diversity--A holistic approach. In Biodiversity (pp. 129-143). Springer. https://doi.org/10.1007/978-3-662-06071-1_9 Naveh, Z., & Lieberman, A. (1984). Landscape ecology: Theory and application. Springer-Verlag. Ryszkowski, L. (Ed.). (2002). Landscape ecology in agroecosystems management. CRC Press.
Sanderson, J., & Harris, L. D. (Eds.). (2000). Landscape ecology: A top-down approach. Lewis Publishers. Steiniger, S., & Hay, G. J. (2009). Free and open source geographic information tools for landscape ecology. Ecological Informatics, 4(4), 183-195. https://doi.org/10.1016/j.ecoinf.2009.07.004 Troll, C. (1939). Luftbildplan und ökologische Bodenforschung [Aerial photography and ecological studies of the earth]. Zeitschrift der Gesellschaft für Erdkunde, 241-298. Turner, M. G. (1989). Landscape ecology: The effect of pattern on process. Annual Review of Ecology and Systematics, 20, 171- 197. https://doi.org/10.1146/annurev.es.20.110189.001131 Turner, M. G., Gardner, R. H., & O'Neill, R. V. (2001). Landscape ecology in theory and practice. Springer-Verlag. Wu, J., & Hobbs, R. J. (2002). Key issues and research priorities in landscape ecology. Landscape Ecology, 17(4), 355-365. https://doi.org/10.1023/A:1020561630963 Wu, J. (2006). Landscape ecology, cross-disciplinarity, and sustainability science. Landscape Ecology, 21(1), 1-4. https://doi.org/10.1007/s10980-006-7195-2 Wu, J., & Hobbs, R. (Eds.). (2007). Key topics in landscape ecology. Cambridge University Press. Wu, J. (2008). Landscape ecology. In S. E. Jorgensen (Ed.), Encyclopedia of ecology. Elsevier. Contributors and Attributions Modified by Andy Wilson (Gettysburg College) and Kyle Whittinghill (University of Vermont) from the following sources: Wikipedia, the free encyclopedia https://en.Wikipedia.org/wiki/Landscape_ecology 21.1: What is Landscape Ecology? is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.
21.2: Important Terms in Landscape Ecology Landscape Certainly, 'landscape' is a central concept in landscape ecology. It is, however, defined in quite different ways. For example: Carl Troll conceives of landscape not as a mental construct but as an objectively given 'organic entity', a harmonic individuum of space (Kirchhoff et al., 2013; Troll, 2007). Ernst Neef defines landscapes as sections within the uninterrupted earth-wide interconnection of geofactors which are defined as such on the basis of their uniformity in terms of a specific land use, and are thus defined in an anthropocentric and relativistic way (Neef, 1967; Haase, 1990). According to Richard Forman and Michel Godron, a landscape is a heterogeneous land area composed of a cluster of interacting ecosystems that is repeated in similar form throughout, whereby they list woods, meadows, marshes and villages as examples of a landscape's ecosystems, and state that a landscape is an area at least a few kilometers wide (1981). John A. Wiens defines 'landscape'--regardless of scale--as "the template on which spatial patterns influence ecological processes" (Wiens, 1999; Wiens, 2005). Some define 'landscape' as an area containing two or more ecosystems in close proximity (Sanderson & Harris, 2000). Scale and heterogeneity (incorporating composition, structure, and function) A main concept in landscape ecology is scale. Scale represents the real world as translated onto a map, relating distance on a map image and the corresponding distance on earth (Malczewski, 1999). Scale is also the spatial or temporal measure of an object or a process, or amount of spatial resolution (Turner & Gardner, 1991; Forman, 1995). Components of scale include composition, structure, and function, which are all important ecological concepts. Applied to landscape ecology, composition refers to the number of patch types (see below) represented on a landscape and their relative abundance. For example, the amount of forest or wetland, the length of forest edge, or the density of roads can be aspects of landscape composition. Structure is determined by the composition, the configuration, and the proportion of different patches across the landscape, while function refers to how each element in the landscape interacts based on its life cycle events (Turner & Gardner, 1991). Pattern is the term for the contents and internal order of a heterogeneous area of land (Forman & Godron, 1986). A landscape with structure and pattern implies that it has spatial heterogeneity, or the uneven distribution of objects across the landscape (Forman, 1995). Heterogeneity is a key element of landscape ecology that separates this discipline from other branches of ecology. Patch and mosaic Patch, a term fundamental to landscape ecology, is defined as a relatively homogeneous area that differs from its surroundings (Forman, 1995). Patches are the basic unit of the landscape that change and fluctuate, a process called patch dynamics. Patches have a definite shape and spatial configuration, and can be described compositionally by internal variables such as number of trees, number of tree species, height of trees, or other similar measurements (Forman, 1995). Matrix is the "background ecological system" of a landscape with a high degree of connectivity. Connectivity is the measure of how connected or spatially continuous a corridor, network, or matrix is (Forman, 1995). For example, a forested landscape (matrix) with fewer gaps in forest cover (open patches) will have higher connectivity. Corridors have important functions as strips of a particular type of landscape differing from adjacent land on both sides (Forman, 1995). A network is an interconnected system of corridors while mosaic describes the pattern of patches, corridors, and matrix that form a landscape in its entirety (Forman, 1995).
