An Introduction to Landscape Ecology

Introduction to Landscape Ecology Instructor: K. McGarigal Assigned Reading: Turner et al. 2001 (Chapter 1) Objective: Describe the focus of the science of landscape ecology, including its historical context and its contrast to other ecology disciplines. Highlight importance of landscape ecology in addressing current resource management topics. Topics covered: 1. What is landscape ecology? 2. History of landscape ecology (impetus for its emergence; European and American versions) 3. Why is landscape ecology important to resource managers? Comments: Material borrowed from Turner et al. (2001) and Dean UrbanÕs Landscape Ecology course notes, Duke University. 1.1  1. What is Landscape Ecology Landscape ecology is perhaps best defined by its focus on: 1) spatial patterns, 2) broader spatial extents than those traditionally studied in ecology, and 3) the role of humans in creating and affecting landscape patterns and process. 1.2  # Space: the Final Frontier Incredibly, space really is the final frontier in ecology. Much of its history has been played out in a nonspatial arena: predators perfectly mixed with prey; ecosystems conceived as homogeneous pools of carbon or nutrients, and so on. This is not to say that there weren't odd souls who worked on spatial problems, but they were definitely in the minority. Yet, space really is inherent in our field: ¥ Ecology is defined as the interaction of organisms and their environment, and their environment is profoundly spatial (everything happens somewhere). Indeed, our casual observations of spatial heterogeneity ("this is a great spot to go birding!") celebrates this spatial variability. ¥ Ecology is also defined in terms of interactions, and one thing that seems to be true of interactions in general is that their strength varies with distance: this is true of planetary gravitation, it's true of people standing in elevators, and it's true of competition for resources between individual plants. And distance implies spatial location. 1.3  Landscape ecology might be defined best by its focus on spatial heterogeneity and pattern: how to characterize it, where it comes from, how it changes through time, why it matters, and how humans manage it: ¥ Characterizing pattern involves detecting it--and the scale at which it is expressed--and summarizing it (statistically or otherwise quantitatively). ¥ The agents of pattern formation include the physical abiotic template, demographic responses to this template, and disturbance regimes overlaid on these. ¥ An interest in landscape dynamics necessarily invokes models of some sort--because landscape are large and they change (usually!) over time scales that are difficult to embrace empirically. ¥ Spatial heterogeneity matters to populations, communities, and ecosystems--and this is the stuff of conservation biology and ecosystem management. ¥ Landscape are large by conventional definition, and so somewhat coincidentally, landscape ecology also encounters humans as agents shaping landscapes. This human aspect of the discipline will guide the applied focus of the course. 1.4  # Broad Spatial Extents Landscape ecology is distinguished by its focus on broader spatial extents than those traditionally studied in ecology. This stems from the anthropocentric origins of the discipline (see below). Initial impetus for the discipline came from the geographers aerial view of the environment, for example, the patterns in the environment visible from an aerial photograph. The focus on large geographic areas is consistent with how humans typically see the worldÐthrough a coarse lens. However, modern landscape ecology does not define, a priori, specific scales that may be universally applied; rather, the emphasis is to identify scales that best characterize relationships between spatial heterogeneity and the process of interest. 1.5  # The Role of Humans Landscape ecology is often defined by it focus on the role of humans in creating and affecting landscape patterns and process. Indeed, landscape ecology is sometimes considered to be an interdisciplinary science dealing with the interrelation between human society and its living environment. Hence, a great deal of landscape ecology deals with ÔbuiltÕ environments, where humans are the dominant force of landscape change. However, modern landscape ecology, with its emphasis on the interplay between spatial heterogeneity and ecological process, considers humans as one of many important agents affecting landscapes, and emphasizes both natural, semi-natural, and built landscapes. 1.6  2. History of Landscape Ecology Landscape Ecology as a discipline has two evolutionary lines, which might be caricatured as the "European School" (which is also strongly represented in the United States and elsewhere), and the "American School" (which is also common in Australia and elsewhere). # The European school ¥ Very long history (as long as ecology itself, almost). ¥ Emphasis on typology and classification and mostly is concerned with "built" systems. ¥ In the U.S., it is found more often in Landscape Architecture, Planning, or Design schools than in Biology departments. # The American school ¥ Comparatively young, gaining a high profile in the U.S. only after the early 1980's. ¥ Launched, for practical purposes, by a workshop at Allerton Park (Risser et al. 1984). This was a pivotal meeting because the meeting decided what landscape ecology was about: its intellectual domain (what would be considered "interesting") and the tools of the trade (officially sanctioned approaches). ¥ In contrast to the European school, much more of a focus on natural systems (or at least, semi-natural ones such National Parks). ¥ Is much more invested in theory and models, including some extremely abstract ones. 1.7  The emergence of landscape ecology as a prominent subdiscipline of ecology in the early 1980's can be traced to a number of factors: 1) growing awareness of broad-scale environmental issues requiring a landscape perspective, 2) increasing recognition of the importance of scale in studying and managing pattern-process relationships, 3) emergence of the dynamic view of ecosystems/landscapes, and 4) technological advances in remote sensing, computer hardware and software. 1.8  # Broad-scale environmental issues Unrelenting demand for more and more commodities and services from global ecosystems has led to numerous ecological crises. Staggering losses of topsoil each year from many of AmericaÕs farmlands demonstrate that these ecosystems are being exploited. Failure of certain tropical humid forests to rebound after clearcutting dramatically illustrates their vulnerability to radical disturbance. Equally compelling evidence of ecosystem limits is seen in