: Basic terms to define landscape ecology (FISGRW 1998) from Understanding Landscape Structure Using Landscape Metrics (Ercan Gökyer) (DOI: 10.5772/55758).
Boundary and edge Landscape patches have a boundary between them which can be defined or fuzzy (Sanderson & Harris, 2000). The zone composed of the edges of adjacent ecosystems is the boundary (Forman, 1995). Edge means the portion of an ecosystem near its perimeter, where influences of the adjacent patches can cause an environmental difference between the interior of the patch and its edge. This edge effect includes a distinctive species composition or abundance (Forman, 1995). For example, when a landscape is a mosaic of perceptibly different types, such as a forest adjacent to a grassland, the edge is the location where the two types adjoin. In a continuous landscape, such as a forest giving way to open woodland, the exact edge location is fuzzy and is sometimes determined by a local gradient exceeding a threshold, such as the point where the tree cover falls below thirty-five percent (Turner & Gardner, 1991).
Ecotones, ecoclines, and ecotopes A type of boundary is the ecotone, or the transitional zone between two communities (Allaby, 1998). Ecotones can arise naturally, such as a lakeshore, or can be human-created, such as a cleared agricultural field from a forest (Allaby, 1998). The ecotonal community retains characteristics of each bordering community and often contains species not found in the adjacent communities. Classic examples of ecotones include fencerows, forest to marshlands transitions, forest to grassland transitions, or land-water interfaces such as riparian zones in forests. Characteristics of ecotones include vegetational sharpness, physiognomic change, occurrence of a spatial community mosaic, many exotic species, ecotonal species, spatial mass effect, and species richness higher or lower than either side of the ecotone (Walker et al., 2003). An ecocline is another type of landscape boundary, but it is a gradual and continuous change in environmental conditions of an ecosystem or community. Ecoclines help explain the distribution and diversity of organisms within a landscape because certain organisms survive better under certain conditions, which change along the ecocline. They contain heterogeneous communities which are considered more environmentally stable than those of ecotones (Attrill & Rundle, 2002). An ecotope is a spatial term representing the smallest ecologically distinct unit in mapping and classification of landscapes (Forman, 1995). Relatively homogeneous, they are spatially explicit landscape units used to stratify landscapes into ecologically distinct features. They are useful for the measurement and mapping of landscape structure, function, and change over time, and to examine the effects of disturbance and fragmentation.
: An ecotone between grassland and woodland. "Ecotone" by Nicholas A. Tonelli is licensed under CC BY 2.0.
Disturbance and fragmentation Disturbance is an event that significantly alters the pattern of variation in the structure or function of a system. Fragmentation is the breaking up of a habitat, ecosystem, or land-use type into smaller parcels (Forman, 1995). Disturbance is generally considered a natural process. Fragmentation causes land transformation, an important process in landscapes as development occurs. An important consequence of repeated, random clearing (whether by natural disturbance or human activity) is that contiguous cover can break down into isolated patches. This happens when the area cleared exceeds a critical level, which means that landscapes exhibit two phases: connected and disconnected (Green et al., 2006).
: Rapid deforestation in Cambodia resulted in habitat loss and fragmentation (credit: Global Forest Watch. World Resources Institute. Accessed on 1/5/2022. www.globalforestwatch.org).
Sources Allaby, M. (1998). Oxford dictionary of ecology. Oxford University Press. Attrill, M. J., & Rundle, S. D. (2002). Ecotone or ecocline: Ecological boundaries in estuaries. Estuarine, Coastal and Shelf Science, 55(6), 929-936. https://doi.org/10.1006/ecss.2002.1036 Forman, R. T. (1995). Land mosaics: The ecology of landscapes and regions. Cambridge University Press. Forman, R. T., & Godron, M. (1981). Patches and structural components for a landscape ecology. BioScience, 31(10), 733-740. https://doi.org/10.2307/1308780 Forman, R. T., & Godron, M. (1986). Landscape ecology. John Wiley and Sons. Green, D. G., Klomp, N. I., Rimmington, G. R., & Sadedin, S. (2006). Complexity in landscape ecology. Springer. Haase, G. (1990). Approaches to, and methods of landscape diagnosis as a basis of landscape planning and landscape management. Ekológia, 9(1), 31-44. Kirchhoff, T., Trepl, L., & Vicenzotti, V. (2013). What is landscape ecology? An analysis and evaluation of six different conceptions. Landscape Research, 38(1), 33-51. https://doi.org/10.1080/01426397.2011.640751 Malczewski, J. (1999). GIS and multicriteria decision analysis. John Wiley and Sons. Neef, E. (1967). Die theoretischen Grundlagen der Landschaftslehre [The theoretical basics of landscape science]. Haack. Sanderson, J., & Harris, L. D. (Eds.). (2000). Landscape ecology: A top-down approach. Lewis Publishers. Troll, C. (2007). The geographic landscape and its investigation. In J. A. Wiens, M. R. Moss, M. G. Turner, & D. J. Mladenoff (Eds.), Foundation papers in landscape ecology (pp. 71-101). Columbia University Press. (Original work published 1950) https://doi.org/10.1007/978-3-662-38240-0_20 Turner, M. G., & Gardner, R. H. (Eds.). (1991). Quantitative methods in landscape ecology. Springer-Verlag. Walker, S., Wilson, J. B., Steel, J. B., Rapson, G. L., Smith, B., King, W. M., & Cottam, Y. H. (2003). Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradient. Journal of Vegetation Science, 14(4), 579-
590. https://doi.org/10.1111/j.1654-1103.2003.tb02185.x Wiens, J. A. (1999). The science and practice of landscape ecology. In J. M. Klopatek & R. H. Gardner (Eds.), Landscape ecological analyses: Issues and applications (pp. 371-383). Springer. Wiens, J. A. (2005). Toward a unified landscape ecology. In J. A. Wiens & M. R. Moss (Eds.), Issues and perspectives in landscape ecology (pp. 365-373). Cambridge University Press. Contributors and Attributions Modified by Andy Wilson (Gettysburg College) and Kyle Whittinghill (University of Vermont) from the following sources: Wikipedia, the free encyclopedia https://en.Wikipedia.org/wiki/Landscape_ecology 21.2: Important Terms in Landscape Ecology is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.
21.3: Applications of Landscape Ecology Research directions Developments in landscape ecology illustrate the important relationships between spatial patterns and ecological processes. These developments incorporate quantitative methods that link spatial patterns and ecological processes at broad spatial and temporal scales. This linkage of time, space, and environmental change can assist managers in applying plans to solve environmental problems (Turner et al., 2001). The increased attention in recent years on spatial dynamics has highlighted the need for new quantitative methods that can analyze patterns, determine the importance of spatially explicit processes, and develop reliable models (Turner & Gardner, 1991). Multivariate analysis techniques are frequently used to examine landscape level vegetation patterns. Vegetation classification is the process of classifying and mapping the vegetation over an area of the earth's surface and is often performed by state based agencies as part of landuse, resource and environmental management. Many different methods of vegetation classification have been used but vegetation classification mapping is usually now done using geographic information systems (GIS) software. Studies use statistical techniques for classifying vegetation based on a combination of remote sensing variables. For an example of a vegetation classification system see the United States Geological Survey Land Cover website. Gradient analysis is another way to determine the vegetation structure across a landscape or to help delineate critical wetland habitat for conservation or mitigation purposes (Choesin & Boerner, 2002; Lyon & Sagers, 1998). Climate change is another major component in structuring current research in landscape ecology (Ochoa-Hueso et al., 2019). Ecotones, as a basic unit in landscape studies, may have significance for management under climate change scenarios, since change effects are likely to be seen at ecotones first because of the unstable nature of a fringe habitat (Walker et al., 2003). Research in northern regions has examined landscape ecological processes, such as the accumulation of snow, melting, freeze-thaw action, percolation, soil moisture variation, and temperature regimes through long-term measurements in Norway (Löffler & Finch, 2005). The study analyzes gradients across space and time between ecosystems of the central high mountains to determine relationships between distribution patterns of animals in their environment. Looking at where animals live, and how vegetation shifts over time, may provide insight into changes in snow and ice over long periods of time across the landscape as a whole. Other landscape-scale studies maintain that human impact is likely the main determinant of landscape pattern over much of the globe (Ellis et al., 2021; Wilson & King, 1995). Landscapes may become substitutes for biodiversity measures because plant and animal composition differs between samples taken from sites within different landscape categories. Taxa, or different species, can "leak" from one habitat into another, which has implications for landscape ecology. As human land use practices expand and continue to increase the proportion of edges in landscapes, the effects of this leakage across edges on assemblage integrity may become more significant in conservation. This is because taxa may be conserved across landscape levels, if not at local levels (Dangerfield et al., 2003). Land change modeling Land change modeling is an application of landscape ecology designed to predict future changes in land use. Land change models are used in urban planning, geography, GIS, and other disciplines to gain a clear understanding of the course of a landscape (National Research Council, 2014). In recent years, much of the Earth's land cover has changed rapidly, whether from deforestation or the expansion of urban areas (University of Maryland). Relationship to other disciplines Landscape ecology has been incorporated into a variety of ecological subdisciplines. For example, it is closely linked to land change science, the interdisciplinary of land use and land cover change and their effects on surrounding ecology. Another recent development has been the more explicit consideration of spatial concepts and principles applied to the study of lakes, streams, and wetlands in the field of landscape limnology. Seascape ecology is a marine and coastal application of landscape ecology (Pittman, 2017).[48] In addition, landscape ecology has important links to application-oriented disciplines such as agriculture and forestry. In agriculture, landscape ecology has introduced new options for the management of environmental threats brought about by the intensification of agricultural practices. Agriculture has always been a strong human impact on ecosystems (Ryszkowski, 2002).
In forestry, from structuring stands for fuelwood and timber to ordering stands across landscapes to enhance aesthetics, consumer needs have affected conservation and use of forested landscapes. Landscape forestry provides methods, concepts, and analytic procedures for landscape forestry (Boyce, 1995). Landscape ecology has been cited as a contributor to the development of fisheries biology as a distinct biological science discipline, and is frequently incorporated in study design for wetland delineation in hydrology (Magnuson, 1991; Attrill & Rundle, 2002). It has helped shape integrated landscape management (Sayer, 2009). Lastly, landscape ecology has been very influential for progressing sustainability science and sustainable development planning. For example, a recent study assessed sustainable urbanization across Europe using evaluation indices, country-landscapes, and landscape ecology tools and methods (Shaker, 2015). Landscape ecology has also been combined with population genetics to form the field of landscape genetics, which addresses how landscape features influence the population structure and gene flow of plant and animal populations across space and time and on how the quality of intervening landscape, known as "matrix," influences spatial variation (Manel et al., 2003; Storfer et al., 2007). After the term was coined in 2003, the field of landscape genetics had expanded to over 655 studies by 2010, and continues to grow today (Storfer et al., 2010). As genetic data has become more readily accessible, it is increasingly being used by ecologists to answer novel evolutionary and ecological questions, many with regard to how landscapes effect evolutionary processes, especially in human-modified landscapes, which are experiencing biodiversity loss (Balkenhol et al., 2015; Manel & Holderegger, 2013). References Attrill, M. J., & Rundle, S. D. (2002). Ecotone or ecocline: Ecological boundaries in estuaries. Estuarine, Coastal and Shelf Science, 55(6), 929-936. https://doi.org/10.1006/ecss.2002.1036 Balkenhol, N., Cushman, S., Storfer, A., & Waits, L. (2015). Landscape genetics: Concepts, methods, applications. John Wiley & Sons. Boyce, S. G. (1995). Landscape forestry. John Wiley & Sons. Choesin, D., & Boerner, R. (2002). Vegetation boundary detection: A comparison of two approaches applied to field data. Plant Ecology, 158, 85-96. https://doi.org/10.1023/A:1014720508155 Dangerfield, J. M., Pik, A. J., Britton, D., Holmes, A., Gillings, M., Oliver, I. A., Briscoe, D., & Beattie, A. J. (2003). Patterns of invertebrate biodiversity across a natural edge. Austral Ecology, 28(3), 227-236. https://doi.org/10.1046/j.1442-9993.2003.01240.x Ellis, E. C., Gauthier, N., Klein Goldewijk, K., Bliege Bird, R., Boivin, N., Díaz, S., Fuller, D. Q., Gill, J. L., Kaplan, J. O., Kingston, N., Locke, H., McMichael, C. N. H., Ranco, D., Rick, T. C., & Shaw, M. R. (2021). People have shaped most of terrestrial nature for at least 12,000 years. Proceedings of the National Academy of Sciences, 118(17), e2023483118. https://doi.org/10.1073/pnas.2023483118 Löffler, J., & Finch, O. D. (2005). Spatio-temporal gradients between high mountain ecosystems of central Norway. Arctic, Antarctic, and Alpine Research, 37(4), 499-513. https://doi.org/10.1657/1523-0430(20...gbhme]2.0.co;2 Lyon, J., & Sagers, C. L. (1998). Structure of herbaceous plant assemblages in a forested riparian landscape. Plant Ecology, 138(1), 1-6. https://doi.org/10.1023/A:1009705912710 Magnuson, J. J. (1991). Fish and fisheries ecology. Ecological Applications, 1(1), 13-26. https://doi.org/10.2307/1941844 Manel, S., Holderegger, R. (2013). Ten years of landscape genetics. Trends in Ecology & Evolution, 28(10), 614-621. https://doi.org/10.1016/j.tree.2013.05.012 Manel, S., Schwartz, M. K., Luikart, G., & Taberlet, P. (2003). Landscape genetics: Combining landscape ecology and population genetics. Trends in Ecology & Evolution, 18(4), 189-197. https://doi.org/10.1016/S0169-5347(03)00008-9 National Research Council. (2014). Advancing land change modeling: Opportunities and research requirements. National Academies Press. https://doi.org/10.17226/18385 Ochoa-Hueso, R., Delgado-Baquerizo, M., King, P. T., Benham, M., Arca, V., & Power, S. A. (2019). Ecosystem type and resource quality are more important than global change drivers in regulating early stages of litter decomposition. Soil Biology and Biochemistry, 129, 144-152. https://doi.org/10.1016/j.soilbio.2018.11.009
Pittman, S. J. (Ed.). (2017). Seascape ecology. Wiley & Sons. Ryszkowski, L. (Ed.). (2002). Landscape ecology in agroecosystems management. CRC Press. Sayer, J. (2009). Reconciling conservation and development: Are landscapes the answer? Biotropica, 41(6), 649-652. https://doi.org/10.1111/j.1744-7429.2009.00575.x Shaker, R. R. (2015). The well-being of nations: An empirical assessment of sustainable urbanization for Europe. International Journal of Sustainable Development & World Ecology, 22(5), 375-387. https://doi.org/10.1080/13504509.2015.1055524 Storfer, A., Murphy, M. A., Evans, J. S., Goldberg, C. S., Robinson, S., Spear, S. F., et al. (2007). Putting the "landscape" in landscape genetics. Heredity, 98(3), 128-142. https://doi.org/10.1038/sj.hdy.6800917 Storfer, A., Murphy, M. A., Spear, S. F., Holderegger, R., & Waits, L. P. (2010). Landscape genetics: Where are we now? Molecular Ecology, 19(17), 3496-3514. https://doi.org/10.1111/j.1365-294X.2010.04691.x Turner, M. G., & Gardner, R. H. (Eds.). (1991). Quantitative methods in landscape ecology. Springer-Verlag. Turner, M. G., Gardner, R. H., & O'Neill, R. V. (2001). Landscape ecology in theory and practice. Springer-Verlag. University of Maryland. (n.d.). GLCF: Global Land Cover Change. Global Land Cover Facility. https://glcf.umd.edu (Archived June 9, 2019) Wilson, J. B., & King, W. M. (1995). Human-mediated vegetation switches as processes in landscape ecology. Landscape Ecology, 10(4), 191-196. https://doi.org/10.1007/BF00129253 Walker, S., Wilson, J. B., Steel, J. B., Rapson, G. L., Smith, B., King, W. M., & Cottam, Y. H. (2003). Properties of ecotones: Evidence from five ecotones objectively determined from a coastal vegetation gradient. Journal of Vegetation Science, 14(4), 579- 590. https://doi.org/10.1111/j.1654-1103.2003.tb02185.x Contributors and Attributions Modified by Andy Wilson (Gettysburg College) and Kyle Whittinghill (University of Vermont) from the following sources: Wikipedia, the free encyclopedia: https://en.Wikipedia.org/wiki/Landscape_ecology Wikipedia, the free encyclopedia: https://en.wikipedia.org/wiki/Vegeta...classification 21.3: Applications of Landscape Ecology is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.
Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time.
Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isolation,
and habitat area. The latter pattern, often called the species-area relationship, has long been a fascination for
demonstrates this species-area relationship for amphibians and reptiles in the West Indies. A study
from around 1957 was included in Robert H. MacArthur and Edward O. Wilson's famous book "The Theory of Island
Biogeography", and showed that among seven islands studied, the largest, Cuba, had the most species, and the smallest, Redonda,
had the fewest. This general pattern has been found in many different islands groups, and across various different taxa.
: Species-area relationship for amphibians and reptilians on seven different islands in the West Indies. An original
study (Darlington c. 1957), published in "The Theory of Island biogeography", showed a strong positive correlation between island
size and number of species (blue line). A more recent study by Gao and Perry (2016) included data for many additional small
islands (smaller than Redonda) and found that while the pattern holds, the relationship is flatter than in the original study--indicated
by the pink line. Figure drawn by Andy Wilson, based on Figure 4 in Gao and Perry (2016).
While studying these species-area relationships for their seminal book, MacArthur and Wilson were drawn to another of the four geographic gradients--that of isolation. They observed that some large Islands had fewer species than would be expected for their size, while conversely, some small islands had more species than expected.
While studying patterns of species richness on islands, two ecologists, Robert H. MacArthur and Edward O. Wilson, noted some exceptions to the species-area relationship. For example, some large islands had fewer species than expected due to their size, while some small islands had more species than expected. These patterns were explained by MacArthur and Wilson's Equilibrium Theory of Island Biogeography, which takes into account the fact that islands are colonized by species from elsewhere, and natural extinctions will occur on those islands, over long periods of time.
Imagine there are two islands (a and b) located off the coast of the mainland. Although the two islands are about the same size, island a is located much farther away than island b. If you are a bird that lives on the mainland, which island are you most likely to find? The answer is generally island b. This means immigration (or colonization) is influenced by the distance of an island from the mainland (a source of colonists). Therefore, islands that are closer to the island are more likely to receive immigrants than islands that are further away.
: Two offshore islands--the Theory of Island Biogeography suggests that fewer species will colonize the more distant island a, in comparison to island b (credit: Andy Wilson, redrawn from Hdelucalowell15 (CC BY-SA 4.0)).
Once a species manages to reach and colonize an island, the rate of extinction is largely influenced by size of the island. This is because smaller islands tend to hold smaller populations (which are more likely to experience extinction due to stochastic effects like genetic drift). Larger habitat size reduces the probability of extinction of the colonized species due to chance events. Smaller islands are also likely to hold fewer populations in general because they have fewer resources and less diversity of resources. Larger islands have larger and more habitat areas, which typically leads to more differences in habitat or habitat heterogeneity. Higher heterogeneity means that there are more opportunities for a variety of species to find their suitable niches. Habitat heterogeneity also helps increase the number of species to successfully colonize after immigration.
Now let's consider the situation if we had two different islands sizes in our offshore archipelago, with c and d, much bigger than a
. We would expect extinction rates to be much lower on islands c and d than on the two smaller islands.
: Four offshore islands--the Theory of Island Biogeography suggests that fewer species will go extinct on the larger
islands c and d, in comparison to islands a and b (credit: Andy Wilson, redrawn from Wikipedia (CC BY-SA 4.0)).
We could plot both immigration and extinction relationships on a single image, as in Figure species (either colonizing or going extinct). Now we see that of the four islands in Figure
. Note the y-axis is the number of , island a (small and far) would
likely have the fewest species, island d (large and close), would have the most, and islands b and c would fall between the two extremes.
: Equilibrium Theory of Island Biogeogaphy (credit: Andy Wilson, redrawn from Wikipedia (CC BY-SA 4.0)).
This basic graph makes a lot of assumptions but also offers a lot of insight. In this graph, immigration rates (blue lines) depend on proximity to mainland. Immigration rates also decline with species richness. That's becasuse its' easiest to immigrate to an island when it is empty because all the resources on the island are available. As the islands get more and more full, colonizing the island becomes more difficult.
Extinction rates (orange lines), as noted above, depend on island size. We also see that extinction rates tend to increase with the number of species. This should make sense: If there are no species on an island, extinction is impossible, but as more and more species arrive (and compete!) extinction becomes more likely.
shows the basic Equilibrium Theory of Island Biogeography. It suggests that islands will reach an equilibrium, or
stable, number of species when immigration and extinction rates are equal! Note this model could be modified in multiple ways.
Size of an island, for example, likely also impacts immigration rate (larger islands are easier to hit!), and islands that are close
together may also share individuals (the Rescue effect!), but even this simple conceptualization has proven useful for understanding
One interesting point to note is that an equilibrium number of species is reached when immigration and extinction rates are equal, not when those processes stop! This means islands may consistently be changing species composition but should maintain fairly consistent levels of species richness. As odd as this sounds, early tests of the Equilibrium Theory of Island Biogeography supported these assumptions. When mangrove islands off the coast of Florida were fully cleared of their invertebrate (insect and arachnid) communities and allowed to recolonize, islands eventually stabilized with communities of about the same richness as they had before disturbance.
Conservation in Preserves as an application of Island Biogeography The island biogeography model has crucial applications for wildlife management because wildlife reserves or patches of habitat can be considered "islands" of habitat in "an ocean" of an inhabitable area. For this reason, the Theory Island Biogeography has become central to our understanding of how habitat fragmentation leads to biodiversity loss. For a more detailed description of how habitat fragmentation leads to biodiversity loss, see the section on "Threats to Biodiversity" in the chapter on Conservation Biology from this book or see the section on "The Scramble for Space" in Conservation Biology in Sub-Saharan Africa (Wilson and Primack 2019).
Establishment of wildlife and ecosystem preserves is one of the key tools in conservation efforts (Figure
area of land set aside with varying degrees of protection for the organisms that exist within the boundaries of the preserve. There
has been extensive research into optimal preserve designs for maintaining biodiversity. Conservation preserves can be seen as
"islands" of habitat within "an ocean" of non-habitat. In general, large preserves are better because they support more species,
including species with large home ranges; they have more core area of optimal habitat for individual species; they have more
niches to support more species; and they attract more species because they can be found and reached more easily. One large
preserve is better than the same area of several smaller preserves because there is more core habitat unaffected by less hospitable
ecosystems outside the preserve boundary. For this same reason, preserves in the shape of a square or circle will be better than a
preserve with many thin "arms." If preserves must be smaller, then providing wildlife corridors (narrow strips of protected land)
between two preserves is important so that species and their genes can move between them. All of these factors are taken into
consideration when planning the nature of a preserve before the land is set aside.
: Mequon Nature Preserve in Wisconsin. Image by Jennifer Tomaloff (CC-BY-NC-SA).
Contributors and Attributions Modified by Andy Wilson (Gettysburgh College), Kyle Whittinghill (University of Vermont) and Natasha Gownaris (Gettysburg College) from the following sources:
21.4: Island Biogeography is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.